Ok, last attempt with this carb before I admit defeat and convert to VM36.

Thought I had it nailed but it’s only happy at 2000 rpm tickover....it never seems to stay constant so I’m wondering if the carb is just worn?
Persistent backfire between gear changes and a proper one when it shuts down but better with more revs.

Foam filter
Long fishtail pipe(I know this won’t help😁)
No white spacer
160 main
57.5 pilot( it’s always had this)

My thinking is it’s lean at idle but the pilot jet and spacer removed say otherwise?

😬

Thanks for the reply.
No leaks in the exhaust but I’ll check again.
It’s an 86 engine and is supposed to have a 155 main and 47.5 pilot I think.

With a 155 in it would not rev out in any gear.

Too rich on the pilot would cause a backfire?
I was wondering if it was unburnt fuel.....

Assuming I’d done the exhaust and filter from standard where would you start?.....as I need a baseline.

Has anyone fitted the VM36 kit from Murrays Carbs?
If it’s plug and play it’s at least a back up plan.
Cheers
Rich

On top of the needle!

With an ‘86 carb try a #50 pilot first, I didn’t catch that at initially.  
Does your needle have 3 needle clip grooves in the top of it  ?  If so, put your plastic spacer Back in and set the clip on the middle groove.

Use the 152.5 main jet for now but don’t worry about it for the time being, focus on getting the pilot circuit sorted out first.
After that recheck the needle for accuracy.
Then do the main jet.
All three continue to feed fuel all the way to wide open throttle.

With a too rich condition over all, as you get to wide open throttle your main jet circuit can be extremely rich and the result is a drowning main jet.  It is really sluggish.  Doesn’t run worth a crap.

Backfires can happen with either too lean or too rich.  Both can leave excess fuel in the pipe.

I don’t know Murray Carbs, which VM36 are they using ?  There is more than one, and if the wrong one you will need to change pilot, main, needle jet, jet needle, which will cost as much as the carb itself, so about double.

The base Carb kit with everything you need for a complete carb swap is $399, nothing else needed.
If you already have a VM36 tell me what pilot, main, jet needle, needle jet, and I will tell you if you have the correct carb.

Where are you located ?

Typo. I corrected it

The white spacer is .110' you need about half that in washers. I run mine on a shaved down spacer .075". I'm also at 4000' elevation.

Hope this helps. By the way, Mikuni slots are .035"/ .9MM apart if you have any slots.

Acidrich wrote on 07/26/20 at 06:52:37:

A #4 washer is .032" (.8mm) thick and .313" (8mm) OD
Might be an M3