Topic: changing sprockets on 77 cb400f?

[sohcphreek]

I think I want to change the chain sprockets on my 77 400f. It revs so high with the stock gearing. I dont want to ruin the performance and Im not sure what to replace the originals with (teeth count). And where to find new sprockets? Do I have to replace the chain , add or remove links ?
Any help would be greatly appreciated! can text 805-801-5635
sohcphreek

[tomkimberly]

These bikes were made to rev high. If you want a slow reving machine, buy a Harley. 

What sizes are your existing sprockets?

Tom

[Speedy]

Mine seems overgeared with the stock sprockets, so you may not have stock.

[Bankerdanny]

If you replace the sprockets it is a good practice to replace the chain as well.

What do you consider high? My GL1000 turns over about 4,000 rpms at 70mph, I think my 550 was more like 5-5500.

[sohcphreek]

Well seems to be 5 thousand at 55mph
on the front sprocket do you go up or down on the # of teeth to lower your rpm?

[tomkimberly]

Up, BTW, you did not answer what the sizes you now have.

[robvangulik]

That makes it 110mph at 10.000revs, which is probably the standard 17 front/38 rear gearing. Does it reach top revs in high gear? It was quite common  to run a 16 tooth front sprocket, which makes it rev even higher, and run a bit faster.

[sohcphreek]

Do I go more or less teeth on the front sprocket to lower my rpms?

[robvangulik]

It was quite common  to run a 16 tooth front sprocket, which makes it rev even higher, and run a bit faster.

Ergo an 18 tooth would make it rev lower..........

[sohcphreek]

Thanks for the info now off to sprocket specialties

[Bodi]

Maybe your tach or speedo are reading wonky? That's a rather high 6th gear rpm for 55mph.
I have a smaller front sprocket than stock. 5th gear runs about equal to mph (5000rpm=50mph) and in 6th I think 70mph is around 6k. Stock sprockets would give you lower rpm.
Count the teeth on both sprockets to see what you have. The wheel one may be bigger than stock and/or the engine one may be smaller. Changing more than three sprocket teeth total usually means changing the chain length: each tooth change equals a half-tooth difference in the axle location and there's not so much adjustment room there.
I agree with recommending a new chain when changing sprockets.

[Bankerdanny]

Bigger on the front, smaller on the rear.

[sohcphreek]

Front is 16 rear is 38, not sure what combo to try but sprocket/chain kits aren't cheap

[tom400f]

Standard front is 17, which is going in the right direction. I tried 16 once but prefer the standard setup, which is good for 100mph plus a little bit lying on the tank. Seems about right.

May be get one on ebay and try it before buying a complete new set?

(btw from the UK site - just passing!)

[sohcphreek]

Well I installed the new 17T gear and what a nice change! So much more enjoyable to ride.
sohcphreek