Fuel issues - carb problem or something more serious?

[PAULJAC47]

Hi Jon, time to start from scratch here,you have ruled out the carbs,your shim clearances would not affect it that much,too much is better than too tight.
Start with basics Plugs(new Denso),ignition timing,valve timing(has it jumped a tooth?)good fuel flow(cap breather not blocked)fresh fuel,all carb rubbers soft, tight,making good seal and not split,spray wd40 around them to see if makes difference,your psi seem spot on but if you can get a leak down test done its far more indicative i have known bikes give good compression readings but show up probs with a leak don test,go through these checks and come back,keep at it mate.just a last thought i know you are running dyna coils but if you still have points change the condensors....Paul J

[pertonpc]

Hi John,
Sorry about you problems mate.

If you have a spark on all plugs you can eliminate them as the issue if you just swap the plugs from the good hot cyls to the two poor ones - if the problem moves it suggests plugs, if it stays where it was you can leave the plugs alone.
It cannot be a complete coil failure or the black + green wires into the coils, or you would be seeing 1+4 or 2+3 affected.

Fingers crossed for you to sort it out soon. From Mark

[JohnC]

Cheers guys.

Update, number 2 is deff defunct as well, had the bike running for 5 minutes and neither 1 or 2 pipe is even getting warm. It's really wierd but I was sure at one point I was getting either 1 or 2 working for a bit, but not both together. If it were a carb problem then I'd have suspected that changing the carbs might have affected difference pots if anything, not the same ones. The bike ran great with the Gixxer carbs and they haven't been sitting about for long.

Changed out the shim and all clearances are .10mm, i.e. spot on.

Changed plugs for new NGKBR8ES, all I could get locally.

All sparking bang on.

All carb rubbers fine m8, bearing in mind I've had both the standard carb inlet rubbers switched out for the GPZ11 ones I need for the Gixxer carbs and the change of carbs made not a bit of difference.

Peter, what would make the timing chain jump a tooth. I've a billet manual cam chain tensioner and I've have thought this could only happen with say a dodgy automatic tensioner? For what it's worth even when running on only 2 cylinders the bike ticks over and is smooth (ish) sounding when it's being revved.

When I spray carb cleaner into three and four carbs the bike starts to stall as you would expect, when I spray carb cleaner into 1 and 2, nothing, i.e. no suction.

Even though the compression seems fine (it was actually highest in No 1 cylinder) I'm now suspecting valves. Does anyone else now think valves?

I really cant be arsed with stripping down the bike to look at the valves, our summer is short enough and I don't have the time or inclination I used to have for engine work, so I think it will be a motorcycle transport service down to Debbens, unless anyone can recommend a similar company up here with a good rep

[PAULJAC47]

Jon as a last test make up, a leak down tester from an old spark plug screwing an air line in,screw into cylinder when piston is a tdc ie when both valves should be shut look at the gauge to see if pressure drops if it does put,your ear at the exhaust and see if you hear the air escape if so exhaust valve issue,repeat for carb inlet if so inlet valve,repeat for all pots ,you can buy these but i have used this method with some success,trouble is once you send bike in for repair its out of your hands,double check those carb to head rubbers if they are leaking even a little will affect induction of fuel..All the best Paul J

[lude]

a few crazy ideas : saves on sending bike many hundreds of miles

how about a quick look with a colour tune (least he should see it sparking)?

what exhaust have you got (blocked / restricted on 1+2 )?

try running it in a dark garage lights out , is there any arcing ?

[JohnC]

Cheers guys for all the help.

I'm definitely thinking bent valves now. My hand was in plaster a few months back and a m8 said he'd check over the shims for me. Thinking back (I wasn't paying that much attention as he'd carried out this sort of stuff in the past) I reckon he's used the cam lobe to hold open the valve, inserted the wee shim tool to hold open the valve, and then he's rotated the cam round fully clockwise while the other valve was still open and bending it, rather than just rotating the cam back round anti-clockwise if you know what I mean.

I don't want to ask him as this is a total schoolboy error of checking / replacing shims, and knowing him he'll never say he made such an easy mistake.


John

[ZedHead]

Cheers guys for all the help.

I'm definitely thinking bent valves now. My hand was in plaster a few months back and a m8 said he'd check over the shims for me. Thinking back (I wasn't paying that much attention as he'd carried out this sort of stuff in the past) I reckon he's used the cam lobe to hold open the valve, inserted the wee shim tool to hold open the valve, and then he's rotated the cam round fully clockwise while the other valve was still open and bending it, rather than just rotating the cam back round anti-clockwise if you know what I mean.

I don't want to ask him as this is a total schoolboy error of checking / replacing shims, and knowing him he'll never say he made such an easy mistake.


John

What type of shim tool did he use? I don't think you can the cam shaft fully with a standard tool fitted. Unlikely to get 150 PSI with bent valves.

[JohnC]

Hi m8, it was the wee skinny one like this: http://www.ebay.co.uk/itm/Kawasaki-Z100 ... 3a81d8ccb1

He couldn't use the supplied tool to compress the springs as I'm running HD valves springs and the wee wedge tool wouldn't even look at compressing the HD springs.

As the tool for holding open the valve sits within the curve of the inner cam surface this means that the cam could easily rotate round 360 degrees no problem.

I'm at a total loss if it's not valves now, nothing else I can think of would be giving me the same symptoms, what with with new coils, new plugs sparking away merrily, 2 sets of different carbs and shim clearances all at .10mm.

I'm ruling out timing issues as I run a manual tensioner as the bike runs and ticks over well(ish) even when only running on only 2 cylinders.

[zman]

This may help as this has just happened to me.
by telling you i know im opening myself to a bit of piss taking.But what ever.

So here goes i will keep it sort.put new values seals & plugs in then started bike.wasnt firing on 4 running shit.
checked timing.good checked carbs good checked all electrics good
got fuel & spark.
Must be compression.test all & good

put plugs in,started bike 4 working 2 not
leaking past plugs.Even though i tightened them to what felt safe i tried to tighten them a bit more.2 turned 1 more turn & the other 3 about 1/4.
After 2 days now sorted

[ZedHead]

Hi John, I have never used one of these tools but i can see now how you could turn the cam through 360. I still can't see it being valves if you are getting 150 PSI also you must have suction on 1 and 2 to build this kind of pressure?

[floydsz1]

try pulling number 1 plug cap (with the engine running) off so its not actualy clipped onto the plug (if this is the cylinder you think is'nt firing). but leave the cap still over the plug, and try the same for the other cylinder thats not working, see if it starts to fire, you will hear it. you wont get a shock, well i never do, use a pair of plyers if your scared
This gives the plugs an extra boost. often my bikes only fire on 3 when left for a while, doing this makes the plug start to fire and after a min or two push it back on. The plugs can spark ok when out of the head but when under load they often fail.

[JohnC]

Thanks again for all the help folks.

Quick update: Craig (oldzed) from the club drove down from Glasgow last night to help me diagnose the problem (a fair drive I might add). Cheers again Craig!!

Craig brought a home made leak down tester with him and we checked all the cylinders. I'm glad to say they all held pressure ruling out bent valves etc.

We managed to get the bike firing on all 4 pots after putting in some old densos I had lying about, but pot number 2 still isn't 100%, but still much better than before and the bike was sounding relatively fit.

Craig reckons the carbs might need some ultrasonic cleaning. I had ruled out carbs as I was having the same problem with the Gixxer carbs I originally had on the bike. With this in mind I've also ordered up some new Dyna HT leads as the silicon Taylor leads on the bike are about 10 years old now so may have degraded a bit over time.

Hopefully I'll yet catch a bit of our summer riding weather!!!

John