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Discussion Starter #1
What are this esteemed forums opinoins on the best CS sprocket for a 904 kit 790 Bonnie? I will not be doing a lot of highway riding (Daytona takes care of ALL that) but do not want the bike to lug around town. Currently had a 16T in it with the stock engine and that was fun around town but gave up TOO much top end required too much shifting. Lets hear it!
 

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The 17 sounds good. I think I'll pop it back on and try it for a while. Baby is all ready for a trip to the dealer. Pulled the tank, seat and side covers. Have you done the 904 yet SM?
 

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I've also been very happy with the 17T; before the big bore, my Speedmaster had the stock 16T count sprocket, I figured that the BB would give me enough additional torque where I could afford to go to a 17T front, and conserve on fuel economy without losing any of the take-off grunt.
 

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I did 22,000 miles on an 18 tooth 790cc,

I've been doing the last 1,200 miles on a factory 17 tooth 790cc,

can't say as any obvious differences have become apparent to me.

Given that you won't be doing any 70 mph touring, and may not wanna act-a-squid 'round town, I think the choice is a given....

go 17 tooth.


:cool:
 

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I have not done the 904 yet. I'll be ordering the Wiseco kit within the next 2 weeks. I have already ordered my oversized valves for the head. In the next 2 weeks I will also order my HSR41mm mikuni carb kit from bonneville performance.
 

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SM,

You using the stock valve seat with the larger valves? Is there enough meat for that or you having new seats fitted????
 

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The service manual is a little vague in that respect, but it looks like the valve seat itself can be modified. The manual (3.24) mentions either repairing a seat (if possible) if the seat width is outside spec, or replacing the head, so I'm guessing that Triumph doesn't recommend removal/replacement of valve seats. ouch.
 

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Hey SW,
Seely Engine told me they could do the larger valves. Do you know if we will get the new seals with the larger valves we ordered? I would think so.
16t will make roll on wheelies easier than a 17t.
 

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The old Triumphs also had cast in seats and no mention of replacing them, but you can. I suspect you can do it with the new Triumphs, too. Find someone with a Serdi machine.
You will get a lot more benefit from larger valves if the throat of the seat is also opened up.
 

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I've got a 19T on my "bionic" Bonnie. My previous bike was an '05 Sprint ST with a 110+ horsepower. Now I won't claim that the 904cc and 19T combination make the Bonneville the equal of the Sprint, but there is plenty of power and much more grinpower! For me everyday riding with the 19T works well.
 

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On 2006-12-10 13:41, Brooksie wrote:
Keef-what do you like about 18t compared to 17?
When I was running with the 17t sprocket I kept finding I was searching for a sixth gear, even before I fitted the BB kit. Since I've changed to the 18t the revs seem to sit quite happily at about the maximum speed I tend to do and, with the BB, I still get fairly reasonable power down low. I reckon you'll find the 18t an improvement over the 17 in that respect.
:cool:
 
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