Burning oil and 90psi compression

  • Scottbob76
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Burning oil and 90psi compression

17 May 2019 07:04
#804018
Hello recently bought a kz440 ltd
After bike warms up it starts smoking lots
I did a compression test and got 90 psi on both cylinders after it had been running a minute
(Probably not fully up to temp but deffo warm)
What would be your next step

Cheers
Scott

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  • Warren3200gt
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Re: Burning oil and 90psi compression

17 May 2019 07:11 - 17 May 2019 07:15
#804019
I don't know what compression your bike should have but 90 sounds awful low. However having said that what colour is the smoke and has it been standing for a long time? It could be the rings are gummed up and a bit of use will free them or it could be they are knackered and need replacing and or a rebore.
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Z1000J2 somewhat modified!
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Last edit: 17 May 2019 07:15 by Warren3200gt.

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  • Grcko
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Re: Burning oil and 90psi compression

17 May 2019 08:01
#804024
Usable compression range is 109 psi-156 psi or less than 14 psi difference between cylinders (from the manual)
As Always,

1983 KZ440

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Re: Burning oil and 90psi compression

17 May 2019 09:54
#804033
The smoke is white
And yes it has been standing years I have just got it and put oil spark plugs and fresh petrol in it

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Re: Burning oil and 90psi compression

17 May 2019 11:23
#804039
White smoke is condensation not oil. Change the oil which may have moisture in it and then let it warm up to full temp. Fingers crossed once its warm right through and dried the exhaust system it'll stop smoking.
[img
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Z1000J2 somewhat modified!
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  • M_a_t_t
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Re: Burning oil and 90psi compression

17 May 2019 15:26
#804052
Make sure your tester has a valve in the tip. For smaller engines that can really throw off readings.
kzrider.com/forum/2-engine/606826-low-compression-s-on-kz1100
83 KZ1100A (shaft)
17 Versys X 300 abs
81 kz650h1
81 kz750e2
90 Honda CBR600F (brother's)
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Re: Burning oil and 90psi compression

18 May 2019 00:39
#804068
Cheers gonna try today a bit later (early for revving motorcycle)
Deffo oil I think as when the exhaust was not tight a black substance was dripping out it was like a very thin oil with a slight fuel smell

I’m gonna leave it running to warm through and burn everything off then strip the head I think

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  • Patton
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Re: Burning oil and 90psi compression

18 May 2019 07:18
#804076
Before stripping the head, would suggest changing the oil and filter, assure the valve clearances are within specs, lube and adjust the chain, assure correct psi in the tires, perform any further obviously needed maintenance, then ride it for at least 100 miles, and re-assess the situation.

Good Fortune! :)
1973 Z1
KZ900 LTD
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  • Warren3200gt
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Re: Burning oil and 90psi compression

18 May 2019 10:31 - 18 May 2019 10:33
#804088
Scottbob76 wrote: Cheers gonna try today a bit later (early for revving motorcycle)
Deffo oil I think as when the exhaust was not tight a black substance was dripping out it was like a very thin oil with a slight fuel smell

I’m gonna leave it running to warm through and burn everything off then strip the head I think
Oil smoke is blue / black not white. The "oil" you had dripping "could" have been condensation with exhaust port soot in it. It would smell fuelish due to the exhaust gases.
As Patton says change oil and filter and ride it.
[img
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Z1000J2 somewhat modified!
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Last edit: 18 May 2019 10:33 by Warren3200gt.
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Re: Burning oil and 90psi compression

18 May 2019 11:14
#804091
Ok thanks guys
Gonna take your advice and ride it for while with fresh oil
I’ll update in a few weeks

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  • Nerdy
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Re: Burning oil and 90psi compression

18 May 2019 14:33
#804101
Warren3200gt wrote: Oil smoke is blue / black not white.


I always associate blue smoke with oil and black with an overly rich fuel mixture.
1979 KZ400 Gifted to a couple of nephews
1967 Yamaha YCS1 Bonanza
1980 KZ440B
1981 Yamaha XT250H
1981 KZ440 LTD project bike
1981 GPz550
2013 Yamaha FZ6R

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