Overdrive 5th gear

Hello TCLBobber,
If you r confused as to which gear to buy, don't feel bad. I bought the larger gear from Mikes only after making careful measurements.
I have a 72, but installed an 81 trans. The large gear fits on both the 72 and the 81 shaft perfectly. Mikes data will conflict with this.

Anyway, to put ur mind at rest, make some careful measurements or bring it to a bike shop or machine shop. They should have capable people who can handle verniers and micrometers. Mikes can usually get the parts to you in 4 to 5 business days, so measure it then order it.

After many unfortunate delays, (although it rain every day lately), I will be installing the engine in the frame this weekend and have it running by midweek. I will let everyone know how it works.

Oh, I also installed the 33 tooth rear sprocket, the improved clutch kit, all new seals and polished the side cases and valve covers. Can't wait!

Good luck!
 
before deciding on buying and installing an overdrive/ 5th gear you might want to read this thread http://www.xs650.com/forum/showthread.php?t=28016&highlight=5th+gearand calculate the actual reduction in revs at cruising speed using a 5th gear and consider what you are hoping to achieve.

Its a bit of a misnomer to call it a 5th gear because its more accurately an overdrive gear that operates on all 4 of your existing gears . It simply reduces the final drive ratio


I used Pamco Petes gear calculator program and was very dissapointed to see the results of adding a 5th gear.

I calculated that the 5th gear would only achieve a rpm reduction of approx 180rpm at 60mph or in other words it would lower the speed from 60mph to 57.5mph which is pretty negligable in terms of vibration reduction I should have thought.

It looks to me that the far better and cheaper option would be to change the rear sprocket to a 30T .

There is a full explanation of my calculations and conclusion at the end of the thread. If I have made any mistakes perhaps someone would kindly let me know so I can amend the thread.

Hugh has an excellent tutorial on installing an overdrive gear on his site here so you can see exactly what is involved http://www.bikermetric.com/techtips-xs650-transmission-assembly-by-hugh-owings/
 
Thanks Marlin, I think I'm up to speed now.

I gather people only started installing newer transmission sets (post '78), replacing older transmissions, so they could use this after-market part when only one part was available for the newer transmissions.

If the new part, which you bought, can fit both transmissions is it still a good idea to use a newer transmission? Yamaha obviously changed it for a reason. I know how and why they changed it but idk if it's worth changing now you say that 5th can fit. Is it worth updating the transmission anyway regardless of the 5th O/D?

I will get measurements taken.

Thanks again.
 
Peanut, I have an HHB rephase ready to go in so I'm not so worried about vibrations so much. This is by no means a stock build. I had no idea this 5th O/D gear affected all gears, really none at all so thanks for that, I honestly thought it only did something for top gear cruising.

All I'm aiming for really is to put the best stuff into it as I rebuild. I come from a place of relative ignorance really as I've never ridden one of these, just bought a rusty old knacker for a project that'll wind up fast and cruise easy. Maybe I should forget this 5th and just build it and play with sprockets?
 
30t rear.....talk about no fun at all leaving lights or accelerating. 33t is the best so far I have found. 32 was okay. I wouldn't update the trans just because. They changed the splines midway through 77 or what ever it was for quieter trans operation.
 
TCLBobber,

I bought the newer trans also thinking that that was the only way to install the OD 5th, but it does fit on the 72.

I cud hav kept the 72 trans in there, but I went with the 81 because the gears were in much better condition. Actually, they were like new. I bought this bike in 1976 after I stopped racing 1/8, 1/4 and 1/2 mile on 250's and 125's. I broke 5th once back in 1980. Lets just say, I wasn't easy on the old XS. I went fast most of the time.

As for the OD 5th, when I put her back on the road in 2014, as in the early days, I was always kicking the shifter up thinking that I might be in 4th. Still do it today. Yes, the total reduction is like 4.7%, which is small, but I'm hoping it will make a slight difference.

30 teeth? That might be where I'm going next. I went to a 33t rear and the OD 5th for a small change because I like feeling G-forces once in a while.:bike:
 
OK...Ready? My old 72 is on the road again. 1981 trans, 1977 shift drum, shifting forks and associated parts and the 5th OD gear.

It shifts like a brand new bike. It's quiet, smooth and doesn't pop out of 5th anymore.

Twomany, you were right. My trans had other issues, and it was the shifting forks. One was clearly bent and severely scraped on one side. The 1977 shift drum and forks also fit perfectly and it came with the fork guide that is plugged on one end. Much better idea.

If I can figure out how to put pictures in these replies, I'll show you the difference between the drum followers on the shifting forks. They're hollow and appear to allow more oil to get down into the cam guides.

Well, it seems extra smooth, but I made several changes. Such as, Mikes clutch kit, (ita no slip now), new seals, (ita no leak now, only from the breathers), a new o-ring chain, new sprockets, 17/33. I also got new plugs, and wires and cleaned and secured all grounds and connections.

I don't get the urge to upshift every 5 minutes when I'm cruising. Yes the OD 5th isn't much, but now I know I'm in top gear. The 33t seems great, so far. A 30t wouldn't work in the North Georgia mountains.

I am very pleased. :thumbsup: My wife is not. :confused:
 
peanut said:
before deciding on buying and installing an overdrive/ 5th gear you might want to read this thread http://www.xs650.com/forum/showthread.php?t=28016&highlight=5th+gearand calculate the actual reduction in revs at cruising speed using a 5th gear and consider what you are hoping to achieve.

Its a bit of a misnomer to call it a 5th gear because its more accurately an overdrive gear that operates on all 4 of your existing gears . It simply reduces the final drive ratio


I used Pamco Petes gear calculator program and was very dissapointed to see the results of adding a 5th gear.

I calculated that the 5th gear would only achieve a rpm reduction of approx 180rpm at 60mph or in other words it would lower the speed from 60mph to 57.5mph which is pretty negligable in terms of vibration reduction I should have thought.

It looks to me that the far better and cheaper option would be to change the rear sprocket to a 30T .

There is a full explanation of my calculations and conclusion at the end of the thread. If I have made any mistakes perhaps someone would kindly let me know so I can amend the thread.

Hugh has an excellent tutorial on installing an overdrive gear on his site here so you can see exactly what is involved http://www.bikermetric.com/techtips-xs650-transmission-assembly-by-hugh-owings/
Click to expand...
Hello Peanut, I can agree with most of what you say, but as for the misnomer of the OD 5th increasing the overall drive gear, I beg to differ. Each gear is independent of each other. When in1st, all other gears are free-wheeling. The trans would bind instantly if they did not. The same goes for all gears. Mikes OD 5th only reduces the 5th gear ratio. All other ratios remain the same.

Hey, no offense, but if I'm missing something or if I read it wrong, please let me know.
 
Last edited:
Hey, Marlin, good to hear! Thanx for the input on the 5th gear ID. If you still have that bent shift fork, some closeup pics of the damaged areas would benefit other members in diagnosing their trans problems...
 
Hey Twomany. The 77 upgrade on the cam followers is much better than the 72, also.

If I could figure out how to get pictures on here I will. You may notice that my avatar is upside down. The 1st one I tried of my bike was only sideways. I need guidance.

Anyway, my new setup is very smooth. It is possible that the new wires, (just replaced the originals), and a fresh set of B8ES's, (the old ones were probably from 1980), have also attributed to the newly attained smoothness and it seems like more torque. Could just be in my head, but that's all that really matters.

As you can attest, spark plug wires from the early 70's didn't hold up very well.

Did anyone find it easy to attach pictures? Where's the paper clip?

One more question, Twomany, was that a shot of u getting into a Super Sabre, or was that a Thud?
 
Hi Marlin,
your avatar (some kinda kittycat?) is too blurry to see anyway.
What I do to post photos is put them on Photobucket and send them from there.
 
Marlin72xs said:
Hey Twomany. The 77 upgrade on the cam followers is much better than the 72, also.
Click to expand...

Hey, Marlin! Very interesting. I like those rollers. Apparently Yamaha was still addressing the shift and find-neutral issues.

I've also wondered about the guide bar. The way the outer forks (which handle 1st and 2nd) ride on that thing, relative to the shiftdrum and slider gears, is a somewhat strange arrangement. I can visualize potential slide/gouge with those offsets. Kinda like the ratchetting basket/trap of that old 'mousetrap' game.

I've considered making a harder/polished closer fitting version, see what happens. You mentioned replacing yours. Any signs of slide wear or gouging on your old one?

Marlin72xs said:
If I could figure out how to get pictures on here I will. You may notice that my avatar is upside down. The 1st one I tried of my bike was only sideways. I need guidance.
Did anyone find it easy to attach pictures? Where's the paper clip?
Click to expand...

There's a few how-to's in here. Sometimes, I've had to edit my pics on my tablet (using Pixlar) to re-orient them.

http://www.xs650.com/forum/forumdisplay.php?f=7

Marlin72xs said:
One more question, Twomany, was that a shot of u getting into a Super Sabre, or was that a Thud?
Click to expand...

Haha, not many folks remember Thuds. They were busy terrorizing the red river valley. The pic was a staged money shot after a T-33 checkout...
 
I refuelled,launched and recovered many a F-100D/F's in the Okla ANG back in '75 and '76. I was just an E-2 or E-3 back then. Worked with many a former "nickle" crew chief back in the day. Both were quite a jet for their day. Man, I feel old now....
 
azman857 said:
I refuelled,launched and recovered many a F-100D/F's in the Okla ANG back in '75 and '76. I was just an E-2 or E-3 back then. Worked with many a former "nickle" crew chief back in the day. Both were quite a jet for their day.
Click to expand...

The century series, loved 'em all.

azman857 said:
Man, I feel old now....
Click to expand...

Uh-oh, time to get back to bikes...
 
Hi Fredintoon,
When my brother owned my bike in 1974, he had a sidecar on it also due to a bum leg he acquired from Vietnam in1970. He didn't care for it much, so he sold it to me in76. Had it ever since. I couldn't get used to the sidecar. Too tippy. It was scary. Be careful!
 
OK guys, I'm back.
Been seeing a lot of talk about micrometers and dial gages but not many numbers. What would help me the most is clearance. Like, the OD of the shaft that goes with the ID of the gear. I suspect there are more combinations than Mike lists. Anyone have a clue on the tolerances of these parts?
No, I have not put her back together yet, I am considering opening her belly back up and replacing the original gear though.
 
Marlin72xs said:
Hi Fredintoon,
When my brother owned my bike in 1974, he had a sidecar on it also due to a bum leg he acquired from Vietnam in1970. He didn't care for it much, so he sold it to me in76. Had it ever since. I couldn't get used to the sidecar. Too tippy. It was scary. Be careful!
Click to expand...

Hi Marlin,
yeah, but they don't fall over, eh?
In the UK, back when sidecars were the affordable family transport of the working poor,
A bike's insurance rate was reduced 50% if it had a sidecar.
It's all in how you ride them:-
Slow before righties and accelerate round them.
Hit righties at hiway speed and snap the throttle closed as you turn.
Sidecar riders are popular on rallies because ten 12-packs will fit in the chair with the tonneau snapped down.
They are also great chick magnets.
 
Looks like they would have designed the gear to gain more then the RPM stated.
jefft
 

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