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XS750 gears in the XS650 for strength
- Thread starter Ratranger
- Start date
Nice way of doing the undercut. Was the XS 750 third gear swap straight forward?
Also considering doing the swap for a new motor, but I have not heard of any problems with the XS 650 third gear.
Also considering doing the swap for a new motor, but I have not heard of any problems with the XS 650 third gear.
The swap is pretty much drop in. The biggest hassle is the snap rings being a pain. Just make sure you get a 750 tranmission not an 850. Best I can tell is pre79 750 transmission has the right gears, later transmissions have one gear that has smaller dogs than the 650 on one side.
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Is the third gear swap just to replace worn parts, or is it a different ratio?
Can you detail the undercut procedure? Maybe do a thread on it?
thanx!
Can you detail the undercut procedure? Maybe do a thread on it?
thanx!
The 750 gears have larger dogs than the 650, http://www.smedspeed.co.uk/tech.html I found the info there as well as pics showing the size difference. Same ratios, just stronger dogs.
Once I get my transmission ready to swap in I'll do a write up on undercutting. I don't have a gear that needs it to get good pics right now.
Once I get my transmission ready to swap in I'll do a write up on undercutting. I don't have a gear that needs it to get good pics right now.
Nice, since I have a later 850 trans here is a close up of the gears I highlighted as "wrong" above. You can see how much yamaha removed from the dogs on the one side and the matching smaller dogs on the mating gear. The older large dog gear won't even fit. So best bet is to check the ebay pics close, you can see the difference if the pics are good.
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ran into this youtube suspect I know the author....
Yep, that's me. Did a little riding yesterday to start tuning. Honestly you don't notice any difference with the xs750 gears in there. They may be an upgrade in strength, but they are unnoticeable in use.
This is very interesting work and quite impressive - but I must ask, is there an extensive history of gear failure in unmodified XS650 trannies?
I can see it if you have increased power markedly, but as far as I am aware, stock XS650s seem to never die (but I may be wrong on that score).
Pete
I can see it if you have increased power markedly, but as far as I am aware, stock XS650s seem to never die (but I may be wrong on that score).
Pete
How is your drum, detent. I realize it's not the exactly the same but had an old BSA which would jump out of 1st. Turned out to be a worn cam plate that moves and holds the shift forks in place. In these trannies it's a cam drum and a some sort of ball or plunger spring detent to hold in position. Also check the spring.
Same principle though, You could be looking in the wrong place. Just a thought.
Same principle though, You could be looking in the wrong place. Just a thought.
The spring and detent are fine, as is the drum itself. The shift fork was worn down, but that is more of a symptom than the problem. When I set things up to do the undercut the dogs weren't straight, they had almost a degree of chamfer that under load would push things apart. The undercut so far has solved the problem.
It may be mainly a racing mod, and honestly I just did it because if I was going to pull the motor, it was going to have the best transmission it could. Did I really need it? Probably not. I think for most people it would be a peace of mind mod, not really needed but you know it's as strong as possible.
It may be mainly a racing mod, and honestly I just did it because if I was going to pull the motor, it was going to have the best transmission it could. Did I really need it? Probably not. I think for most people it would be a peace of mind mod, not really needed but you know it's as strong as possible.
My first XS650 broke it's second gear. One of the dogs broke off. No transmission lock up when it occurred. It just went into the oil sump and stayed there until the next oilchange. I could hear the tranny "chirp" when it was in second but, other than that, it was fine. I did do a shaft swap out one evening to fix it.
weaselbeak
XS650 Junkie
I went thru a few XS650s in my youth, when I rode with a bit of "enthusiasm". Neve broke a 650 trans or saw one with a problem, aside from the sticky clutch BS.
