[supersparky750]

I'm having a weird problem with my idle when I start the bike after being off for a short time (i.e. fuel stops). It starts great first thing in the morning, and idles just fine after warming up, but if I stop for a couple of minutes, it misses on one cylinder for about 30 seconds at idle. The missing cylinder seems to pick up if the engine is revved, but drops out again at idle. Then it settles down and everything is fine. It seems to do it reguardless of engine temp. Plugs look good and have about 2000 miles on them. Any thoughts?

 

[1fast750ss]

Hi Andy,

I'm no expert, but look at your cylinders fuel line. It might be pinched or have a vacuum issue. Another option could be that you have a pinhole leak in the line, which could put air in the line until it gets hot(?) again and swells the hole shut enough to function.

Either way, sounds like a fuel line issue.

Brian C.

 

[jbarnsey]

Hmmm just wondering wether it needs the throttle boddies balancing and tps adjusted.. That would be where i would start looking anyway.

 

[supersparky750]

Thanks for the tips, I've been leaning toward a vacuum or fuel problem, and I know I'm due for a balance and tps adjustment. It occurred to me last night though, that it could very well be my battery. Is it possible that my battery is getting weak enough (as far as I know it's seven years old) that it starts the bike okay on the first try, but if stopped before it gets a chance to charge fully it draws down enough on the second start to cause the alternator to sag, thereby freaking out the ecu or preventing the coils from saturating properly?

 

[jbarnsey]

if the engine is winding over at normal speed, then your battery is not to blame, also if that was the problem you would think it would probably missfire on both cylinders ???
in the injected system both of the injectors run off the same high pressure fuel rail, so i doubt it is a fuel problem if it only misses on one cylinder.
If you bring up the idle speed another 200 or so RPM with the cold start lever does the miss go away ?? if it does i would be looking at throttle body balance, that will tell you if there is a vacuum leak for a start..
Let us know how you get on.
jas

 

[supersparky750]

I installed a new battery a couple of day ago (decided it was time reguardless of whether it was the source of the problem), and it made it much better but didn't cure it completely. This evening I stopped for gas after about a half hour of riding, so the bike was good and warm. I started it back up and it stumbled for a few seconds then settled out. And with the new battery I can reliably restart it if it dies. So the problem isn't fixed, but it has been reduced to a manageable level. I've begun compiling notes from previous posts on tps and tb adjustments (gotta love those archives) and will give that a try when I get a chance.

 

[jbarnsey]

process of eliminaion... keep us updated.

 

[900too]

I'll bet the airbleed screw on the cyl that dies has vibrated closed, or the idle air circuit is blocked. A quick check would be to put a mark (pen mark or other) on the body where the air scew slot lines up, then turn in (counting the number of turns or increment) and see if it's turned all the way in or almost all the way in. If it's about 3/4-1 turn out (turn it back out to where it was) then the idle air circuit may be blocked with carbon/oil (from oil breather into airbox). On my throttle bodies (900ssie) one has no resistance at all to turn in or out, so to make sure that one doesn't "self adjust" I have a glob of silicon seal to hold the airbleed screw head from turning.

Also check the air bleed screws for the evaporative canister hoses where they attach to the throttle body - in case one of them is loose, allowing air to enter throttle body. Check spark plugs, plug boots, all grounds etc.

Also check to make sure the new battery is being charged - otherwise at idle it may be drawing more power than available (to run headlight, ECU/Electronics, and spark the cylinders). Could be a failed regulator/rectifier (happened on another bike of mine).