Z900A4 running rough

[sprint]

Are you totally happy with the valve clearances and timing. Sounds like it could be a tooth or two out? Just a thought!

Valve clearances are fine, all between 0.1 and 0.15. Did enquire here that the timing was OK which it was deemed to be. Chevron at front just above top of head and rear one just below. When turned over by a couple of cycles marks come back the same. If they were moved by one tooth the front would be just below and rear just above.

[sprint]

What about between the carbs and the head are you sucking air there ? 😊

As far as I know there are no leaks between carbs and head. Vacuum gauges readings are OK, but 1 and 4 seem to be running slightly weak and 2 and 3 sightly rich.

[sprint]

ive had lots of bad ngk plugs so I got denso..much better and not off ebay www.sparkplugs.co.uk get the carbs right as well.also is the fuel cap breather clear.

Have just fitted a new pattern cap from Saisei, so can't be 100% sure that it is breathing OK but I have problems from the go. If it were a breather problem I would expect it to get worse as time goes on and a partial vacuum is created in the tank reducing the flow and I don't get a sudden rush of air when it is opened?

[Mowjoe]

Are you totally happy with the valve clearances and timing. Sounds like it could be a tooth or two out? Just a thought!

Valve clearances are fine, all between 0.1 and 0.15. Did enquire here that the timing was OK which it was deemed to be. Chevron at front just above top of head and rear one just below. When turned over by a couple of cycles marks come back the same. If they were moved by one tooth the front would be just below and rear just above.

I still think it's worth checking your valve timing again. You don't sound convinced that its correct and it needs to be Mine was a tooth out on exhaust and was not that bad running and only noticed when doing valve clearance check. My exhaust cam has no marks on it so I used this info from Z1bman using the cut outs on the end of cams. It worked for me.

if you look at the end of each camshaft you will see a section cut out from from the cam. with the engine set to top dead centre on 1&4 cylinder half of this cut out section should be below the cylinder head mating surface when the valve timing is correct. inlet cam cut out should be facing towards the rear & the exhaust cam cut out should be facing foward.

[sprint]

Are you totally happy with the valve clearances and timing. Sounds like it could be a tooth or two out? Just a thought!

Valve clearances are fine, all between 0.1 and 0.15. Did enquire here that the timing was OK which it was deemed to be. Chevron at front just above top of head and rear one just below. When turned over by a couple of cycles marks come back the same. If they were moved by one tooth the front would be just below and rear just above.

I still think it's worth checking your valve timing again. You don't sound convinced that its correct and it needs to be Mine was a tooth out on exhaust and was not that bad running and only noticed when doing valve clearance check. My exhaust cam has no marks on it so I used this info from Z1bman using the cut outs on the end of cams. It worked for me.

if you look at the end of each camshaft you will see a section cut out from from the cam. with the engine set to top dead centre on 1&4 cylinder half of this cut out section should be below the cylinder head mating surface when the valve timing is correct. inlet cam cut out should be facing towards the rear & the exhaust cam cut out should be facing foward.

[sprint]

Thanks for replies.

I do feel reasonably confident that the valve timing is OK but clearly do not exclude that it may be part of the problem?

Changed the plugs and took it for a ride and there was no change, poor pick up '8' stroking etc.

Stopped to check the plugs and noticed that with the engine running pulling off No 1 plug cap made little difference to the running though you can hear the spark jumping from the cap to the plug from about 1cm away. Tried all the others and it more or less stalled as soon as you pulled the respective caps off.

No 1 exhaust pipe mildly warm that you can hold with your hand all the others too hot to touch.

Changed No 1 and 4 plugs over and it made no difference, so not a plug problem. Got it home and tried another cap, no difference so not a cap problem.

Swapped the coils over, still no difference so not a coil problem?

At tick over speed pulling the cap off No1 does make a difference but at revs above 2K pulling the cap makes no difference?

Indications are that it is not getting any fuel? When you take the plug out it is not wet?

So what am I looking for? When I got the bike it started and ran sweetly and picked up cleanly when the throttle was opened, though I never took it for a ride. All the carbs have been stripped and all the jets, valves etc ultrasonically cleaned as the bike had a known history of running rich. I injected alcohol though all the body orifices followed by air from a foot pump, so I am at a bit of a loss as to why No 1 would not appear to be getting any/sufficient fuel?

Any suggestions as to what I am looking for. I can get to No 1 carb fairly easily with respect to the jets and valve etc and don't want to be pulling them all off again unless I have to.

When I opened the drain screw fuel come out so the valve would not appear to be sticking?

[Pigford]

Whip the plugs out and turn engine over (kickstart) with thumb over each plughole... see if No.1 feels same as others.

[paulmceleney]

I would remove the pilot jets and clean this happened to me on my z900, it also could be a loose battery lead check, or valve timing I spent hours messing about with carbs and jets to find out the battery lead had came loose check battery lead first

[z1bman]

check the valve clearances & do a compression test

[sprint]

Thanks for the replies.

Well it was the pilot jet in No 1. Clearly picked up something since they were cleaned.

Fitted a new one and problem solved. Still a bit rough on tick over, but I will put a few miles on it and then check the ignition timing and carb balance but after a week of hassle it's good to have it finally running.

Only problem now is that one of the spark plugs threads had an insert which has come out with the plug. This happened to my RGS I thought that the ends were supposed to grip the end so they could not be removed?

Screwed it back in again so hopefully it just requires another insert being put in?