TOPIC:

Hi all,

Had to strip down my carbs on my A5, wasn't running right. Cleaned out, set float levels which were all out, re-fitted and balanced. Also adjusted air screws with color tune, near perfect idle, awesome low end pull with no hesitation, overall runs beautifully. Only I noticed slight exhaust pops on deceleration! Not that bad but since I've almost perfected it, wondered what this could be. I started out with 3,1/2 turns out and had to adjust very little for a perfect blue flame. Any thoughts?
I'm running a stock exhaust and air filters, only the 2 mufflers seem to have been replaced at some stage, i.e. Slightly shorter than the originals.

Thanks, Chris

Hi Chris,
To some extent I consider some popping on decel as normal. However, an exhaust leak it will sometimes let oxygen rich air into the system and cause the symptom you're describing. Fresh air entering into the open end of very short pipes can cause the same popping, although I doubt that your shorter mufflers are the cause.
Check the pipe connections at the head and also look for leaks at the head pipe to the muffler connection.
Good Luck
Bill

My 1979 kz1300 likes to pop and bang out of the exhaust, especially if I am going down a steep hill. If yours is otherwise running well, I wouldn't worry about it. Besides, it gives pedestrians something to look at.

Have you looked at the section in the KZ1300 manual which explains the function of the "Coasting Enricher System" - it might be worth checking that system in case it is the source of your problem.
Good luck!

biltonjim wrote: Have you looked at the section in the KZ1300 manual which explains the function of the "Coasting Enricher System" - it might be worth checking that system in case it is the source of your problem.
Good luck!

Jim's right here. The Coaster Enrichening Valve is the culprit. When you pull off the triangular side cover piece on each of the carbs underneath will be a diaphragm, a spring and a brass plunger. The brass plunger likes to stick in the aluminum bore due to moisture and dissimilar metals. Galvanic corrosion. Clean the brass piece up and ensure it freely rotates in the bore of the carb and then put it all back together. I really like "Autosol" metal polish for cleaning up all the brass parts. Works a treat !!

I'll also agree with the culprit likely being the Enrichment Valve. I have seen these so gummed-up, the small brass "plunger(s)" wouldn't move. It's one of the easier things to check for this issue although the carbs will have to be separated to remove and clean them. Also check the tiny metered vacuum port that operates this valve. One per carb, per enrichment valve and is the larger port on the "engine-side" of the throttle-plate. Compressed air should clear it. Easy to check with a bright/small flashlight shining into the bore. This metered vacuum-port is very small but whether you can see light through it, will indicate if it's blocked or not. Check the plunger diaphragms for cracks or holes. DON'T touch the set-screw in the cover plate! As KB suggested, polishing the plunger with "Autosol" is a good way to shine it. A "Q"-tip and some lacquer thinner will clean the plunger-bore.