Z900A4 carb set up

[Stagman]

Hi guys,

Recently bought an A4. Its a US import but not a KZ. After warm up its very flat picking up from idle, often dying when pulling away. Its spitting back thro no 4 Carb, so assume its unburnt fuel. I can see it doing this with the carb tops off during balancing, witnessed by a flame in the carb body accompanying the spit back. Apparently the carbs were ultrasonically cleaned and rebuilt with new jets just before sale as it had been stood for many years. Looking at the plugs, all cylinders are running rich. Once underway it runs ok.
So, I've removed the carbs and on checking i have the following.
1. 113 instead of 115 main jet fitted. Strange that its rich with smaller mains? Pilots are correct though
2. The float heights are between 24-27mm from the gasket face. I have found a thread on here stating 22mm from carb body face but that just doesnt seem or look right to me as its such a big change from existing. I've also found other info elsewhere stating 24-26mm from carb body which seems more like it. I prefer to use the fuel height check process as at the end of the day thats what matters. Strange that if 22mm from carb face is correct then that would make it run even richer if i changed to that dimension?
3. So my humble question is can anyone please point me in the direction of the definitive official kawasaki factory carb setting specs for an A4? I would like to start from fresh and check everything - needle positions, fuel level etc.
4. I saw some advice on making a fuel height measurement tool from aquarium tubing - does anyone have anymore tips on making such a tool please? The thread size and type would be a good start if anyone knows?
5. Finally am i correct in that vacuum pull adjustment on an A4 is through the carb tops as i cannot see any other method available?

Oh and btw all shims are at correct tolerances

A thousand thanks in advance guys!
Mark

[Al]

Hello Mark, i'm sorry i dont know youre carbs or the answer to youre question but spitting back through the carbs can also be a function of a weak condition. In youre case this could perhaps be wrong jets (a mix of US and UK market items), poor quality after market replacements, fuel height or maybe air leaks. Despite the fact that the plugs show up rich and the mains are apparently too small the transition from each section of the carbs needs to be seemless and in order to correct the low running issues, other steps may have been taken to rectify / off-set this which have not worked well. The true size of the main jets will not be apparent until the jet needle is clear of the needle jet at 3/4 throttle and above so making judgements about main jet mixture strength will be misleading unless you run it at 3/4 throttle for an extended period and cut the engine. Even then, it will depend on any number of other factors like heat range of the plugs and the amount of timing advance you are getting, compression ratio etc etc.
I believe that fuel height gauges (plug and tube) for some models are readily available (ZPower etc.)
Later https://www.z-power.co.uk/carb-float-height-tool
Early https://www.z-power.co.uk/carb-float-height-tool-z1z1a

AL

[Stagman]

Thanks Al, much appreciate the effort in replying.

Regards

Mark

[Philippe]

Hi Mark

I would suggest that you buy 4 Keyster carb refurb sets for your Z900A4, dismantle the carbs completely, clean them ultra sonic in the correct way( US cleaning with ALL the parts removed from the carb, after cleaning, rinsing it under water, blowing compressed air through all the little channels in the carbs) , putting the new parts in the carbs, synchronise them statically and set the float height correct using the float height gauge. The slides must be synchronised from the top of the carb. Loosen the two M5 bolts when setting the slides equal, once the slides are all correct, fasten these two M5 bolts.
If all these things are done correctly, check out the rubber admission parts between the carbs and the cylinder head. If those are old, replace them with new ones. Make sure that the connection between the cylinder head and the rubber is air tight.
All these things, provided they're done properly, should cure the problem.
If it still blows back through the carbs, check the camchain timing (one dent off can make a huge difference but the engine will run)
and finally check the ignition timing.
If you have no experience in doing this yourself, find a good mechanic who knows the old engines and is able to work with them.
If you want to learn it yourself get an original Kawasaki workshop manual. It's all explained in there, step by step.
Good luck!
GrtZ
Philippe

[Al]

From the Kawasaki parts catalogue

AL

[Stagman]

Many thanks for the excellent reply. Is there any point in doing the static slide set up when i always balance the carbs dynamically after installation anyway?

Thanks and regards

Mark

[zed1015]

Many thanks for the excellent reply. Is there any point in doing the static slide set up when i always balance the carbs dynamically after installation anyway?

Thanks and regards

Mark

Not really if the slides are somewhere close to each other.
The main thing is to ensure that they are mid range on the adjusting screws so they don't top or bottom out when syncing.

[Stagman]

many thanks for the reply. Great links attached - will find some time to enjoy those!

[Ultim8pc]

Just seen this post as I have been away on holiday.
If you get stuck get in touch, I'm happy to offer advice. I have refurbished/rebuilt lots of Z900 carbs.
I also supply Keyster rebuild kits, spares and gaskets.

[sprint]

Just seen this post as I have been away on holiday.
If you get stuck get in touch, I'm happy to offer advice. I have refurbished/rebuilt lots of Z900 carbs.
I also supply Keyster rebuild kits, spares and gaskets.

Can you clarify the static float height for the Z900A4's with the 26mm carbs as some state 26mm and others 22mm, which is correct?

Thanks

[zed1015]

Just seen this post as I have been away on holiday.
If you get stuck get in touch, I'm happy to offer advice. I have refurbished/rebuilt lots of Z900 carbs.
I also supply Keyster rebuild kits, spares and gaskets.

Can you clarify the static float height for the Z900A4's with the 26mm carbs as some state 26mm and others 22mm, which is correct?

Thanks

Just do them at 24mm to 25mm it'll be fine.

[sprint]

Just seen this post as I have been away on holiday.
If you get stuck get in touch, I'm happy to offer advice. I have refurbished/rebuilt lots of Z900 carbs.
I also supply Keyster rebuild kits, spares and gaskets.

Can you clarify the static float height for the Z900A4's with the 26mm carbs as some state 26mm and others 22mm, which is correct?

Thanks

Just do them at 24mm to 25mm it'll be fine.

Thanks

[sprint]

Just seen this post as I have been away on holiday.
If you get stuck get in touch, I'm happy to offer advice. I have refurbished/rebuilt lots of Z900 carbs.
I also supply Keyster rebuild kits, spares and gaskets.

Can you clarify the static float height for the Z900A4's with the 26mm carbs as some state 26mm and others 22mm, which is correct?

Thanks

Just do them at 24mm to 25mm it'll be fine.

Perhaps you could follow my Z900A4 float levels post and advise as setting the float heights to 25mm fails the 'wet' test by a high margin.