1999 Vmax Sx 700 Triple Help

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ncandrick

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Mar 7, 2018
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Maine
Hi I have a 1999 Vmax Sx 700 Triple. The engine was replace by a previous owner so it has unknown miles. It is a red top 700 triple. Fist when I was having trouble with my sled I was bogging out every time I went to go full throttle. I did a compression test and it came 90 psi in each cylinder. So I went to a dealer bought new gaskets, pistons, and rings. Took the engine apart and put the new parts in. When I put the new gasket on the top, I cut the ribbit holding them together and took the middle layer out to build more compression. When I put everything back together, I did another compression test. It came out as 100 psi in each cylinder. I figured it was bad seals in the crank. So we bought a known good crank from a sled that had bad pistons. The sled that the crank came from was a 2001 sxr red top motor. I switched the cranks. Putting everything back together I noticed that the plugs from stator was different. So I took the recoil off my original crank. I've own this sled for 2 years and its the first time I've taken the recoil off. When I taken it off I noticed the fly wheel nut was missing. So I think this is the reason why my sled wasn't running right. But any way I switched the plugs from the stator. Now every things back together. I took the sled down the street and back. Now it sounds like its running on two cylinders. The cylinder furthest from the PTO side isn't firing. So I put a never been used BR9ES spark plug in. Still sounds like its running on two cylinders. So I did another compression test and i'm still reading 100 psi. Am I doing something wrong? Everything is torque to specs. I put in new gaskets for everything. Carbs have been cleaned recently.
 
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a fresh rebuild needs time to seat in the rings as well. compression might not come up until you have run 2-3 tanks of gas through it. with what you have done, i would expect 120-130psi in each hole minimum.
 
Maim said:
a fresh rebuild needs time to seat in the rings as well. compression might not come up until you have run 2-3 tanks of gas through it. with what you have done, i would expect 120-130psi in each hole minimum.
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Ok. Ill see if that works.
 
Have you tried to verify compression with a different compression tester?
 
You may also want to swap out coils and see if that makes a difference. I usually keep extra spark plug caps on hand, I've had issues in the past with them.
 
Replace or switch the spark plug caps. On my 97 models, the coils are hooked in series, yours might be different, so you could simply take the plug wire from and adjacent cylinder and see if that changes anything. Non firing plugs should be wet. I had some issues with running yesterday, checked the plug caps with Ohm meter, and didn't show any current flow, so I swapped out the plug caps, with some NGK, caps. LB05E, but sure any 90 degree NGK plug cap will work. They are supposed to be 5K Ohms. You cold also check, by pulling the plug cap while running and see if the rpm changes to isolate the problem cylinder.
I have yet to run the sled to see if the caps cured my problem. Might have just been some bad gas as well.
 
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