Won,t run off choke

[BFC]

Al,

Thanks for the info.

When I throttle it from the carbs it cuts out just the same as throttling from the handlebars.

It certainly does surge when started on choke, prob up to about 5k then dies back quickly. The choke can actually control the engine revs until the bike warms up. I can get it to a steady tick over using the choke but it will cut out in time. If I was starting from scratch blocked jets would seem to be the most likely cause but I know they are perfectly clean as they were when I first checked them.

The bike had been standing for some unspecified time before I bought it. According to the previous owner it was running well when he laid it up. When I first got it started the only smell was burning everything. Since then it smells as similar z's did 30 odd years ago. That is of course if my memory is holding up. Don't see much from the exhausts to be honest, maybe a little white smoke when i kept it struggling on with full choke and the bike up to temparature. Only very slight though.

Throttle screw seems to work normally. If I use it to increase revs too much the engine stalls.

Doesn't have a prime on the fuel tap. The tap has been thoroughly cleaned

How do I measure the carbs? If it's the diameter of the throat on the engine side the they're 28mm. As it's supposed to be a Z900 shouldn't they be 26mm?

Ill try to block off each inlet in turn and see if it tells me anything.

Once again thanks for your advice. Although this problem has been somewhat frustrating i'm still enjoying the challenge.

[Al]

Making the assumption that everything checks out OK as above in this thread; the only thing you have hinted at that deviates from normal is the size of the carbs.
Just had a look at the manual for Z900 (supplement in Haynes copy) on my computer and it says 26mm for that model. Though to be honest i am not at all familiar with the early bikes.

Question then; what are the jet sizes in your setup?

Are we looking at high comp pistons, or lumpy cams, or big bore kit and therefore uprated carbs?

Or is it possible that the carbs themselves are just wrong!



AL

[BFC]

Checked the fuel level in the carbs when bike not running. All look to be at the right height. Also checked when running. Fuel level dropped when choke put full on and didn't recover. Level dropped further when I reduced the choke and also didn't recover. As mentioned at the Berks meet i'll put these carbs in for ultrasonic cleaning now. Anyone know a good place to take then not too far from Maidenhead?

[kev edwards]

If the fuel level is not recovering itself quick enough in the bowls it's a possibility you are suffering fuel starvation and picking up air as suggested by Russ , but sticking needles may well be restricting fuel flow , check the needle valves , on my one when i replaced them with new ones a couple of them were sticky , i gave the three ribs on the valve needles a quick rub with 1000 grit wet and dry, problem solved free moving float valves , but don't over do it just a cuple of light strokes down the ribs on each one , this may be the answer to the problem.
Good luck with the project. Kev

[Al]

http://www.ultrasonicclean.f9.co.uk/

These are at the Godalming end of Guildford. No idea if they know what they're doing but could be worth a ring to see.

http://www.google.co.uk/search?q=ultrso ... =firefox-a


AL

[BFC]

Thanks for the advice chaps, i'm slowly eliminating the potential causes. Just discovered the needle jets are for a Z1R (according to clymer). The carbs are 28mm (if they are measured from within the throat). I suppose that suggests Z1A,B carbs with Z1R needles. Based on that info (if i'm right of course) anyone know what height I should set the floats? as in set the floats against the needle size or against the size of the carbs. They are currently at 22mm. Next step is to give it a go at 26mm. Any advice much appreciated as always.

[DogsbolloxofZ1B]

Send the carbs over to me & I'll take a look, I have oodles of spare parts so shouldn't be a problem. (I'm over in Eastcote or you could drop them off with Bedlow in High Wycombe).

Sounds a little like the slow running jets aren't playing ball, if you have good vacuum, adequate fuel level then these should operate upto 1/4 throttle. Difficult to comment without seeing them.

Mike
07515 367071

[Yellow]

Hi BFC
Had same problems fitting Z900 carbs to a Z1000 engine, heres how I got it running.

1. Raised needle to second last position.
2. Adjusted float height on each carb very slightly.
3. Opened air adjuster to 4 turns out as apposed to 1&1/2 as per the manual.
4. Adjusted slide height as per manual(approx 2mm)ensuring all are the same height when viewed from inside the intake side.
5.. Put all back together and sealed up carbs and airbox clamps.

Bike started up and is ticking over off choke, even drove it 10 yds to confirm,
will readjust air adjusters and re-balance as necessary.

As I said this worked for me, hope it helps with your bike.

[BFC]

Thanks chaps,

Anythings worth a try.

[BFC]

Problem finally solved. It seems that the carbs on my Z900A4 are actually off a Z1000A2. The carbs have been refurbed and the appropriate jets and needles have been fitted (Thanks Mike, top job). I've waited 30 + years to ride my own Z and i've just done it this evening. Unbelievable feeling. I'd forgotten how quick these bikes are

Thanks for all the advice on this forum chaps it's been invaluable. Thanks also to Guy and the Berks meet lads for putting up with me whining about my blxxdy carbs each month.

For those novices (like me) who suffer similar probs with carbs, start by confirming that you actually have the right carbs for the bike and the jets and so on are correct. It was something mentioned to me months ago by Zorded (Al). Sound advice which if followed would have saved me considerable heartache.

[HARRY4448]

Well done mate.


What a Godsend the club really is.


I had images of you taking the bike to a Kawasaki dealer and being told you needed new carbs and having to empty your bank account to pay for them.

Or chucking the bike off a cliff.

So pleased you're on two wheels again.

[GUYZED]

Great news BFC - the carbs looked the muts nuts in the back of your car.

So glad you got it sorted out in the end.

[DogsbolloxofZ1B]

Blimey you don't hang about! Glad to hear the bikes running well.

Mike