Longer primary chain for 45 cu in

My 33t sprocket won’t fit with this primary chain

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flatheadDave
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Longer primary chain for 45 cu in

#1

Post by flatheadDave » Sat Nov 09, 2019 10:18 pm

Hello forum peeps!

I currently have a 27 tooth sprocket in my 45 cu in flathead.

I bought a 33 tooth to get more top end.

But with this 100 link standard chain, this 33 t won’t fit even when I move the trans all the way forward.

What would you do in this situation?

I don’t see any extensions for the primary chain or any sold longer than 100 links for that matter.

Thanks flatheaddave !



1950Panhead
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Re: Longer primary chain for 45 cu in

#2

Post by 1950Panhead » Sat Nov 09, 2019 10:48 pm

In the olden days the factory sold 102 link primary chains, however those days are over, I advise a smaller sprocket.

svkiwi
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Re: Longer primary chain for 45 cu in

#3

Post by svkiwi » Sat Nov 09, 2019 11:48 pm

I just buy a box of chain, cut it to suit and join using a regular chain link. Who said you need continuous chain?

Buddhahoodvatoloco
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Re: Longer primary chain for 45 cu in

#4

Post by Buddhahoodvatoloco » Sun Nov 10, 2019 12:20 am

Yup :)
svkiwi wrote:
Sat Nov 09, 2019 11:48 pm
I just buy a box of chain, cut it to suit and join using a regular chain link. Who said you need continuous chain?

kitabel
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Re: Longer primary chain for 45 cu in

#5

Post by kitabel » Sun Nov 10, 2019 12:25 am

Double master repair link

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Re: Longer primary chain for 45 cu in

#6

Post by svkiwi » Sun Nov 10, 2019 12:39 am

3/8 pitch duplex

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Re: Longer primary chain for 45 cu in

#7

Post by liberator » Tue Nov 12, 2019 8:58 pm

A 27 teeth sprocket is something you want for hauling a rig or for Servicars.
A 33 sprocket is a tad top tall I guess for a solo 45...city traffic will be a pain and kill your clutch.
Why not 31 or 32?

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Re: Longer primary chain for 45 cu in

#8

Post by kitabel » Tue Nov 12, 2019 10:02 pm

All sprocket sizes are a compromise, especially with the 3-speed transmission. Only in relatively flat areas with little low speed traffic are the largest sprockets entirely satisfactory.
The "crawl ratio" (how much torque multiplication takes place in 1st gear) is a product of the 1st gear ratio X the overall sprocket ratio (which is the primary drive X final drive).
Of course, the cure is not more ratios (although they offer 2 intermediate gears instead of 1, some British 4-speed boxes have 1st gear very similar to the stock 45) but a higher 1st gear, such as the original big twin 4-speed.
45: 2.47:1
BT: 3.00:1, over 21% more torque
Even the Frantisek 4-speed for the 45 is only 2.66:1, not much help @ +8%.

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