Topic: 750 6 speed transmission?

[MRieck]

The 5-speed close-ratio kits are probably available on eBay still: I saw one ).

Yes....Todd Henning was selling a Nova unit.

[mlinder]

I have little trouble leaving a light in second.

I'm about to change out my 18/48 to 17/48.
I'm a little worried, because 9k rpm already comes very, very fast. I've been over-revving a bit here and there. With 18/48, you can probably hit your bikes top speed in (stock)4th at around 9-9.2k rpm. I think 5th is pretty much a fuel-saving gear.
I wouldn't mind just changing out 5th gear to be a little shorter, so it actually has some use.

Hondaman, it sounds more like the quality, lightness, and efficiency of the Yoshimura 6 speed was responsible for the increase in top end (less HP loss to rear wheel?).
Wonder what it would take to replicate in our stocker 5 speeds?

[Geeto67]

rather than figure out cockamamie ways to make more problems for yourself, why not do this...make sure your bike is running the best it possibly can. Sounds to me like yoru bike just isn't running right and you are looking at an atomic bomb solution to band-aid problems.

how do you do this? Go find a bike dyno and dyno the bike as she sits. If she makes more than 50hp at the rear wheels then come back and start looking for more answers on different cb750 gear ratios. If she doesn't begin tuning the bike until you can get 50 rwhp or more out of a cb750. Any good condition cb750 motor should be able to at least pull this number if not more so if you aren't here you probably should try to just get the motor there. I am not talking hop up parts, I am talking just a good clean motor where the vales are all in spec, the timing is set right, the plugs are new and giving good sparks, and the carbs are clean. When in this state of tune my K5 (arguably the slowest of the cb750s) could still loft the front wheel if I gave a good yank and take off from a light in second no problem (which by the way...what is so wrong with starting out in first).

Right now I am batteling carb and timing issues on my personal K5 (and yes I am still riding her because she is my transportation) and she is making about 36hp at the rear wheel and running hella lean (loud backfire lean). Still faster tham most cars and she still will do 90mph, but as compared to what she used to do when running tip top I am just flat embarrassed as how she runs now.

If you aren't saying this in your hear at least once a day: "Holy crap my brakes are inadiquate"  - then your bike isn't running it's best. 

[mlinder]

Who are you talking to, geeto?
 

[Geeto67]

Who are you talking to, geeto?
 

myself apparently....

Half the time I see someone ask about something weird like a 6 speed gearbox, overdrive, manual brakes, or something like that it is usually because they have a problem in their bike that they don't realize is a problem. I am just jumping to that conclusion in azuredesign's case because some of the things he has said indicate he is either not satisfied with the perfromance of his bike and that may be because his bike is not running up to peak performance.

[ekim98]

Half the time I see someone ask about something weird like a 6 speed gearbox, overdrive, manual brakes, or something like that it is usually because they have a problem in their bike that they don't realize is a problem. I am just jumping to that conclusion in azuredesign's case because some of the things he has said indicate he is either not satisfied with the perfromance of his bike and that may be because his bike is not running up to peak performance.

Maybe I'm missing something here, but it sounds like a lot of you ride with your tach in or near the red zone about 80% of the time, have a death wish or want to be on "Cops" Most wild Chases. Don't get me wrong I get on mine too, but if you really want a bike that preformes like it has 125+ HP then you should buy one that has that hp. At what point do you say that you no longer have a cb750 and now ride something that Honda never made!

[mlinder]

During 'spirited' riding, which happens every few weekends, yes, I am mostly between 7 and 10k rpm.
The engine feels best there. It's smoothest, most willing, and I believe, happiest there. I keep it there for hours sometimes.
I don't ride it like it has 125hp. I ride it like a cb750 runs near, at, or over redline.
It's a beautiful thing.
Try riding a gixxer 1000 at, near, or over redline for any length of time. You will get a ticket, wreck, die, or go deaf. Or any combination of those.
These old, slow bikes are awesome fun at their envelope. Can't do the same with new bikes without screwing something up.

[Geeto67]

During 'spirited' riding, which happens every few weekends, yes, I am mostly between 7 and 10k rpm.
The engine feels best there. It's smoothest, most willing, and I believe, happiest there. I keep it there for hours sometimes.
I don't ride it like it has 125hp. I ride it like a cb750 runs near, at, or over redline.
It's a beautiful thing.
Try riding a gixxer 1000 at, near, or over redline for any length of time. You will get a ticket, wreck, die, or go deaf. Or any combination of those.
These old, slow bikes are awesome fun at their envelope. Can't do the same with new bikes without screwing something up.

agreed. I am WFO at every chance I get. When I used to work nights I would get out at 5 am on a saturday or sunday morning and there would be no one on the road. perfect for over the ton excursions. that K5 saw redline in 5th repeatedly. It would take me 15-20 minutes to get into manhattan and 7.5 to get home.

I hate to say it but new bikes almost feel too light. There is this short rise on the LIE eastbound in Queens where at 100 mph my cb750 suspension will unload pretty severly but won't leave the ground. Hit that on the Duc at 85 mph a couple of weeks back and the bike definatly left the ground. Not a big jump but more like a short skip with both wheels. Had I not been expecting it that definatly would have been a brown moment. 

[azuredesign]

rather than figure out cockamamie ways to make more problems for yourself, why not do this...make sure your bike is running the best it possibly can. Sounds to me like yoru bike just isn't running right and you are looking at an atomic bomb solution to band-aid problems.

how do you do this? Go find a bike dyno and dyno the bike as she sits. If she makes more than 50hp at the rear wheels then come back and start looking for more answers on different cb750 gear ratios. If she doesn't begin tuning the bike until you can get 50 rwhp or more out of a cb750. Any good condition cb750 motor should be able to at least pull this number if not more so if you aren't here you probably should try to just get the motor there. I am not talking hop up parts, I am talking just a good clean motor where the vales are all in spec, the timing is set right, the plugs are new and giving good sparks, and the carbs are clean. When in this state of tune my K5 (arguably the slowest of the cb750s) could still loft the front wheel if I gave a good yank and take off from a light in second no problem (which by the way...what is so wrong with starting out in first).

Right now I am batteling carb and timing issues on my personal K5 (and yes I am still riding her because she is my transportation) and she is making about 36hp at the rear wheel and running hella lean (loud backfire lean). Still faster tham most cars and she still will do 90mph, but as compared to what she used to do when running tip top I am just flat embarrassed as how she runs now.

If you aren't saying this in your hear at least once a day: "Holy crap my brakes are inadiquate"  - then your bike isn't running it's best. 

Thanks for your thoughts concerning my cockamamie idea.
My bike runs pretty well and while I have other options for riding and messing with, I really love how much fun the Honda provides, both because it's darned fun to ride, and it is so tinkerable due to the availabilty of parts and help from folks on this newsgroup.
I enjoy alternative ideas and strategies for implementing them. I learn a lot from each attempt, and it's exciting.

That all being said, I haven't ridden a cb750 since the seventies, and was probably 80 pounds lighter then. I'll ask someone with some familiarity with these bikes to test ride it for me. Perhaps you're right! I hope your tuning issues resolve quickly,
Ben

[andy750]

Ill happily test ride it for you Ben 

cheers
Andy

[S-Dog]

Your bike seems to run more than fine... You should have held back with me and Andy when we were testing out how quick the bikes were.(we were pretty close -  his k2 compared to my k5 and me with +85lbs) we were going from about 20-25 to 90ish....

[azuredesign]

Ill happily test ride it for you Ben 

cheers
Andy

Your bike seems to run more than fine... You should have held back with me and Andy when we were testing out how quick the bikes were.(we were pretty close -  his k2 compared to my k5 and me with +85lbs) we were going from about 20-25 to 90ish....

Thanks Guys,

Andy, when we made that pass on the rt27 straight between Sherborn and Medfield, I'm pretty sure we were both running full out in 5th gear. You may not have seen me as you were leading, but I think I had more than you did by a bit. (Unless you were running in 4th! )While you're welcome to ride my bike anytime, I am going to try a K&N air filter with more holes in my airbox, and  then 115 or 118 mains instead of the 112's I have in there to see if the revs accumulate more rapidly between 3500 and 5k RPM. The speed seems to be going up quick enough, but it doesn't seem like much is happening. Last time I looked my sparkplugs looked good. If it's nice out on Sunday, do you and Scott want to do a bit of back road riding around here?

All best,
Ben

[Geeto67]

The speed seems to be going up quick enough, but it doesn't seem like much is happening.

what does this mean? maybe your bike runs fine but your clutch is mal-adjusted or slipping.

[andy750]

Hey Ben, I was never flat out on that ride. I was likely in 4th on that run, but Im still sure your bike could out run mine considering my K2 has 50,000 miles and no top end rebuild  .....but hey it was still enough to beat Scott  . My bike takes off after 4000rpm and then you have to hold on as it gets fast quickly.

Id love to ride this Sunday but I have a conference to attend in Boston so no riding for me this weekend 

Have fun in any case!
cheers
Andy

[S-Dog]

I am available.... 

[andy750]

Ok check out the video from the ride...I was cruising along at 40mph and then have to accelerate up to +80mph (see speedo at 19secs into it) to catch up. And this was one-handed! 

cheers
Andy

[azuredesign]

Hey Ben, I was never flat out on that ride. I was likely in 4th on that run, but Im still sure your bike could out run mine considering my K2 has 50,000 miles and no top end rebuild  .....but hey it was still enough to beat Scott  . My bike takes off after 4000rpm and then you have to hold on as it gets fast quickly.

Id love to ride this Sunday but I have a conference to attend in Boston so no riding for me this weekend 

Have fun in any case!
cheers
Andy

Hmm, then maybe you should ride my bike. Let me know when you're available and I'll have a beer waiting for you.

Thanks,
Ben

The speed seems to be going up quick enough, but it doesn't seem like much is happening.

what does this mean? maybe your bike runs fine but your clutch is mal-adjusted or slipping.

I'm pretty sure my clutch is cool no slipping under full throttle in 5th, pulls fine from 2000 on up. Thanks for the thought though!

[andy750]

Ben,
One thought - could your lack of power be related to your bikes habit of stalling at idle sometimes? Perhaps your slow jets are clogged or as you already surmised at speed your main jets are too small.....quick change over to 115s or 118s will tell you that. Are you checking your plugs to see how much to turn your air screws out?

good luck,
Andy

[azuredesign]

Bem,
One thought - could your lack of power be related to your bikes habit of stalling at idle sometimes? Perhaps your slow jets are clogged or as you already surmised at speed your main jets are too small.....quick change over to 115s or 118s will tell you that. Are you checking your plugs to see how much to turn your air screws out?

good luck,
Andy

I should check the slow speeds again although I cleaned them thoroughly before replacing them as I was putting the bike back together. I'm also pretty sure my air screws are correctly set, as I've checked and reset them as I broke the bike in over the last 800 miles, by checking the plugs after idling for a while. I've also checked the plugs at 2-3000, and then after normal riding. I've synched the carbs, and then resynched them after going up to 112 from the stock mains.
I've got to adjust my valves and I'll check the slow jets at the same time.
Thanks for the thought!

[MRieck]

 I'm going to tune Ben's bike. Enough of this.

[andy750]

Silence!!...the Master has spoken   

[Don R]

CB900 with the 5 speed and hi / low range, then put on a sohc head!