madsledhead
New member
Hey guys, great forum.
Here's the story.
I'm a mechanic and my hobby and sideline business is rebuilding bikes/atvs/snowmobiles/etc.
I recently bought a 93 vmax4 in really great shape. I got it for almost nothing ($100).
The guy said it starts but doesn't run strong.
I do my first engine tests, compression very good. So, as I do with all my projects I descided to pull the engine and start a complete inspection.
Before I strip the engine down, I noticed that there was something odd with the crank phasing.
Cylinders 1&2 are at 180 deg exactly, cylinders 3&4 are at 180 deg exactly. BUT heres the wierd part. I would assume that cylinders 3&4 should be indexed at 90 deg from 1&2. this would seem logical to balance the engine having it fire at 90 deg apart.
They are not, in fact I have calculated the angle and cyl 3&4 crank index is at 20 deg from 1&2.
Can someone confirm for me that they should all be at 90 deg from each other?
Also, can someone give me a link where I can download the manual. the vmax4.com site has one but it is not working.
thanks
Here's the story.
I'm a mechanic and my hobby and sideline business is rebuilding bikes/atvs/snowmobiles/etc.
I recently bought a 93 vmax4 in really great shape. I got it for almost nothing ($100).
The guy said it starts but doesn't run strong.
I do my first engine tests, compression very good. So, as I do with all my projects I descided to pull the engine and start a complete inspection.
Before I strip the engine down, I noticed that there was something odd with the crank phasing.
Cylinders 1&2 are at 180 deg exactly, cylinders 3&4 are at 180 deg exactly. BUT heres the wierd part. I would assume that cylinders 3&4 should be indexed at 90 deg from 1&2. this would seem logical to balance the engine having it fire at 90 deg apart.
They are not, in fact I have calculated the angle and cyl 3&4 crank index is at 20 deg from 1&2.
Can someone confirm for me that they should all be at 90 deg from each other?
Also, can someone give me a link where I can download the manual. the vmax4.com site has one but it is not working.
thanks
YAMMIEGOD3:16
Active member
JUST A GUESS HERE. WHEN A VMAX 4 ENGINE IS TIMED TO FIRE AT 180, THATS USUALLY DONE FOR ADDED BOTTOM END TORQUE. ALOT OF THINGS COME TOGETHER BECAUSE ENGINE ACTUALLY ACTS LIKE TWO TWINS. HIGH RPM PIPES, PORTING, BIG CARBS , 10,200 PIPES etc. NOW IT SOUNDS LIKE SOMEBODY HAD SOME PLAINS FOR YOURS. AND YES I WILL CONFIRM 90 DEGREE FIRING IS STOCK. 3:16 (yammie tony)
Last edited:
jabber800
New member
Tear the crankcase apart!! Check the splines on the crank gears, my bet is a gear has spun on one of the crank halves.. Re index them for 90 deg firing and weld them.. Common problem with 750 quad max. Seen it happen when a belt blew on a freinds sled..
madsledhead
New member
Thanks guys - just to make absolutely clear (because re-reading my own garbage wasn't clear)
The crank indexing should be at 90 deg.
This means that everytime one piston is at TDC, another should be at bottom dead center and the other 2 should be at equall height, eacatly half stroke, one going on compression and one comming down.
is this more clear?
Thanks
The crank indexing should be at 90 deg.
This means that everytime one piston is at TDC, another should be at bottom dead center and the other 2 should be at equall height, eacatly half stroke, one going on compression and one comming down.
is this more clear?
Thanks
tedgoesfast
New member
the gears have stripped seen it many times were cranks spline together