One Cylinder Blues

Outdoor · Posted: September 12, 2006, 5:37 pm Post subject: One Cylinder Blues

My xs was awesome, had some pogging and rpm troubles but ran always. I took it on a longer ride and now once it gets hot the right cylinder doesnt run. Bike sounds terrible and has no power. I have cleaned and rejetted the carbs and it runs great for about 12 minutes. When i cleaned the carbs i found the air filter on the right (dead) side was torn allowing air to bypass the filter (perhaps creating a lean situation).

Then its warm i have to rev it above 3k before the second cylinder will catch. Its like a kick in the pants, and the bike tears off! As I continue to ride and the bike gets hotter the threshold of where the second cylinder fires gets higher (3k, 4k, 5k) untill it just doesnt fire at all.

Let the bike sit overnight and its fine again, till its warm.

Other things i have noticed....

The bike now makes a ticking noise from the right (dead) side all the time could just be a valve adjustment is needed.

When the bike is idleing (hot) on one cylinder there is a distinct rythmic and click noise from the right side. I suspect this to be a result of the first cylinder kicking the second through its compression stroke.

The ignition system has been replaced and from mikes so i dont think it is an ignition problem.

Any suggestions or insight will be greatly appreciated.

xsjohn · Posted: September 13, 2006, 6:23 am Post subject: Re: One Cylinder Blues

If you think the ignition is ok and you have good compression on that cylinder and the timing is right maybe pull the carb on the cylinder that is giving you a hassel and double clean it and blow it out good. Good luck. John Underwood

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

If you have always had some pogging or rpm troubles -
I would agree - clean the carbs -
But Then Make sure they are in Sync.

There are a number of articles on this site on syncing carbs.
Good Luck
Jim

royfisk · Posted: September 13, 2006, 8:07 pm Post subject: Re: One Cylinder Blues

You say the ignition is new does this include the coils? If so did they send you the right ones? I went through a simular experiance once before and received a coil that was for a electronic ignition and I chased for two days before I put on a old coil and had all my problems go away. I also have seen brand new coils be no good on more then one occasion. If you havent changed your coils mayby you might reverse the two coils and see if the problem follows. just a thought

royfisk · Posted: September 13, 2006, 8:13 pm Post subject: Re: One Cylinder Blues

That ticking noise your hearing isnt a coil or wire going to ground is it?

Outdoor · Posted: September 14, 2006, 9:24 am Post subject: Re: One Cylinder Blues

I may have fixed the problem. Knew the carbs were clean (just cleaned/re-jetted them) took the bowls off just to look for any floaters that may have appeared, there were none. I did however find a new vacuum leak at the intake manifold (sprayed carb cleaner, engine raced). So i pulled the carbs and gaskets, found some old nasty silicone insta-gasket. Cleaned all the surfaces and put a new copper in a can gasket on. The problem was gone when i rode the bike home from where i work on it.

I took it out for a longer ride last night and it was clear that the larger jets i put in were too large, i am going to try dialing in the air mixture a bit to see if i can fix the problem before more jets arrive from Mikes.

Not sure about a new coil or not, but I dont belive the noise to be electrical in nature. I will look so i can rule that possiblity out.

Thank you for all the help

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

jimdi · 650Rider Supporter Joined: Oct 27, 2005 Posts: 512

Bingo - on the single coil -IF BOTH of your plugs< and plug caps are good -
I am betting either one carb is really out of wack and needs to be rebuilt - or someones got the sync way off.
The lower the rpm (idle) the more important sync is to keep the side firing.

Think of sync in terms of 2 throttes - if you only open one side only one side will fire.

I would start with a good cleaning - rebuild of the carbs - and go right through the process of idle mixture to syncing them up.

Grizzly · Full Member Joined: Sep 15, 2006 Posts: 17 Location: VT

The symptoms described in your original posting are exactly like what's happening to my '79 (see above). Only when I sprayed the carbs around the throttle I get white smoke out the exhaust.

I did have a tear in the seal of the air filter, did this fix have much of an effect for you?

Grizzly

Outdoor · Posted: September 16, 2006, 8:03 pm Post subject: Re: One Cylinder Blues

When you spray the carbs you are looking for a vaccum leak, so somewhere there is air getting into the cylinder without going through the carbs. Fixing the filters had a large effect as well.

I sprayed the carb cleaner at the intake mount on the motor, the space between the carbs and the head of the motor. Do this while the motor is idleing, if the motor races at some while you spray one portion you have found your leak. Once you find one you should pull off the carbs clean both sides of the mounts with wire brush (get them real shiny) and apply some copper gasket adhesive between the two before you reassemble.

On mine I cleaned and reassembled while waiting for mikes parts to arrive, swapped out the mounts, and now the bike has never run so well.

As for the air filter, a torn filter let air into one side eaiser than the other. Both sides carbs were getting the same amount of fuel but one ran much leaner as there was no resistance to incoming air. So the filter is more of a fine tuning type of problem.

I was a real genious and tried to fix the filter with electrical tape before parts arrived, and it worked, till i opened the throttle up wide (highway). At which point a 4" piece of tape was pulled through the engine. It must have been, as it is no longer on the bike anywhere. Frankly I am not sure i have had a better day of riding before today so clearly no harm done.

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