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BIKELAND > FORUMS > ZX12R ZONE.com > Thread: zx12 blow up NEW TOPIC NEW POLL POST REPLY
joel29x


Parking Attendant
Posts: 1
posted July 18, 2014 06:32 PM        
zx12 blow up

Hi I'm new to these forums and just hoping to find a little help with the problem i have with my engine.

I have a zx12 running in a lighting sprint speedway car, it runs through a quick change diff. The car is self start still using the clutch and gear box in standard formation. I have blown up two engines in two meetings both breaking the number 3 big end and kicking a leg out. my question is has anyone heard of now no if there is any oil starvation problems on the 3rd big end. when we pulled the engines down all the other bearing are fine with no wear. Both times when the engine blew up it had 40 pound of oil pressure. On the first engine we ran all the gears in the gear box, but removed all the gears bar 1st and 2nd in the new engine, we were thinking maybe because the car is constantly turning left the oil might have ran up the gears and coursed a starvation. On the new motor we also changed the sump and pick up to a better location to try and avoid any problems but with no luck. I have read a few forums and guys were saying the zx12s struggle with cavitation and bearing slip. If this was a problem wouldn't it hurt the other bearing in the engine aswel ?.
The only thing I can see which may have a impact is the 3rd main bearing provides oil to the 3rd and 4th rod along with the oil supply down to the balance shaft, the first engine had the balance shaft removed and the 2nd engine still had the balance shaft in. There have been a few other guys running these engines and having the same problem with the 3rd bigend or main.

Any help would be greatly appreciated.

Thanks
Joel

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dougmeyer


Needs a job
moderated
Posts: 2703
posted July 20, 2014 01:14 PM        

Joel
Since you describe your system as running through a QC diff, I will assume that you've turned the engine 90 deg to it's orientation in a bike. Your problem is starvation, mostly because of poor drain back. Oil is hanging up in the head. Remember, in a motorcycle the g-loads are always perpendicular to the crank (the bike banks in a turn and the oil flows "down" (perpendicular to the crank) back to the sump. The engines have no design consideration for drain back from the top end with any lateral or fore and aft g loading. You can move the pickup to the rear to account for acceleration loads, but that doesn't help get the oil down out of the head.
You may be able to cure it with external drain backs (-10 minimum,) which we did on the ZX-11 applications, but it is unlikely. I have a quite a bit of experience with the issue. Unlikely that you will succeed without going to a dry sump. Please do a search of this forum on the topic of dry sumps, etc. Tons of discussions from 2000-2003.
Bottom line is that there is a GREAT DEAL of bad info on the entire ZX-11, ZRX-1200, and ZX-12 claiming bad oiling. The problem was ALWAYS air at the pick up and can be remedied in a variety of ways.
____________
It's not that I think you're dumb, it's just that so much of what you know isn't true....

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frEEk


Administrator
ummm... yeah
Posts: 9649
posted July 27, 2014 01:36 PM        
God I love posts like this.
I don't even understand half of it, which is probably what makes me just a little hard.

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