Won't Stay in 1st Gear

[DeathGrip-IronWorx]

Hey guys, how's it going!? My name is Brandon and about a month ago, I bought my first XS650. Its a 1971 thats been hardtailed with a suicide shift and left foot clutch from BlackSmith Billy. The guy who built the bike did a phenomenal job. However.......this bike will not stay in first gear. I'll shift to first at a light, hear and feel a click or thud, go to take off, and the bike will stay in neutral. I'll have to do it a few times usually. I have noticed that if I push the bike forward with my free leg while shifting to first, it has a better chsnce of catching the gear and staying in place. I've seen some other guys describe the same issue and discussions of "Under Cutting the Dog Ears". I dont know if this would solve my problem. I'm planning on rebuilding the entire bottom end. So I wanted to see what you guys thought. Any help or advice is greatly appreciated. Thanks fellas!!!

 

[jetmechmarty]

Hi Brandon!

That bike looks like fun. The four bolt exhaust valve cover on the left side says the engine is later than a 1971.
I have never heard of a need to undercut gear dogs on an XS650. I do not believe that’s your issue. Many Yamaha’s of the late 70’s early 80’s suffered blown 1st or 2nd gear due to worn dogs. The XS650 is not one of them.

Beyond that, someone else will have to chime in. Shift fork?

 

[Its been a long time]

Hi Brandon!

That bike looks like fun. The four bolt exhaust valve cover on the left side says the engine is later than a 1971.
I have never heard of a need to undercut gear dogs on an XS650. I do not believe that’s your issue. Many Yamaha’s of the late 70’s early 80’s suffered blown 1st or 2nd gear due to worn dogs. The XS650 is not one of them.

Beyond that, someone else will have to chime in. Shift fork?

Yes, you're right. I think without opening it up, it's just guessing.

 

[DeathGrip-IronWorx]

Hi Brandon!

That bike looks like fun. The four bolt exhaust valve cover on the left side says the engine is later than a 1971.
I have never heard of a need to undercut gear dogs on an XS650. I do not believe that’s your issue. Many Yamaha’s of the late 70’s early 80’s suffered blown 1st or 2nd gear due to worn dogs. The XS650 is not one of them.

Beyond that, someone else will have to chime in. Shift fork?

Hey thanks Marty its been great so far minus the the seat needing to be replaced haha.

Oh ok, interesting, I vaguely remember the guy telling me that the frame was one year and the motor another. I cant remember if that was a different bike I looked at though. However, he bought the bike as a whole running unit. So, if the block is older than the frame, then the swap must have occured prior to him. If that is true, are you insinuating that this is one of the original XS1 motors? I don't know enough about these bikes yet to pick out the minor details.

Also, heres a link to the thread on undercutting 1st gear and just one of the ones I've read on this forum. Let me know your thoughts. I greatly appreciate all of the knowledge, info, and feedback you share, positive or negative! Thanks Marty!!!

https://www.xs650.com/threads/undercut-1st-gear.54503/

 

[DeathGrip-IronWorx]

Yes, you're right. I think without opening it up, it's just guessing.

Hey LongTime, I appreciate any input or feedback you have. However, in my response to Marty above, theres a link to one of the undercut threads I've dug into. Let me know your thoughts, thanks man!!!

 

[gggGary]

Start with the easy things? Double, triple check you have full range of motion with your shift set up to get full engagement into first, Is the weight (vibration) of the shifter enough to back the trans out of first? Then look into centering the star gear, and shift spring broken, threads.
I suppose undercutting dogs is doable but complete transmissions, bottom ends, engines are dime a dozen so why bother?

 

[Its been a long time]

My guess? Is that if you put the clutch and gear shifts back to how they're supposed to be, the problem goes away.

Regarding XS1 motor - I believe it's possible to have a later head and rocker box on an XS1 bottom end. Four bolt valve cover means the top end is not XS1. The engine number and lack of electric start facility will confirm or not if the engine bottom end is an XS1 or not.

 

[ckahleer]

+1 on the last 2 posts. you could also put a bungy cord to your shift lever in a way that it provides some forward force. If that keeps it in gear, a permanent solution may be adding a torsion spring to the shifter shaft.

 

[Jan_P]

Start with the easy things? Double, triple check you have full range of motion with your shift set up to get full engagement into first, Is the weight (vibration) of the shifter enough to back the trans out of first? Then look into centering the star gear, and shift spring broken, threads.
I suppose undercutting dogs is doable but complete transmissions, bottom ends, engines are dime a dozen so why bother?

That is what I would do also . These gearboxes don't wear out so easy. . Solid and not so much power.
I would check out the star wheel and " Sharkfin " thing that moves it so everything is adjusted.

Shift forks also rather solid ..but everything can happen.

Post 47 # there
https://www.xs650.com/threads/shift-cam-issue-post-rebuild.67300/page-3#post-862095

I don't remember but there are springs involved . I replace those rather quick .Based on experience from other machines
Usually not so expensive and can bring the " Clonk " back into the functionality.
If I remember there are springs at other places for this also.

Clutch adjustment check.