Can't get my nitro engine to idle without constantly adjusting bias trim on remote

[hueyc586]

Hi Nitro gang,

I am having issues with my RedCat Hurricane XTR with Sh28 M28-P3 engine. I’ve tried everything from sealing the backplate, carb and putting the HSN, LSN and idle back to factory and it won’t start. I am only able to get it to start with wider than expected Idle gap which don’t make any sense. One thing i do know is when I am able to start it and get it idle, again gap wider than usual and steam air bubbles on the fuel intake line, also sounds bogged down.. too rich. When I throttle, it has good initial torque but then will die when back to idle. See short video of running air leak intake fuel line. The air bubble appears to be at the inlet of the fuel nozzle.

 

[hueyc586]

Ok, I did manage to find a crack in the fuel line after the intial post above. Went ahead and replaced new fuel line but still having to constantly chase the tuning to keep from stalling. I am constantly having to ramp up/down the idle gap using trim bias on remote. When i apply throttle, it has good acceleration and then let off throttle it will cut off. I don't understand why I need wide idle gap to keep engine idled, help? Is there something wrong with my SH 28 OS carb? I am suspecting that is the case since I've done everything else; sealed backplate and carb intake port.

Here's a video of me constantly adjusting the idle gap using bias trim on my remote just to keep it running, Won't hold idle, constantly opening gap using bias on controller

If the carb is bad, I am having a hard time finding OS SH28 carbs on eBay. If there is one, the price is skyrocket... Anybody know if Force 28 engine carb will work? I've order one as backup for parts... like the power of my M28-P3 came with my Redcat XTR. I don't believe anythingn wrong with Nitro engine or compression... plenty of it if I can get it to hold tune but for the life of me, no matter what settings I can't tune the engine. Just whenI think got it tuned, it quits on me. I could swap out with Force 28 that ordered but prefer to fix this engine. If the Force 28 carb is compatible with SH28 engine, I will try swapping it out and attempt tune again.

 

[tudordewolf]

I'd check that the clutch bell isn't applying drag, either due to a bad bearing or a broken spring or debris that got caught inside...That could be the problem entirely, disguised as tuning issues.

If it's still having issues, I would start by setting the idle gap screw at whatever position it takes to keep the engine running, even if that's wider than expected and higher than you'd like. You won't get anywhere trying to tune it while using the remote to keep it running. After that, try the "pinch test" to get an idea of whether it's running rich or lean, and then make small adjustments to the low speed needle and idle screw to bring the idle down without stalling.

 

[CertifiedMike]

Is your exhaust connected to the fuel tank clean, clear and blowing thru easy? No blockage in the tank?
Does you fuel tank seal up? No air leaks?
I would replace all your lines. If 1 is junk, more are possible if not likely. Its cheap insurance.
This sounds like a pressure issue to me. When the motor stops drawing, theres no pressure in the tank to equalize the pressure change and the motor cuts out.
Just a theory. I was unable to open the link here.

 

[hueyc586]

Is your exhaust connected to the fuel tank clean, clear and blowing thru easy? No blockage in the tank?
Does you fuel tank seal up? No air leaks?
I would replace all your lines. If 1 is junk, more are possible if not likely. Its cheap insurance.
This sounds like a pressure issue to me. When the motor stops drawing, theres no pressure in the tank to equalize the pressure change and the motor cuts out.
Just a theory. I was unable to open the link here.

Hi Mike,

Yeah, the exhaus connected to fuel tank is cleaned. Already replaced fuel lines x 2. Just curious, you weren't able to open the links provided above? I've uploaded short vid in my utube channel. let me know, thanks for help!

 

[hueyc586]

I'd check that the clutch bell isn't applying drag, either due to a bad bearing or a broken spring or debris that got caught inside...That could be the problem entirely, disguised as tuning issues.

If it's still having issues, I would start by setting the idle gap screw at whatever position it takes to keep the engine running, even if that's wider than expected and higher than you'd like. You won't get anywhere trying to tune it while using the remote to keep it running. After that, try the "pinch test" to get an idea of whether it's running rich or lean, and then make small adjustments to the low speed needle and idle screw to bring the idle down without stalling.

Thank you, I'll give that a try and post my results.

 

[CertifiedMike]

Its my firewall, not your link.

Is your exhaust tight? No leaks? Def not plugged inside the muffler?

 

[hueyc586]

Its my firewall, not your link.

Is your exhaust tight? No leaks? Def not plugged inside the muffler?

Oh ok, yeah exhaust tight. Oil spits out of it when idling. I have taken it off the buggy and flush with brake cleaner.

 

[hueyc586]

Thank you, I'll give that a try and post my results.

When it does run, it's got good low end torque and able to do 360 spinout. If bell clutch is bad, would I still be able to do that?

 

[tudordewolf]

When it does run, it's got good low end torque and able to do 360 spinout. If bell clutch is bad, would I still be able to do that?

Yes, it wouldn't affect your ability to apply power, it would just apply drag at idle that stalls the engine.

 

[fstnd]

I sometimes have bubbles in my fuel lines too, it's really not a problem It'd be nice to see you apply throttle, because the engine sounds completely OK at idle. The idle gap doesn't matter as long as your engine is idling, and if it's tuned well and not overheating of course. The idle gap might differ with each carburetor.
The clutch should not engage, if it does, get new clutch springs. From the video it looks perfectly fine.
If your engine is stalling when letting off the throttle, I'd adjust the idle screw to higher the idle manually (not electronically)
I'd reroute your fuel line so it doesn't touch the hot cooling head.