How esential is it to weld the crank?

[Metal4130]

How necessary is it to weld the crank in a 701 yamaha motor? Will it move if it isn't welded? Also can you weld it when it is completely built? Thanks

 

[Freestyleriverrat]

Its not that important for freestyle. It is mainly done for racing when the motor turns high rpm's. Definatly not worth tearing the motor apart to do.

 

[Mile9c1]

I've never seen a welded stroker crank, and they are primarily (or were primarily) for racing.

 

[Sanford]

I've had welded cranks and even had one get out of 180 degree and end with a slight wobble. My OEM Yamaha crank was not welded and its still true and good.

My 6mm stroker crank isn't welded either.

Because of the extreme heat from welding (even with a Tig), its not uncommon that a true crank needs to be bent or tweaked back into shape after welding the pins in place (go figure right).

 

[waxhead]

i havent ever run a weilded crank
and i have never had issues with cranks moving

 

[orange flattop freestyler]

Ive always had my cranks trued, balanced and welded and never had a problem.

Each to their own :biggrin:

 

[Mile9c1]

I figure if it's not necessary, why do it? it's going to make it a lot harder to rebuild.

 

[crammit442]

I figure if it's not necessary, why do it? it's going to make it a lot harder to rebuild.

They're just tacked. It's really no more difficult to rebuild. They just grind the spot off and press them apart.

Charles

 

[Mile9c1]

The one's I've seen welded looked like more than a little spot. It looked like they'd be a PITA to get apart IMO.

 

[Phill]

what parts move? Does the entire crank "slide" back and forth?

 

[Sanford]

what parts move?

Since the big end rod pin is just pressed in, it can "technically" move or rotate. Like I mentioned above, I've had a welded crank get out of sync (not 180) so YMMV.