78 550E ..will changing sprockets give me more low end torque?

[Super]

Hi all...On the project 78 550E me and the boys are working on, we are going to get a new chain for it. During this process, we plan to get new sprockets also. From what I understand from reading other posts here, these bikes make the most of their power from 6,000 RPM's and up. We have the original stock VM carbs on it.

We were wondering if we change out to other than stock sprockets, would we be able to get some more lower end torque to make it a bit quicker? If so, which ones would we need? Like how many teeth on each sprocket, front and back? What is the best chain to use to match up to the new sprockets? And finally, would we see enough of a performance change to make it worth the outlay of money to change out from stock sprockets? We're not looking to be racing it or anything like that. Thanks

[hampshirehog]

If you put a bigger rear sprocket on there, or a smaller front one, she'll be higher in the rev band for any given speed. She'll also hit the red line in top earlier. You won't go any faster - other than you may be able to 'get away from the lights' a tad quicker. I would advise you to keep stock gearing and just use the gearbox a lot - just make sure that it sits between 6k and 10k or 11k (upper limit is up to you) all the time and you'll be going as fast as the bike is capable.

[Super]

Thanks hampshirehog. If I wanted to get some lower gear "quickness" by changing one of the sprockets, do you think it would be noticeable? Seems to me that city driving might like a little more quickness gearing up in traffic. If I do decide to do this, which sprocket would be best to change out? The front or the back? Thanks

[7981GS]

Add 2 teeth to your rear sprocket since you will be changing both anyway along with the new chain.
The axle will be forward a bit due to the lager gear when the chain is adjusted properly. (with stock length chain)
You may need a few more sections of chain length as well so get a longer than stock chain and cut to fit.

Daniel

[Super]

Thanks 7981GS. Sounds good. Was wondering if anybody has done something like this already and can tell me if there's a noticeable change?

[hampshirehog]

Standard front is 15 teeth which is already below what is theoreticaly optimum (somebody much cleverer than me explained optimum to me a long time ago so don't ask me how it is defined) so I would go up on the back and yes, 2 teeth is about it. You will notice a snappier getaway from the lights but you will be changing gear sooner so 'you pays yer money you makes yer choice'.

Easier to wheelie!

[Super]

Thanks hampshirehog, that's what I was hoping to find out. Up 2 teeth on the back sprocket. This is about the outcome I want. Just a bit quicker on take off but not a major modification. Anybody else want to add to the converstion, please do.

[gpd211]

Read on any sport bike or sport touring forum and the -1/+2 mod is usually the first thing done. On any bike you change sprockets on you loose top end. On a 160 mph bike this isn't a big deal. On a 550E it MIGHT be. Not sure how much highway riding you do now and what rpm you see on the highway, but the rpms will go up if you go smaller in the front or larger in the back. Not sure how much fun that would be cruising at 70mph at 9k rpm (pry an exaggeration but you get the point)

[Nessism]

I'd use the stock gear ratio. The 550's are already geared pretty low so the bike will be screaming on the freeway if you lower the gearing from stock.

[Super]

Thanks gpd211 and Nessism, I understand your reasoning. I guess my next step is to take her out down the highway and see just what rpm's I'll be turning at 55 and 65 mph. That will probably decide if I change from stock sprockets or not. I greatly appreciate your experience and wisdom on this.

[7981GS]

With 2 more teeth on the rear sprocket, you might gain as much as 500 rpm in 6th gear.
Probably closer to 300 rpm.
That's about it.

Daniel

[Super]

Thanks 7981GS. So I'm guessing that the added 300 to 500 rpm's would help it in the lower gears be a little bit quicker. But since it has a 6th gear, it shouldn't cause too much more vibrations at higher cruising speeds. I will take her out and check the rpm's in 6th gear at around 55, 65 and 70 mph just to see what the tach reads. Thanks again.

[7981GS]

As you will buying new sprockets to go with the new chain anyway, also order a front sprocket with one more tooth than stock and
you can change that one out easily for when you will be doing more highway type riding and effectively change the final drive ratio to
similar to reducing the rear tooth count by one tooth from stock while keeping your new 2 extra tooth rear sprocket on the rim.

Daniel

[Super]

Great idea!! Sounds like a good plan. Will do. Thanks again!