'79 kz1000 fresh rebuild but wont fire off and run

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08 May 2009 16:01 - 08 May 2009 16:04 #289117 by mikey8506
'79 kz1000 fresh rebuild but wont fire off and run was created by mikey8506
This is a 1979 kz1000st, it has spark and gas but the compression seems to be low and it will only back fire thru the exhaust. The motor has been just been rebuilt so i have ran out of things to try if any of you guys out there have any ideas pease let me know.
Last edit: 08 May 2009 16:04 by mikey8506.

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08 May 2009 16:03 - 08 May 2009 16:04 #289118 by bountyhunter
Replied by bountyhunter on topic '79 kz1000 fresh rebuild but wont fire off and run
Valve clearance too tight or valve timing being off will cause low compression.
1979 KZ-750 Twin
Last edit: 08 May 2009 16:04 by bountyhunter.

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08 May 2009 16:06 #289120 by RonKZ650
Replied by RonKZ650 on topic '79 kz1000 fresh rebuild but wont fire off and run
Recheck the clearances. You may have the cams in wrong which is easy to do. If you heard any strange noises while turning over the engine the cams are in wrong and you have bent valves.
321,000 miles on KZ's that I can remember. Not going to see any more.

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08 May 2009 16:06 #289121 by mikey8506
Replied by mikey8506 on topic '79 kz1000 fresh rebuild but wont fire off and run
I have reset the timing b/c the guy that worked on it had the intake cam 180 degrees out and as far as i can tell the valve clearances are ok

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08 May 2009 16:08 #289124 by mikey8506
Replied by mikey8506 on topic '79 kz1000 fresh rebuild but wont fire off and run
how can i tell with out pulling the motor completely back out and apart if the valves are bent?

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08 May 2009 16:14 #289125 by buckinrut25
Replied by buckinrut25 on topic '79 kz1000 fresh rebuild but wont fire off and run
run a compression test if its ok your good

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08 May 2009 16:17 #289126 by mikey8506
Replied by mikey8506 on topic '79 kz1000 fresh rebuild but wont fire off and run
thats the problem, im trying to figure out is why its got lower than "normal" compression and why it will only back fire and not run

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08 May 2009 16:31 - 08 May 2009 16:32 #289128 by Patton
Replied by Patton on topic '79 kz1000 fresh rebuild but wont fire off and run
mikey8506 wrote:

thats the problem, im trying to figure out is why its got lower than "normal" compression and why it will only back fire and not run


Would double-check valve clearances being to specs.

Then perform a leakdown test to determine where compression is escaping from combustion chamber.

Fresh rebuilds often have less than than "normal" compression until the rings have seated.
But the valves should of course be fully sealing when closed.

Good Luck! :)
1973 Z1
KZ900 LTD
Last edit: 08 May 2009 16:32 by Patton.

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08 May 2009 16:38 #289130 by buckinrut25
Replied by buckinrut25 on topic '79 kz1000 fresh rebuild but wont fire off and run
if your cams are right and your valve clearnce are with in specs try to put a little oil in the cylender and see if it helps compression and make sure throttle wide open if that helps may just mean your rings havent seated yet to explain a compression being a little low what are you getting on your test that may help narrow it down

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08 May 2009 17:01 #289138 by mikey8506
Replied by mikey8506 on topic '79 kz1000 fresh rebuild but wont fire off and run
ok if it is the rings not seating besides putting oil in the cylinders what is the best way to get them to seat? i know im sounding like a complete idiot trying to work on a bike but i have never done any major mechanicing on motorcycles

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08 May 2009 17:44 #289153 by PLUMMEN
Replied by PLUMMEN on topic '79 kz1000 fresh rebuild but wont fire off and run
if its the rings that are leaking that bad you should hear lots of air coming out crankcase vent under carbs.if cam was 180 out and motor was turned over im betting the intake/exhuast valves took themselves out :(
Still recovering,some days are better than others.

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08 May 2009 18:01 #289157 by mikey8506
Replied by mikey8506 on topic '79 kz1000 fresh rebuild but wont fire off and run
what do yo mean by took themselves out?

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