Picco 21 runs ok but no low end punch

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2revo1maxx

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Hey guys I've got about 3/4 of a gallon through this max 21 and it has good top end but no wheelie power in my maxx. I've tried everything, it's sealed, Idles well, tried different fuel, fuel line/plug configs, clutches and pipes, it won't outrun a 3.3. In fact I have a 3.3 that'll wheelie just fine. There's no dirt or crud or leaky lines......nothing. All I can figure is that the carb is screwed up. It says the lsn should be flush, but it won't do anything but lean stutter and try to go when I start to turn it in. It's about 2.5 turns out from flush and the idle gap is about 1mm. I've had the lsn out to replace the o-rings and it did finally start to idle right, but something's goofy.
 
If you can't get it to punch off the line after it's properly warmed up, you'll need to start leaning the LSN. Just a little at a time, barely 1/16 of a turn, then run it around and check the temps. Lean a little more till it takes off with good power, but remember to keep checking the temp. Too lean of a LSN can overheat the engine very quickly.
 
If you can't get it to punch off the line after it's properly warmed up, you'll need to start leaning the LSN. Just a little at a time, barely 1/16 of a turn, then run it around and check the temps. Lean a little more till it takes off with good power, but remember to keep checking the temp. Too lean of a LSN can overheat the engine very quickly.

That's my problem, as soon as I start to turn it in it does that lean buzzing that I know is not right. I've gotten it to idle well for 15 seconds without loading up, but it's still a dog. I'm going to lighten my clutch shoes and turn them around (trailing edge) and see what happens. I'm about a month away from a red dot so if this doesn't work it's going in my beater revo where I know it'll rip.
 
Almost does just sound like a carb problem. Not a problem on your part, but like it's not milled properly to let the LSN be where it needs to be. Maybe take the carb out and measure the neck to try to find something else to try in it.

Sounds like you've covered everything else.
 
Once I get my 26 I'm gonna see if she'll run with the 26 carb.
 
Pull the carb, seal the joint where the aluminum ends meet the composite body. Just run a thin bead of silicone around it. Common Picco air leak.
Drop the idle gap to 1/2 mm. My Picco has less than that actually, and it idles nicely. At 1mm you are setting it up for a false tune. Whenever you have a 1mm carb gap and it starts to stutter when you lean it, close up the idle gap and it should start to sound right. Make sure you have the HSN slightly rich for this part. Once you get the bottom end sorted, tune the HSN to your driving conditions.
 
Pull the carb, seal the joint where the aluminum ends meet the composite body. Just run a thin bead of silicone around it. Common Picco air leak.
Drop the idle gap to 1/2 mm. My Picco has less than that actually, and it idles nicely. At 1mm you are setting it up for a false tune. Whenever you have a 1mm carb gap and it starts to stutter when you lean it, close up the idle gap and it should start to sound right. Make sure you have the HSN slightly rich for this part. Once you get the bottom end sorted, tune the HSN to your driving conditions.

I knew it liked a smaller gap! I tried that and it seemed to idle nicely, but when I took off the a/f I thought it didn't look right. I'll try both, thank you. I did get it to run a little better....by taking off some super heavy mip splines.:hehe:
 
Well I tried all that and I'm sure it would help, but I dunked it in water and blew through the fuel line. There's a whole lot of air getting through the nose bearing even though it feels tight and showed no oil seepage at all. I guess I'll try some new bearings, if that doesn't work I'm giving up on it til I get the 26. Then I can at least try that carb once.
 
What are the measurements on the 21 carb? The neck length and outer diameter?

I had an axial that is running like yours... It became a dust collector in a drawer after half a gallon of fiddling/sealing/tuning/running... Easier to give up on a $99 engine than it is a $199 engine.
 
SH, Mach, XTM, LRP carbs are interchangeable with the Picco. Big block carbs anyways.
At Olds, run that Axial at 280F, that's how hot I had to run my POS Axial .28 to get it to perform. No signs of actually being lean either. It still did not produce power worth a damn. Axial's bad about their timing being way off from specs. A modder can correct it and make it run very well. ExtremeRCMods is a wizard with the Axial .28. First thing he does is throw away the stock bearings though!!! Axial makes horrible bearings.
 
Sold it to someone as a parts engine. It looked like brand new... $40 shipped to canada. So, wasn't a complete loss. It and an STS D28. Both exhibited the same problems. No power, lean bog or overly rich. No happy middle regardless of pipe, tune or fuel.

I've learned to give up when I know there are less aggravating things out there. The STS came in my savage when I traded it for a buggy I had.
 
I'm just gonna let it sit for now. My 3.3's are a dream to tune vs. this picco. I'm pretty sure the bearings will help me to get that lsn in where it belongs, but I'm still gonna wait.
 

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