298 Rustler????
 

My girl has a nitro rustler, when it's cold it runs good, but when you do two good high speed passes it just boggs and dies. the temps get about 270-298 at the highest. I can see air going backwards thru the fuel tube and it won't start again until it gets cooler. then you can do about one good pass and it dies...then it won't start at all. the idle barely can be tuned down either, anyone knwo whats up with it???????????? thanks!

I'm about 298% sure if needs a rebuild. When it gets hot, it looses compression and dies, then will start, and die after a pass or two. My Revo did the same thing.

Traxxas engines run hot, but it shouldn't be that hot.

Sounds like you have an airleak - erratic idle, fuel not going into the carb, high temperatures.

is there anyway tp seal air leaks?
i have rebuilt the motor with a bored out crank shaft and new piston now, but i want to make sure i have no air leaks...how? thanks!

Check the O-rings.

Not having a proper seal on the fuel tank lid can cause the erratic behavior since there is no pressure to help get the fuel to the carb. That can also cause overheating since fuel also has lubrication and cooling oil.

I had replaced the cap first thing, then i replaced the blue boot on the throttle (lsn). tightened the hsn, then replaced o-rings all around, the carb and motor, the gas tank is the only thing i haven't changed...i also replaced my fuel lines, just got done with that.

Check the carb and backplate also.

If that fails also, chances are it's the crank bearings

What's an easy way to remove the crank bearings? And is that common on a newer motor? I haven't had much luck with these trx 2.5's....my 3.3 is nice, no worries except it revs a little high off a high speed pass then goes to normal idle, not sure about that. But doesn't over heat and runs really well other than that.
Also, is there a better fuel tank or lid for the rustler? haven't found one yet, searched all that i can think of....

Crank bearings are a bugger to get out.

You usually have to take the whole engine apart then put the crankcase in an oven to warm it up to allow the bearings to come free.

Never done it myself though.

If the front bearing isn't leaking, chances are it's ok :)

Thanks Tom....really appreciate all the advice! Also, can you tell me if there is something to stop air leaks in a carb? I've heard of something, but can't remember what it is. You put it inside and it selas everything up?

It's this stuff called RTV, (Room Temperature Vulcaniser).

It's similar to liquid gasket i think, but slightly different - i think it's a bit more goopy.

You should be able to get it from a car supplies shop, just put a thin bead of it round the carb neck, and round the backplate seal.

It may not be the problem - as BrianG said - it could still be a fuel system problem, but it sounds like you've done a pretty good job of going over that and checking it all over.

I just think it's the darn gas tank lid on these things. My jato has no problems, but that has a rubber seal, not foam....I'm trying to find an alt tank to use. I took my fuel lines off again and blew thru them with soapy water on the outside and no bubbles at all, no leaks. Will keep trying! thanks guys!