Kawasaki Concours Forum

The C10, aka Kawasaki Concours - The Original => The Bike - C10 => Topic started by: Hwy 49er on December 17, 2011, 07:38:40 PM

Title: Low compression tuning?
Post by: Hwy 49er on December 17, 2011, 07:38:40 PM
I have a #2 cylinder compression down about 10%. Lots of missing. Can the carb be tuned to make the cylinder run better in this condition? Like a smaller jet or pilot adjustment? I assume it's quite a polluter in this condition. I've riden it this way for 15K. Four valve adjusts. Four syncs. SISF jets, overflow tubes and foam in the intake. I guess i'm going to keep riding it this way a while. I don't have enough money for another bike and this one is worthless. Sell for parts? Part it out? Used engine? Ghost ride it off a cliff? I haven't been able to find a engine.
Title: Re: Low compression tuning?
Post by: Steve in Sunny Fla on December 17, 2011, 07:54:02 PM
no, you don't select - tune a cylinder that way, as it's compression that's different, not displacement. actually, 10% isn't that bad, i'd keep riding it til it pukes, which may be a long time - steve
Title: Re: Low compression tuning?
Post by: T Cro ® on December 17, 2011, 07:55:32 PM
Depends on the reasons why it is down; which BTW 10 percent is really not a lot.... If your down because of non sealing valves then there is little to be done by way of carb tuning to minimize the missing as your passing combustion gases either into the carb or into the exhaust when it should not be there. When was the last time the carbs were properly cleaned and tuned? Syncs do not count.
Title: Re: Low compression tuning?
Post by: Hwy 49er on December 17, 2011, 08:36:10 PM
Depends on the reasons why it is down; which BTW 10 percent is really not a lot.... If your down because of non sealing valves then there is little to be done by way of carb tuning to minimize the missing as your passing combustion gases either into the carb or into the exhaust when it should not be there. When was the last time the carbs were properly cleaned and tuned? Syncs do not count.

10% is enough to make it miss a lot and smell rich. I guess it's not rings by the results of the dry vs wet compression readings. Steve had the carbs in February. That's about 5K ago.
Title: Re: Low compression tuning?
Post by: T Cro ® on December 17, 2011, 09:16:58 PM
10% is enough to make it miss a lot and smell rich. I guess it's not rings by the results of the dry vs wet compression readings. Steve had the carbs in February. That's about 5K ago.

You could also be dealing with a non or poor firing cylinder due to an ignition problem by way of a fowled spark plug, rotten high voltage wire, bad plug boot. As commented by Steve 10 % is not a lot of loss if you have all your other ducks in a row.
Title: Re: Low compression tuning?
Post by: kreaky on December 18, 2011, 09:02:47 AM
You could also be dealing with a non or poor firing cylinder due to an ignition problem by way of a fowled spark plug, rotten high voltage wire, bad plug boot. As commented by Steve 10 % is not a lot of loss if you have all your other ducks in a row.

Good thought. Might be a good idea to check the boots & plug wires.
Title: Re: Low compression tuning?
Post by: Steve in Sunny Fla on December 18, 2011, 09:19:59 AM
10% is not enough to make it run rich and to miss. That' sounds way more like either a carb issue or an ignition issue. Since if it were a carb issue it would have to be pouring fuel into the cylinder to cause it to miss, my vote is as T's, it's an ignition issue. Steve
Title: Re: Low compression tuning?
Post by: George R. Young on December 18, 2011, 09:33:09 AM
Sounds like you have stock ignition so the same coil drives cylinders 2 and 3..

You could interchange the ignition wiring for cylinders #2 and #3 and see if the problem moves or goes away.
Title: Re: Low compression tuning?
Post by: Hwy 49er on December 18, 2011, 06:02:55 PM
You could also be dealing with a non or poor firing cylinder due to an ignition problem by way of a fowled spark plug, rotten high voltage wire, bad plug boot. As commented by Steve 10 % is not a lot of loss if you have all your other ducks in a row.

I've had two different sets of wires on the bike. The wires and boots that were on the bike and a new set from Murph's, and three sets of plugs in there. The last set went in there about 3K ago at Steve's suggestion. I've checked the wires as recent as 1K ago when #1 boot came loose. I also found and replaced a vac cap on the #3 carb at that time.
Title: Re: Low compression tuning?
Post by: Hwy 49er on December 18, 2011, 06:03:45 PM
Sounds like you have stock ignition so the same coil drives cylinders 2 and 3..

You could interchange the ignition wiring for cylinders #2 and #3 and see if the problem moves or goes away.

I'll try that and report back.
Title: Re: Low compression tuning?
Post by: Hwy 49er on March 02, 2012, 01:25:32 PM
Instead of  interchanging the ignition wiring for cylinders #2 and #3, I put on stick coils and the problem is still the same.
Title: Re: Low compression tuning?
Post by: jim snyder on March 02, 2012, 02:39:01 PM
Have you tried going to the hotter range plug (DR7EA) Not saying that will cure it but its one more idea to throw in the mix.
Title: Re: Low compression tuning?
Post by: jworth on March 02, 2012, 02:46:25 PM
Just curious.  How do you know for sure it's just the #3 cylinder that's missing?
Title: Re: Low compression tuning?
Post by: Hwy 49er on March 03, 2012, 01:04:46 PM
Have you tried going to the hotter range plug (DR7EA) Not saying that will cure it but its one more idea to throw in the mix.

No. I'll give it a try if it can't hurt anything.
Title: Re: Low compression tuning?
Post by: Hwy 49er on March 03, 2012, 01:06:10 PM
Just curious.  How do you know for sure it's just the #3 cylinder that's missing?

I read my posts and don't see where I said #3 is missing.
Title: Re: Low compression tuning?
Post by: jworth on March 03, 2012, 05:27:29 PM
Ok, smarta**, #2.  Question still stands.
Title: Re: Low compression tuning?
Post by: Mettler1 on March 03, 2012, 06:56:45 PM

  Who's the smarta$$?? :o
Title: Re: Low compression tuning?
Post by: Hwy 49er on March 04, 2012, 10:17:07 AM
Have you tried going to the hotter range plug (DR7EA) Not saying that will cure it but its one more idea to throw in the mix.

Could you explain why?

Are you suggesting just running the DR7EA in the #2? Because of the lower compression (cooler temperature)? Does lower compression=lower temperatures? I would guess that the DR8EA would show some dark carbon if the plug is too cold. The #2 and #1,3,4 plugs were golden brown last time I changed plugs about 4000 miles ago after installing SISF 2 minute mod w/ power jetting.

Or, are you saying to put them in all four because of other factors like low-speed riding, or rich mixture contributing to cooler temps?
Title: Re: Low compression tuning?
Post by: jim snyder on March 04, 2012, 10:43:32 AM
If the plugs are golden brown then leave them alone that means real close on jetting. I was only suggesting the hotter plug if you might have been experiencing any plug fowling issues in the lower compression cylinder. If you could do a leak down test on all four cylinders that would tell you alot. If a little carbon is stuck on the valve seat it could cause your one cylinder to have lower compression.
I would have bet it was a tight valve but you mentioned that you adjusted the valves already.
Title: Re: Low compression tuning?
Post by: jklhill on March 08, 2012, 03:13:02 PM
You say "lots of missing" but you don't give any details. Is it all the time and throughout the entire rpm range? Or is it just at idle? Does it change as the engine warms up? What about at wide open throttle?
Title: Re: Low compression tuning?
Post by: Hwy 49er on March 12, 2012, 02:19:57 PM
You say "lots of missing" but you don't give any details. Is it all the time and throughout the entire rpm range? Or is it just at idle? Does it change as the engine warms up? What about at wide open throttle?

The missing is most noticeable at idle and low speed cruising. Enough to make the bike feel like the the final drive is bouncing at the soft coupling. At highway speeds it is very faint. It is not as severe as if you just pulled a wire and it was no spark missing. More like missing because of vacuum, intake boot, insulator, or dirty filter.

At idle it would no be: brrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

More like: brrrrrbabrrrrrrrrrrrbababrrrrrrrrrrbrrrrrrbabrrrrrrrrrrrrrbrrrrrrrrrrrbrrrrrrrrrbabrrrrrrrrrrrrr
Title: Re: Low compression tuning?
Post by: jklhill on March 12, 2012, 03:16:43 PM
A quick guess would be dirty carbs. You might want to give them a thorough inspection and cleaning. I did read that Steve had them about 5,000 miles ago but carbs can get dirty and jets/orifices clogged a lot quicker than that. I could be wrong but if it were my bike I would want to eliminate the possibility. jmho
Title: Re: Low compression tuning?
Post by: Hwy 49er on March 12, 2012, 09:05:01 PM
A quick guess would be dirty carbs. You might want to give them a thorough inspection and cleaning. I did read that Steve had them about 5,000 miles ago but carbs can get dirty and jets/orifices clogged a lot quicker than that. I could be wrong but if it were my bike I would want to eliminate the possibility. jmho

I wish I had a set of carbs to throw in to check.
Title: Re: Low compression tuning?
Post by: jklhill on March 12, 2012, 10:09:36 PM
I wish I had a set of carbs to throw in to check.

I hear ya