Longer primary chain for 45 cu in

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

All flathead topics
Post Reply
flatheadDave
Site sponsor
Site sponsor
Posts: 105
Joined: Mon Aug 05, 2019 8:07 pm
Bikes: 1948 G 45", 1969 FLH, 1963 FLH, 1965 FLH
Location: LA
Has thanked: 98 times
Been thanked: 18 times

Longer primary chain for 45 cu in

#1

Post by flatheadDave »

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
Posts: 1917
Joined: Wed Jul 07, 2010 4:28 am
Bikes: 1950Panhead
Location: USA
Been thanked: 219 times

Re: Longer primary chain for 45 cu in

#2

Post by 1950Panhead »

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

svkiwi
Posts: 146
Joined: Mon Jun 03, 2013 2:58 am
Bikes: 1946 WL
Location: Masterton, New Zealand
Has thanked: 23 times
Been thanked: 21 times

Re: Longer primary chain for 45 cu in

#3

Post by svkiwi »

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
Site sponsor
Site sponsor
Posts: 1543
Joined: Wed Sep 07, 2016 7:13 pm
Bikes: 1969 FLF
1937 EL
1940 U
Location: san diego
Has thanked: 728 times
Been thanked: 113 times

Re: Longer primary chain for 45 cu in

#4

Post by Buddhahoodvatoloco »

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
Posts: 1021
Joined: Tue Aug 03, 2010 7:10 pm
Bikes: 2008 96" Fat Boy TC
Location: Lynbrook, New York
Been thanked: 144 times
Contact:

Re: Longer primary chain for 45 cu in

#5

Post by kitabel »

Double master repair link

svkiwi
Posts: 146
Joined: Mon Jun 03, 2013 2:58 am
Bikes: 1946 WL
Location: Masterton, New Zealand
Has thanked: 23 times
Been thanked: 21 times

Re: Longer primary chain for 45 cu in

#6

Post by svkiwi »

3/8 pitch duplex

Pascal
Posts: 311
Joined: Wed Aug 13, 2014 8:27 pm
Bikes: WLA
Has thanked: 4 times
Been thanked: 36 times

Re: Longer primary chain for 45 cu in

#7

Post by Pascal »

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?

kitabel
Posts: 1021
Joined: Tue Aug 03, 2010 7:10 pm
Bikes: 2008 96" Fat Boy TC
Location: Lynbrook, New York
Been thanked: 144 times
Contact:

Re: Longer primary chain for 45 cu in

#8

Post by kitabel »

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%.

Post Reply

Return to “Flathead and Servi-Car”