350 GTR/GTO REAR SPROCKETS

[moonpup]

Recently in another thread the topic got diverted somewhat with the subject matter turning to the discussion of increasing the "driveability" of the 350's by increasing the number of teeth on the rear sprocket by 4 teeth.

To quote..... "By the way if you plan on riding consider using an additional 4 teeth on rear sprocket. You will be astounded on increase in around town driveability as well as highway performance including use of 6th gear."

I posted some pic's of the 2 sprockets I had but at the time didn't know the exact number on the larger one. Turns out, the smaller one is the stock sprocket with 36 teeth and the larger one has 46 teeth.

I'm guessing that's a few too many.......  

[slawsonb]

Depends. Might be perfect if you are planning to pull stumps...
 
...bert

[moonpup]

Depends. Might be perfect if you are planning to pull stumps...
 
...bert

That or I thought it might make it 2 & 1/2 times more driveable! 

[slawsonb]

An excellent point! Shoould we coin this the driveability ratio?...or Moonpup's Coefficient of Driveability?
 
...bert

[moonpup]

Awww shucks..... 

[Colin]

  ten teeth more, I thought it looked a little bit too big, you'd be lucky to travel more than 15 feet in 1st gear before you needed to shift up , chuckle chuckle
However I have been busy on the internet and it seems that rear hub size with the six bolts is only on the BS GTR, I cannot find a Yamaha or Suzuki rear sprocket to fit, I researched the T and GT series Suzuki's
and the Y and RD, RZ Yamaha's.
Maybe somebody will have a bit more luck, there is a company I found who will make them and they do one offs but I suspect it going to be expensive for one rear sprocket.
I guess I'm going to look at a smaller front though that can be a problem with the chain on a lower run eating away at the swinger arm, I will know better once I have my bike back together and can see how much clearance there is.

[farmerdl]

What company does the one offs.  Sometimes what seems to be really expensive might be worth it.  I've had local machine shops fab various parts for everything from bike to ag equipment parts and sometimes was pleasantly surprised.

[moonpup]

What are the dimensions one should be looking for? Like rear hub size, etc. I spend a lot of time on the net (waaaay too much actually  ) and could spend some of it searching for a source.

[wonkyworks]

I had a rear sprocket made for my Wards Riverside Benelli by Rebel Gear  http://rebelgears.com/ two years ago, it was $49.14 for the sprocket and $12.88 for the shipping. They did a nice job. Doug

[slawsonb]

http://www.sprocketspecialists.com/
It looks like these guys could do the job, but i haven't had time to fill in the info to get a quote...
Thanks to Jimmer for the pointer...
...bert

[farmerdl]

One thing to remember is the need for tooth count of both sprockets and the number of drive chain links to be prime numbers.  For all three to be prime is best, two next and at leas one.  If none are possible odd numbers should be used as they fewer possible factors.  This came up on Do The Ton a while back.  Kopcicle (that's his online name and you will find him on a number of forums) had a good post about this back in mid Sept. if I remember right.  You might find some more about this at gearmasters.com.  I hope that's right.  I'll try to check back on that as I am sometimes a veritable fountain of misinformation

[Skinny]

moonpup & all
After reading these posts on sprocket rear sprocket size, I am somewhat relieved.
When I ordered and tried to install a new chain with the correct number of links,
it was too short. After getting my head out- I realized my rear sprocket was 38
teeth, not 36. This has bothered me a little because I wondered if the bike would
be geared too low.
I know that you should replace sprockets when the chain is replaced. After checking
availability it was not a cheap or easy option. Besides, both front and rear seem to
be very nice- showing very little wear.
From what you guys are saying, maybe two more teeth might make the GTR a little
more ride able and pull high gear better?
Cheers,
Skinny

[slawsonb]

Can't hurt to add a couple of teeth. I have replaced chains without replacing sprockets in the past in a similar circumsatnce (very little sprcket wear) and had good results. I plan to do this again when the old hoss starts running again as the chain ws rusty enough that I don't want to trust it, but sprockets are good...
...bert

[Colin]

I wonder if any of you have spotted this little gem on Ebay
http://www.ebay.com/itm/BRIDGESTONE-350-GTR-GTO-front-sprocket-special-made-by-SUNSTAR-/331104793560?pt=Motorcycles_Parts_Accessories&fits=Make%3ABridgestone%7CModel%3A350&hash=item4d176233d8&vxp=mtr
Look at the different sizes, so here we have it an easy way to lower the gearing on the GTR by fitting the one tooth less front engine sprocket and thereby making top gear more useable, might be at the expense of 5-10 mph off the top speed but hey it's a small price to pay and it should make the bike accelerate a little quicker too.
Colin.

[husker]

I had Rebel Gears make a 40t rear sprocket and I did not get the center hole measurement right. Remeasuring I get 78mm. The bolt circle I had correct at 120mm with the holes being 10mm. Thickness at the center hole is 7.5mm.  Could some of you guys measure the center hole and see if we can get a consensus of the size.  I will give Rebel a call and give them the correct measurement.  Thanks..............Rod

[disc_valve]

Site member Kotaro had some of these 14T "Sunstar" sprockets for sale a while back. I bought one and have been running it on my  own GTR since last summer. It makes the bike a lot more "driveable" around town, and I am now able to use all the gears comfortably. As standard, 6th gear was really too high to use in the 30mph speed limit. I always felt the urge to change up if I left the bike in 5th, so I ended up constantly swapping between 5th and 6th.

The smaller sprocket doesn't seem to make the bike sound "busy" at higher speeds, so I reckon the GTR was simply geared way too high from the factory - presumably to allow it to reach the absolute maximum top speed. Talking to mechanics and dealers who rode GTRs when they were new, the accepted practice for top speed was to run the engine up to 7500rpm in 5th before snicking into top and tucking down out of the wind, which again suggests super high gearing. Needless to say, I don't subject 45 year old engine internals to that sort of stress these days!

The advantage of using a small front sprocket instead of adding 3 or 4 teeth at the back is that I could use the standard length chain.

Graham

[OldSwartout]

FWIW - Looking through my service manual, I found a note from years ago - a Kawasaki F9 front sprocket will fit the GTR/GTO.  These should be available if anyone wants to change the front sprocket size.  The problem is that they were held on with a nut, so do not have the holes to bolt the BS retainer on.  You have to use a snapring (you would need a fairly heavy section ring to keep it on at high speed) or drill and tap at least one hole in a fairly hard sprocket.