Random Full Revs

[bongo]

Hey all, noobie to Nitro but learning.
I have been given a damaged revo 3.3 that I have now repaired and got running however.
I can start and drive around then randomly when stationary it will what I can only describe as peak revs but doesn't accelerate. I freak out and pinch fuel line to kill the car in fear of blowing the engine. I have only noticed this when hot. The throttle does NOT appear to open but still peak revs.... doesn't appear to have any fuel leaks from block BUT....... Can some one please point me in the right direction..

25% nitro Fresh fuel
Traxxas M/L glow plug

 

[D3MON]

Hey all, noobie to Nitro but learning.
I have been given a damaged revo 3.3 that I have now repaired and got running however.
I can start and drive around then randomly when stationary it will what I can only describe as peak revs but doesn't accelerate. I freak out and pinch fuel line to kill the car in fear of blowing the engine. I have only noticed this when hot. The throttle does NOT appear to open but still peak revs.... doesn't appear to have any fuel leaks from block BUT....... Can some one please point me in the right direction..

25% nitro Fresh fuel
Traxxas M/L glow plug

I'm really curious if you are having some sort of intermittent air leak. do you happen to notice if it occurs during a specific level of fuel? i had some internal line on a fuel tank of mine pop off and would do something similar to that after about 1/2 tank. had another one the fuel tank seam was failing so would release air after the level went beneath the seam.
also side note, what brand fuel are you running?
i highly recommend not using traxxas top fuel as it has way too much oil in it and makes the engines run hotter than necessary.

 

[Rolex]

when stationary it will what I can only describe as peak revs but doesn't accelerate.

Not sure here. It's sitting still, the engine revs high but it doesn't move forward?

 

[bongo]

I will have a look at the above tonight and come back to all.
I'm confused as the next person as to why revs but no motion. I will go more in depth tonight
and try and replicate conditions.

 

[cbaker65]

I would think ,if it is an air leak ,it would do it all the time!

It seems that the way your describing it ,is that when the fuel gets to a certain level ,an what I would think ,it
is going on a rev in which the engine is starving of fuel ,sense the fuel tank is full when you first run ,then it runs
ok then ,then that tells me that it does ok from the fuel syphon ,an once it gets past that level ,it leans out ,an
revs higher ,that tells me that it is a leaky fuel tank lid seal ,or the muffler is not pressurizing the fuel tank like
it should!

 

[bongo]

Not sure here. It's sitting still, the engine revs high but it doesn't move forward?

Answer to this was a stripped spur gear ... yippee...
As for the possible leaks, I guess only time will tell. I stripped it down last night and used sealant
on all locations, now waiting for it to dry a little before i drive it. Plus I need to replace the spur gear so 2 for the price of one I guess

 

[Rolex]

Great. Quick, cheap fix.

 

[cbaker65]

Answer to this was a stripped spur gear ... yippee...
As for the possible leaks, I guess only time will tell. I stripped it down last night and used sealant
on all locations, now waiting for it to dry a little before i drive it. Plus I need to replace the spur gear so 2 for the price of one I guess

Do you know what stripped the gear ,might need to investigate that ,make sure that the gear mesh is set proper ,an all
of the rest of the running gear moves freely an like it should!
Make sure that all of the wheel pins are in place ,wheels tight ,an check that the drive shafts set screws are there
an tight!
Sometimes those set screws ,or grubs screws on the drive cups & joints will vibrate loose an cause slippage as well!...

 

[bongo]

UPDATE:
It looks like the sealing worked and the new spur gear has been reset, aligned and is now working. Car is now operational.
I just need to learn about tuning as this 3.3 got upto 300F on runs around back yard whilst back yard temp was ~77F.
I am using 25% Nitro-X, traxxas plug (standard).

Thanks all for the advise