Kz650 b3 no compression on 2 and 3
- Warren3200gt
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Re: Kz650 b3 no compression on 2 and 3
28 Jun 2023 15:01And as the compression is low on 1 & 4 the whole top end needs a refresh, possibly a rebore. No point in doing half the job whilst it's this far apart.Due to the large valve clearance and zero compression, i bet you will find some bent valve stems on #2 and #3
Z1000J2 somewhat modified!
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- Wookie58
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- faceplateman
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- Nessism
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Re: Kz650 b3 no compression on 2 and 3
29 Jun 2023 16:17Please tell me you didn't order the Athena kit!I just ordered a complete top end seal kit from z1enterprises. I already got the new cam shaft end plugs. I took the exhaust off last night. Tonight if i have enough energy after work ill take the carbs back off (for the 3rd time) and then take the head off. I gotta say though the most painstaking thing ive done on this bike is removing and installing the carbs. Its the worst. Even with a heat gun to soften the boots up and my 3d printed tool i made for carb boots its still my least favorite thing to do on this bike.
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- faceplateman
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Re: Kz650 b3 no compression on 2 and 3
30 Jun 2023 01:14
Well i just took the head off and all my problems seem to be valve related. All the cylinder walls look nice and shiny. No scoring or anything. The valves however are a different story. All the exhaust valves look like they are slightly open. Number 2 ex valve is even more open than the rest. Next step is to buy a valve compressor and take all the valves out. Im gonna replace all the guides and springs. Repair any damage to the seats and replace any damaged valves. Completely clean everything and replace all the seals.
1979 kz650 b3
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- Wookie58
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Re: Kz650 b3 no compression on 2 and 3
30 Jun 2023 01:32 - 30 Jun 2023 01:34
Looking at the "witness marks" on the pistons it appears the exhaust cam timing was incorrect. I would suspect the valve stems are bent as a result of impact
(probably worth measuring your piston heights before putting the head back on just to make sure you haven't bent a rod (unlikely as it looks like the "mechanical love making" was gentle !!)
Last edit: 30 Jun 2023 01:34 by Wookie58.
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- hardrockminer
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- Nerdy
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Re: Kz650 b3 no compression on 2 and 3
30 Jun 2023 09:58Hard to say if you have any valve issues until you remove them and see if they move freely and if the seats are OK.
Don't forget to change the valve seals and check the valve guides for wear.
He covered all of those things in his last post
Im gonna replace all the guides and springs. Repair any damage to the seats and replace any damaged valves. Completely clean everything and replace all the seals.
1967 Yamaha YCS1 Bonanza
1980 KZ440B
1981 Yamaha XT250H
1981 KZ440 LTD project bike
1981 GPz550
2013 Yamaha FZ6R
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