intermittent breaking down at revs... Kawasaki 1000GTR

I thought I'd throw this one out to the collective masses. Not an XJ problem but of similar vintage... a Kawasaki 1000GTR or as some of you guys would know it, Concours C10.

I'm trying to determine where the problem lies, fuel or ignition, so...

The engine itself is fine. Valves are fine. Carbs on these things don't generally give trouble (Keihins) although I did have them out for a clean 18 months ago.
I use a ryco in line fuel filter as the tank does have a little rust in it.

I've recently replaced the pickups as one had failed.... moment the bike got hot it would break down with all the grace of a demented demon having a hissy fit, backfiring and losing power.

I have fitted new plugs and also stick coils to the bike from a ZX6R , a fairly common mod on the GTR. I am also going to look into this on the XJ an see if it is a feasible mod.

That's the bike in a nutshell. The problem is this.....

Ride for about 40km at highway speed (bike is now heat soaked) and it won't rev over about 4500rpm. You can roll the throttle all the way to the stop and it just won't accelerate.
It almost feels like it is out of fuel but is intermittent. It'll pull like a demented angel from one intersection and fall on its bum at the next. (rev cleanly to about 4k then won't go any further)
Let the bike cool down for a couple of hours and it comes good for another 40km....

Oh, and to annoy me further, the bike will rev nice n clean in the shed....

My thoughts still tend to ignition.

open to ideas, suggestions and opinions... on working out fuel or ignition problems

 

If seems to run well (no backfiring, obvious miss, etc.) but just runs out of power as the RPMs go up you can almost bet the ignition advance isn't there.

 

May not be related but I remember some 900r's had similiar symptoms with blocked tank air vents.Easy enough to tick off the list.

 

I was with Carl and the timing until I backed up to ask a couple of questions first......has this come up all of a sudden or has it gradually gotten worse and worse? If all of a sudden, what reference did it have with the installation of the fuel filter. Some don't flow very well, at all!

Also, does it run consistantly all the time...even if it's running bad, does it run bad all the time or is it only when hot? If so, look at the timing base, if cracked, it will do exactly what yours is doing.
The more info you can post, the more help the forums can be for you.

jeff

 

My guess -- It is, for some reason, top-end (i.e. main jets), too rich -- They richen up as they heat up... (Both ambient temp and bike temp and humidity makes for richer runs). I personally wouldn't guess that it's electrical (exception: timing). When you cleaned carbs did you reset float levels? Did you "clean" out jet holes or emulsion tube "holes".

To validate this theory (uber rich occurring when hot) plug chop at the higher revs when this occurs or "just before" it occurs to see what kind of ratio you have at the higher revs (i.e. up on the mains).

Hope this guess helps

 

Thanks for the replies gents.

I'll address each item as best I can.
Fuel filter Ryco Z91 (very common filter parts here in Aus) .... been fitted since I've had the bike (+15000km .. changed as required of course). No probs with fuel flow. Tap is good too.
Carb float levels are fine. Wet set last time I did them. The Keihins are no where near as problematic as the Hitachis. There was a small amount of fine sediment in the bowls but nothing to write home about.

My thoughts is that carby problems will happen hot or cold. It only breaks down when its hot/heat soaked after 40km or so.

The ignition timing is a valid point and was discussing this with a couple of mechanics yesterday. They both said change the black box. I have a spare so no probs with that.
reason is that the ignition timing is built into the box and the symptoms are similar to that of loss of timing.

I will change back to the standard coils this weekend and try that just to make sure one of the stick coils isn't failing with heat soaking.

Hopefully it will be dry on the weekend so I can test ride.

Its cold and wet over here at the moment as we're in the middle of winter so all moves a bit slower...

It is an intermittent problem so more difficult to find. One set of lights it'll be good, next set... buggered....

 

Usually coils will first show failure under load, not necessarily heat soaked.....sure sounds electrical though.....which is actually a good thing....change a part, all fixed!

jeff

 

OK, well, maybe pull the plugs, when it has died to be confident that you can eliminate a fuel mixture issue... Just a suggestion to factually eliminate a possibility.

Sounds like your organized and on the right track, I am curious to find out what it is too

 

I did have the bright idea of putting a damp rag on each exhaust header to see which one was cold or at least cooler than the others.
Unlike an XJ which has exposed headers, the GTR has its headers buried behind a radiator... another idea buggered ....

Pulling plugs while its running don't happen either cause they are buried deep under the tank.... :-( and by the time I get to them..... its self corrected ***bangs head against wall****

The most frustrating thing is the bloody thing behaves perfectly in the shed

Hail XJ's :-D

 

Well, not to press this because I could be wrong, but a "plug chop" would entail allowing it to heat up till running poorly, and after it shuts down or runs sloppy (you kill it) -- then pull the plugs -- to see what's going on in the cylinders...

 

I did have a look at all the plugs when I got home and nothing surprising in there. I was kinda hoping to find a majorly sooted up plug or something but alas, no cigar....
Because of the intermittent nature of the beast, I will do a chop but probably as a last resort.... it generally plays up where I can't just kill it and having a chair on makes it more difficult to just park :-/

 

OK, it stayed dry enough for long enough to sort through issues.

I swapped the stick coils back out for the standard coils then took it out for a 60km flogging.....

It would appear to be problem solved. No hints of breaking down at all .... bloody bikes ....

Thank you all for your suggestions. Its problems like these that help us learn our diagnostic skills.

Next I get to start work on the XJ