Brent Davis

A noise started today after some hard runs. At idle, the transmission and clutch aren't spinning so I know it isn't that. I rotated the flywheel by hand and there seemed to be no binding and the compression is still great on this motor. What could that noise possibly be? The engine still runs hard and fine, just has a rattling noise that seems to be right at the flywheel area.

Thanks in advance, oh BTW, a new PICCO .26 MAX engine is on it's way too.

86revo

i have know idea what it could be but traxxas makes the engine so if you contact them or your local hobby shop they could probably tell you whats wrong

SAVAGEJIM

If you can, can you vid your Revo running with the truck emitting this noise and post this vid? That would probably help us determine what is the problem.

steven16

your fly wheel isnt wobbly? cuz it could be touching the carb

Brent Davis

Thanks Steven but no the flywheel is straight while idling.

steven16

have you checked in side the engine? maby the crank pin is wore down or something is in side. if you check it out look for metal shavings also hope that helps
steve

Brent Davis

Found the problem. The bearings that are at the hub up front are making alot of noise. I took the engine, boxed it up and it's off to RB Mods for their custom work. I am told that 90 MPH can be had with the 4-tec with that 3.3 Traxxas motor after he's done. He guessed about 30K RPM's is what the stock 3.3 is turning but with their mods, it will be more like 60K[X(] RPM's and then that beast will fly. He said that they make a custom rod that will "NEVER" break too so I am happy about that as well.

SAVAGEJIM

90MPH? I hate to say that I am quite skeptical of that speed out of a TRX3.3 and the stock gears of a 4-Tec. If you want to see 90MPH out of a 4-tec, even from a very very powerful engine, you must really gear it very very high, higher than any Traxxas gears could give you. You would in effect have to fabricate such gears. Then, you would have to find an engine capable of turning thes steep gears at at least 40000RPM. Nitro engines are very very weak in the torque department, even though thier max HP might be very impressive. At about 30000+ RPM, a very large majority of nitro engines see their torque curves plummet towards zero oz-in.

njsmith1087

my engine (also a 3.3) makes the same noise.  What are these bearings that youre talking about and where are they?  Also is it a problem if they rattle (need to be replaced or are they fine)  Thanks a lot

rpg711

this is a problem with most engines, the front bearing wears down and you need to replace them BEFORE they fail, even bigger problems could happen, much like a crankshaft or connecting rod wearing down

NovaSavage

I doubt that 4-TEC will hit 90 mph just with an engine mod. You'd need huge gears to hit that, or change out the engine for a brushless motor and a 6SLiPo, not counting the aero adjustments you'd have to accomplish. I can see it hitting the 75mph mark(like it says on the box), but not 90mph.

Over_revO

He lied to you if he said 90mph with just the mods lol i remember seeing that claim on his website a long while ago.. he said that for the Jato as well..


the fastest i ever went with my 4tec usign the tallest gearing i could find is 81mph. and it was with a Picco .21 P9R Abmods stage 2
And thats a pretty high reving engine with a lot more power what so ever you can do to a 3.3...


With a 3.3 that lightly modified i got 75mph using that same gearing. On stock gearing, stock 3.3 engine i got 68mph.

It could have handled more gearing with the Picco .21 P9R thats for sure, but theres no gearing available, i searched a lot. It would need to be converted to single speed with custom gearing.