Topic: Close ratio trans for CB 500/550, can we build one from parts?

[kayaker43]

In a few past threads I mentioned the Yoshimura 5 and 6 speed CR sets for the 500/550. Many people took an interest and I promised to get back with more info. I spend winters in FL and just returned back to MI where I keep things. Unfortunately I also returned to a job with long hours so my spare time is gone. I should be happy I have a job in this economy but I like to whine anyway.

I have both the 5 and 6 speed CR gearboxes from my racing days. I ran the 5 speed with good success for several seasons, and purchased the 6 speed with a spare motor but never used it. I bought the 5 spd new from a dealer but someone had opened the packaging, there were still a few parts in OEM Honda bags so I scribbled the numbers down. I always suspected these kits were built up from different model bikes and a CR trans kit was always right under our noses?

I'll share what I have in the hopes others can add to it? I started a new thread so it will be easier for others to find in a search.

First off, many people won't be happy with a CR trans. They really are only usefull for racing. Imagine starting off in second or even third gear but with the same top gear and having 5-6 speeds crammed in between. Its extremely abusive on the clutch and intolerable for street use.

If on the other hand your bikes powerband is between 8-12,000+ rpm with very little below that, then a CR trans is pure magic if your clutch survives the holeshot. You can keep a peaky engine right in the sweet spot.

Regarding interchangability, here's some second hand info I've heard over the years... The old CB77 305 superhawk racers used cb350 gears to make a cr trans. The CB350 racers used CB 500/550 gears and in fact the entire gearbox will interchange if you use the old bearings and inner clutch hub because the splines are different. I've heard of people stuffing a cb450 crank in cb350 cases, so possibly the CB450 gears will fit too? The CB/CL/and even SL350 engines all interchange but possible have different ratios. The CB650 gears will fit the 500/550 but only have slightly different ratios.

The message here is that we can potentialy pick parts from all these bikes to find a close ratio set. Its hard to guess at what we need but fortunately I can supply the ratios for the Yosh 5-6 speed sets and a few others. I'm hoping someone with more spare time than me can hunt down the ratios for various 305/350/450 models etc. so we can see if its possible to grow a CR trans from OEM parts?

The other challenge is to see if we can create a six speed box? I have mine for reference and Nova racing makes a CR 6 speed for the 350 racers that should fit the 500/550's but it costs big $$$. I suspect the CB/CL/CJ 360 twin or CB400 four bikes may be a source of parts there? Again maybe someone can help dig up those ratios. If anyone else has these parts in hand or is willing to collect them from ebay, I can compare them directly to the Yosh gearboxes.

I'll post later today with pictures of the 6 speed and my notes of various bikes gear ratios. I'll have to dig out the old 5 speed motor and split the cases to get that info. I'm hoping we can make this a group effort through shared information, even at the risk of making my valuable Yoshimura parts worth less if we find out they aren't so special

[kayaker43]

Well I'm afraid I can't be as helpful as I hoped. The 5 speed gearbox is not within my reach for a while. Its buried in the back of the garage behind a trailer inside a motor, inside a crate underneath some junk. Thought I could use the holiday weekend to get to it but yard chores ate up all my time. No time during the week and next weekend is a  friends wedding. I can't even guess when I'll have some time to try again.

Going from memory and a few notes, it used both shafts and inner clutch basket from a cb350. The few part numbers I have are:

23471-286-010  29 tooth countershaft 4th gear.
23451-286-030  28 tooth Mainshaft 4th gear
23220-286-030  countershaft
22120-312-010  Inner clutch hub.

I thought I had more numbers but don't. The 350 shaft and clutch hub have different splines. Oddly, the only gear pair I have numbers for is 4th gear 28/29 which is exactly the same as the 500 ratios?? There seems to be some confusion because most of the books list the 500/550 first gear (mainshaft) as 24 teeth, but they all seem to be 17 teeth exactly like the 350? Here's another thread with details on that

http://forums.13x.com/showthread.php?p=2524719#post2524719

I don't have a stock 500/550 gearbox to verify. I found the following info on a cb350 racers site showing some alternate ratios for the SL 350's

CB250/350/500-4
Std. Gear Ratios:  (1) 2.353, (2) 1.636, (3) 1.269, (4) 1.036, (5) 0.900 
K0 SL Gear Ratios (1) 2.353, (2) 1.636, (3) 1.280, (4) 1.036, (5) 0.900
K2 SL Gear Ratios: (1) 2.866, (2) 1.800, (3) 1.333, (4) 1.035, (5) 0.870 (US Set)

Also the cb650 has some ratio choices but without counting teeth on my Yosh 5 speed box, we don't know what to shoot for?

[kayaker43]

Not as helpul to most but I do have pictures and ratios for my Yoshimura 6 speed CR gearset. I hoped it would be straight from a cb360 or cb400F but it may very well be all custom parts. If anyone has one of those gearboxes apart, compare to the pictures below and let us know if it matches?

The mainshaft does use the course splines like a cb350 so it will need the 350 clutch hub. The special shift drum appears to use stock cb500 forks (550 is different) but with a small clearance notch milled into one of them. The ratios are

Gear   Mainshaft    Countershaft   Ratio

1st         20              37             1.85
2nd.       23              35             1.521
3rd.        25              33             1.32
4th         26              31             1.192
5th.        28              30             1.071
6th         29              29             1.00

These appear to have much closer spacing than any stock gearbox so they are most likely special parts. Notice from the pictures how they are all very close in size.

[bwaller]

Well thanks for digging into this kayaker. I have a couple 400F's for parts and a couple 350 twin engines (a CL & a CB I think) I just had the 550 transmission undercut but as I mentioned earlier, 1st gear won't be much use except to launch so I quess it's time to see what can be done to mix & match what I've got here.

[kayaker43]

According to this forum, there is an elusive 24 tooth mainshaft used on some 500's that will raise first gear closer to second, then maybe use a 650 top gear?

http://forums.13x.com/showthread.php?p=2524719#post2524719

I really want to get the tooth counts from the Yosh 5 speed so we have a target to shoot at.

[turboguzzi]

Hey Kayaker

I remember going through similar searches (and results) three years ago while building my race bike. Was really worried at the time that engine will be too peaky for the stock ratio spread but it really works fine.

The yoshi 6spd would be awesome, just cant believe it is based on any stock parts. The CB360 cluster on the other hand sounds like worth checking into

From my experience, wouldn't give too much importance to a higher first gear, in the few second gear hairpins I found in some circuits, engine didnt have too much trouble pulling. Considering that at the end of the day, you usually gear so you can pull redline on the straights, what is really needed is a closer 2nd to 5th gear ratio spread.

Peter C. from england (who's no longer on the forum I'm afraid) sent me the name + phone of a guy in UK who makes the few extra parts to transform the stock gear set to CR. He took over that little business niche from nova who no longer make the parts

Let me see if I can track down the threads & info

Tg

[kayaker43]

I ran for a season with the stock gearbox and also thought it worked fine. Then I added the Yosh racing pipe and it intensified the high rpm hit because of the shorter primaries. I still thought it pulled stock gears Ok. When I fitted the close ratio box I was shocked at how much better it suited the powerband. Those Yoshimura guys knew what they were doing.

There was just less RPM loss between gears and downshifting was more controllable in smaller steps,... les chance of tire chatter and you never dropped out of the power.

The high first gear is an issue with starts, you really had to abuse the clutch, but if you got it right, first gear carried you further. It seemed like you lunged ahead when everyone else shifted to second and you were still pulling a high first gear. I rode two tracks that had first gear turns with the CR box but normally you would take them in second with stock gearing, The close spacing was very noticable when I could use all 5 gears down the straight when everyone else only used 4 of theirs. Even spectators commented on the difference in sound and performance.

I regret never having a chance to try the six speed. I think it would have made the bike easier to ride smoothly on tight circuits by keeping a more constant RPM?

I do seem to remember the kit re-used at least a few of the stock gears but it did come with at least one shaft and an inner clutch hub. I'm also realizing that its unlikely to find a much lower fith or higher first gear from Honda, so a custom one might be needed there. We might be able to juggle middle gears using OEM parts though.

I need to get actual tooth counts from my 5 speed before digging any further. I see now that the 6 speed box has extremely tight spacing.

[bwaller]

I'm hoping to muddle through this for a while. Amoung all the other junk, I have access to a CJ360 engine too but it appears these are 5 speed?? I wonder why when the rest of the 360's were 6spd.

I'm sure there is no easy swap of 400F 6spd. parts or someone would have done it by now, but has anyone investigated?.... maybe I'll pull one apart, maybe a VF500F as well.

[lordmoonpie]

You can get a close ratio gearbox combining a CB450 with 2nd and third from a CB500T - did that initially on my race bike before buying a Nova (dreadful!) 6-speed. Can you use the CB50 box in a CB550?

There was a racer here in the UK that built a 6-speed gearbox from standard parts for his CB350 K4. He wouldn't give any details away on how he did it but he switched back to a 5-speed box the followign season due to unreliability in the smaller gearsets...

[turboguzzi]

OK, found Peter's posting, here it is:

"If you get a set of gears to bring the ratios closer and give also a higher first gear from a supplier in the uk what you get is a new main shaft,the one the clutch fits on, new gears for this shaft and you use standard 350 gears to make up the box,fairly simple and no engineering. The 550 and also some of the late 500s have a thinner 5th gear,the one at the sprocket end of the shaft because the 550 hase a direct oil feed to this bearing,also on a 550 you would need to use the clutch actuation on the sprocket end of the shaft. There are hundreds of these boxes in use over here,much cheaper than a full nova box.I Have personally used this setup in my 500 for 3 years and used the same on my two 350s in the past.Hope this is of some help.I must say for racing it's the best tuning going,increases lap times a lot.
You will need to use the 350 clutch centre as the splines are different"

Bwaller, seen the 400 box, no way.....

but the 250-350- 500/4 are known to have the same between the axes distance so sounds like a CB360's  (essentially  a 350 ?) 6 spd should work

moonpie, what was so bad about the nova transmission? at the prices that they are asking it sounds like it's better work!

TG

[HB-1fan]

Hopefully, Mark Mc Grew will chime in on this topic for he has surely had his hands in a few of these boxes.

 Thanks for bringing this topic up again, Kayaker. Now that I am in a different family situation, its time to get the "POPS" stuff out of the boxes and do something(in his memory ofcourse) with it. I have pretty much everything but the gearbox. So, I will be paying attention.
 Thinking about building a custom frame!
I have a  76 550ss gearbox  in a box some where it any of those dimensions will help the cause.
Rick

[kayaker43]

Wow, CB450, CB500T and even the CB77!! I keep hearing how all these parts might fit. The bigger question is,.. do any of them have a higher first or lower fifth gear. I do believe there are enough middle gear ratios to pick from.

The first step would be listing the ratios for all elegible models to see if any of the numbers make sense?

I miss the days when I was a dealer mechanic with easy access to all these bikes.

It seems a stock six speed gearbox is usually a wider spread than a 5 speed. They use the extra gear to get a lower first.

[bwaller]

I'd like to drag this back up and get some opinions. I'm in the process of building a bike to go vintage racing and before I button up the bottom end wanted to give the transmission a little more thought.

I was in touch with a guy that was quite succesful roadracing a 550/650 and at some point he made up a composite g-box using 550 shafts and a mix of both 550 & 650 gears, ultimately bringing 2nd closer to 1st gear, and spreading ratios slightly 2nd through 5th. He was pleased with the changes saying it was a nice result for his race bike. His success can't be argued so don't flame him (or me)

I did happen to find an old Yoshimura catalog and they have a page comparing their close ratio boxes to stock. So I followed the catalog scenario for fun comparing a stock 550 transmission to kayaker43's Yosh CR 6speed and this composite 550/650.
The idea is to use the % drop between different gear ratios to determine RPM after the gear change, and then ultimately how much HP was available when picking up the next gear. They use two upshifts as an example, but I'll run through all four (or 5).

Their example is for an engine that's shifted at a redline of 10,000 RPM with the following at 7000 RPM - 45 BHP
                                                                                                                           8000 RPM - 50 BHP
                                                                                                                           9000 RPM - 55 BHP
                                                                                                                         10000 RPM - 60 BHP
I think this is reasonable for a 500/550 race engine.

So ratios for a stock CB550, 1st gear 2.353, 2nd 1.6363, 3rd 1.269, 4th 1.0357, 5th 0.900

Gear change from
1st to 2nd (1.6363 divided by 2.353 = .6954 x 10000 for 6954 RPM or 44.8 BHP)
2nd to 3rd = 48.8 BHP
3rd to 4th = 50.8 BHP
4th to 5th = 53.5 BHP

Yoshimura close ratio 6 speed (1st-1.85, 2nd- 1.521, 3rd -1.32, 4th- 1.192, 5th- 1.071, 6th -1.00)

1st to 2nd = 51.1 BHP
2nd to 3rd = 54.3
3rd to 4th = 55.1
4th to 5th = 54.9
5th to 6th = 56.7

550/650 "race box" (2.353, 1.722, 1.333, 1.074, 0.900)

1st to 2nd = 46.6 BHP
2nd to 3rd = 48.7
3rd to 4th = 50.3
4th to 5th = 51.9

I fully realize this bit of crazy math is misconstrued to help sell product, but I find it interesting none the less. This fellow I spoke to claims the changes he made were an improvement over the stock transmission, but this little example doesn't show it. It does show that the close ratio 6 speed never dips too far out of the power. Wonder what the ratios for that Yosh 5 speed are

[kayaker43]

I used the Yosh 5 speed for several seasons and it was a very real improvement over stock. Unfortunately its still inside an engine that's buried in storage so I don't have the ratios handy. I was hoping an old catalog would surface with the numbers to save me the effort?

Interesting numbers, thanks for the effort.

[Bill/BentON Racing]

Cool 6 spd on the way,I did not have time to read all posts but the part #s are from CB350 (286) and SL 350(312).We used to use SL350 clutch springs in the 750's.,Bill

[bwaller]

I would like to find out the length of a CB500 twin mainshaft. Seems 1st gear on that mainshaft is 18T and if it fits in 550 cases it might open up some options.

Does anyone have a scrap 500 twin or spare mainshaft and the matching c-shaft 1st gear (41T)?? 

Thanks

[paulages]

I would like to find out the length of a CB500 twin mainshaft. Seems 1st gear on that mainshaft is 18T and if it fits in 550 cases it might open up some options.

Does anyone have a scrap 500 twin or spare mainshaft and the matching c-shaft 1st gear (41T)??  

Thanks

...or cb450, right (same cases?)? i have a cl450 i may be pulling part this winter. i have cb350T and cb550 trans parts in the shop. if i get that 450 engine apart, i'll take measurements for sure. i would love to see this kind of cross-referencing come together.

[bucky katt]

I would like to find out the length of a CB500 twin mainshaft. Seems 1st gear on that mainshaft is 18T and if it fits in 550 cases it might open up some options.

Does anyone have a scrap 500 twin or spare mainshaft and the matching c-shaft 1st gear (41T)?? 

Thanks

actually i have a cb500t with a mostly complete motor. it spent around 10 years outside before i rescued it and brought it home but if theres anything off it you want, let me know

[bwaller]

From online sites I gather the 500T mainshaft 1st gear has 18T and the matching c-shaft 41T which is slightly taller than the stocker.

I have been gathering all kinds of different g-box sets trying to come up with something, but I have nothing from this particular twin model.

bucky, if you want to sell the tranny and it's not ruined with rust I'll take it and try to pursue this further. I have access to a CJ360 5spd and think a mix 'n 'match of these two might be interesting.

[bwaller]

Paul,

I'm just not sure if the 450's mainshaft 1st gear isn't a 17T. Seems like the 500T is 18 on the other hand.

Not sure though.

[paulages]

Paul,

I'm just not sure if the 450's mainshaft 1st gear isn't a 17T. Seems like the 500T is 18 on the other hand.

Not sure though.

gotcha. i had noticed that the 450 also lists a 41T countershaft 1st gear, but doesn't list the tooth count on the mainshaft 1st gear. i assumed that the MS would have to be the same to mesh properly with the CS gear, but i didn't actually cross-reference part numbers.

carry on... i'll only pipe in when i actually have something helpful to share. 

[kayaker43]

Well guys, sorry for the wait. I was hoping that when the time came to open up the old crates, I would be ready to start my project. Unfortunately another year passed with no time and none in the near future. a lot of people want to know the Yoshimura close ratio 5 speed ratios so I dug out the old race motor and split the cases. It was like opening a time capsule,... lots of memories in there. Here's what I have







Now for the ratios

1st.   21/38  1.809
2nd.  24/33  1.375
3rd.   26/31  1.192
4th.  28/29   1.035
5th.  30/28   .9333

The kit was new but open box and only some of the parts came in  honda bags with part numbers, I wrote those down:

- The kit came with a new countershaft (23220-286-030 CB/CL/SL350)
- New mainshaft, no part number but 21 tooth and larger splines.
- New inner clutch hub (22120-312-010 CB/CL350, CB/CJ/360)
- New countershaft 4th gear (23471-287-010)
- New mainshaft 4th. gear (23451-286-030) the dogs were possibly milled from oval to square shape to mate with new M3 gear
- New one piece mainshaft 2nd/3rd gear. No part number but this looks special and has milled and undercut gear dogs.
- New mainshaft 5th gear, same 30 tooth count as stock but also looks special with milled and undercut dogs to engage mainshaft 2nd gear.

So it looks like every gear on the mainshaft is either special or modified stock parts. I don't know if the countershaft was a new stock part or something special? I just know I copied the part number down?

It now seems less likely its all stock parts because there was a lot of milling on some gears. The shift forks and drum appear stock. At least it gives us some ratios to shoot for?

[bwaller]

Thanks for all your work Kayaker. The 350T gears were square dogs, but at least that mainshaft with 21T and the 2nd/3rd gear on the MS must be special, or not something I can find.

Interesting stuff indeed....better keep that in a safe somewhere. 

[turboguzzi]

1st.   21/38  1.809
2nd.  24/33  1.375
3rd.   26/31  1.192
4th.  28/29   1.035
5th.  30/28   .9333

Yep, that's really tight spacing!

the overall gear span is 48%

compare to Nova Racing's current 750 5-spd (bellow), its 52.8%



1st 2.055 : 1
                      )      27%
2nd     1.5 : 1
                      )      17.3%
3rd   1.24 : 1
                      )      14%  
4th 1.065 : 1
                      )      9%  
5th 0.969 : 1
 
Overall 1st -5th  52.8%

I think that yosh 5spd cluster would be really nice in fast flowing tracks, less so with today hairpins and tight elbows. Yep, tracks have changed in the last 30 years in case you havent noticed.

Big thanks for the effort kayaker, I think this issue has been haunting some members for a long time!

now then, until we are rich enough for a complete 6spd CR box from Nova,  is there any UK forum member that's willing to give this Saunders guy a call to find out what he is offering?

"Remake of 5speed race kits for Honda CB350/450 only available from Bernard Saunders Tel 0044(0)1451 822397"

Peter C told me at the time that's the setup most of the vintage hionda guys are using in the UK in 350'-450's and 500-4's

TG

[kayaker43]

The tightest track I ever ran on was Grattan raceway in Michigan. I don't think they get any tighter now?? Turn 13 at Nelson Ledges is another crawler. The tall first is only an issue on launches but just right for the tightest turn you can imagine on a racetrack. I don't see any downside to this tight spacing? I suppose a really fast track that forces higher gearing (think Daytona) but also has one hairpin might be the worst case??

I haven't figured it out but the Yosh 6 speed near the top of this thread seems to have even tighter spacing than the 5 speed.

I'll bet your all making shifty noises in front of our computer right now Make sure no ones looking when you do that