One cylinder not cutting out

www.wgcarbs.com/index.php?option=com_con...view&id=27&Itemid=27

I compared both sparks. One is a good blue and the other is a bright white. Its just the spark plug though becuase when I switched them, the spark stayed with the plug. I'll probably just end up taking the carbs off again.

I dont suppose tipping the engine when I had it out would have gotten oil in the cylinder or something? just a thought that I had when I saw some black liquid on the plug threads.

KZCool wrote: I compared both sparks. One is a good blue and the other is a bright white. Its just the spark plug though becuase when I switched them, the spark stayed with the plug. I'll probably just end up taking the carbs off again.

If the coil produces white spark from the same plug wire regardless of testing with a brand new correct spark plug, and the same coil produces fat blue spark from the other plug wire regardless of testing with a brand new correct spark plug, would suspect an issue in the "white-sparking" plug wire, such as faulty connection to coil, deteriorated plug wire, and/or faulty connection to the new cap.

Would rule out defective plug wire before again addressing the carbs.

Good Fortune!

You say you took apart and cleaned your carbs... and it seems to fire fine when you throttle up or use the choke...

Me thinks you screwed up the carb balance. If the slides are not nearly perfectly same height/vacuum balanced, then at low rpm/idle, you can get a cylinder that barely fires intermitantly because its just not getting enough of anything.

Make absolutely certain there are no air leaks around the carb intakes/filters/exhausts etc. and perform a proper bench sync and running manometer vacuum balance.

Eliminates all sort of big cylinder twin running issues.

Good luck.

through all tis I actually have them synched more exact then ever. I have a set of vacume gauges that are telling me that they are near perfect. And te white spark stays with the plug. It's just the plug that makes it white. Sorry if my wording was bad. Either way both sparks are hot and seem to fire every time.

Forgive me if this has been mentioned but I only skimmed the forum. Have u checked for a vacuum leak.? I had this problem after replacing my carbs after cleaning them.

How do I check for a vacuum leak and where is it prone to happen? The carbs were synched with a vacum gauge too so i gues if there is a leak then they are off too lol.

Vacuum/air leaks can happen anywhere their are rubber hoses or pieces, as sunlight and ozone attack it/them.

Several places to look:

1.The carb holders(between the engine and carbs); sometimes they develop small cracks, letting in air/vacuum, making the engine run lean.

2.The rubber ducting(boots) from the air filter box to the carbs.

3.The rubber vacuum lines can split or crack.

4.The rubber sync plugs will get cracks, letting in air/vacuum.

To trace down the leaks, use a spray like WD-40,brake cleaner, or an UNLIT propane torch on the rubber pieces, while the engine idles. If the rpm goes up while spraying, you've found a leak.

Make and model??

Clean air paraphernalia still there?

KZCool wrote: How do I check for a vacuum leak and where is it prone to happen? The carbs were synched with a vacum gauge too so i gues if there is a leak then they are off too lol.

Exactly buddy.

Bench sync the carbs for now and leavem that way till you get everything else figured out. Then perform a vacuum sync after youve been riding around for a while and all is good.


If you're a smoker, just blow a puff around the usual leak areas and you'll see them pretty quickly.
Alternatively you could use a smoke machine or the like.
Also... if you turn the air/mixture screws on the carburetors, the engine should falter at close the the same number of turns in/out on all the screws identically. If you have to adjust a particular carb much richer, then viola - most likely air leak.

Best of luck.