GK73a SP will not rev out!

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moforockband
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GK73a SP will not rev out!

Post by moforockband » Fri Oct 16, 2015 1:20 pm

Struggling to fix this. It get's to 12000 and then struglles to rev any more, could be electrical??? Just been on pdq's dyno
Image It should make low 60's not 50 odd.

I've changed coils, put a known good cdi, the fuellings about correct. Not sure if the engine has ever been fully apart. It has an aftermarket 4-1 with a yoshi can.

All that's left in my head is
- cam timing
- ignition pickup

Any ideas?
Cheers .

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Re: GK73a SP will not rev out!

Post by moforockband » Fri Oct 16, 2015 7:04 pm

Image
Image

I think I may have found something: the rotor tips look like they've machined themselves off a bit?! now too much clearance to the pickup?
The cam timing is spot on, just checked that.

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Re: GK73a SP will not rev out!

Post by Variablevalves suck » Sat Oct 17, 2015 10:49 am

They usually look pretty tatty, definitely not a precision machined part and no clearance given for the pick-up.
I'm no expert regarding dyno graphs but surely it should (if correct) run at around 12/13, the sudden dip at high revs looks all wrong! I don't know which way it is, think lower is rich, but it would kill the motor revs.
What did the dyno guy recon?

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Re: GK73a SP will not rev out!

Post by moforockband » Sat Oct 17, 2015 8:38 pm

PDQ recommended to check the cam timing- which turned out to be spot on. Or they said the exhaust might be restricted, but it hits such a wall at 12K that I think the exhaust is not really the problem. I have a gk76a 4 into 1 Yoshi system.
I've ordered a new rotor so hopefully will fix the issue. As said I've tried 2 ecu's, and 1 without the restrictor green yellow wire. and they both run the same!
I've worked on loads of bikes but this is really a head scratcher!
trying to get hold of a 35 x 1.0mm puller. They are thin on the ground.
I do know the bike had a fast lowside lh crash at some point, so may have broken the lh casing and damaged the rotor.
Last edited by moforockband on Sat Oct 17, 2015 11:28 pm, edited 1 time in total.

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Re: GK73a SP will not rev out!

Post by Variablevalves suck » Sat Oct 17, 2015 9:01 pm

Ive seen the puller for £12 on ebay listed as a Kawasaki item.
Maybe some on here know a little about dyno graphs but surely the af shouldn't drop off like that.

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Re: GK73a SP will not rev out!

Post by moforockband » Sat Oct 17, 2015 11:27 pm

Variablevalves suck wrote:Ive seen the puller for £12 on ebay listed as a Kawasaki item.
Maybe some on here know a little about dyno graphs but surely the af shouldn't drop off like that.
Which kwak puller chris?

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Re: GK73a SP will not rev out!

Post by Variablevalves suck » Sun Oct 18, 2015 10:05 am

Hi mate, sure its 35x1.5
In the workshop manual ive scribbled Suz- 09930-34960 Yam- ym-01404. Kaw 57001-1223

These are all same so an equivalent to any of these, the one I got was about £12 or something.

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Re: GK73a SP will not rev out!

Post by moforockband » Sun Oct 18, 2015 7:53 pm

Yep you were right, it is 1.5mm pitch. Will order one up and report back if misfire vanishes

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Re: GK73a SP will not rev out!

Post by wullie3xv9 » Thu Oct 22, 2015 7:48 pm

Variablevalves suck wrote:...I'm no expert regarding dyno graphs but surely it should (if correct) run at around 12/13 (to 1 air/fuel ratio). The sudden dip at high revs looks all wrong! I don't know which way it is, think lower is rich, but it would kill the motor revs. What did the dyno guy recon?
I'm with you, VVS. From 11,500 rpm upwards the fuel/air ratio goes rich. (Too much fuel).
I reckon smaller main jets are needed. It's also rich at 2,500 - 3,000 rpm. Between 4,500 & 7,000 it's a touch lean.

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Re: GK73a SP will not rev out!

Post by moforockband » Sat Oct 24, 2015 2:23 pm

Replaced ignition trigger with no improvement :( Was a bitch to put back on, as I didn'[t realise you have to clean ALL the oil off the crank taper before fitting it as otherwise it slides on too far and the starter clutch ends up binding. Sigh!
Looks like compression issue may be on the cards, I'll start another topic LOL


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