Author Topic: Sprockets front and rear GTO 350  (Read 2044 times)

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Offline Jens Jessen

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Sprockets front and rear GTO 350
« on: March 22, 2017, 04:06:00 AM »
1. Would like new sprockets, but can't find any. Where can I buy? Something else might fit - but what?

2. Need better accleration. Have a 15 teth in front and a 36 rear. Would like a 14 front and a 38 rear - good combination?

Offline rwgibbon

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Re: Sprockets front and rear GTO 350
« Reply #1 on: March 22, 2017, 08:17:59 AM »
Have you tried the owner of this site?

Randy

Offline Jens Jessen

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Re: Sprockets front and rear GTO 350
« Reply #2 on: March 22, 2017, 10:26:27 AM »
No. I was planing on buying something within Europe (EU). That will save me a small fortune in tax and costoms. I allways tripels the price!

Offline AlanJohn

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Re: Sprockets front and rear GTO 350
« Reply #3 on: March 22, 2017, 12:55:20 PM »
Where ar you based l may be able to help

Offline OldSwartout

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Re: Sprockets front and rear GTO 350
« Reply #4 on: March 22, 2017, 01:11:36 PM »
The front sprocket for a Kawasaki F9 (350 single dual sport from the early 70's) will fit. The only issue is that the F9 used a nut to hold the sprocket on, therefore the sprockets don't have the 3 holes for the retainer bolts. You can either drill and tap the holes in metal with a VERY hard surface, or find a heavy-duty snapring to hold it on the shaft. The good thing is that sprockets are available in nearly any size (at least in the U.S.).
Karl Swartout
Mooresville, IN
BS175 Roadracer. BS200RS, BS175HS
BS350 GTR

Offline Jens Jessen

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Re: Sprockets front and rear GTO 350
« Reply #5 on: March 22, 2017, 02:10:55 PM »
I am based in Denmark.

Offline OldSwartout

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Re: Sprockets front and rear GTO 350
« Reply #6 on: March 22, 2017, 04:54:47 PM »
I was hoping that model got imported into Europe, but probably not.

I checked, the JTF 437 you asked about on Facebook has the correct spline. The retention clip might need a little modification.

« Last Edit: March 22, 2017, 05:57:09 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer. BS200RS, BS175HS
BS350 GTR

Offline moonpup

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Re: Sprockets front and rear GTO 350
« Reply #7 on: March 22, 2017, 06:12:46 PM »
Jens, here's some previous discussion on 350 sprockets.....

http://bridgestonemotorcycleparts.com/index.php?topic=3301.msg17057#msg17057
Confucius say... "Better to have Bridgestone than Kidneystone"

Offline ziggy stardust

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Re: Sprockets front and rear GTO 350
« Reply #8 on: March 22, 2017, 06:15:54 PM »
Some times you just have to pay the price Jens, :'( doubt if you would ever need to replace them again? :)

Z
I am only responsible for what I say, not for how you interpret it.

Offline Jens Jessen

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Re: Sprockets front and rear GTO 350
« Reply #9 on: March 23, 2017, 05:33:35 AM »
 :) Well. You might be wrong. I drive a lot, last year I coverd 5.500 kilometers (+ 3.000 miles) on my Honda CL450K6 from 1974. Even went to Cuba on it, and drove arround the island! Nice place. Wrote an article about in Classic bike - January issue 2017.

Planing to do many miles on my Bridgestone GTO from 1970. I has only unbeliveable 1.586 miles on it since new!

Offline Jens Jessen

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Re: Sprockets front and rear GTO 350
« Reply #10 on: March 23, 2017, 05:38:19 AM »
Thank you som much - that was very usefull.
Jens, here's some previous discussion on 350 sprockets.....

http://bridgestonemotorcycleparts.com/index.php?topic=3301.msg17057#msg17057

Offline Gonzo

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Re: Sprockets front and rear GTO 350
« Reply #11 on: January 05, 2020, 09:01:58 PM »
The front sprocket for a Kawasaki F9 (350 single dual sport from the early 70's) will fit. The only issue is that the F9 used a nut to hold the sprocket on, therefore the sprockets don't have the 3 holes for the retainer bolts. You can either drill and tap the holes in metal with a VERY hard surface, or find a heavy-duty snapring to hold it on the shaft. The good thing is that sprockets are available in nearly any size (at least in the U.S.).

So I had a bit of time over the holidays and decided to give this a crack.

I found that the F9 sprocket is common with the S1, and much easier to find when searching for this as there were many more S1s than there were F9s. It's a JTF506, if you're sourcing from JT Sprockets (as I did). Spline pattern is the same as the Bridgestone.

With the boss the new sprocket is about 0.5mm too thick to fit onto the output shaft and still use the stock retainer, so I used a bench grinder to, uh, reduce the kerb weight.

Marked out the new sprocket using the 15t stocker as a guide and drilled and tapped 3x M6 holes for the standard retaining clip.

Drilling and tapping was an adventure. HSS bits made very little impression, even at very low speed and using cutting fluid, so I ended up using a brute-force approach with a selection of masonry bits in a pillar drill. It wasn't very pretty, but it got the job done. Took it slowly, started with a 3mm and worked my way out to 5mm. Chewed up a few bits along the way, but it was for a noble cause.



Invested in new taper and intermediate M6 taps to get the thread in. A bit of force required by the third hole as they were no longer pristine. Omelette, eggs.





Installed the sprocket with the ground-off boss facing the casing and the retaining clip bolts screwing into the flat side of the sprocket. Just like a bought one!



Haven't done a lot of miles with the new gearing (14/40), but initial impressions are very, very positive. Much less clutch required off the line, the bike will comfortably trickle along at walking pace and it cruises happily in 6th at 60-65mph without having to drop back to 5th for the hills. It's a proper useable 6-speed gearbox, not a 5-speed with an overdrive. I like it a lot.

After trying something different, I'm not sure why Bridgestone went with the 15/40 gearing. May have been something to do with being able to put the magic 100mph on the spec sheet?

Offline srpackrat49

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Re: Sprockets front and rear GTO 350
« Reply #12 on: January 06, 2020, 01:11:02 AM »
and thats watt a old schoolguy does.... they make do... just like if you have bent fork tubes.. putt them in a press,,,, done,,, don,t  need no stiken new parts........ been doing this for over 40 years........

Offline Jeff Bar

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Re: Sprockets front and rear GTO 350
« Reply #13 on: January 06, 2020, 08:32:08 AM »
Looks like a lot of work when all you had to do was contact Richard and get both sprockets, he has them in stock. At least he did when I bought my set.   popcorn. Jeff Bar
« Last Edit: January 06, 2020, 08:33:51 AM by Jeff Bar »

Offline dcr

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Re: Sprockets front and rear GTO 350
« Reply #14 on: January 06, 2020, 01:31:23 PM »
Nice work Gonzo. I respect and appreciate your ability to modify modern parts to improve on a not so modern bike. The sense of accomplishment can not be purchased on this site - but it can definitely be shared.

Looks like you are in Australia? If so, be safe - that fire is no joke.

Dan
1966 175 DT and 1968 350 GTR

Offline Gonzo

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Re: Sprockets front and rear GTO 350
« Reply #15 on: January 06, 2020, 09:39:31 PM »
Thanks Dan. All good, we're not in a vulnerable location. The smoke has been horrible. Long way to go, though. February is usually the worst of the fire season.

Hope RayK is alright.

Jeff - Does Richard have the front sprockets in 14t? There have been a lot of threads about changing the gearing over the years, and I've always been under the impression that the standard 15t front and 40t rear are all that Richard has, which is why I went my own way. Happy to be corrected if that's not the case.

 


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