pop on decel

[smelly$cat]

I took my 426 out this weekend for the first time in quite a while (3 mo).

I noticed it seems to be making a popping noise out of the exhaust every time it decelerates. Kind of a "Pop, pop... pop....pop pop" noise.

It also dies at idle occasionally.

I'm thinking it could be a few things.

1. Air filter might be getting dirty (i kind of doubt this would be the cause, but, open to input. I'm going to clean it as it has been a couple rides since I've done so).
2. Valve adjustment might be needed. (I haven't checked or adjusted the valves since I had the engine rebuilt ~6 rides ago) And I do notice a bit of a "tick" on the top end (more than normal) that wasn't there when I first broke in the engine. The valves were replaced with kibble whites during the rebuild.
3. I started using a bit lower octane fuel (100LL Avgas, down from 114 Trick)(Has a 12.5 to 1 CP piston in it / stock cam / stock carb). Wondering if this might require a change in jetting in my carb. Bike ran great under acceleration and I didn't noticed any funky noises or "pinging".

Anyway, these are my thoughts and the facts.

Let me know if you have any thoughts on this.

Thanks!

[uchi]

from what ive read a popping on decel is either a lean condition or an exhaust leak. try turning out your fuel screw a half turn and see if it goes away, and if not then jump up a size on the main jet.

[scuzz]

or...it's REALLY rich.

[smelly$cat]

I'm thinking it's lean. It doesn't blow any noticeable unburnt fuel or smoke out the pipe. Good call on the fuel mixture screw. I'll try that. I'll also take care of the other maintenance items that are due.

[BEAVER.989]

Check for holes in the airboot and be sure it's conections are solid, as well.

[BassHunter0123]

i was having the same problem on my 450carb. i came out on the air/fuel screw a bit and adjusted my needle. now its good

[smelly$cat]

Ok, will do. Good call. Something may have come loose.


Originally posted by BEAVER.989
Check for holes in the airboot and be sure it's conections are solid, as well.

[katch26]

Ive ahd it happen before and fixed it with a larger pilot jet........but check for any air leaks first