johnnyb1216

i just bought a used t maxx 2.5 from a friend that i dont think was able to get running right and i have a little more tiime to tinker. here is the problem... after about 2 minutes on the ez start it gets going , idles good and even runs pretty good ( im very new at this so explain any ideas or directions in great detail , thanks) will run for about 5 maybe six minutes, enough to get hot then dies and will not start till it cools down. then it all starts again
what i did to try to fix.... i pulled motor and cleaned all the gunk pulled head and checked out cyl and piston looked good except little pits in the top of piston not alot and not all the way through but they were there. i checked crank and i looked good. .i set the carb back to factory settings. cleaned everything and sprayed with w-d. put back together andlearned how to prime the engine by plugging theexhaust. my hope were raised when it started right up but again after 6-7 minutes it died. was wondering if the engine is just worn to where the cyl get hot and expands that i loose compression. the engine does have compression when cold but againim new and dont know how much compression it should have. if the engine isbad how hard is it to change sleeve and piston? andcan i change those without changing the crank and so on? if icant only changepiston and sleeve i mightas well just get a newengine. thanks for any help for avery new person to rc, john

Picco_Revo27

try changing out the glow plug, it sounds like that might be the problem. and yes you can change the piston and sleeve with out replacing anything else, but try the glow plug first.

let me know if that works.

motorhead91

i think the pits on the piston may be from detonation. try a cooler plug.

johnnyb1216

thanks guys goin to the LHS on mon to try a different plug any suggestions on what kind or are they all the same

Montana Mike

My Feedback: (1)

Iuse the OSLC3 or the OSLC4 in my 2.5 depending on the time of year

DaveG55

Hard to start, dies after it gets hot, won't restart until after it cools, pitting on the piston...

IMHO, that engine has been run hot too many times and has lost it's pinch. In other words, I do think that your engine is bad.

Go ahead and try a new glow plug, reset thecarb to factory and retune it - can't hurt to try - but don't be too surprised when it does the same thing.
Traxas offers an engine exchange program that allows you to get a new 2.5 for around $90 I think or the 3.3 for around $115. Both are easy swaps. Or there are always several aftermarket options, but they will be more expensive and may require some modification.

absolutemayhem

+ 1...sound like a worn out motor.....save your self the trouble, and just buy a new motor on ebay..</p>

johnnyb1216

thanks for the info guys goin to try the plug first but here is another question i've seen on ebay a used motor that needs " pinched" they looked pretty beat up what exactly does pinches mean ?

DaveG55

These engines do not have rings on the pistons like larger engines do. Instead they have tapered pistons and sleeves. When the piston approaches the top of it's stroke the tapers cose off any gap betwee the walls of the sleeve and the sides of the piston, sealing the combustion chamber and allowing the air/fuel mix to be compressed. The area where the sides seal is known as the "pinch" After an engine wears for a while, whether due to normal wear or abuse, this area no longer seals and the engine is said to have "lost its pinch". This is what I believe has happened to your engine.
There are some companies that can "repinch" the piston and sleeve to restore lost preformance. They do this by basiclly heating the sleeve to a certain temp and then  squeezing it in a preformed die. The usual charge for this service is, if I remember correctly, $25 -$30 plus shipping. Some have said that they have had good results with this but I don't really care for it. Another way to repair the engine is to replace the piston and sleeve with new ones. That can cost as much as $50 - $100 depending on the engine. With either of those two methods you still have a mostly worn out engine with no warranty. It is for that reason that I almost always reccomend just buying a brand new engine. The cost is not that much greater and you have a fresh engine with a warranty.</p>

In other words, the thrashed e-bay engine should be avoided. After all, you already have one in that condition</p>

johnnyb1216

thanks dave for the education read about that in the manual but you helped me understand it alot more

del1969

That motor is toast