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air leak in the crankcase

 
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andreas_h92



Joined: 16 Feb 2009
Posts: 63

PostPosted: Wed Jun 17, 2009 5:33 am    Post subject: air leak in the crankcase Reply with quote

hello, i have a force 32 engine and it overheats. i tried everything and still overheats but i didn't look for any air leaks in the crankcase. is it possible to have air leak in the crankcase? if so, how i determinate it? thanks
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DJ



Joined: 22 Jun 2006
Posts: 979

PostPosted: Wed Jun 17, 2009 1:27 pm    Post subject: Reply with quote

What plug do you have in it.
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andreas_h92



Joined: 16 Feb 2009
Posts: 63

PostPosted: Wed Jun 17, 2009 11:17 pm    Post subject: Reply with quote

MC-8
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andreas_h92



Joined: 16 Feb 2009
Posts: 63

PostPosted: Sun Jun 21, 2009 12:27 am    Post subject: Reply with quote

are you willing to help me?
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MotionMachine999



Joined: 20 Oct 2005
Posts: 1722
Location: Land of Oz

PostPosted: Sun Jun 21, 2009 7:35 am    Post subject: Reply with quote

Stting possible tuning and other deficiencies aside...

You can typically find an air leak using WD-40 w/ straw tip. With the chassis resting on a block so the wheels are elevated and engine running slightly faster than idle, (dial up the trim on the TX so RPMS/throttle input remains consistant.
Spray it behind the flywheel, listening for any change in RPM, sound, tone, performance, and/or if the engine suddenly stalls.
Following the same spray and listen procedure, continue with the carb base, carb body, LSN, HSN slide, (try not to spray the filter), around the back plate, PS assembly, ect.
If theres a leak, chances are you'll find it using this method.

Also, make sure there are no pinholes, cracks, or splits in the fuel and pressure lines. I'd suggest you zip tie them in place.
Ensure the tank is completely sealed, no cracks, leaks, and the lid is completely shut. Ensure the exhaust system and pressure nipple isn't leaking.

Describe how its running.
Will it idle all day?
After idling for 30 seconds, will it take off at WOT?
Does it bog, stutter, hesitate, stall under rapid accelleration?
Does it maintain a high RPM for a few seconds before dropping to normal idle?
Is there a THICK, THIN, NON EXISTANT smoke trail throughout all RPM ranges?
What brand and type of fuel?

Its most difficult to diagnose and troubleshoot a nitro engine "on-line" so tell us as much as you can so we can give you a more informed GUESS.
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andreas_h92



Joined: 16 Feb 2009
Posts: 63

PostPosted: Sun Jun 21, 2009 2:02 pm    Post subject: Reply with quote

hello there and thanks for your help,

Before 2-3 weeks I sealed the Carburetor(a new one), the backplate, and the bolt that keeps the carb in place. I also replace the fuel tank and the fuel lines. The exhaust is new too. also i am running with 3 head shims(added 1). The fuel i am running is a rapicon Car fuel 25% (local hobby shop told me that this fuel is good and the engine will not overheat).
After all these the engine was still overheating. The temperatures where taken from a temp gun so i guess they are right.

Today the engine wasn't idling for long and at WOT the engine bogged and stopped. This happened for a few times but when i changed the glow plug with a new one(MC-8) the engine was running good. I don't know if it can idles all day with the new glow plug (let me check it in the next days). Anyway, after running my truck for 5 minutes, the engine started to stall under rapid acceleration. As for the smoke i think was all the time thick.

I have to check if idles all day and if it maintains a high RPM for a few seconds before dropping to normal idle. I will try to check these two things asap and post back the results.

By the way i heard from somebody that if the cylinder head of any engine removed and bolted back in place for 2-3 times, new shims must be fitted. Is that true?

Thanks for any help
Regards
-Andreas
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andreas_h92



Joined: 16 Feb 2009
Posts: 63

PostPosted: Mon Jun 22, 2009 8:13 am    Post subject: Reply with quote

today a had e few free time and i tried some things.. I left the engine idling for 30 seconds and then when i pull the trigger to throttle the engine shut off(stopped). Also i realize that after driving the car for 1 minute it started changing RPM (higher rpm to lower and lower to higher).

so what do you think?
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andreas_h92



Joined: 16 Feb 2009
Posts: 63

PostPosted: Tue Jun 23, 2009 10:57 pm    Post subject: Reply with quote

Today i sprayed some WD-40 behind the flywheel. Nothing changed. Also i sprayed WD-40 in the entire engine but i didn't found an air leak.
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MotionMachine999



Joined: 20 Oct 2005
Posts: 1722
Location: Land of Oz

PostPosted: Wed Jun 24, 2009 5:01 am    Post subject: Reply with quote

Sounds like bad fuel and/or a faulty tune to me..
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Eggbert



Joined: 27 Jan 2006
Posts: 331
Location: Nova Scotia, Canada

PostPosted: Wed Jun 24, 2009 12:55 pm    Post subject: Reply with quote

1/ What temp do you consider "overheating"?

2/ (i) Cutting out as rpms start to build (on application of throttle)
(ii) Lots of smoke
(iii) too hot
(iv) fluctuating rpms.....does it stay high after getting off the throttle

All lead me to believe the following:

Your HSN is too lean and your LSN is too rich.

So:

Richen your HSN 1/4 turn (CCW) and then lean your LSN in a bit at a time until you have good acceleration from idle after idling about 10 seconds (with a warmed up engine).

Of course, I could be wrong. Good luck.



ps: No, removing the head and re-installing it won't damage the shims
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andreas_h92



Joined: 16 Feb 2009
Posts: 63

PostPosted: Wed Jun 24, 2009 2:15 pm    Post subject: Reply with quote

it might be the fuel, but i will try some more tuning before try a different fuel.

Eggbert:
1/ i consider overheating a temp over 300F.
2/ (is that a question or just like a summary? :P )

Anyway i will try to re-tune it. Do you know the factory settings for both LSN and HSN?
And what fuel do you recommend? Maybe some trinity 20%?



I really appreciate your help guys. Thank you very much
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Eggbert



Joined: 27 Jan 2006
Posts: 331
Location: Nova Scotia, Canada

PostPosted: Sat Jun 27, 2009 11:20 am    Post subject: Reply with quote

Yes, 300F is my magic number for "too hot". Not that the engine will melt, but I seem to get erratic operation and sometimes detonation when I exceed 300F. Not always. Depends a lot on the engine.

#2 was a summary of your symptoms that lead me to believe the following:

Your HSN is too lean and your LSN is too rich.
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andreas_h92



Joined: 16 Feb 2009
Posts: 63

PostPosted: Mon Jun 29, 2009 4:12 am    Post subject: Reply with quote

I don't think that my HSN is too lean and my LSN is too rich because i riched the HSN and leaned the LSN and nothing changed. I have had some good smoke but my glow plug turned black! The button head didn't. I guess i will go with different brand of fuel.

thanks for the help :)
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