Unclutching (fixing / welding up) a Yamaha XV starter clutch

 So imagine this, your beloved steed (in my case a Yamaha TR1, but the same will also apply to XV700s, late 750ies and of course 1100s), instead of greeting you with the much beloved sound of grinding and crunching starter gears, greets you with this noise

So it's disconnect the battery and take the left sidecover off time.

The name starter-"clutch" might be a bit misleading as it really is a one-way-clutch and as you can see in the clip below, the clutch in this engine is more an "open for everything" clutch. (Which is a great mindset in general, but a bit problematic, when the clutch is supposed to drive the engine in only one direction.)

As you can see, if you look at it closely, I already welded up the clutch once, but this didn't quite yield the results I wanted. (The tacks on the back sheered off.) 

In order to fix this mess, we need a starter clutch (I am using a broken one, which luckily I didn't throw away last time, a shaft for alignment of the parts (your starter will do just fine, I had the shaft from a broken starter, at least an angle grinder and a welder with some chest hair as the parts are relatively thick. I will do it in a slightly more elaborate way on the lathe, but that's really totally unnecessary as will come apparent over the course of this post. (But it's been like four or five years since I modified my last starter clutch and the first time to do it this way.)

All the parts as outlined above and an 18 tooth (XV1100) starter clutch, for a regular TR1 with the original starter, you'll need the 19 tooth version. 

The whole starter clutch is held together by the folded over lip on the back, which I carefully removed on the lathe. A simple cut through the thin metal shield perpendicular to the axis of rotation with an angle grinder would achieve exactly the same result in a lot less time. 

Peeling the metal shield back reveals the actual retainer plate and because everything is rather worn on this clutch, the gear can be pulled out. 

 

Plate, springs and pins inside can be discarded and the gear and the clutch housing be reinstalled on the shaft, in order to trim it back substantially, so it can be welded, where the two parts meet up.

At this point I have to admit, I used my trusty lathe as a rotary head and cut the housing with an angle grinder as it is STUPIDLY hard.

 

And yes, I cut it too far towards the end initially, but we'll call this a lightening cut to reduce rotational mass and improve starter acceleration. 😅
 

After cleaning the two parts can be welded together, obviously while assembled on the shaft, so they are in proper alignment. I did it with TIG and quite a few amps, but probably it could have done with even more and probably some quenching in between, because I think I properly tempered the part. (Undid the heat treating/hardening of the steel.)

 

If you trim it down a little further, so it is the same diameter as the gear on the back (or less), you can make it small enough so in theory the start can be removed w.o. taking off the cover. (Not yet tested, but in my mind none of the other starter components in there can fall out...)

 

Additionally I had to ream the bronze bushing inside the gear of mine, because it always had been an overly tight fit on the starter shaft and while this is a good thing for alignment, having to install it by hammering it onto the shaft certainly isn't for either the starter OR the starter clutch. (Normally this isn't necessary, but the clutch shown was one of the cheapest ones I could - and apparently for a reason.)

 And that's what it looks like, reinstalled. 

 Reinstall the cover, fill up with oil, hook up the battery and all the other bits you removed, cross your fingers, hope for the best ... you get the idea.

 And then... nothing.

 It does help to hook up the wire to the actual solenoid. Probably to the great dismay of a bunch of Yamaha engineers, it works just fine without the extra clutch between starter and flywheel. 

 

... but boy oh boy does the old girl sound fine, when she "just" fires up right. (Added bigger pilot jets and turned the air-screw in half a turn and she just starts like it's an EFI bike... perhaps even a bit better.)

 

So it does work remarkably well with the welded up / one piece drive sprocket. Even the initial repair would probably have been sufficient, if I am honest, but a few carb issues made starting a lot more difficult and the constant backfires eventually broke the welds. Not sure what would break this time, admittedly I am not overly keen to find out...