GS550 47 tooth rear sprocket

[byrdman76]

Does anyone know if a 1983-86 rear 47tooth or 48tooth sprocket will fit a 1979 gs550 cast rim. I am looking to change the 50 tooth out to lower my HWY RPM.

Any one looking to sell a rear sprocket that has less that 50 teeth for 79 GS550? I'd be willing to try anything - has anyone been down this road before?

Thanks,

Byrd

 

[80GS1000]

http://www.z1enterprises.com/catalog.aspx?pid=GS550EN-1979-MP0

 

[humblepie]

will bigger mean higher top speed?

 

[Nerobro]

Yes it fits. Why do you want to lower the RPM? It won't do you any good at all. Your'e only turning 5500rpm at 70mph with the 50 tooth sprocket.

That's to say, yes I've been down this road. I'm quite sure it's a bad idea. if you had a GS650 top end it might be a different story, but only might.

 

[Nessism]

http://www.z1enterprises.com/catalog.aspx?pid=GS550EN-1979-MP0

According to Z1 both generation's of GS550 use a JTR816 rear sprocket. To lower rpm you can also go up one tooth in the front - only $14.

 

[Guest]

will bigger mean higher top speed?

No the other way around. Think of how a ten speed works. Same concept.
I went from a stock 40 tooth rear sprocket to a 42 to get off the line better but it lowered the top speed. Not by much though. Three tooth on the rear = to one on the front. The front sprocket is the opposite to the rear in changing gear ratio.

 

[Nessism]

One tooth on the rear = to three on the front. The front sprocket is the opposite to the rear in changing gear ratio.

Actually...it's the other way around. One on front = three on rear. 8-[

Lowering the gearing, higher numerically, makes the bike accelerate faster but reduces top end (assuming the original configuration of the gearing was optimized). Also, makes the bike rev higher for any given speed on the highway.

 

[Guest]

Actually...it's the other way around. One on front = three on rear. 8-[

Lowering the gearing, higher numerically, makes the bike accelerate faster but reduces top end (assuming the original configuration of the gearing was optimized). Also, makes the bike rev higher for any given speed on the highway.

Damn it! I need to proof my words better. Thanks! \\/

 

[byrdman76]

Thats the problem...

Thats the problem...

Yes it fits. Why do you want to lower the RPM? It won't do you any good at all. Your'e only turning 5500rpm at 70mph with the 50 tooth sprocket.

That's to say, yes I've been down this road. I'm quite sure it's a bad idea. if you had a GS650 top end it might be a different story, but only might.

The speed limit here on the HWY is 70MPH. I need to run 75-80 for about 30 miles during my daily commute. If I don"t, I get run over and tail gaited (regardless of the lane). This pushes the RPM range into the 7000 area. A little high for 30 miles straight in my opinion on a 26 year old motor.

If I could get the RPM to around 5500rpm at 80mph I would be happy.

Thanks for the replies, I'll check into Z1

 

[Nessism]

The speed limit here on the HWY is 70MPH. I need to run 75-80 for about 30 miles during my daily commute. If I don"t, I get run over and tail gaited (regardless of the lane). This pushes the RPM range into the 7000 area. A little high for 30 miles straight in my opinion on a 26 year old motor.

If I could get the RPM to around 5500rpm at 80mph I would be happy.

Thanks for the replies, I'll check into Z1

As you gear the bike up the rpm's will drop on the freeway but the bike will have a harder time getting away from a stop and will accelerate slower during roll on acceleration since the engine will be in a lower part of the power curve. The amount of engine speed reduction you are talking about is huge; from 7000 to 5500, and is not realistic. If you move up one tooth on the front sprocket and a couple down in the rear you will drop about 500 rpm which is about as much as is advisable.

 

[byrdman76]

Only 500RPM - are you sure?

Only 500RPM - are you sure?

As you gear the bike up the rpm's will drop on the freeway but the bike will have a harder time getting away from a stop and will accelerate slower during roll on acceleration since the engine will be in a lower part of the power curve. The amount of engine speed reduction you are talking about is huge; from 7000 to 5500, and is not realistic. If you move up one tooth on the front sprocket and a couple down in the rear you will drop about 500 rpm which is about as much as is advisable.

I thought that I would get a bit more than that - but I could very well be missing something here...

Please let me know if this doesn't sound right

Lets take the ratio of 5500RPM = 70MPH Then take the gear ratio of the drive train. 15:50 = 3.3333333333

5500RPM/3.3333333 = 1650 (rear wheel RPM)

1650 RWRPM = 70MPH

Now take the 16:47 Gear ratio = 2.9375.

5500RPM/2.9375 = 1872 RWRPM

1872 RWRPM = 78.82MPH @ 5500RPM.

This would put me where I would want to be on the HWY. What it would do to the bottom end would be a different story. The only way to find out would be to try it but if I would only drop my RPM's by 500 as you said it wouldn't be worth it.

Has anyone truly tried this on a 550? what sprocket changes (specific teeth) were made and what was the out come.

Thanks -

 

[Nessism]

I thought that I would get a bit more than that - but I could very well be missing something here...

Please let me know if this doesn't sound right

Lets take the ratio of 5500RPM = 70MPH Then take the gear ratio of the drive train. 15:50 = 3.3333333333

5500RPM/3.3333333 = 1650 (rear wheel RPM)

1650 RWRPM = 70MPH

Now take the 16:47 Gear ratio = 2.9375.

5500RPM/2.9375 = 1872 RWRPM

1872 RWRPM = 78.82MPH @ 5500RPM.

This would put me where I would want to be on the HWY. What it would do to the bottom end would be a different story. The only way to find out would be to try it but if I would only drop my RPM's by 500 as you said it wouldn't be worth it.

Has anyone truly tried this on a 550? what sprocket changes (specific teeth) were made and what was the out come.

Thanks -

Your numbers look about right. By going up one in front and down three in rear (I suggested 2 down in rear) you will drop the rpm from 5500 rpm @ 70 mph to about 4847 rpm @ 70 mph. Using my suggested sprockets, 16/48, the rpm would be about 4950.

If you gear the bike up that much it's going to run like a dog and have very little roll on power. To maintain any given speed on the highway you are going to have to use a good deal of throttle. To pass, you will have to downshift quite a bit.

Suzuki designed the GS engines to rev. It doesn't seem to hurt them one bit. In fact, engine loads are lower with the engine spinning at higher rpm. I say go up one on the front sprocket and be done with it. The bike will be slow to accelerate but not tragically so. Just my opinion of course.

 

[byrdman76]

Your numbers look about right. By going up one in front and down three in rear (I suggested 2 down in rear) you will drop the rpm from 5500 rpm @ 70 mph to about 4847 rpm @ 70 mph. Using my suggested sprockets, 16/48, the rpm would be about 4950.

If you gear the bike up that much it's going to run like a dog and have very little roll on power. To maintain any given speed on the highway you are going to have to use a good deal of throttle. To pass, you will have to downshift quite a bit.

Suzuki designed the GS engines to rev. It doesn't seem to hurt them one bit. In fact, engine loads are lower with the engine spinning at higher rpm. I say go up one on the front sprocket and be done with it. The bike will be slow to accelerate but not tragically so. Just my opinion of course.

I'll get the 16 for the front first and try it in stages. I'll make sure to also post up on my findings. The bike just seems to be wound up pretty tight at anything above 6000RPM - it gets buzzy. The bike will pull to 100MPH and approx 9000RPM but it sounds and feels like it could blow at any moment. The tach is a little strange, sluggish almost. It dosent seem very quick to respond to change - is this normal? The drive inside the valve cover seems fine but I have to maintain the same rpm for a few seconds to get a reading that seems correct. The tach cable seems fine as well.

I adjusted the valves when I first got the bike about two years ago - maybe 2000 miles. I might go back in and check them again just to make sure I'm not loosing power in that area - I'll also knock out a compression check at the same time. I'm confident the rest of the fuel and ignition is solid.

 

[Nerobro]

The speed limit here on the HWY is 70MPH. I need to run 75-80 for about 30 miles during my daily commute. If I don"t, I get run over and tail gaited (regardless of the lane). This pushes the RPM range into the 7000 area. A little high for 30 miles straight in my opinion on a 26 year old motor.

If I could get the RPM to around 5500rpm at 80mph I would be happy.

Thanks for the replies, I'll check into Z1

It's not a little high. What you'll be doing is pushing the bike out of where it makes power. which means you may not even be able to achieve 90mph. With the stock gearing, the bike is drag limited, not redline limited.

The age of the motor is irrelevant. Chronological age does not affect the strength of components in a motor. Mileage can.. but Suzuki designed their motors well and they effectively do not wear with age.

I have at least 12 hours of 100+ mph riding on my 60,000 mile 1980 GS550E motor. 100mph is 8250rpm IIRC.. It's been a while since I've ridden my 80. You have absolutely nothing to worry about.

 

[byrdman76]

It's not a little high. What you'll be doing is pushing the bike out of where it makes power. which means you may not even be able to achieve 90mph. With the stock gearing, the bike is drag limited, not redline limited.

The age of the motor is irrelevant. Chronological age does not affect the strength of components in a motor. Mileage can.. but Suzuki designed their motors well and they effectively do not wear with age.

I have at least 12 hours of 100+ mph riding on my 60,000 mile 1980 GS550E motor. 100mph is 8250rpm IIRC.. It's been a while since I've ridden my 80. You have absolutely nothing to worry about.

I rode into work today at about 75mph/6000rpm - and it didn't blow up :-D If i keep the rpm sustained it seems to settle down vibration wise, but it sure seems like its working hard. The vibration at anything above 5grand just seems excessive (any gear).

I'm going to check the timing, valve clearances, compression, and I might even check the clutch since I haven't ever inspected it. Maybe its slipping at higher RPM's? It doesn't feel like it though.

My problem may be that I grew up on ZX-6's, CBR's, and Gixxer's. Maybe I'm a little cautious since this vibration isn't typical on modern sport bikes. The level of vibration may be perfectly normal for this bike.

I'll let you know...

 

[byrdman76]

Checked the compression tonight and this is what I found. Engine warmed up, all plugs pulled, full throttle. Typically turned the motor over 8-9 times to get these results. Repeated several times to get an acurate number.

cyl 1 = 135psi
cyl 2 = 125psi
cyl 3 = 145psi
cyl 4 = 145psi

Is 125psi on cylinder 2 too low? Is this much variation typical - what is too much?

Pulled the valve cover and tomorrow night I'll check the valve clearances once the motor cools down.

Thanks for you help,

Byrd

 

[badbrown]

I'm running a 45T in back and stock 15T in front with a 108 chain on my 78550. And it's much more comfortable on the highway. I'm thinking I could have went with a 43T in back and got away with it. Check the ratios on the JT sprocket website. I think I lowered it 1000 rpm at highway speed. Less wear on the engine too.

 

[byrdman76]

I'm running a 45T in back and stock 15T in front with a 108 chain on my 78550. And it's much more comfortable on the highway. I'm thinking I could have went with a 43T in back and got away with it. Check the ratios on the JT sprocket website. I think I lowered it 1000 rpm at highway speed. Less wear on the engine too.

Thanks for the heads up man. Did you loose much bottom end?

 

[byrdman76]

Went with the 16 up front

Went with the 16 up front

Man what a difference. The bike is much happier with the 16 vs 15 tooth sprocket up front. The highway is a breeze now - 75MPH at 5400-5500RPM. In addition I didn't loose any bottom end. I feel i gained a bit since I feel i can stay in first and second longer.

I did however discover something that I can not explain nor figure out and I dont believe its a coincidence. I was inspecting the clutch adjustment and noticed that the pinion assembly to engage the clutch came out when i was messing around with it. I got to looking at it and noticed that it had 4 positions that it could go in that would effect the final position of the pinion. I tried each location until the pinion in its final position would keep the dust seal on the ring assembly throughout its range of motion with the cable installed. The pinion was not in this location before it was further out or closer to the clutch rod.

I greased up the pinion and put everything back together. As soon as i fired the bike up i noticed my tachometer was actually very responsive. This thing has been sluggish since Ive had the bike and i have torn apart everything to found out why with no success - everything has always looked great.

Maybe its a coincidence, but I rode this bike the day before, have ridden it a couple of thousand miles in the same condition and as soon as I messed with the clutch pinion position and adjustment it started working like a dream.

Am I crazy or is this somehow connected?