Bonneville America Forums Forums Technical Forums General Tech Deep "cough/sputter" at idle.....right cylinder

2005 America, 69,000 miles, completely stock, runs and pulls strong with no other adverse symptoms. At idle, strong persistent "induction" cough from right pipe, is best way I can describe it...very strange.
I did have carbs off recently to correct single cylinder dead problem, turns out, my air cleaner was installed upside down ...
New squirrel condoms, no exhaust leaks that I can feel, any ideas would be appreciated....

Perhaps "induction" is a bit misleading. I mean that the right cylinder is producing a persistant "cough" at idle, at the tailpipe, but only after the engine gets hot...nice and smooth when first started...

You could try a couple of types of spray around the intakes. Use a spray can with the long plastic tube inserted into the nozzle. you can pinpoint where the vacuum leak" is. Vacuum can't "leak " out but air can leak into it because the seal is not sealing. A ether base spray would speed the engine up and a spray like WD 40 may smooth it out for a few seconds before it gets pulled in by the vacuum.

Probably not the issue but when was the last time you adjusted your valves? If an exhaust valve is too tight it could cause a slight miss at idle and clear up at higher speeds. If this is the problem, don't drive the bike till the clearances are fixed otherwise you'll be looking at a valve job.

One other thing, did this problem show up right after pulling your carbs or some time after? Right after usually means the problem was self induced.

Not sure when the problem showed up, I just noticed it the other day. Rode the bike to work yesterday, went to start, running on one cylinder again. Reached up under tank, jiggled wires to coils, now running on two again, long enough for me to get it home. Removed seats, tank, Procom, plug wires and valve cover to measure valves, Only 3 out of 8 valve clearances outside of dimensions, 2 intake and 1 exhaust are out of tolerance. The 1 exhaust is at like .31mm, and 2 intakes are slightly out, but nothing major. Will correct the 3 that are out, then re-assemble and snug up all electrical connections, replace plugs and wires...She'll be alright...

If the problem went away after moving the coil wires, sounds like you might have found the culprit. The noise from running on one cylinder is a lot different that an induction cough though. Same problem?

Concerning the valve clearance, that was a long shot not knowing when the last time your valves were checked. From what you stated, none are tight.

Keep us posted and good luck.

Yeah, we don't want to talk about the LAST time the valve clearances were checked! Bent 4 valves! I placed my trust where I shouldn't have!
Me and this bike have been through ALOT! I will NEVER sell, but will be looking for an engine before too much longer..Carbureted of coarse...

All valves now in tolerance, no help....sounds like ignition timing maybe...not a big deal, may select another setting on the procom because she is backfiring ALOT

Did you try swapping the coil and plug wires around to see if the problem switches sides?

Yeah, tried that, something to do with the right cylinder...Nearly totaled the thing Saturday, gonna be sitting awhile till I get the nerve up to ride it again...Death approaching you is hard to shake...

Time to do a compression check? I have checked compression on 3 865 Triumph twins and all 3 were 152 lowest to 160 max lbs.

Screwed out the needle on the right carb to match left carb, all is good...she runs SWEET...

OK great you found it, BUT! why did it change from the other carb? Did you disturb it or did something cause it to loosen up? An old trick was to put a dab of nail polish on the threads where it screws into the carb body, of course that was well before loctite was invented.

The O ring should keep it from turning, if it doesn't then it is probably leaking air too. They will probably not be the same number of turns on both carbs.