New Sprockets

My '81 550 ltd has two severly worn sprockets. Just had the rear wheel off for a new tire. amd some teeth are broken. i know the front is really cupped. So i need two new sprockets. I have a 16 tooth in the front, and a 38 tooth in the back. ( 38/16 = a 2.38 gear ratio correct?) I want to gear my bike up, or make it faster, meaning lower rpms at a designated speed. right now its about 3,800 rpms at 45 mph in 6th gear. it was 4,000 rpms with my old tires! I can get a 17 tooth front sprocket from bike bandit. making my ratio 2.24. will that do what i want? the only rear sprocket available is the 38t. however, there is a 37tooth available for the '81 750 ltd. Will the sprocket fit on my wheel? if i went to a 17t/37t combo. that would be 2.18 final drive. because im adding a tooth in the front, and subtracting one in the rear, i wont need a new chain i think. any help will be appreciated.

Have you checked Z1enterprises Changing sprocket sizes
link ?

Going from 2.38 down to 2.18 will drop your cruising RPMs to about 92% of what it is now. I don't know if that is what you want.


You can get any rear sprocket you want from Sprocket Specialists but they are pricey. 32T is the smallest rear that can go on my KZ750.

ok while we are on the subject what size sprockets should i buy for a 78 kz1000 to increase speed ? i need a new chain so i would like to upgrade. is it wise to mess with factory sizes??? motor is bone stock. btw laymans terms will be just fine!!!!

so, if im doing 45mph at 3,800 rpms. 2.18 will be about 3500 rpms at 45mph? i get that by multiplying 3800 by .92 which is 3496 rpms. im not sure.

I use www.gearingcommander.com when changing sprocket sizes.

1981kz550ltd wrote:

so, if im doing 45mph at 3,800 rpms. 2.18 will be about 3500 rpms at 45mph? i get that by multiplying 3800 by .92 which is 3496 rpms. im not sure.

correct

That is my goal. to lower my rpms. I think my engine is powerful enough to handle the higher gearing. it just means i might have to downshift to 5th where i never used to, i dont mind. its just i dont like highway driving at 60 mph cuz its like. 5,000sum rpms.

Sorry to burst your bubble, but you need a new chain. Drive chains that have run on worn sprockets are worn to match the sprockets. Using them on new sprockets will lead to excessive wear on the new sprockets and greatly shorten the life of the sprockets. Sprockets and chain should always be replaced as a set. Ed

haha, my bubble is still intact! a new chain shouldnt be too expensive cuz its not an o-ring chain. like $30.

I have 17/38 on my 550. It turns 4600 or so @ 60mph. It pulls it OK. Get a good 0-ring chain, well worth the extra $20 or so IMO

I run 17/38 on my 550 also. At cruising speed I see a 300 - 400 rpm reduction. I don't really notice a big difference in acceleration from stop. Also, I'm not sure there is room to go any larger than 17 tooth on the front sprocket.