New Project...

[minichris94]

Hey guys!

So not to long ago, I picked up a new project. I traded an old blown up Warrior for it. Its a 1994 Vmax4.



This is the problem...
When i picked up the sled, it was running, but not strong at all, not like my 92. So, me being a certified Yamaha silver tech, I do my normal test's and such.
Compression was, 160, 165, 160, 165 so that was good. Go through and test all of the electrical components, check fuel, and any other odds and ends. Everything checks out okay. So through all of this i check the crank. #1 was at 20 degrees after TDC, #2 at 20 degrees after BDC, #3 at BDC, and #4 at TDC.



So I pull the engine and tear down, come to find the left crank half was not welded and had spun. Looking at the cases, this think had been apart before, The case was welded on the inside, and the right side half, was welded. So i just got the new crank seals in today, and i'm about press the crank apart tomorrow. Any tips on how to re-time the crank? I have another crank out of another 94 that i can use for reference, but i just would like some input on this.
Thanks guys,
Chris.





Just some more pictures for you to enjoy

 

[opsled]

Crank phase issues are not uncommon on 750's. Most run forever without any problems but it does happen. Quad pipes requiring higher than stock rpm or a hydro locked cylinder from a bad O ring on a carb needle seat are the usual culprits. Timing the gears correctly is not a job you should do unless you know you have the right tools and knowhow to do it right. I send mine out to a guy here (Pete Nydahl) who has the tooling, jigs and experience to do the job. They should also be welded now that you have them out to stop it from happening again. There is a proper way to weld them too as there is a crank seal right behind the gear that needs to be welded. I've seen some that have been butchered.

Many threads and write ups on this very issue at Vmax4.com. Check them out.

opsled

 

[minichris94]

Thank you for the information! I have timed and trued cranks before, just never on these vmax's. I am an experienced tig welder so im not worried about welding it. I just have never pressed apart the gears before. My 92 spun the crank too, But that came with a parts engine that had a good crank in it. I have two spun cranks and i just want to know if anyone has done this before.

Chris.