Gpz900 stutter at 6k and lack of high end power

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:08
#789255
I have worked on cars for many years of my life and I have gotten pretty good at valve adjustments. I'm confident that the valves are adjusted as good as can be. compression is also consistent across all four cylinders at about 170psi. Installed a new cam chain adjuster and the motor does not burn any oil or smoke.

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:10 - 18 Aug 2018 19:11
#789256
Well now it's in your hands and that's good. If he still has the old jets that the mechanic changed try to get them. Or if he remembers what they were, or if someone has a similar bike with a working setup.

It'll be fun for you to figure this out.
Get your motor running!

84 GPZ750
81 R100RS
83 GSX750ES
80 KZ1000 LTD
Last edit: 18 Aug 2018 19:11 by Togoster.

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:11
#789257
Yeah, it's likely the valves are fine with that
Get your motor running!

84 GPZ750
81 R100RS
83 GSX750ES
80 KZ1000 LTD

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:12
#789258
That's a good baseline, plenty of compression means plenty vacuum.
Get your motor running!

84 GPZ750
81 R100RS
83 GSX750ES
80 KZ1000 LTD

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:15
#789259
Try to do that chop and then post plug pics okay?
Get your motor running!

84 GPZ750
81 R100RS
83 GSX750ES
80 KZ1000 LTD

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:21
#789260
I like to re-read these posts and something came to mind with regard to atomization. Back in the late 70s or thereabouts Yamaha engineers touted the TSCC or Twin Swirl Combustion Chamber and I doubt it was just marketing hype but a bona fide way to get more fuel air into chamber as well as have it burn fully. The EPA was up their butts big time so they adjusted and overcame to try to win the horsepower war.
Get your motor running!

84 GPZ750
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83 GSX750ES
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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:24
#789261
Try to do that chop at around 6k
Get your motor running!

84 GPZ750
81 R100RS
83 GSX750ES
80 KZ1000 LTD
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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:37 - 18 Aug 2018 19:39
#789262
I will do the plug chop sometime tomorrow and I will post the results and a picture here. Should I go to 6K in every gear or just maybe 3rd gear before the chop? I will also check the float levels when I find the specifications. Thank you man.
Last edit: 18 Aug 2018 19:39 by pcbisnice.

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 19:56
#789263
I'd likely try one when it's pulling strong then another at the problem throttle opening.

Keihin CVK34 (x4)
Main Jet 132, (U) 135, (Cal) 138.
Man Air Jet 100.
Jet Needle N27B, (U) N27A.
Pilot Jet 35.
Pilot Air Jet 160.
Starter Jet 42, (Cal) 38.
Pilot Screw 2 1/2 (turns out).
Fuel Level -0.5 mm.
Float Height 17.0 mm.

These are your stock setting.
Get your motor running!

84 GPZ750
81 R100RS
83 GSX750ES
80 KZ1000 LTD

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 20:00 - 18 Aug 2018 20:01
#789264
One last thought before I go. Prior, the bike ran good except for a stumble at around 2k, then the trip to the mechanic, then it got worse.

I'm not suggesting the mechanic was incompetent, everyone has a bad day and can make an error. But when I hear those words that a mechanic did this or that, it gives me no false sense of security.

It's good that you are taking over the responsibility of working on your bike.
Get your motor running!

84 GPZ750
81 R100RS
83 GSX750ES
80 KZ1000 LTD
Last edit: 18 Aug 2018 20:01 by Togoster.

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 20:06
#789266
You'll have to chop in one gear, maybe like 3rd or 4th, you wouldn't want to break the law by speeding now would you?
Get your motor running!

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Re: Gpz900 stutter at 6k and lack of high end power

18 Aug 2018 20:06
#789267
Bring a plug socket and check all four
Get your motor running!

84 GPZ750
81 R100RS
83 GSX750ES
80 KZ1000 LTD

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