Exhaust pop.

[red1100]

Just got done rebuilding all carbs,valve adjustment,one was 001 tight,one was 001 loose.carb sync and went for a 100 mile ride in 85 to 90 degree weather. Runs great pull hard to the top but still has a light pop,pop on deceleration. Very light but noticeable probably more so because of a 4 to 1 pipe. I’ve had all the jetting done by Yoshimura in 1984 and everything has been spot on till this summer. Mixture screws out 3 1/2. Too much or is it advisable to back them out anymore? Boots are perfect no cracks supple around perimeter on engine and pod side.Cannot find any obvious vacuum leaks. I see folks talking about this and setting their screws out at 1 or so. What else should I be looking for? Thanks.

[allojohn]

Popping on decel is an indication of a lean mixture, reset your air screws. Which model are we talking about here?

[red1100]

83 1100e....

[Tom R]

Did you disturb the exhaust gaskets? 3 1/2 turns out is about the limit before going to larger pilot jets, but if it never did it before... o rings on mixture screws still intact?

[red1100]

New exhaust gaskets done at the same time

[red1100]

Finally found/solved my popping troubles. When I rebuilt the carbs I forgot to put in the new mixture screw hole plastic plugs,did that and popping went away. Took a 2 hour ride at 100 degrees out ran beautifully, screws are at 2 out and I may turn them in a half, plugs are light tan, oil was at 200,hot day. Starts instantly pulled hard from stop to 9,000 in 4th and I backed out and called it good. 44 mpg. Job done.

[allojohn]

Magic! Ride on!

[londonboards]

Which bit are you calling the mixture screw plastic plug?

Is that the small washer that goes on the mixture screw?

Or are you talking about the rubber plug that goes next to the main jet in the float bowl?

[red1100]

These plugs.1E8881D5-DAAC-4C59-B3D5-5772C2F1F041.jpg

[2BRacing]

These plugs.[ATTACH=CONFIG]55998[/ATTACH]

Well, I do not have a 1100, but I would not have thought those plugs, or rather the absence of those plugs, could cause an air leak.

The tiny o-ring below the washer and spring on the mixture screw should be all that is required to seal at that point.

[GRAND ROUGE]

These plugs.[ATTACH=CONFIG]55998[/ATTACH]

Those plugs are the pilot jet plugs.....inside carburetor and secured in place because a snug fit and when float bowl 'pad' contacts them. Any leak at the mixture screw would be because the tiny 'o' ring that is placed on the 'pointy end' of the mixture screw....after the spring and washer are slipped on....is not sealing. defective, missing, etc. Or, there could be a mixture screw tip that has been broken off previously and is lodged in the mixture screw bore.

Canadian and European Spec GS 1100E machines did not have any type of cap covering the mixture screws.

[red1100]

After riding almost daily now since the last post everything seems to be fine. Starts instantly,runs hard all the way up to hauled to jail speeds,plugs are a clean light tan,getting 44 mpg in freeway/city mixed. Rode to the last Backfire Moto in Seattle 350 mile round trip no issues. It’s as good as I can get it.

[850 Combat]

Exhaust leak is a good source of backfires on deceleration, as stated by others.

[londonboards]

I promise you ... those plugs do not belong there.