My revo 3.3 is not getting full power..

[Lethal]

Last month I chewed through the plastic spur gear. So I decided to purchase a new 38T steel spur gear along with a new clutch bell.

I put everything together, and now my truck is not getting full power that it was getting before.

When it shifts gears, it sounds like the truck is struggling or bogging down. It also does not do wheelies at all now. When I lift the truck up and give it full throttle, it sounds great. It shifts and sounds great.

It just feels like the truck is only getting 70% power if that. Any ideas?


I have tried adjusting the high and low settings, but no change.

 

[HPI-Killer]

Have you tried setting all the needles back to factory and going from there? Also are you running the same gearing as you did with your previous cb & spur? Have you sealed your mill with rtv, leaks can occur at any time.

 

[Lethal]

I am running the same gearing as before. I went from a 40T to a 38T spur gear. I will check to make sure everything is sealed and set all the needles to factory and go from there.

I will do this tomorrow and check back in. Thanks!

 

[wwit]

Smaller spur is for more speed. Lots of things effect the final drive ratio. Gears, spur/pinion, and tire size are the easiest way to make final drive ratio changes and not always for the better. Going to a smaller spur or larger pinion and larger tires can make a dramatic effect from the base line of how the truck came out of the box.

Engine bog is usually a rich condition, but something binding somewhere in the drivetrain can have the same effect as the engine can't take the fuel as fast as you give it, if the engine is under stress from improper spur/pinion mesh(too tight or misaligned) or from just having gearing that doesn't match the tire size.

But could be something simple in carb adjustment. What are the engine temps?

 

[Lethal]

It is starting to get a little better. Temps are around 240F and seems to be running better. I adjusted the carb as the low end seemed open a bit too much. I am wondering if the spur gear is a little tight, but everything spins freely, so it is hard to tell. I am also not sure if the clutch bell should be tight with the spur gear? Do I till the engine all the way so the teeth are up tight, or do I give it a little resistance?

 

[griff7373]

When setting the spur to the clutchbell I take a piece of notebook paper folded over once to give me a little bit of play or backlash, you do not want to have the mesh to tight or it will destroy one or both of them.

 

[wwit]

Yeah you do really want to use paper to set the mesh. Cramming them tight together without that slight space will create problems. Usually the spur will melt quickly if plastic. If all metal spur/Bell or pinion, then its usually the pinion will break teeth off. And in general can lead to poor running engine, blown bearings, bent or broken driveshaft.

 

[Lethal]

Thanks guys! I will adjust it tonight.

 

[Elwood34]

If you chewed up the plastic spur gear, chances are is was either misadjusted or a mount came loose. I am running a Dynamite Mach 26 in my Revo and am using the stock plastic spur gear. The only time I ever chewed up a spur gear on my Revo was when it still had the 2.5R in it, the motor mount had loosened up on it and I didn't catch it in time. The paper method is a pretty good method but I do it by ear.