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Old 09-10-2010, 10:29 AM   #1
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Default Hpi rs4 3 troubles

Hey guys my names mike. i just picked up my first nitro about two weeks ago. Last weekend was the first I got to run it and it ran great. I made little adjustments but they helped. I ran into a sand pit twice so when I got home I decided to break it down and clean it up. I pulled all the suspension components, servo tray, and the fuel tank. I cleaned everything up and put it all back together. I went to run it and I killed my pull start. So this week I picked up a roto start setup and everything. And now it is a pain to start and when it finally does start the idle is low and it's very unresponsive on the low end. After it gets rolling it's more responsive but still not how it used to be. And if I stop it for more than like 2 seconds it dies. I'm running an 1800 mah battery with my roto start and using a hobbico hot shot igniter. Anyone have any ideas on possible issues?
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Old 09-10-2010, 12:24 PM   #2
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That has the sound of an out of tunned engine, as in too rich on the low-end needle.

Maybe when you swapped the starters, you might have accidently made change to the needles or didn't tighten the backplate of the motor when you put on new roto starter.

I would check for these thing and see if it just need reseating or tunning.
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Old 09-10-2010, 01:06 PM   #3
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A cold engine will not run as well as a hot one, you may need to mess with the low speed and idle adjustments and re-tune once warmed up. Or you can always return to the stock settings (high and low speed needles flush with the carb).
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Old 09-10-2010, 03:32 PM   #4
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I've returned to what the manual says to start at 3.5 turns ccw for low/mid at wide open throttle and 3 ccw from fully closed for the high fuel needle
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Old 09-10-2010, 08:29 PM   #5
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Bump
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Old 09-11-2010, 09:24 AM   #6
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I think I found the problem. I pulled the cooling head off and found dirt between it and the gasket
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Old 09-11-2010, 12:31 PM   #7
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I think I found the problem. I pulled the cooling head off and found dirt between it and the gasket
Clean it up and try again. Also check your idle adjustment, if it starts but idles very low and doesn't hold well, try increasing the idle speed slightly. Not a whole lot, try 1/16 or 1/8 at a time and try it. Always tune in small amounts.
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Old 09-13-2010, 07:35 AM   #8
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I took it to the hobby shop and I was told the piston and sleeve were shot. Makes sense since I hit a sand pit twice without an air filter. I bought a os 18 cvrx and just broke it in last night. I tore the old motor down and fom what I've found online the piston and sleeve are bad. The piston comes outta the sleeve about a quarter of an inch with no resistance. What piston/sleeve can I use? It's the 12r ss motor and hpi stopped producing the setup. I read somewhere I could put a .15 piston and sleeve if it's a small block. True?
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Old 09-13-2010, 11:42 AM   #9
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Work time bump
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Old 09-13-2010, 06:34 PM   #10
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Quote:
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I took it to the hobby shop and I was told the piston and sleeve were shot. Makes sense since I hit a sand pit twice without an air filter. I bought a os 18 cvrx and just broke it in last night. I tore the old motor down and fom what I've found online the piston and sleeve are bad. The piston comes outta the sleeve about a quarter of an inch with no resistance. What piston/sleeve can I use? It's the 12r ss motor and hpi stopped producing the setup. I read somewhere I could put a .15 piston and sleeve if it's a small block. True?
Dude!!...if the sleeve is shot because of sand, the piston is most likely shot too....and what are you doing running you car/engine without airfilter on it?!?! You could have told us that up front and saved us alot of trouble.

As far as swapping a .15 piston and sleeve in .12 engine, its not your worth your effort. drop the .18 in there or buy a used .12 from one of the veteran here on the forum, or, or, or just a buy a new .12. They are not that expensive.
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Old 09-13-2010, 07:13 PM   #11
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Haha my bad. I thought I mentioned that. The .18 is super torquey. It pulls hard to one side and chirps a little. Anyone have any tires they recommend?
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Old 09-13-2010, 07:28 PM   #12
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Haha my bad. I thought I mentioned that. The .18 is super torquey. It pulls hard to one side and chirps a little. Anyone have any tires they recommend?
Foam...

Rubber tires might have cool looking wheels and come with the car, but a set of foam tires will let it hook up better and grip much better. They come in different shore ratings. Lower number is softer and higher is harder. For your use I'd go with a 40 or higher rating. There's many manufacturers of foam tires. Jaco, Matrix, K Factory, GQ Racing, Enetti, and many more. Right now I'm running GQ Racing Tires. They've been great so far and the rim holds up fabulously.

Note: The tires for the back wheels are wider than the front with foam tires and both the front and back are wider than rubber tires. More contact surface. Also remember that a shaft driven car will torque steer under power. It's the nature of the model.
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Old 09-13-2010, 07:34 PM   #13
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Haha my bad. I thought I mentioned that. The .18 is super torquey. It pulls hard to one side and chirps a little. Anyone have any tires they recommend?
An 18 in a 1oth scale shaft driven car will have bad torque steer.
Way to much torque for that car.
There are many extremely quick 12 engines that will produce more power than you can handle.
A lot of newbies think the bigger the engine the better, and drop 18s into their cars, only to have the same problem you are having.
Like the post above, its better to pick up a good used 12,than try and control the torque of an 18
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Old 09-14-2010, 05:09 AM   #14
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I'm not too worried about the torque steer. I might be able to manipulate the suspension a little to compensate. Thanks for the help. I'll go look at foams sometime soon
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Old 09-15-2010, 02:24 PM   #15
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I'm not too worried about the torque steer. I might be able to manipulate the suspension a little to compensate. Thanks for the help. I'll go look at foams sometime soon
You may want to adjust the weight of oil in the differentials instead. Go lighter...if you adjust the shocks, then you have to deal with the change in steering characteristics, when off throttle.
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