Triumphrat

SMJoe

According to Haynes Manual (just purchased as dealer only had the up to 06 until recently) the final drive on my 07 Speedmaster is 16T front and 43T back. Imagine my surprise when I was lead to believe by service dept. that it is bigger and can anyone verify this to be the case? It is no wonder I find the revs high at highway speed. Assuming this is correct what would be the max size front one might use given the chain length supplied. Considering the previous 19T talk I can't guess what the difference would be going that tall. If there was a smiley for eating crow I'd post it here.

Pokeyjoe

I believe all 865 engines come with an 18T countershaft sprocket. The 790s came with 17T. I don't know where that 16T data came from.

It takes all of 10 minutes to remove the cover and count the teeth, btw.

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John
3-7-77
Some people are like Slinkies. They're really good for nothing. But they still bring a smile to your face when you push them down a flight of stairs.

SMJoe

It occured to me that it might be a typo in the latest Haynes manual but it does state 16 for Speedmaster and America 18 for all the other twins.

modre

there's only one way I know of flushing out a factoid.
move all the experts off to the side and count the teeth.

...then wash your hands.

PAAS

For the record, Triumph's own shop manual gives the final drive gearing on an 865cc Speedy as 16/43 (with a 112 link chain). Bear in mind that the Speedy has a 15" rear wheel when comparing the gearing with Bonnies, Thruxtons and Scramblers, which have 17" rears, so the sprocket sizes would need to be different to achieve the same effective gearing. You can go from an 18T to 19T on a Bonnie without needing a longer chain, so I suspect you could go up to 17T on your Speedy if you wanted to. It doesn't cost much to give it a go to see if you like it (or not).

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Paul.

Herts. UK
Aubergine & White 05 T100 (865cc) with numerous mods.
(Previously Ducati Monster S4 and several UJMs)

Pokeyjoe

I (humbly) stand corrected.

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John
3-7-77
Some people are like Slinkies. They're really good for nothing. But they still bring a smile to your face when you push them down a flight of stairs.

SMJoe

Not hidden but in very small print I found it in the manual says on the 07 Speedmaster and America its 18 on the front and 42 on the back. Guess I better heed that phone call message from my eye doctor and keep the order for the 19T sprocket.