Bridgestone Motorcycle Parts Discussion Board
Bridgestone Tech Talk => 350 Talk => Topic started by: tjingers on May 25, 2021, 11:11:43 PM
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Hey all,
Nearing the end of my 350 restoration and came upon this while looking for a NOS front sprocket. Took measurements and looked around for 525 pitch sprockets on ebay, and found one for a DR650 which matches the spline exactly that comes on our output shafts... and it even has 3 tapped holes already in it (I've heard of the Kawi F9 sprocket but drilling and tapping hardened sprockets on center accurately sounds like a bad time). Here's the one i ended up with: http://www.jtsprockets.com/catalogue/part/JTF1448/
I think it was like 15 bucks on ebay for a 14t... I'm giving 14 a try after reading suggestions that the 15/36 ratio is just anemic in higher gears. JT offers a 15t too for the stock ratio.
The holes are a little closer together than the stock 350 retainer plate wants, so I chose to make a custom plate out of some scrap metal, but I believe the stock one could be used and just opened up to accept the closer bolt pattern. I was able to make the normal hex bolts go in, but it felt like they were rubbing the splines so i dug up some M6 socket head cap screws to clear the splines better.
The only real caveat to making it fit is that the DR650 has a bit of a boss on one side, which bumps up against where the splines "feather out" closer to the cases when you try to fit it up. I just took the boss off with a flap disc, keeping it cool by spraying water the whole time to not mess with the temper.
Here's what i ended up with: https://photos.app.goo.gl/Es2K5FSsbiaLUHTz9
Someone please call me out if that album doesn't work, it should be shared to anyone with the link.
Anyway, thought this might be useful since i know i had a hard time scavenging for a good sprocket. This bike came with an absolutely hammered 11 (yes, eleven) tooth front sprocket. Must have been an absolute blaster.
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Maybe I am missing something, I just buy a new front sprocket from Richard........Jeff Bar
Not sure there's anything to miss, richard doesn't publicly list the front sprockets on 6x6 or ebay, and if he did (correct me if i'm wrong?) they would be the standard 15t factory sprocket.
Anything wrong with having documented, relatively easy parts interchange with the aftermarket on a much newer bike?
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I like the idea of finding another sprocket source, especially for other sizes. The 14/36 ratio in place of 15/36 puts 6th gear almost exactly where 5th gear was. If anyone wants to split that and just bring 6th down a little, go to a 15/38. That requires a special rear sprocket which is more difficult. There is a thread on this forum about it, about 6 yeas ago Rebel Gears in Nashville made one and should still have the dimensions. There are actually several threads on this forum about the tall 6th gear issue.
FWIW, when I set the ignition timing on mine by using 25ยบ BTC (3.43mm/.135 in) instead of using the crankshaft timing pin, 6th gear became more usable. It still doesn't accelerate well into a headwind, but pulls well on most interstates at speed. I never even try to use it below 55 mph.
I know the issue of trying to drill and tap hardened sprockets, needing to use various sizes on my 175 road racer. I finally just put two snaprings back to back in the retaining groove in the shaft to hold them on; worked fine.
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Come on you guys, we all like BS's, isn't that enough! :)
Richard Clark
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It is for me. Glad you intervened - this was getting childish.
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I know the issue of trying to drill and tap hardened sprockets, needing to use various sizes on my 175 road racer. I finally just put two snaprings back to back in the retaining groove in the shaft to hold them on; worked fine.
Oh, so you just let it float but have the snap rings to keep it from flying off, basically?
I had been wondering how important the retainer design was, not being that familiar with the intricacies of motorcycle chain drives. I'd imagine the chain tension itself is enough to keep it sort of where it's supposed to be, and maybe the 3 bolts on a 1/8" retainer plate is overkill. I figure for not knowing enough, i should probably duplicate the original design as much as possible.
I did decide to do an o-ring chain, so keeping it right where it's supposed to be might be prudent in my case, since the chain is a bit wider than the stock one.
Yeah didn't mean to start anything nasty here, just wanted to have this out there for the next guy to google around about where to get sprockets. No shade intended if you do indeed have these in stock, richard, just putting it out there.
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Yes , just let it float. The two snaprings take up about the same space as the retainer, so it floats about the same. Design-wise, a snapring can be forced out of it's groove with constant axial force and some movement of the part it is retaining, but that's not the case here.
Different brands used different configurations. Some use a nut tightened so the sprocket can't move at all relative to the shaft, with a spacer on the shaft that has to be tight to prevent oil leaking between it and the shaft.
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Yes , just let it float. The two snaprings take up about the same space as the retainer, so it floats about the same.
When we were having this discussion, I forgot I also did the snapring trick on my GTR. Was looking for a leak today and realized my 350 had snaprings holding the sprocket. Poor photo, but you can see the snaprings.