Engine Issues

[snmhanson]

I have an RC10GT with an OS .12 CV-X in it. I can't seem to get the engine to run well without reaching what seems to me unacceptable temps. First off I have the mixture control valve set at 2 1/2 turns out and the needle at ~1 1/4 turns out. If I go out any farther with the mixture valve I can't get it to start. Any farther out with the needle and it seems to lower my top end. When I am running my car and I'm on and off the throttle the engine temp seems to hover around 200 degrees. If I open it up for more than a few seconds I get readings of up to 275 degrees (so far). I can't find any recommendations on ideal engine temps but that seems pretty hot to me. So I guess my questions are: 1) Is my engine running too hot and what temperature range should it be running in? and 2) What could be causing the problems I am experiencing? Could I have my needle valve turned in too much or does it sound like something else? Thanks for any help on this.

Matt

 

[jon2]

Well first off it sounds you have an air leak somewhere. Check the fuel lines. If you don't know its goof to just go ahead and replace them. If the problems persists then check your Tank for any craks or leaks. I recommend plugging up the inlet nipples and submerse it under water. If you see any bubbles start rising, then replace the tank. Probnlem persist still, Seal your Engine back plate and carb neck with RTV silicone. Let this silicone cure overnite.

Get back to us...

 

[ElectriKid3]

YA I agree with him you should check all those things but also it might be the engine itself. HOW OLD IS THE ENGINE? If it is kinda old you might consider getting a new engine.

 

[.21Rc10GT]

I know that my OS .15cvrx always ran hot. No matter what, it ran hot. Had a smooth idle and powerband, good smoke... just ran hot, like 280-300... I guess i could have put a new head on it...

 

[snmhanson]

The engine is not old at all. I've maybe run a dozen or so tanks through it. I broke it in the best I could following the directions and didn't push it hard for the first several tanks. I will check to make sure for no air leaks as recommended and take it apart and do a thorough cleaning (I did clean it recently but will do it again). It is nice to know that someone else had a hot running cvx as well. Maybe a new head would help cool it down a little as well. If I can't find anything wrong with it I guess I will just run it as it is and if it blows up I will buy a new engine. Thanks for the input. I'll update this when I figure it out but it probably won't be for over a week before I have time to do it.

Matt

 

[.21Rc10GT]

Dont just take it apart and clean it... put some rtv sealant around the top of the carb neck and around the base of the backplate. Remember, a little goes a long way.

 

[Pinblaster]

Replace the bronze bushing in the rear cover plate and the shaft for the PS, I bet that is where your air leak is coming from. Also if it has that square block head on it, replace it with the new head that's on the CVR's. Temps should be between 230 and 280 for a safe range. And as everyone one else said...seal it up. :hammer:

 

[Buggyracer28]

I would just put it back to factory settings. I did that with my gt and it worked wonders lol. Then tune from there.

 

[snmhanson]

Thanks for the advice. We just got back from vacation so as soon as I get the house back in order I will start messing with it again. I'll do everything that was mentioned here. Incidently, I ran it just before we left a week ago and it ran great but still got up to 300 degrees by the end after running it wide open for a few seconds. I'll check it out and let you all know.

Matt

 

[racin_38]

just curious ,are you running wit hthe body on and if so..
do you have the windshield cut out and the rear window cut to alow air to flow thru over the head ,,
no one asked and i was curious ,

 

[snmhanson]

just curious ,are you running wit hthe body on and if so..
do you have the windshield cut out and the rear window cut to alow air to flow thru over the head ,,
no one asked and i was curious ,

Yes and yes. I even went out last night to make sure that I didn't do anything stupid like cut the opening on the wrong side of the windsheild. I think if I can keep it below 300 degrees I'll be ok. Hopefully I can work on it in the next couple of days.

Matt

 

[snmhanson]

OK, I cleaned the carb and engine really well and sealed the back plate as recommended. The engine seems tight with plenty of compression and I don't think any air is getting into it. I replaced the fuel hose and checked the tank and it all seems to be holding pressure just fine. After getting everything put back together I still can't say it starts and runs much better than before. I need to lean out the high speed needle to about 1 1/4 - 1 1/2 turns out (compared to 2 turns out per stock) to get it started and the mixture valve needs to be at two turns out or less (versus the 2 1/2 stock). Once it gets warmed up I can back them both off very slightly but the engine still runs up to 260-270 degrees when it is pushed. Typical temp range seemed to be around 255ish so it is a little better than it was but still seems hot. A wierd thing is that if I richen the needle up it seems to really effect acceleration from a stand still which I though was more of a mixture control valve issue. As a matter of fact, the mixture control valve doesn't seem to impact performance much as long as it is in the correct approximate range. The needle seems to be the major influence for everything from idle to WOT and is the major factor in determining the engine temps. Too lean and the engine sizzles, richen it a little and I get a hesitation on acceleration, richen it more and it runs like crap. Any other ideas here or should I just try a different engine? Also, is it normal for a small amount of light smoke to come out of the gas tank when I open it immediately after it is drained from running the car? As always, thanks for any input here.

Matt

 

[rocknbil]

... A wierd thing is that if I richen the needle up it seems to really effect acceleration from a stand still which I though was more of a mixture control valve issue. As a matter of fact, the mixture control valve doesn't seem to impact performance much as long as it is in the correct approximate range. ...

Look at it this way: the High speed needle is really mis-named, it should be called the "main needle valve." Look where it is, right over the fuel inlet. So when you adjust this, you're adjusting ALL the fuel going into the engine, and this affects the entire range.

The LSN is really just a bar that moves close or farther from the fuel jet inside the carb and adjusts the flow/atomization at lower levels. Your comment that it doesn't affect the performance at all says that your high speed mixture - maybe the needle, maybe something else is messing it up - is still not in the correct place.

One of the things I've noticed about about the OS engines is they are way sensitive to HSN changes. Try this: reset the LSN/mixture valve to factory, and just fiddle with the HSN a bit, but make changes in 1/16 turn or less increments. When you get to that 255° range, click it to rich one tick and let it run for a lap or two, giving it time to settle in to the setting. See if this helps.

Besides all the other input on air leaks, etc., carefully extract the high speed needle and examine it for burrs or dings at the tip, and make sure the jet is clear (don't stick anything in there.) Also verify the O-ring is good and soft.

EDIT: One last thing: Is this the stock clutch on your GT?

The stock clutch has no springs, they fly free. So if the idle is too high, this will cause the shoes to stay engaged prematurely, causing a little more drag on the engine, causing you to have to adjust the fuel mix to compensate so it will stay running. Also bushings in the clutch bell instead of bearings will add some drag.

This will also make it run a little on the warm side. Been there, done that, adjust the idle as low as it will go and when you can, chuck it for an MIP 4-in-1 clutch.

 

[seajj2]

Sounds like you have a head clearance issue. What is your head clearance set at? You may have to add a shim. Also what plug are you running? If it is hot where you are running go to a mc9 plug. I ran my truck in my winter series and ran with no problems. I did not have to change my needle setting once and it ran at 216 degrees. Now the weather is getting hotter the engine is changing needles all the time and left a nice tatoo from the head on my arm. I added the shim and problem fixed.

 

[snmhanson]

Thanks for the continuing support. I am running #8 plugs. I have no idea what my head clearance is and I'm not even positive what head clearance is. I still need to get a new head for the engine as I am currently using the stock V-groove head that came with it. Hopefully this weekend I'll be able to get out and pick one up. I'll talk to the LHS about it then.

On a side note, does anyone know if I can get a roto-start or easy-start system that will work on my OS engine? I would like a system where you just get different plates depending on what engine you have so if down the road I get a different engine all I will need is a new plate. Ideally I would also like something that sends a charge to the glow plug automatically. Is there anything out there that will work or is a starter box my best bet for non-pull starting?

Thanks again for all of the help.

Matt

Matt