RE: Engine Rip -Offs: Post your GMS 120 nightmares here!
Ok I lost my original post due to timeout, but the points I wanted to make are: 1) Its not reasonable to expect to have to fiddle excessively to make a new motor run right, even though most motors can eventually be made to run right. 2) When time and weather is limited, flight time is precious, and fiddling is the last thing you want to do. 3) Returns are not a viable option at the Tip of Africa, unlike in the US. Things go missing. I once waited 6 months for my faulty speed controller to be declared lost and a new once sent after insurance payout. Its just not viable, even though we would love to give the the supplier a chance to rectify. 4) I have obseved 3 of these motors at the same field. The one good one was in a pattern ship running 3/4 to flat out ran just fine. The replacement moki ran fine on same plumbing and fuel. Sounds like carburation causing over or underheating. 5) Nitro costs an arm and a leg here so we try to run reduced amounts which makes tuning trickier. I prefer to run 0% but in larger capacity motors like the Moki and OS 1.60 to make up the power
Posted on: 3/23/2006 7:19 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=4071666

Balancing Lipo questions
After 30 cycles I decided to open up my TP2100 gen2 packs to check the cell balance. My Fluke DVM only goes to 2 decimal places, I see that the Duratrax ICE displays voltage to 3 decimal places but only while charging/discharging. Doesnt seem to be much point when you consider the voltage drop over the cable except when using the same cable to compare cells. My questions are: Is comparing to 2 decimal places sufficient? Can I use the ICE to say discharge at the lowest discharge setting (100ma) and stop the cell discharge at the same place on each cell eg. 4.125V? It would appear to be a good idea to stop the charge at the last trickle stage at say at 100ma charge rate, so that any imbalance would not cause a cell to be overcharged. It would save time too as a disproportionate part of the charge time is spent putting the last 5% charge in. Any problem with doing that repeatedly over the long term? FYI - both my packs were only out by 0.01V after about 6 months, 30 full cycles of use. This seems pretty good, is it? At the moment, my tap wires are push fit into the crimped tabs, is it safe to solder them, or do I need a special solder paste for these packs? Thanks Mark
Posted on: 8/29/2005 3:34 AM by Author "Squid" in the forum "E-Flight Power Sources"
http://www.rcuniverse.com/forum/fb.asp?m=3308913

RE: Mass blancing ailerons
Thanks for your input Brian, I was able to extract the information pertinent to the problems were are currently experiencing with our models and will factor it in when applying fixes accordingly. I for one and glad to have input from any angle and find the 'non relevant' parts very interesting non the less. Then again, I watch all the aviation programs on Discovery and have closely watched the A380 maiden recently, and any behind the scenes info is most welcome, even from their competitors! :) Dick, your models are not aberrations, its all avaiation and its all good! We all have to flight the "Its only a toy" mentality sometimes, now drop, stay...good boy!!!
Posted on: 5/10/2005 3:58 AM by Author "Squid" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=2960581

RE: Mass blancing ailerons
Yea Dick, I guess we work hard and play hard, which makes it a bit tough on our planes but thats the way we like it! Maybe when I retire, I'll settle down with a nice Sig Rascal and potter round the sky.[:D] What we both didnt mention was that the motors were brand new on these planes and as such, were running coarser props to keep the load on (the GMS/Webra tend to richen up in flight otherwise, the Moki transitioning after only 2 tanks is also a bit poor) and need to keep the revs up a bit to reduce the chances of flameout. This obviousely makes it even trickier to stay within the recommended speed range. We could laugh or cry about this, but at the end of the day, its all about having fun, keeping it safe and taking responsibility for ones actions, however insane they may appear to be at the time! Each new plane I build/fly is a new learning experience, sometimes in an unexpected area such as this F90 flutter saga. Im actually enjoying the challenge of increasing the flight envelope for this thing even though the test flights are fairly disasterous at this stage, all good stuff!!! Anyway, dont wanna get too philosophical, lets go FLY!!!! PS thats a nice plane Dick, wing reminds me of my ol Electrostreak, kinda looks 'right'...!
Posted on: 5/6/2005 11:21 AM by Author "Squid" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=2949111

RE: Mass blancing ailerons
Dick are you telling me that a Moki 1.35 with a 8 pitch prop running rich at 1/3 throttle on a 10 degree descent into the landing circuit is too much for the plane? Im shocked! But not surprised really looking at the minimalist build of the plane...:) Ive got some 17X5 APCs on the way to slow things down, and I promise i'll excersise my left thumb a bit more next time! I guess our flight performance requirements should have included medium speed flight as well when looking for a 3Der. I still feel a certain amount of extra engineering in the wing dept, is required to allow boneheads like me to at least get a couple of flights in before planting it! Its odd how my Uproar 40 just loves to dive at full throttle (Irvine 40) in combat, and even my Green Models 72" LAser 200 nicely overpowered with an OS1.60 regularly survives an 80% throttle dive on strafing the runway with an 18X8 apc.... Oh well, whats a nice replacement 3Der for a Moki1.35 that wont break up in mid air??
Posted on: 5/6/2005 9:24 AM by Author "Squid" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=2948747

RE: Mass blancing ailerons
Rodney, yourself and Alisdair both have valid points. If I can expand on one of your comments: >>"Mass balance has nothing to do with that unless, in the process of adding it, you have changed the stiffness of the structure." I feel it would be more accurate to say "resonant frequency characteristic" instead of "stiffness". This resonant frequency characteristic is a function of both stiffness AND inertial mass around the axis of flutter, ie. by adding mass to the object (mass balance or otherwise) it increases its inertial mass (resistance to twist), effectively lowering its resonant frequency. It shouldnt matter whether you lower or raise the resonant frequency as long as it is out of the range of the frequency of the excitation force being applied. When applying this fix, it is important to locate the mass as far from the centre of twist as possible to be effective. The Aileron and wing should also be looked at as a system rather than independently and they act upon and influence each other. After witnessing Spoilers wing failure, I was facing my F90 maiden with some trepidation, so I made up some weights on the ends of dowels glued onto the ends of the wings facing forward and some facing backward from the ailerons as well. It wasnt pretty, but I got 2 flights out of it before the flutter set in on the third flight on a slight overspeeding. I acutally saw the wing rather than the aileron flutter this time. IMO the wing is under built. If it had been build stiffer using less rib spacing and cross bracing (as per the ailerons), flutter could have been designed out. In fact Im going to have to apply this mod retrospectively as all the wing ribs broke along the lightening holes. The weight addition should be minimal and the stiffness increase 'maximal'! F90 designer please take note!
Posted on: 5/6/2005 8:27 AM by Author "Squid" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=2948592

RE: GMS Engine Tuning Problem
Wayne its been a pleasure! It is great indeed how the internet can bring together modellers from all over the world to help solve problems and reach a common goal. I look forward to hearing how others are getting on with their GMSs and how much the other capacities of motor are affected apart from the 47s. Cheers Mark
Posted on: 12/9/2004 3:25 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2416003

RE: GMS Engine Tuning Problem
Hi Wayne, Opps I forgot to mention, I have been running an exhaust deflector all along, maybe thats why It doesnt seem to need an additional baffle in the exhaust. Your tuning method seems pretty spot on. I use a non scientific method, combining a pinch test and acceleration test, just peak on the main needle, then do the following: 1) High speed run 10 secs 2) Idle 10 secs 3) Pinch fuel inlet pipe as near to the carb inlet as possible (should run 2-3 secs, picking up slightly). No need to wait till motor cuts. If picks up (and possibly dies) immediately, too lean. If takes 5 secs to pick up, too rich. Adjust idle screw 1/8th turn accordingly and repeat 1-3 until happy. 4) Repeat 1 & 2 5) Test transtion from idle to full power with a smart shove forward on the stick. Should accelerate cleanly. If not, probably a tab rich. Lean idle screw 1/8th turn are repeat whole procedure from 1. 6) If ok, re-peak the main needle if necessary and check the vertical. If too lean on the vertical richen a click the main a click or two. Hope that helps! Regards, Mark
Posted on: 12/8/2004 3:09 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2412566

RE: GMS Engine Tuning Problem
Hi Wayne, Had two good flights on sat. More power than I every had before due to being able to lean out better in the horizontal plane, and no cut outs due to leaning in the verticle plane or when the fuel level drops, and that was a HOT day, 28 deg and 99.99% humidity (there was condesation on the carb on landing!) I think if one can reduce the fuel flow restriction by doing the mods we did, and keep the tank close in to the carb, then theres no need to restrict the exhaust outlet further to obtain more pressure. If its not possible to get the tank close enough, a baffle like yours should certainly help matters. I would now say that the GMS is performing comparably to my Irvine 40, in fact it starts better and is half the price, so Im very happy!! Thanks for making the info available on this thread. I would still be struggling and cursing GMS otherwise!! Regards, Mark
Posted on: 12/7/2004 6:49 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2409315

RE: Irvine 53
Looking at the JEn carb, it reminds me of the GMS carb a bit. Can anyone verify the similarity? The GMS carbs run well, but there were some issues with mine which required drilling out the brass insert as the hole did not line up with the fuel inlet! Also have some leaks in the needle valve area and carb to engine. Once cured, a great running carb.
Posted on: 12/7/2004 3:36 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2409201

RE: GMS Engine Tuning Problem
I agree that the GMS is a great engine and is well priced. It starts better than any engine I gave ever owned and certainly delivers power, I dont think thats an issue. What we are trying to do is address the running consistancy which seems overly sensitive to the aircraft orientation (compared to other motors) and results in lean running and unexpected engine cuts. Some manufacturing quality issues have been found, such as leaking carb interface, needle seals and now the fuel inlet hole lineup. From f/b, it appears GMS are addressing at least the hole lineup. Hopefully the other issues will be addressed too as I believe they do contribute to the overal running consistancy to a greater or lesser extent based on other factors such as tank placement , % nitro etc. With the mods I have done to date, the biggest improvement was made by moving the tank closer to the carb. That is not to say the other mods did not make an improvement and im glad I did them. The one thing I have not tried, and I belive will make a significant improvement is increasing the muffler backpressure. It appears that before moving the tank previously, the pressure was insufficient to raise the fuel the 8 inches or so required without excessive decrease in flow. Ive eliminated fuel restictions with the mods, so it follows that the insufficient pressure must be the culprit. I am talking about leaning out at full throttle between the horizontal and vertical atiitudes here, so I dont *think* part throttle carburation is the issue here. Others may have other issues, I can only comment on my findings here, hope it helps! I am now happy with the running with the mods so am ready to flight test. My next step would be to insert a baffle or different silencer to increase the muffle pressure. (im using the dull finned one). But maybe not required now. It would have allowed the tank to be placed more rearward, at the loss of a few hundred rpm. Wayne, I drilled the exhast to 2mm right at the beggining (see my detailed post) and it made no difference. I dont think air has a problem flowing through a 1.5mm hole, fuel however does seem to! Captn, I use a perry pump in my 1.60Fx equipped 1/4 scale lazer, I cant seem to justify (in my head at least!) spending on one for a GMS in a spad type plane!! Will hopefull get some test flying in this w/e, good luck to you all! R. Mark
Posted on: 12/3/2004 9:52 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2397752

RE: GMS Engine Tuning Problem
Ran the motor again last night with the tank moved forward. That seemed to do the trick, only about 5% drop in power between horizontal and vertical orientations now which is acceptable. I guess the low muffler pressure due to lack of baffles combined with the rearward tank location was causing my leaning out blues. GMS really should fit a baffle, they are noisy without, and the running improvement would certainly be worth a few hundred rpm drop imho.
Posted on: 12/2/2004 2:27 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2394456

RE: GMS Engine Tuning Problem
Hi Chaps, Had a good go at it yesterday evening. I was able to simulate the leaning overheating problem quite easily in the garden so was able to do all the tests necessary yesterday. It appears my motor just cuts when it gets too hot (measured over 210deg C on the head!), so now to find the reason for the overheating. It appears to be excessive leaning when the model is in a climing orientation. In its current configuration, this motor appears to be much more sensitive to this than others (eg Irvine) which I have. So lets see if these mods help at all: 1) Ran the motor with only the new hole in the brass insert, 1.5mm, needle more sensitive (could have been the sealing of the needle end with fuel tubing), no change to climb/leaning sensitivity. 2) Drilled out the exhaust pressure nipple to 2mm. No change in anything. 3) Drilled out fuel inlet nipple only to 1.8mm (brass insert hole still 1.5mm), needle the same, slight reduction in climb/leaning sensitivity. 4) Drilled out the brass insert hole to 1.8mm to match the fuel inlet nipple, needle the same, slight reduction in climb/leaning sensitivity. 5) Replaced head shim (total 3). Starting easier (less compression), no apparent loss of power, no change in needle or leaning sensitivity. (running 5% nitro at sea level, 24 deg C) After all this, the excessive leaning was still a problem. but could be tuned sufficiently for flight, about 30% power loss in horizontal orientation when peaking in the verticle. Still not acceptable. The one thing I didnt try was a baffled muffer. Im running the standard noisy instrument. This in conjuction with the previous mods would have helped the most I suspect. My conclusion is that although these mods helped, they have not fully solved the problem in my case. I took another look at the fuel tank location and decided to relocate it closer. Previously, the tank centre was 8 inches (about 210mm) from the carb. I have relocated it to 6 inches (170mm). I ran out of light for testing, but am hoping those extra 2 inches will make a difference (!!).
Posted on: 12/1/2004 2:36 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2391578

RE: GMS Engine Tuning Problem
Cheech, if your motor doesnt cut smartly then the throttle barrel is fully closed, then you need to do this. If the motor is out of the plane, it may be easier to just do it anyway and save yourself future hassles. On the muffler side, I did not use the paper gasket supplied, they always compress after a while and blow through or cause the muffler to fall off! Just a thin smear of RTV sealant is all thats required.
Posted on: 11/30/2004 2:10 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2388324

RE: GMS Engine Tuning Problem
Well, guess what guys, the hole in the brass insert was exactly half blocked by the carb body! Seems like they didnt pay enough attention when assembling the carb and they probably passed it on doing an air flow check (blowing through the hole) which would not pick up the restriction. This 'anomaly' has GOT to restrict the high speed running fuel flow! I drilled out the hole only with a 1.5mm drill using the inlet nipple as a drill guide. If I had not promised to leave the nipple alone (!!) to determine if the this one mod made a difference, I would have drilled the whole thing through with a 1.8mm drill. Watch out for breaking the drill bit, I had mine snap off inside as the hole completed and the drill fell to the back end of the brass insert. MAnaged to pick/flush it out phew! Cleaning is very easy blowing through with some wd40 using the plastic tube extension into the holes. Remove the barrel before drilling and remember to backflush from that side afterwards, then use a strong light one side to check all shavings removed. Use a smidge of locktite on the nipple threads, needle holder threads and barrel retaining screw on reassembly. For y'all out there with suspicious running motors, this is such an easy check to do. Remove the fuel inlet nipple with a 5mm spanner, shine a light in the hole and it will become immediately obvious if the hole in the brass sleeve is in alighnment with the carb fuel inlet or not, a 2 minute check. Will run and set up the motor this evening, may not pick up the motor cutting, but should be able to see the motor leaning reaction to nose up test and needle sensitivity. Test flight report will only be available monday unfort.
Posted on: 11/30/2004 2:05 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2388319

RE: GMS Engine Tuning Problem
I too have this problem. Running 5% nitro, 16% pure castor, rest Methanol. Dont want to up the Nitro, too expensive here. Started with the not being able to shut off problem and cutting at full throttle. Sealed the carb, fixed the cut off. Put the engine cuts down to not fully run in/overheating. Indeed after a couple more flights got it to run well. Then suddenly (after removing a shim to get more power), it ran like a pig, after peaking, it would cut if held vertical of splutter if ran a little rich. Also the main needle could be turned +- 1/4 turn without a noticeable difference. Fuel system checks out ok, no bubbles in the feed and no leakes under pressure. Just tried using some silicone tubing to further seal the needle (the o rings were lookin a bit worn, esp the outer one which doesnt get much lube). HAvent run it yet to see if it helped. I was also thinking maybe a cooler plug to compensate for the increased compression until I read this thread. I shall investigate the holes lining up, and fix it if so (without drilling any nipples) and report back in a couple of days.
Posted on: 11/29/2004 6:54 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2385051

RE: Unbelievable......rusty engine AGAIN!?!
Use at least 50% castor in your oil package and at the last run of the day, pull the fuel line off while engine is hot (heat will evaporate any excess methanol/nitro, leaving oil) and run dry. Dont restart the engine from cold to run out the fuel, thats worse than not running it dry. I usually dont even bother to run it dry or use afterrun oil. I use 100% castor in a 16% fuel mix in my Irvire 40, GMS 47 and 18% in my TT36H all 5% nitro. Live by the sea, no special storage, never had a problem with corrosion. 2 reasons CASTOR and NOT RUNNING A COLD ENGINE DRY!
Posted on: 11/25/2004 3:04 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2374108

RE: OS 1.60FX Break in and settings
Hey Kevin, My Dad should be bringing a couple of Mokis back from Hungary in Jan. Probably the 1.35's, hoping they will be a good fit for the Funtana90. Still breaking in the OS on the stand, 1/2 gallon so far, gonna mount it on the Lazer200 shortly (once I fixed the fuz!) I think my test stand blocked too much cooling air as the big flat board the engine was mounted to was causing a local pocket of dead air at the back of the motor. I kept getting over 200deg C after a minute flat out run! Hopefully no damage as I stopped it soon after, so Im just gonna mount it and fly like the experts told me to! Cu at the field sometime! Cheers Mark
Posted on: 11/23/2004 2:30 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2368462

RE: OS 1.60FX Break in and settings
Surely someone who has run in a 1.60Fx can comment? I was thinking of 22% oil for the 1st gallon, 20% for the next, 18% for the 3rd, 16% for the 4th and subsequent gallons, (full castor, no synth). Anyone? Thanks Mark
Posted on: 11/5/2004 5:10 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2319074

RE: MVVS 160 Glow- What's your experience?
jaka, I was lead to believe that less that 16% will shorten your con rod bearing life. How many gallons do you have through the motor at 10% oil so far? Are you running glow or gas? Does the same ratio apply for using pure castor oil? Dar, Im confused as to how you have needle bearings unless maybe you got the last of the old stock. Heres an extract of the email I got back from Just Engines last week: > >Im keen on your MVVS1.6 in glow or gas version. glow has now standard rod - so higher oil fuels, say 17% min upgrade costs [from glow to gas] are therefore bigger than they were - around 140 gbp Thats very interesting news thanks guys.
Posted on: 11/2/2004 8:29 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2310178

OS 1.60FX Break in and settings
Hi, Im taking delivery of one of these shortly. Mixing up my own fuel, pure castor, no nitro. What % oil should I use for break in, for how many (US) gallons or liters and whats the lowest oil (pure castor) content one can safely go to? Also, with the perry pump, what are the inital starting needle points? Will an A3 plug work, or is a no8 better. Can I use my APC 18X8 for beak in as well as for running. (Hoverbatics with a Green models LAser 200 1/4 scale) On the Bisson 2300 Pitts muffler, is there any further gain to be had by sawing off the outlet crimps? Sorry for all the questions, I have searched the forum, honest!
Posted on: 11/1/2004 10:47 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2306919

RE: MVVS 160 Glow- What's your experience?
Volfy, Watch out! The newest MVVS 1.6 glo motors are back to the old bushed con rods and therefore need the higher oil content, 17% or more. Got this info from Just engines. Was dissapointed as I was looking to buy one with the needle roller control so I could run 10% oil 0% nitro. Maybe open your backplate to check which one you have, sorry for the late post....
Posted on: 11/1/2004 10:25 AM by Author "Squid" in the forum "Glow Engines"
http://www.rcuniverse.com/forum/fb.asp?m=2306855

RE: Homelite "ZipStart" ???
I was wondering if the Zip Start reffered to the choke device. My 30 has a non butterfly fuel enrichment lever which latches on, and releases on increasing the throttle. I removed the latching part for the rc conversion, and so now hold down the lever for 5 priming flips and release for starting, works well. The enrichment jet does take up some room in the venturi though, and I was wondering if I may be loosing a few rpm from the restriction... Btw, dont remember seeing any extra holes in the 30 head.
Posted on: 8/26/2004 8:20 AM by Author "Squid" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=2120071

RE: homelite 30cc blower conversion
Make sure the pulse hole on the carb lines up with the one in the head and is not blocked by the gasket, else the carb wont pump.
Posted on: 8/25/2004 5:57 AM by Author "Squid" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=2116266

RE: Homelite 25/30cc questions...
>>The 30cc engine has a bigger counter-balance on the crank and the rod is bigger/heavier, too. Yea, you probably could get away with going to a 30cc cylinder/piston/rod on a 25cc engine...but I'm thinking it wouldn't run as smooth as a 'for real' 30cc would...do what you gotta do though. My experience exactly! After stuffing up my 25 piston and cylinder due to FOD, I took the 'opportunity' to upgrade those components to the 30. Our distributor in South Africa bought a batch of 30 or so engines for trial, they may well be the last... I bought the complete motor and swapped out the piston/cylinder as it was a long shaft and I only had the short shaft crank and prop adaptor to hand. I asked this forum at the time if it could be done and was told that the head/pistons were interchangeable. I could not see how, as the 30 piston would have to be heavier and counterbalanced in some way. I managed to determine that the counterbalance was not in the flywheel, so must be in the crank web, although I never determined the actual differences between the two webs. On bolting together and running the vibes were real bad. The fuel foamed and the wingtips on my 80" span LAzer200 were a blur! The only way I managed to reduce the vibes to an acceptable level was by adding a couple of eccentrically ground large washers to the propshaft at the same orientation to the crank web to increase the counterbalance. Not perfect but it works! HAve now run about 1.5 gallons through it, and it will just hover my 6.5kg Lazer, but only turns about 6900 on an APC18X8W. I think the timing may be off (home made coil mount) and the vibes are definately killing a few hundred rpm. Starts and runs sweetly though! 5 prime flicks, one start flick, 45 min flight 3/4 to full throttle using 2/3 of my 500cc tank of 95 octane mogas/oil mix at the coast. My next step will be to get a long shaft adaptor and grind down that cranckcase so the parts are once again matched and see if that kills the vibes. So, to sum up, it can be done but the vibes imho make it unpleasant and are unacceptable without some kind of fix.
Posted on: 8/25/2004 5:04 AM by Author "Squid" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=2116242

Zama carb enrichment lever blues
Ive got a Zama carb with an enrichment lever like the one in the wacker engines banner at the top of this section (yellow lever). It appears to function by introducing an enrichment jet and OPENING the throttle butterfly rather than the usual choke arrangement. The interefering of it with the throttle is causing me problems as my linkage is rigid to the servo and wont tolerate overriding from the lever. Some questions: Is it worth leaving this lever on, or just priming with raw fuel on startup (this is a pain but works)? Should I disengage the throttle override part and if so, how to stop the lever springing back immediatly? Thanks
Posted on: 4/21/2004 6:28 AM by Author "Squid" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=1743880

Crazy Main needle design on Homie 25cc
From a Zama carb, the main needle is just a fat plug. It can move in and out by friction but thats about it! What a cr*p design, could have cost me an engine as it was running lean and I slotted the end, kept turning it out (thinking it was threaded!) and wondering why it didnt richen up. Swapping to another Zama carb (this time from a 30cc) with proper needles. Gonna keep the enriching device on it this time to save having to prime the motor with raw fuel every time. Anyone else see this kind of needle design? I hope Im the only one!
Posted on: 4/20/2004 3:30 AM by Author "Squid" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=1740570

RE: Carb pressure balance problems
Has anyone else had to do this? I read in RCME (I think?) recently that the guy who put the 'Big Stuff' plane together had to run the pressure monitoring pipe into the fuz because thats where the carb was and the carb needed to measure the static pressure in the fuz not to overcompensate the carb. Thats why I think Ive got a similar problem by measuring pressure at the carb in the cowl vs drawing air from the slipstream outside the cowl. Ive tuned the motor for straight ahead running, however if the slipstream changes by sideslipping or knife edgeing, there will be a pressure difference between the carb diaphram and the intake. What I need to know now, is where to position the sensor pipe. I was thinking of running it along and behind the velocity stack, terminating at the entrace to the stack. BTW, and NB, after reading this forum a bit more, I see that everyone is facing their velocity stack AWAY from the slipstream. Im facing mine forward. Maybe this is contributing to the problem...? I would have thought a slight ram effect would be better than a slight vacuum effect, but maybe not, as the mixture will run lean if the ram effect is removed in a slide slip away from the stack. Anyone fiddled with this with any success??
Posted on: 4/19/2004 9:57 AM by Author "Squid" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=1737579

RE: Disappointing results
Av8or, I belive the common Zama/Walbro carbs fitted to most of these motors are atmospheric pressure compesated, using a diaphram with an airhole allowing atmospheric pressure to enter/leave on the diaphram cover plate. This means that unlike a glow engine, you will not need to readjust the mixture in day to day running once set correctly. Have a look at the chromed plate (on a Zama carb) and you will see the hole. I belive Zenoah allow you to fit a pipe to the hole to allow static pressure to be sensed from inside the fuz if you are drawing air from there, so that the mixture is not incorrectly compensated when cowl pressure is sensed.
Posted on: 4/19/2004 9:14 AM by Author "Squid" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=1737479

Carb pressure balance problems
Since fitting the cowl to my Homelite 30cc powered Lazer 200, the motor coughs and loses power on the knife-edge. Im thinking its a pressure differential formed between the carb diaphram pressure sensing inside the cowl and the carb inlet which is outside the cowl. On knife-edge right to left (when it happens), the carb maybe sits in a lower pressure pocket developed behind the front of the cowl edge and then with less air entering the carb runs rich, causing the spluttering power loss. Has anyone else had this problem, if so, whats the cure? I was thinking of tapping an exhaust pressure nipple in to the carb diaphram plate hole and running a pipe out to the carb so that the pressure detected is the same as carb pressure. IF this could work, the carb will automatically compensate for the reduced pressure and keep the mixture constant. Speaking of pressure, I have to get this sorted out before the end of the month because the plane is due to feature in an advert shoot at that time, AND Ive got to keep the day job going!! - HELP!!!
Posted on: 4/19/2004 7:15 AM by Author "Squid" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=1737294