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

[bwaller]

Yes the overall reduction for that Yosh 6spd. is a tight 46%.

What are the feelings of the race crowd, would you rather use a 5 speed or 6 on the track? I suppose it depends on the track and whether or not a 6spd would be needed.

My hope is to shoehorn a CB360 g-box into my 550 and at least for now use the stock 360 ratios. Kevin TTR400 may have some close ratio options for the 400F which can also help the 360.

1st    2.5:1
2nd   1.8:1
3rd 1.375:1
4th 1.111:1
5th 0.966:1
6th 0.867:1

1st is obviously only to launch the thing, then ultimately have five gears to use giving a 2nd through 6th reduction of 52% (overall 1-6 is 65.3%)

On the other hand I'm sure TG isn't using the stock 1st gear anywhere else on the track but getting away at the start. So the 500/550 2nd through 5th reduction is only 45% (overall 1-5 is 61.8%)

What do y'all think?

[kayaker43]

Depends how much work it is to make the 6 speed work? If you gear that tall 6th so it redlines, first might be too low even for a launch. You might need to grab second right away? You'll probably end up launching in second? What about removing first gear to make the gear stack easier to fit without narrowing all of them. Even if first is part of the mainshaft, it could be ground off.? Just ideas because I've never seen the 360 box.

A tall first gear was abusive to the clutch but when I launched it right, I went farther before shifting than the others. At my home track, the first turn was close to the start, so when everyone shifted to second, they fell back just in time for me to lunge ahead and grab the inside line.

I either bogged badly or wheelied and got the holeshot.

What about fitting a modern gearset? Anyone know the shaft spacing on a CBR600?

[bwaller]

Well it will be quite a job to make it work, but at this point I still feel it's do-able.

I hear what your saying about gearing for redline. I fiqured even a quick launch in 1st gear (even a low 1st) and short shift to 2nd might be the quick way to turn one.

[bryanj]

If you are sure of that number i will try and contact the guy but first i need to know what questions you want answered (if he will!)

[turboguzzi]

Bryanj, the questions would be:

How is that 350 CR box made?

what are the stock parts it keeps and from which model

what the new parts does he adds?

Cost?

final ratios?

my last race was in a very tipical track for us here in italy. Geared to redline in 5th in a rather short main straight, I was using 2nd in the tightest hairpin. So the 45% reduction span is sort of OK but just a taller 1st is not going to help me much. What I would really need is bunching up the four top gears or better, have them split in 5 + a launch 1st of about 2-2.2:1.

That's why a 360 6 spd could be fun if it is doable.

Kayaker, why dont we move this to the racing section?

Cheers

TG

[kayaker43]

I asked about moving this too. Is there something I can do?

[lordmoonpie]

Good luck with getting the info out of Bernie - he's a goldmine of RSC info but he does run a business so doesn't share all his sercrets. He's a real genius with Honda race stuff and we all know what genius is close to.....

There is a guy over here who has built a 6-speed CR gearbox for his 350 K4 twin by using parts from other hondas, I seem to think it was the G5 250 he took most bits from. Never had the time to research it myself but he managed it and ran it for a season before going back to the 5-speed CR box.

The tall first gear is also availble from CAT Engineering in the UK and they have a website so much easier to deal with. Ask for Len - he'll sort you out no problem...

OH TG - on my Nova CR box on the 450 the selector arms fouled the inside of the crankcase so I could only get 2,3,4th gear until I took material out of the inside of the crankcase walls, the largest cog fouled the dipstick and chewed half way through it ( took it out before it completed the job!) and once mated up to the clutch, the primary drive gear on the clutch locked solid with the crank case casting when torqued down. Had to chamfer off the primary drive teeth to get the clearance to run it without any hassle.

Nova offered to have a look at my bike and fix the issues but only after it was already away being looked at by a race engineer. They hinted at later product updates to remove the issues - too late for me after I lost two seasons racing trying to locate the problem sources. Yes I paid £2500+ for my gearbox and clutch and didn't expect anything other than to be able to drop it straight in, certainly not machining bits to make it work.

However, the quality and materials used by Nova is exceptional. I've had them do one off engineering bits for my CR750 and the work is just without peer. I think they got caught out (as do many suppliers) by the slight variations in Honda's build quality and configurations so that when they tried to provide a one product for all 450s type item, it just didn't work in all variants that came off the production line.

[turboguzzi]

found about CAT by chance just yesterday, Ellis should get back to me with the ratios he uses for his simple 1st and 5th gears swaps.

on the other hand, at 600 pounds, his C/R 5 spd is a pretty good deal, one third the cost of a 6 spd nova. waiting to hear about the ratios on that one too.

He seems indeed cool and willing to try stuff, so who knows, we could end asking him to do a yoshi 5 spd replica!

TG

[Rod]

found about CAT by chance just yesterday, Ellis should get back to me with the ratios he uses for his simple 1st and 5th gears swaps.

on the other hand, at 600 pounds, his C/R 5 spd is a pretty good deal, one third the cost of a 6 spd nova. waiting to hear about the ratios on that one too.

He seems indeed cool and willing to try stuff, so who knows, we could end asking him to do a yoshi 5 spd replica!

TG

TG the people doing my rebuild (http://www.d-mengineering.co.uk/) use Ellis, so clearly rate him. I had already sent my gears to NOVA for overhaul before finding out about him. 

[turboguzzi]

OK kayaker, here's the info from CAT

option A - 250 $ - higher 1st + lower 5th - rest of box remains the same.

the new ratios are

1st - 2.176:1
5th - 0.931:1

so from the original box with a 61% span

2.353
1.636
1.269
1.036
0.9

you get a "CR" box with 57% span

2.176
1.636
1.269
1.036
0.931

option B - 1000$ - a totally new gear cluster with true CR - 48.5% span

1.810:1
1.375:1
1.192:1
1.036:1
0.931:1

from my experience with my stock box, the 1.636 2nd gear covers very well the slowest corners, so cant see the advantage of Option A.
Only a slighty higher 1st, you'll never use it in the race. Maybe better starts when you are geared for 110mph @ 12K, say 15:36-15:37 final ratio, at that point stock first is almost useless.

The option B on the other hand sounds really good, the ratios are almost like in the Yoshi 5spd CR. Geared right, 1st would be usable in hairpins and then you'll get that extra ratio for better acceleration. Launches might be hard on the clutch but this is would only be solvable with a 6spd from Nova at 1600$ more.

So: anybody interested? 

TG


 

[kayaker43]

Interesting,.. $1000 isn't bad, If it was a six speed, I'd be all over it. I'll feel guilty about using up my rare Yosh parts. I agree the 1-5 conversion isn't much gain but still probably worth the money.

The Yosh six speed has that same tall first gear as the 5 speed, so no advantage 6 vs 5 on starts, just closer spacing.

[turboguzzi]

quote author=kayaker43 link=topic=52012.msg648508#msg648508 date=1255177387]
Interesting,.. $1000 isn't bad, If it was a six speed, I'd be all over it. I'll feel guilty about using up my rare Yosh parts. I agree the 1-5 conversion isn't much gain but still probably worth the money.

The Yosh six speed has that same tall first gear as the 5 speed, so no advantage 6 vs 5 on starts, just closer spacing.
[/quote]

that yosh 6spd must have been very IOM oriented, where you AVERAGE 100 mph if you are good. not that many tracks left that are so fast and flowing

Nova admit this and state that their current 6spd are not close ratio as those of the works bikes, they have indeed a relatively low 1st.

let me know if you are into this, who knows, there might be a rebate for an order of three!

TG

[kayaker43]

I loved the Yosh's total gear spread even on tight tracks. I commented on the tall first, but it was no big deal. I don't think its just a fast track thing. The close spacing is better regardless of track layout, it just keeps you in the sweet spot.

I do think its only real benefit is when used with radical cams and high rpm peaky motors. It wouldn't make sense on a torquey motor or street bike.

I'll have to pass for now, I need the money for some Dymags.

[turboguzzi]

I'll have to pass for now, I need the money for some Dymags.

you'll be just as fast with spokes   

[kayaker43]

I'll have to pass for now, I need the money for some Dymags.

you'll be just as fast with spokes   

Or just as slow,... but better looking

[bwaller]

I don't have a CB500 apart, but the 550's center shift forks' fingers are wider than the other two. (MS 2nd-3rd gear fork groove is wider than the grooves on the 4th & 5th CS gears)

Are the 500's the same?

This may be a deal breaker on my 360 6spd conversion as all three of these gears have the wider fork grooves.

The online fische I use is confusing. If the three 500 sliders use a wide groove I may still have an option of going to Nova ($$$) for a shift drum & use the three 500 shifter forks on the drum. As is I don't have forks to complete the job.

Kayaker what about the Yoshimura 6spd?

Thanks

[turboguzzi]

assuming Nova will send you just a shift drum.....

my tuner friend tells me that he often hard welds worn shift forks, adding material in the groove contact area, so you co do that too.

TG

[bwaller]

Thanks, I thought about that & wondered if they might distort with the heat, but I quess it's an option.

So I take it the 500's are the same as the 550's?

[lordmoonpie]

assuming Nova will send you just a shift drum.....

Talk to Graham - he'll sell you any parts you want. He'll even make a custom shift drum if that's what you want...

Incidentally in the new Classic Racer magazine they talk about the CB72/77 racers from down under where they made a close ratio box in the 350 "by using parts from a CB360" and that's all!

[kayaker43]

I'm heading out the door for work but will check the Yosh 6 speed forks this evening.

[bwaller]

The worst problem I have now is making the shift drum/forks/shifter cam plate work. The 82 CB450 drum is very short, although I have modified it to fit the engine case. If I use this drum I need to use the three offset forks too. With this set-up there are two separate shafts, two forks on one, one on the other. I'll need to weld some aluminum in four places inside the cases and line bore holes for the shift fork shafts.....a little complicated and no going back if the whole thing doesn't work.

The shift pattern will be the same and the "throw" should also if the trans fits the cases, that's why I thought maybe a drum using stock shift forks and a cam plate that will work with the stock shift mechanism might be a smarter option. I haven't ground any of the 360 gearsets thinner yet so maybe I'll pursue this drum first.

Thanks for the info lordmoonpie, I'll try to check that mag too.

kayaker43 I'll PM with the measurements that would help.

 

[turboguzzi]

Thanks, I thought about that & wondered if they might distort with the heat, but I quess it's an option.

So I take it the 500's are the same as the 550's?

he does grind them straight after welding

no, they are not, 500's all ride on the drum, but doesnt matter, welding the fork pads should yield same result.

LMP, got the name of those aussie guys? might be worth contacting them

[ohiocaferacer]

Glad I came across this thread.....as I was just talking about this exact topic this past weekend at Barber with a couple of the guys in the 350 sportsman class.

One had a Nova cr 5 speed in his bike and overall liked it....but hated the fact it took so much clutch to get a good start.

Over the winter....I plan to play around with some gear sets also......so, i'll post anything I find.

[bwaller]

Sorry I missed you at Barber this year Greg. I'll add any GOOD info here as I go along IF I go along!

Nice thing about the 360 1st gear ratio is just easier on the clutch getting launched. I've talked with ttr400 about tightening ratios after if I can get this to work.

[turboguzzi]

LMP, is the guy from down under jerry kooistra? a quick search led me to him, but he's got no site or contact info

Ohio, not so sure what happens with 350's, but with the 1.810 1st of Yosh or CAT CR + a 15:37 final you get almost a stock first gear overall! (2.353  + 17:34), cant see why it would hurt a 500's start so much.

Maybe starts get worse with really fast gearing, the longest I ever went with was at Vallelunga, the SBK track, 16:36 but cant believe its so bad. I surely feel stupid on race starts with my ultra short 1st, having to change gears after a 20 yard wheelie.

Yep, the more i think of it, the more that 5 speed CR cluster calls me.....

TG