Zongshen RX3: How the 6-Speed Transmission Operates - Page 2

SpudRider · 12-01-2015, 12:50 AM

Now that's a real gear box.

FastDoc · 12-01-2015, 10:45 AM

Quote:

Originally Posted by SpudRider

Thank you, Brother Bill.

Indeed, the motorcycle transmission is amazingly rugged, yet elegant in design.

P.S. Have I told you how nice it is to have you back with us.

Thank you again, Brother. Happy to be back and grateful for the (re)welcome home.

FastDoc · 12-01-2015, 10:50 AM

Quote:

Originally Posted by Jay In Milpitas

Very nice work, Spud.

Many folks ask why it's difficult on most motorcycles to shift to neutral while at a stop.

If you look VERY close in entry #9 you may be able to see that the engaging dogs have a slight angle in the portions that mate together.
It's most evident in the pair on the upper shaft, the 2nd & 3rd from the left. That back cut forces the dogs together while they have load applied.

When you are at a stop with the bike in gear and the clutch lever pulled in, there is still drag between the clutch plates which applies load against the dogs.

So when you are trying to find neutral at a stop, it takes more effort with the toe to move the shift drum because the dogs don't want to release. Add to that the knowledge that you only want to move the toe shift lever a tiny bit and you start to tense up. Suddenly Second, now First again,,,,, darn it!

Anyway, we've all been there, but hopefully now you understand why.
And practice catching neutral before fully stopped.

Thanks for that explanation, Jay.

What bike does that transmission go to?

FastDoc · 12-01-2015, 10:51 AM

Do any other machines use motorcycle transmissions?

Jay In Milpitas · 12-01-2015, 11:49 PM

Quote:

Originally Posted by FastDoc

Thanks for that explanation, Jay.

What bike does that transmission go to?

That was the Suzuki RP68, a liquid cooled three cylinder 50cc. A web search should show you more. I think their power peaked about 19,000rpm. I understand there were also rumors of 15 and 16 speed boxes.

Juanro · 06-29-2018, 01:45 PM

Just to add to the archive

sqwert · 07-02-2018, 11:41 PM

Gear ratios:

1st 2.583333
2nd 1.80000
3rd 1.33333
4th 1.10000
5th 0.958333
6th 0.880000

Excellent ratios for a very thin power band, high revving, high peak output engine. If you want a race or café or sport engine, this is a good set of gears, and I expect tweeking the RX3 up to about 35hp, maybe more, this trans won't run out of practical gear usage. I've had that problem with some race engines I've built--the more peak the narrower the power band.

RPM from 9000 at each shift:

1st-2nd 6279
2nd-3rd 6650
3rd-4th 7427
4h-5th 7840
5th-6th 8264

These ratios are too close to take maximum advantage of the limited power band of a brand new engine with a horsepower peak of 9000rpm and a torque peak of 8000rpm.

For instance, the XT225 transmissions in two of my TWs have a 3.090 1st and a 0.793 6th. One of my TWs has a TT230R trans, 2.92 1st and 0.793 6th.

The XT trans ratios are

1st 3.090
2nd 2.0
3rd 1.428
4th 1.125
5th 0.925
6th 0.793

RPM from 9000 at each shift XT:

1st-2nd 5825
2nd-3rd 6426
3rd-4th 7090
4h-5th 7400
5th-6th 7716

I believe a broken in stock engine would pull those ratios just fine, what with its extra 25cc. There is plenty of power band, just have to be a little more aware of what gear the trans needs to be in--you'll only have 2 gears to choose from rather than 3 or 4. BUT, reconfigure the final drive to the same overall ratio we have now and we will have a granny for pulling a substantial adventure load into some relatively remote areas. Gears similar to the XT ratios would better suit my riding, even with the 300cc bore kit. I'd like to go to more aggressive knobbies but worry about the clutch pulling a taller tire.

12-01-2015, 12:50 AM	#16
SpudRider Join Date: Jul 2008 Location: Idaho Posts: 25,054	Now that's a real gear box. __________________ Spud "Never argue with an idiot. He will drag you down to his level, and beat you with experience." Mark Twain 2015 Zongshen ZS250GY-3 (RX3) 2006 Zongshen ZS200GY-2 (Sierra 200) 2005 Honda XR650L 2004 Honda CRF250X 1998 Kawasaki KDX220 Mods made to my Zongshen ZS200GY-2: http://www.chinariders.net/showthread.php?t=6894
	0

12-01-2015, 10:51 AM	#19
FastDoc Join Date: Mar 2009 Location: Southeastern Washington desert Posts: 14,761	Do any other machines use motorcycle transmissions? __________________ Happy to serve.
	0

07-02-2018, 11:41 PM	#22
sqwert Join Date: Jun 2017 Posts: 382	Gear ratios: 1st 2.583333 2nd 1.80000 3rd 1.33333 4th 1.10000 5th 0.958333 6th 0.880000 Excellent ratios for a very thin power band, high revving, high peak output engine. If you want a race or café or sport engine, this is a good set of gears, and I expect tweeking the RX3 up to about 35hp, maybe more, this trans won't run out of practical gear usage. I've had that problem with some race engines I've built--the more peak the narrower the power band. RPM from 9000 at each shift: 1st-2nd 6279 2nd-3rd 6650 3rd-4th 7427 4h-5th 7840 5th-6th 8264 These ratios are too close to take maximum advantage of the limited power band of a brand new engine with a horsepower peak of 9000rpm and a torque peak of 8000rpm. For instance, the XT225 transmissions in two of my TWs have a 3.090 1st and a 0.793 6th. One of my TWs has a TT230R trans, 2.92 1st and 0.793 6th. The XT trans ratios are 1st 3.090 2nd 2.0 3rd 1.428 4th 1.125 5th 0.925 6th 0.793 RPM from 9000 at each shift XT: 1st-2nd 5825 2nd-3rd 6426 3rd-4th 7090 4h-5th 7400 5th-6th 7716 I believe a broken in stock engine would pull those ratios just fine, what with its extra 25cc. There is plenty of power band, just have to be a little more aware of what gear the trans needs to be in--you'll only have 2 gears to choose from rather than 3 or 4. BUT, reconfigure the final drive to the same overall ratio we have now and we will have a granny for pulling a substantial adventure load into some relatively remote areas. Gears similar to the XT ratios would better suit my riding, even with the 300cc bore kit. I'd like to go to more aggressive knobbies but worry about the clutch pulling a taller tire.
	0