EFhatchy

I bought some used Revos from a guy who didn't know anything about them. He got them on trade for some audio stuff and never touched them. It came with a Revo 3.3 and a parts 2.5Revo . I got the 3.3 to fire but it won't idle unless the throttle is cracked open a little bit. It will rev and keep a high idle. But once the throttle totally closes it bogs down and dies. I started with the low speed needle about a turn and a half out, and the high speed 2.5 turns out as per the base settings here http://rcvehicles.about.com/gi/o.htm...eng-tuning.htm I tried about every position for the idle screw as well. I also noticed that the left rear wheel is bound up somehow. It spins but not nearly as free as the rest of the wheels. The other 3 will spin at speed with the engine RPM, but the left rear barely moves. Could I swap the 2.5 diff onto the 3.3 and be fine? And what could be the issue with my 3.3 bogging down? Just needs to be tuned right? Can anyone point me in the right direction? Starting with all the needles zeroed out and the idle screw fully closed?

Thanks,
Sawyer

Snook Man

The 3.3 base factory setting are HSN - 4 turns out.
LSN - Flush with the end of the slide valve. Idle gap - .7 to 1 mm
2.5 turns out on the HSN is most likely too lean...

Check the wheel and wheel hexes for stripage and the wheel shafts for missing/broken pins before you tear into the diff. Yes the 2.5 diff will fit the 3.3 if needed.

ArloRogers

My Feedback: (1)

Also ck the bearings in the bad wheel.

EFhatchy

Are the bearings in the knuckle?

Jgaff2

yes. Just take the wheel off and you should be able to see everything. They pop right out, too

EFhatchy

No special tool needed to take the bearing out?

EFhatchy

Got the binding issues fixed. Just took it all apart and put it together.

But it still won't idle at all. I don't know if the carb is gummed up or what. But it will idle as long as I dump fuel into the carb. Is it too cold for it? Probably been less than 50 degrees every day I've tried to run it.

Mclovin350z

I'd say something is definitely wrong with your used engine. Check for obvious stuff like cracks in the carb or block, bad exhaust gasket, fuel line, tank etc. If that stuff checks out I'd lean the low needle some more until it idles. Make sure the idle gap looks good, you can find pics online.The engine or carb is probably toast but it could also be an air leak or worn engine etc.

jrwizbang

check the cheap and easy stuff first. pull the carb off and clean it real good making sure to open any clogged orifices (carefully) 9 out of 10 time it's just clogged with castor oil if it has been allowed to sit for any length of time.

EFhatchy

The engine starts and runs amazing when I'm pouring fuel into it. Starts within a couple seconds. I don't know what a worn engine sounds like, but my engine sounds just like all the other ones I've ever heard. I'm planning on pulling at apart tomorrow. I'll be sure to check all those things too.

Will just normal carb cleaner work? What should I use to clean the orifices?

EFhatchy

Any truth to this test? If so my engine is no good.

Snook Man

Yep, that’s a good indication of a worn out engine.

 

Since yours appears to be toast, disassemble it and push the piston up through the sleeve. If the top of the piston can be pushed (with moderate effort) even with, or past the top of the sleeve its worn out…

EFhatchy

Has anyone done the Traxxas exchange program? I was thinking about upgrading my 2.5 to a 3.3 if I go that way.

Mclovin350z

Most of the time a new engine can be had on ebay for less than the cost of exchanging it.

EFhatchy

I've looked on Ebay at them and noticed that there's also rebuild kits. How tight are tolerances if I rebuild one?

ArloRogers

My Feedback: (1)

As long as the bearings are good a rebuild is the way to go. You can buy a Traxxas block with bearings for less than the bearings only on E-Bay.

jord_trx2.5

new piston and sleeve will see you right, around 40 dollars and easy and quick to do and aslong as bearings are ok and engine is properly sealed afterwoods should end up with an engine as good as new

Mclovin350z

^That's if the rod is ok. You can buy a new 3.3 minus carb for 80.