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Old 07-27-2005, 09:02 AM   #1
rko
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Hi guys, i currently have an engine problem that i cant solve. Hope to hear some some suggestions. I'm currently running a force .15 engine that came with my Hyper10 pro kit. i got it off secondhand cheap, so i aint complaining about the condition of the car. Anyway, the car is running fine except for the engine(i think). When i first fire up the engine for the day(engine cool), The car has too high an idling speed but good speed on the track. However, as i ran for another 10 mins, the engine looses its low rpm power. It cannot accelerate as quickly as it was when cold. Sometimes, it will just remain at low rpm for the whole straight(size of basketball court), and sometimes it will pick up speed again during the middle of the straights. The first time i played the car, i used some 16% nitro/No.8 plug and it was much worse than the 25%/No.8 plug i use now. Also, once the engine warms up, The idling becomes good. I also notice that the car seems to brake once i off throttle although the braking linkage is working perfectly. I have tried adjusting the engine to the best i can. But anymore leaner/ richer will cut-out the engine or i will have difficulty starting again. Can anyone gives suggestions. Thanks.
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Old 07-27-2005, 09:28 AM   #2
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thats happened to me b4 too. try another glow plug and it might be to rich.
and if that doesnt work then just upgrade to a O.S .12 tr or a .12 tz
O.S is the best and there cheap.
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Old 07-27-2005, 03:12 PM   #3
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mostly likley the reason the car is braking when you let off the throttle is because the linkage is set so that when at idle (no throttle or brake from the transmitter) there is a little tension on the brake cam. you'll need to adjust the linkage so that there is less brake (if desired) action

also sounds like the engine is running a bit on the rich side. you may wish to lean out the mixture needles a bit (a small amount at a time, about 1/8 a turn) then run the car and see how it goes.
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Old 07-29-2005, 05:21 AM   #4
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Quote:
Originally Posted by MikeBtc3
thats happened to me b4 too. try another glow plug and it might be to rich.
and if that doesnt work then just upgrade to a O.S .12 tr or a .12 tz
O.S is the best and there cheap.

Hmm, what plug do u suggest? Its kinda hot and humid here in singapore. u think i should change to a colder of hotter plug? Actually, if all doesnt work, i will change to an OS. But should be the cheaper cv series.
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Old 07-29-2005, 09:30 AM   #5
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generally the rule is is it's hotter outside, you lean the mixture a bit, same with the high huminidity.
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Old 07-29-2005, 10:36 AM   #6
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Hi RKO,

I would like to try to understand what's happening to your .15:

1. Is there any fuel/oil around the engine or tank?
2. At full throttle, does the engine rev up and then chokes and sputters?
3. When you let go of the throttle, does it idle high for a second and then returns to normal?

From what I remember about plugs, hot plugs have thinner elements and requires less heat for combustion, good for low nitro fuels.

Cold plugs have thicker elements and requires more heat for combustion, good for high nitro fuels.

In short, the fuel will dictate what plug to start with. The weather is used to fine tune the plug choice 1 or 2 steps.

I noticed you were switching between 16% to 25%. Please keep in mind your engine need to be set up before switching fuels/plugs. In general, low nitro (0-16%) needs high compression (less head shims), high nitro (over 25%) needs low compression (more head shims) for optimal running.

When set up properly, 16-20% with O.S. #8 plug can work and you can leave the head shim as it came from the factory.
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Old 07-29-2005, 07:35 PM   #7
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Quote:
Originally Posted by vapourtrail
Hi RKO,

I would like to try to understand what's happening to your .15:

1. Is there any fuel/oil around the engine or tank?
2. At full throttle, does the engine rev up and then chokes and sputters?
3. When you let go of the throttle, does it idle high for a second and then returns to normal?

From what I remember about plugs, hot plugs have thinner elements and requires less heat for combustion, good for low nitro fuels.

Cold plugs have thicker elements and requires more heat for combustion, good for high nitro fuels.
Spot on. i found fuel, in fact lots of them around the pull-start area. As for the full throttle, i did not notice any choking and sputter. When i off throttle, the car seems to come to an adrupt stop, like though it is braking. I had checked the brake linkage yesterday and they seem fine.

Hmmm, what does it means by head shims? The washers for the plugs?
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Old 07-30-2005, 04:42 AM   #8
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with regards to engine tuning - it's always better to run your car a few laps and get it up to race temp before you start tunning for ideal settings. Better to run with half a tank of fuel as well. Usually when you start (cold condition) the idle tends to be higher than actual race conditions, this is normal. After a few laps it will reach race idle timing. So if your low end is set too rich in the begining that also increases the idle. Try leaning out your your LSN about 3mins and simultaneously reduce (open) your idle needle by 3mins. You should start to get a better and consistent idle and low end punch throughout your run.

Do keep me posted.
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Old 08-04-2005, 05:27 PM   #9
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Hi RKO,

Pardon the late reply.

Whenever you see fuel coming out/leaking from somewhere, air is coming in through those leaks. In this case, the pull start is causing the air/fuel leak. I've seen this quite often. The rubber o-ring that seals the pull-start shaft wears out and causes the problems you are experiencing. To fix this, simply replace the pull-start back plate. The back plate itself could be loose and just needs tightening. If you notice any other spots that has leaked fuel, that will need attention too (fuel tank, fuel line, etc).

You probably noticed the engine will not respond to tuning changes if it has an air leak (warmed up or not). Once everything is tight and sealed up, the engine responds almost instantly to tuning changes.

The car should coast when you are not braking (in neutral). Your brakes may be engaging too early.

Head shims are big but thin washers between the head/button (where the plug screws into) and the sleeve. The amount of shims will alter your compression.

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