mag side piston problems

vmax-540 · Post by **vmax-540** » Sat Feb 21, 2009 5:48 pm

Question, is that the intake or exhaust side of the piston ?

1987vmax · Post by **1987vmax** » Sun Feb 22, 2009 10:36 am

I am going to tear the bottom end down tommorow I will post some pics. I have since sent the mag cylinder back to the place I got it they are going to try & get me a new one

vmax-540 · Post by **vmax-540** » Sun Feb 22, 2009 11:49 am

One other thing to check is the fuel pumps ,on the Vmax the mag side cylinder works the fuel pump for the pto carb and vise versa. You could have a bad or weak pump I had that happen to a friends sled about 10 years ago. Not saying it is it but something else to check .

1987vmax · Post by **1987vmax** » Sun Feb 22, 2009 12:44 pm

I had intentions of taking both fuel pumps off & checking them I also wanna paint the engine compartment so basically everything is getting a going over.

sxr1000 · Post by **sxr1000** » Sun Feb 22, 2009 1:53 pm

here is a pic of a piston that had the crank bearing go out.

Joe · Post by **Joe** » Mon Feb 23, 2009 2:29 am

My OPINION of what happened is this:

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Broken rod bearing debris entered the combustion chamber through the transfer ports.

Debris got caught between the piston and the top of the exhaust port breaking the top ring land and pinching the upper ring.

The upper ring failed near the exhaust port.

The ring caught in the exhaust port and broke the land between the upper and lower ring grooves on the exhaust side of the engine.

The debris from the shattered piston and ring got smashed between the piston and squish area of the head until the debris went out the exhaust port.

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I would suggest removing the exhaust and inspect any metal pieces that you find.

Piston land is alumunum.
Rod needle bearing is cylndrical steel.
Piston ring is recangular steel.

My OPINION is that some (but not all) of the dents in the top of the piston were made by cylindrical debris indicating that a rod bearing failed.

1987vmax · Post by **1987vmax** » Mon Feb 23, 2009 6:04 pm

I dissambled the bottom end today everything with the crank looks fine all main bearings spin really good no noise at all & the rods look really good aswell I am going to take more pics to show you guys.

1987vmax · Post by **1987vmax** » Thu Feb 26, 2009 10:46 pm

1987vmax · Post by **1987vmax** » Thu Feb 26, 2009 10:50 pm

Joe · Post by **Joe** » Fri Feb 27, 2009 4:41 am

Is that metalic debris in the crankcase bottom?
Is it magnetic or non magnetic?

sxr1000 · Post by **sxr1000** » Sun Mar 01, 2009 11:38 am

Man that sure looks like bearing debris to me,could it have come from the gearcase and somehow got past the seal?

jipcee · Post by **jipcee** » Sun Mar 01, 2009 11:08 pm

See where the white part on the seal is and part off the seal is missing, I would say that is the culprit right there (sucking air leaned it out)
From the looks of the head the left (PTO) side is running WAY rich.
Also that head is junk unless you get it machined.

1987vmax · Post by **1987vmax** » Mon Mar 02, 2009 10:03 pm

I have a friend that I apprenticing under a while ago he remembers these machines like it was yesterday.I showed him the parts & he thinks someone machined the head & it wasn't true he said the pattern on the crown of the piston is not even & ran hot because of too much comression.the head i had on there i got from ebay & that motor was ported so if anybody wants to buy a set of ported jugs let me know I will keep you posted

1987vmax · Post by **1987vmax** » Tue Apr 21, 2009 1:54 pm

I have recently assembeled the engine the previous head had been shaved down & had alot of combustion chamber work done to it.Hopefully everything works out next winter.The other thing I wanted to ask was about the side panels is the original paint gloss black or meduim black I want to restore it. thanks

Post by **Vmax540** » Thu Apr 23, 2009 12:09 pm

I'd say more of a meduim black ?