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Kz900 won’t rev over 3k

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z1bman
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Re: Kz900 won’t rev over 3k

#16 PostAuthor: z1bman » Wed Jan 01, 2020 11:40 am

cam timing should look like this note the position of the cutaways in the end of the cams
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zed1015
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Re: Kz900 won’t rev over 3k

#17 PostAuthor: zed1015 » Wed Jan 01, 2020 12:28 pm

Nick.s wrote:I just had a look at the carbs and there is a number on the engine side flange, it’s hard to see but the offside carb has 299 04 or 01 it’s hard to see. Does this help with id?

I have six sets of these hanging up and another couple in bits and every one has different numbers, even those from the same model and year .
They are factory markings and most likely denote, batch, month, year and possibly build spec etc.
I doesn't really make any difference as all the bodies are the same like for like and they are only jetted differently to suit whatever model they were used on because of the varying styles of exhausts and airbox fitted.
All you can tell without taking them off is that fuel mix screw means 26mm.
Whether they have been bored out or modified is another story.
These can be bored out to a max of 30mm as I did in my Café build thread.

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Re: Kz900 won’t rev over 3k

#18 PostAuthor: Nick.s » Wed Jan 01, 2020 2:26 pm

Quick update, I took the rocket cover off, counted from above the arrow “29” teeth to the 28 mark :biggrin
What a plonker :down. Hopefully that will do the trick, I can’t finish it until Friday, so will keep you informed.

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Re: Kz900 won’t rev over 3k

#19 PostAuthor: kev edwards » Wed Jan 01, 2020 5:54 pm

Do they have a vacuum stub on number 3 carb, if so the chances are they are thou A2 carbs if not they are possibly B 2 carbs i have a set of each with the difference being the vacuum stub and pilot jets being much longer in the B carbs and accelerator pump models for the A3a thou.

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Re: Kz900 won’t rev over 3k

#20 PostAuthor: Nick.s » Wed Jan 01, 2020 7:39 pm

There are vacuum stubs on all carbs. I’m pretty sure they’re z1000 1977 probably 26mm I expect I measured them wrong. :hah!

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Re: Kz900 won’t rev over 3k

#21 PostAuthor: kev edwards » Wed Jan 01, 2020 8:38 pm

should only be 1 vacuum stubb on number 3 as the drilling goes into the carb throat, others are vents and drilling's go into carb bowls.

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Re: Kz900 won’t rev over 3k

#22 PostAuthor: Nick.s » Thu Jan 02, 2020 3:10 pm

I can’t see a vacuum stub on number 3
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Re: Kz900 won’t rev over 3k

#23 PostAuthor: zed1015 » Thu Jan 02, 2020 4:48 pm

They are not vacuum carbs so you don't have a vacuum tap do you ? (unless you are running the vac tube from one of the intake rubber balance ports)
The stubs on 2 and 4 are float bowl vents and should just have a short open ended tube to the atmosphere on them.

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Re: Kz900 won’t rev over 3k

#24 PostAuthor: kev edwards » Thu Jan 02, 2020 8:05 pm

So to hazard a guess from the jetting you have in them, they are probably 78/79 26mm ltd carbs, look out for leaks around number 1 overflow once you get them back on and running..

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Nick.s
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Re: Kz900 won’t rev over 3k

#25 PostAuthor: Nick.s » Fri Jan 03, 2020 1:14 pm

Well I’ve just set the valve timing properly, and checked the ignition timing. It’s still the same, all ok to 3 k revs then it splutters and won’t go any higher unless I back off the throttle then I can ease it up a bit :sad
What to check next? Could it be carb problems or electrical?

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Re: Kz900 won’t rev over 3k

#26 PostAuthor: Gus » Fri Jan 03, 2020 2:29 pm

Hi Nick.

Whereabouts are you? I am in Tewkesbury.
"Set the GRINDER on it"

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Nick.s
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Re: Kz900 won’t rev over 3k

#27 PostAuthor: Nick.s » Fri Jan 03, 2020 2:44 pm

Near Wotton-under-Edge, about 30 mins.
I’ve just taken the plugs out and they are really black sooty, looks like it’s running really rich. I’m trying a new set of coils just in case it’s that.

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Re: Kz900 won’t rev over 3k

#28 PostAuthor: z1bman » Fri Jan 03, 2020 4:30 pm

it does sound like a coil breaking down

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Re: Kz900 won’t rev over 3k

#29 PostAuthor: Nick.s » Fri Jan 03, 2020 4:34 pm

New coils fitted, no joy :sad

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Re: Kz900 won’t rev over 3k

#30 PostAuthor: zed1015 » Fri Jan 03, 2020 4:39 pm

Does sound over rich.
Have you checked the carb mouths for Air corrector jets.
if they are fitted when using the airbox it will cause this.


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