os .30vg not shifting with revo?

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jbyrd141

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Converted my revo to a big block. Had an os .21vg on it and it ran and shifted fine. Put a os .30vg on it and now it doesn't want to shift. Made sure clutch was tight and turned tranny shifting point all the way to left, still doesn't want to shift. Tried leaning out the motor until it started stalling out on top end. Temps are still low, around 175, but stalls on top so quit leaning. New engine, ran 5 tanks on it about half throttle and such. SMokes quite a bit. can't figure it out. Acts like it needs leaned to shift, but when i scream it out, it stalls. still not shifting.
 

charliejp

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Are you sure it's not starting off in second? Try readjusting the 2 speed.
 

ajames942

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I dont think 5 tanks is really good enough break in. The engine isnt fully broken in untill about 10 tanks. keep running it and leaning it gradually. Try to get them temps up there.

Also, How cold is it where you are?
 

jbyrd141

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I live in KY. It's been around 45 degree or so, and wet. Also, i keep breaking it in. Ran another two tanks, still no shift.
 

olds97_lss

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I'd run a bit more fuel through it before worrying about it shifting. Then if it still doesn't shift, with the truck running, push down hard on the truck to hold it in place, then give it some throttle to see if anything is spinning.

If your flywheel is loose, it will slip on the shaft/collet which won't transfer enough power to get the trans going properly. Also check your clutch shoes to make sure it isn't slipping due to oil or wear.

Also, by holding it on the ground and not letting the wheels turn when you give it gas, you can make sure your slipper isn't slipping earlier than you think it is.

That's how I test my slipper adjustment. Just don't do it too long if you don't notice anything slipping.
 

jbyrd141

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Good advice, i did notice the flywheel collet wasn't as tight as normal when i took it off the old .21.
 

jbyrd141

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It finally shifted today, does have to rev up real high although. Still wants to bog out on top when leaning on top. Temps top out at 170.
 

ajames942

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Your temps should be around 250. Thats why its not shifting, its too rich.
 

jbyrd141

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yeah, i try to lean it out, but then it bogs on top/hesitates.
 

olds97_lss

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I don't know the engine well enough to know what the temp range should be. However, considering how light the revo is, I could see it running good with plenty of power in the 210-240 range. I've never had an OS that liked to run below 200F and give me much performance.

That's a drawback to an OS. They can run really lean or really rich, because they are very forgiving. Not sure that's a drawback per say... having a wide tuning window is nice though.

I don't know the engine well enough to know what the temp range should be. However, considering how light the revo is, I could see it running good with plenty of power in the 210-240 range. I've never had an OS that liked to run below 200F and give me much performance.

That's a drawback to an OS. They can run really lean or really rich, because they are very forgiving. Not sure that's a drawback per say... having a wide tuning window is nice though.

You may be getting too aggressive with your tune. Plus, until you have 10+ tanks through it, you shouldn't be expecting good performance anyway. Especially considering the size of the tank on the revo, a bit on the small side. I had 11 tanks or so through my LRP before it started to shape up a bit. That's 11+ tanks from a 150cc tank, not a revo 125cc tank.
 
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jbyrd141

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Finally started shifting. Thing flies with that .30vg on it. I switched out clutch bells. I went to a 16, must have been the problem. Was using a stock revo cb.

Finally started shifting. Thing flies with that .30vg on it. I switched out clutch bells. I went to a 16, must have been the problem. Was using a stock revo cb.

Have ran 11 tanks now too, temps are still low, around 160 now. Any one know the stock setting for the low speed adjustment. The high speed is 2.75 out, and on my .21vg they say flush for the low speed. But it doesn't seem to run good flush on the .30vg. I have it probably two screw turns lean from flush. Runs good at 3 turns out on top and 2 on bottom.
 

olds97_lss

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What's your ambient temps? 160 seems aweful low. What was the stock CB? Smaller?

Larger displacement engines usually do run lower RPM's, but they have more torque than a comparable 21. A lot of racers stick with 21's even in the stadium trucks just for that. They really get it screaming in the straights.
 

revo-4tec-mike

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big blocks run cooler than sb's because of the extra mass of material. my os 21vg liked to run about 190-210 max in the summer. my os18tm liked to run 225-235 and my 3.3 ran around 245-255. sometimes even when you compare the same mills you will find every nitro has a prefered temp range. i wouldnt worry about temps too much. the only time i check temps is when i think it might be too hot. just as long as you have a good trail of smoke and good power and no bogging then i wouldnt be too worried.
 
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