Blown up 750 . . . . Twice

C

Chris

New member
Joined
Jun 5, 2006
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111
Age
35
Location
Ontario Canada
So i buaght a VMAX 750st and i got a smoken deal on it So i got it home from the dealership and cheaked the plugs to find one was melted off with a hole dead center of the piston. So i braught it back and the "fixed it " Cleaned the carbs they said it was due to water in the gas witch i had a hard time to believe because i didnt drive it and they had it in the summer , , , , So new piston rings , carbs cleaned base gasket and head gasket , took it 20 km and it blew agan same cylinder same senerio plug meted and hole dead center of the piston there telling me timeing , i was thinking more along the lines of crank seal ? any ideas ? ?
 
Which cylinder? PTO being #1 in a vx750..and check where the wiring harness loops under the steering post in the B'pan..ps..wth is a "Mini" member :whine: lol
 
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So igot a call from the dealership today , It was 3 from the PTO 2nd from the pull start , Witch wiring are you talking about ? and how would that cause a melt down , There telling me it was a twisted crank they said some one Re phazed the crank 180 degrees out for more power but it has a stock ignitions and coils ,Is this possible , or did they not cheak any thing, Regardless there not going to fix it but i think i havce them talked into getting me a crank piston and all gaskets witch i think it should fix it , they said a hole dead center is a timing issue witch would be the crank out of phaze , any ideas ?
?
 
Chris said:
So igot a call from the dealership today , It was 3 from the PTO 2nd from the pull start , Witch wiring are you talking about ? and how would that cause a melt down , There telling me it was a twisted crank they said some one Re phazed the crank 180 degrees out for more power but it has a stock ignitions and coils ,Is this possible , or did they not cheak any thing, Regardless there not going to fix it but i think i havce them talked into getting me a crank piston and all gaskets witch i think it should fix it , they said a hole dead center is a timing issue witch would be the crank out of phaze , any ideas ?
?
Click to expand...

Seriously, go to vmax4.com...the gurus live there...
 
First.. Your sled can't have the phased crank (180) without either a piggy back CDI or a homemade twin box/ pulse coil set up and I dont think the spur could twist a perfect 90 between the cranks, so your dealer might be on glue. 180 would not run @ all with stock ignition. Stock uses 2 pulse coils (90 degrees apart) ..one box / waste spark firing @ 90 degrees ( one @ TDC, one @ BDC, one @ 90 degrees, one @ 270 degrees) The wires I'm talking about are in the belly pan right under the steering stem. That harness has the wires from the pulse coils going to the CDI Box mounted left side of the chassis beside the pipe. The harness can chaff thru and short the pulse signal (changing the timing[ holed piston] ).
I've seen it on 750's over the years and if ALLSEASONRIDER wants to go out and compare his '93 and his '96 he can tell you the boxes are in a different location to keep the harness away from the steering stem. (750 vs 800). Why else would they bother?
Just thought I'd give you a another place to look for your problem. Good luck
 
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OK thank you i will have to check that out , is it under neeth the motor ? I do not have the sled right now it is at the dealership at the moment. I am going to pick it up some time this week , They are supplying me with a new crank , berrings , pistons and seals to rebuild and i am going to rebuild it myself for i know what im into insted of a BOMBI dealership who shouldent ever touch a good yammy , them Japaneese knows how to do things unlike the french lol
 
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