Cylinder / Rod / Piston compatibility question

Started by uranys, Sep 17 2009 01:51 PM
8 replies to this topic

  • uranys

Posted 17 September 2009 - 01:51 PM

#1


The motor in my 650L is from 600R, but it has a JE 10.5:1 650L piston. The small end on the rod was pretty close to the service limit, so I think I'm going to replace it over the winter.

I have a spare 650L crank & rod assembly, so my question is can I just swap it in instead of putting a new rod on the 600R crank?

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  • cleonard

Posted 17 September 2009 - 01:55 PM

#2

No better way to find out if what you think you know is wrong than to open your mouth, so here it goes...

I thought that the starter gear on the L crank makes fitting it to a 600 case a no go.

  • uranys

Posted 17 September 2009 - 04:02 PM

#3

Quote

I thought that the starter gear on the L crank makes fitting it to a 600 case a no go.

Do you mean the gear on the inside of the L flywheel? I was going to stay with the 600R flywheel if it would fit the L crank.

  • HeadTrauma

Posted 17 September 2009 - 11:52 PM

#4

If you use the XR600 JE piston with the 650L crank, it will be about 0.75mm further down the hole and will lower compression accordingly. I don't know about fitment of the other parts like the flywheel.

  • valvesrule

Posted 18 September 2009 - 11:08 AM

#5

I know the L crank is longer on the left side and I think the fit for the flywheel is larger too. If an L crank did somehow fit in 600 cases you would have to use the L gen cover to accomodate the longer crank. I doubt there's anything to gain from this experiment but the knowledge it doen't work.

  • uranys

Posted 19 September 2009 - 04:44 AM

#6

Quote

I know the L crank is longer on the left side and I think the fit for the flywheel is larger too

oh, i see what you mean

Picutre of zippers 600R crank from his rebuild thread:

Posted Image

and my spare 650L crank:
Posted Image

So is it possible to make a franken crank by pressing out the flywheel mounting pin and pressing in the 600R pin?

  • zrxer

Posted 19 September 2009 - 05:21 AM

#7

Excellent picture comparison uranys. Sure would be nice to put these somewhere on the forum where they could be easily accessed, kinda like what HeadTrauma is trying to accomplish with his piston spec thread.

  • valvesrule

Posted 19 September 2009 - 01:05 PM

#8

uranys said:

So is it possible to make a franken crank by pressing out the flywheel mounting pin and pressing in the 600R pin?

It's not pressed in, it's part of the left half forging. It could be machined but it would be a lot of work to do it. Probably not worth it for 2mm more stroke. Most likely easier to stroke a 600 crank and get 4/6mm.

  • uranys

Posted 20 September 2009 - 07:27 PM

#9

After closer inspection the small end on the 650L rod is out of spec, and it's at the service limit for side to side clearance too.

Looks like i'll have a hot rod pressed on the 600R crank.

Thanks for the advice.



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