Changing rear sprocket sizes on my 78 GS550E

[crc1214]

I am currently running stock (15T front, 50T back) sprockets on my 78 GS550E, and the gearing is a bit too torquey for my taste. I can cruise fine in a 35 mph zone in 6th gear. I also top out at about 70 mph on the highway. Too much vibration and the rpm's are at about 5800.

Anyhow, I can get a 46 T rear sprocket or a 40 T rear sprocket to change to. Which one would work best for me? Has anyone made such a drastic change as to go from a 50T rear to a 40T rear? Will that small of a rear sprocket make it a royal PITA to take off from a dead stop?

Thanks,

Chad
Columbus, OH 1978 GS550E

[lhanscom]

10 teeth is a big jump, but I don't think the 50 you have on it now is stock. I would go with the 46, that will make quite a difference. You could also change both sprockets and do a 14/40, which would give you about the same as a 15/43.

[Anonymous]

I had a 14/52 I believe. lhanscom suggested to me that I just go with a 15 front sprocket. Much easier to install and a hell of a lot cheaper. I went down a tooth. Not too sure as to rpm-speed ratio but I know that it made a difference. Payed $17 for it. Try that first, maybe a 16 or 17, if your chain will fit!

[lhanscom]

The trick will be if you have enough clearance to go with a front sprocket bigger then 15. Check it before you do it, unless of course someone here has used a 16 front. 1 tooth front = 3 teeth back. Roughly.

[Anonymous]

well Im sure that you could get a 16 on. I had to loosen the chain a little @ the rear tireto get it on. I have about another 1/2 of wheel space.

[Anonymous]

The stock gearing for a '78 GS550E is 15/50 as Chad said. I also have a '78 GS550E and decided I wanted higher gearing for the highway. I needed to replace chain and sprockets anyway so I got a 16T for the front and kept the 50T on the rear. As it turns out, my bike already had a 16T on the front and 50T on the rear, so I'm not changing anything. Mine turns around 5500 at 75mph in 6th, which is a little high but acceptable. It has decent takeoff in 1st, not tire-spinning wheelie-popping, but not so high you have to feather the clutch or anything.

15T is 94% of 16T, so you can figure on the engine turning 94% of the speed it does now in every gear and speed if you change to that - your 5800rpm on the highway would become 5452rpm (which is basically what mine is now). 40T is 80% of 50T, and 46T is 92% of 50T, so the same applies for either of those gearings, assuming you only change one sprocket. Front sprockets are cheaper and easier to change, and my 16T has plenty of clearance, it looks like a 17T would fit in there just fine. I recommend going to a 16T or 17T front and leaving the rear the same. If you're going to replace both anyway, you might want to try some combination like 16/46, which is 86% of 15/50 and would give you 4988rpm instead of 5800rpm. It's your choice, but you can do all the math before you start playing with it.

Alex

[Anonymous]

Yo Chad.....Will you hurry up and get those damn sprockets fixed already....LOL

I want us to go riding Saturday morning as we planned and I don't particularly feel like having to drag your butt out of a ditch and strap you sideways on Elsie to go get you fixed up. hahahaha

Just meesing with you. Missed you at the Rice Paddy earlier tonight somehow. But I did get the bar I was after.

Keep me posted on how it's going. We can always fall back to Sunday if needed. But hey, I'd rather go both days.

:twisted: :twisted: :twisted: :twisted: :twisted:

[jimcor]

On my 80 550L I have a 16T front and a 48T rear. Requires a bit of clutch on take off but, cruises nicely, although she won't pull redline in 6th. Hey, but that's what the Kawasaki is all about!

[Anonymous]

I was just researching this subject for my '80 GS550E, for exactly the same reasons - seems to rev a bit high on the highway for my taste, and it's zippy enough on the low end that I wouldn't mind giving a little of that up in exchange for a lower RPM on the highway. I, too, am comfortably in 6th at 35mph, and the bike doesn't seem too comfortable past 70mph, or even beyond 65 (which makes a little sense, having been built in the days of the 55mph speed limit - it feels just fine at 55).

And then some of the RPM figures you guys tossed around confused the heck out of me. 5500rpm at 75mph? I run an indicated 8000rpm at 70! With a 9500 redline, I really don't feel comfortable pushing it any faster than that for extended lengths of time. As far as I know, everything on the bike was stock when I bought it last year with just over 5k original miles. But the gearing may be weird. Or for all I know the tach may be messed up and reading way too high.

What do you think? Is my indicated 8000rpm really more like 5500? I'd rather not redline the thing and learn the hard way by fragging the motor.

[SqDancerLynn1]

I would think your tac is way off

[Anonymous]

What length chain do ya'll think I need? Stock is a 530x110 w/ 15T front & 50T rear. I am going to a 16T front w/ 50T rear, maybe a 530X118?

Thx

[Anonymous]

I would say that a 118 is way too long for going up 1 tooth on the front. I would either stay with the 110 length or maybe 112.
I'd be willing to bet if you went with 118 length that you would have to remove several links to get it right.
I dont think the increased diameter in the larger front sprocket will make much difference in you chain length.

[first timer]

you 550 guys are nuts if you think a 15t 50t combo gives your motor to much rev. keep in mind these bikes top out at 9000 and the power is at 7000-8500 rpms. i just droped my front to 14t and my back is a 50t, i am much happier. now i actually can play with the 1000 and 1100 boys and not get lost.

i would be very scarared to lower my rpms espscially on a 550 for the sake of getting rid of the buzz, you will lose substanial abilty to do a roll on accelration when you need to. which is a very good thing to have on the highway. like i said these bikes don't have much till 7500rpms.

if your bike is that buzz and uncomfortable i would look into why it so bad, maybe you timing is off, you wheels are unbalanced, your chain is loose. your not firing on all 4.

my point is these bikes are not to bad at the higher rpms, if maintained well, some gel biker shorts and some gel grips would be better hten upping a tooth in the front.



-ryan

[Anonymous]

1st timer, I do alot of highway commuting, 150 miles around trip. I was thinking (1) size up in order to save some gas $$$, I really don't have an issue w/ the ride at all. I was going on research thats all. So you don't think it is a good idea?

[first timer]

zook if you are running 8000 rpms at 70, you need to get out of second gear my friend 8O i am running a 14/50 combo and am turning 6500/7000 in 6th at 75 mph. when i had a 15/50 i was running about 5500/6500 at 75 mphs.

it sounds like you maybe running a 14/51 combo or sumtin if you are turning that many rpms at 70.

don't worry to much out over reving these bikes they are very tough and i have been giving mine a good work out for 2 years run well past 6500 rpms and its fine. just use a little mobil 1 if you are worried.



aschessla
150 miles is about a tank of gas and a tank of gas costs 2 buck a gallon and a 4 gallon tank, thats 8 bucks man not a lot of money. the money you spend on a new gear will be the money you save on gas.
i think i spent maybe 40 bucks last weekend and i did about 700 hard fast miles no highway crusing. not to be a jerk but i would not cut my 550 short of power just to save a few pennies. lets be honest here you are saving a bunch of money now driving a bike and not a car.



-ryan