8000ft

my 21bb just started to act funny. it wont hold a tune, it starts off the line ok then in mid range area it starts to sputter( not to rich, not to lean) then it clears out and takes off. if i lean it it dies, if i richen it burbles. i have about one gallon through it of 30%(i need to run this % due to altitude) i knew that it would wear out quicker but i didnt expect it this soon. this is my first nitro and i just was wondering if these are signs of a worn out p&s and what other simptoms i should be looking for?
also what does a new p&s cost?? a new force 26 is in the near future and im wondering if it would be more economical to just save my $ for the force or rebuild the 21.
thanks for your help.

rcblaze

I'd say the easiest way to tell is to check the compression by hand. By trying to turn the fly wheel with you finger. Your looking for a pinch when that piston gets to the top of it's stroke. This is not an exact thing but it will give you an idea if you have compression or not. Then you may want to take it apart and look at the piston and sleeve. See if the piston is in bad shape. Also see how the piston is fitting at the top of the sleeve. From what your describing if it starts easy you may just have tuning issues. Usually in my experience a worn out engine is really hard to start and to tune. I'm not sure about the rebuild price but if it's over $60 I would just get another engine, you figure you want more performance anyway and for another $60 to $70 bucks you can get something like a XTM, Hyper 8 port, or the Force .26 you mentioned. Hope this helps. Anyone else with more info?

8000ft

its not hard to start(except when above 150 deg.) i pulled the head and every thing inside looks great, all shinny no discoloration at all. however no pinch what so ever with the head off.

rcblaze

So I take it the Fly wheel doesnt turn freely then with the head on. If this is the case I would start it up run both needels rich and start to tune again. Just take your time and let it heat up to running temp before tunning. If you still can't egt it maybe your LHS could tune it for you ususally they will do that for free.

8000ft

i havs sealed the carb and back plate but i think i need to check the fuel lines. i can't take it to my LHS because its 87 miles away and more importantly its at 5200ft elevation in Denver and i live in Granby elevation 8026ft so tuning it down there wouldn't do any good.

Savage_Dias

It might not hurt to get them to tune it & be sure to ask them what they are doing & why. Learn all you can because unless you have the same conditions every run (elevation, temp, humidity, driving area, aggressiveness) your engine won't run the same as when they tuned it.

BUGGIES_R_US

When you say no pinch. I dont quite get you:

With the glow plug OFF, how easy is it to turn/pull the engine?
Pull on the stringg SLOWLY (not fast like you do when starting).

If the sleeve is shiny.. that means its worn!
(ok dont quote me on this.. but more shiny= more worn)

Ram

Knoxville

My Feedback: (1)

hey ram i dont get it my sleeve was shiny from the time i got it till now all ya have to do is take the plug out stick your pinky down in and cover the hole and roll the engine over if you can feel the air pushin on your finger and trying to suck it in then it is fine you can do this with head off put your thumb over cylinder and roll it over and look for the same things as mentioned above that is how i tell or you can just buy a compression gage

BUGGIES_R_US

LOL.

Well when theyre worn, they get extremely shiny. Your right this is NOT a way to tell if its worn.

But I dont want anyone thinking that shiny= new! :|
Ram

yrral

i found this at: http://monster.traxxas.com/showthrea...hreadid=161277

Hope this helps


How do I know if my engine is worn out (worn piston and sleeve)?
The symptoms of a worn piston and sleeve are overheating, stalling after running for a minute or two, and difficult starting. The usual complaint sounds something like this: the engine has to cool for 5-10 minutes before it will restart, then it runs super fast for a few passes, and then stalls out, repeating the cycle. At this point the only cure is to replace the piston and sleeve.

“Why does my engine act like the piston and sleeve are worn out? I think I did everything right.” We’ve seen some intelligent posts from some customers who believe they are doing everything “by-the-book” and still experienced inconsistent tuning and questionably short engine life. In this case, there could be a problem with the fit of the internal engine components. For example, the pistons and sleeves are hand-fitted, speced, and tested by people just like any of us, and people can occasionally make mistakes. In this case we would like the opportunity to examine the engine to see if a defective component was at fault. If it was then we will be happy to take care of the problem and get you back on the road. Obviously, if the engine has been poorly maintained, is full of sand, and/or burned beyond recognition, we can’t replace parts for free. But if the engine has been properly broken in, run, and maintained and yet for some reason still shows excessive signs of internal wear or possibly a defective component is revealed then the Traxxas support you counted on when you purchased the engine will kick in and get you fixed up. Our support staff comes to work each morning to do just this very thing (with all our products, not just engines).