DOHC CB750's

seestheday said:
rocket, I also noticed a badly rusted set of cams

img0274ng.jpg


I recommend throwing those in the landfill and picking up a set of 900's for a nice little performance boost.
Click to expand...

Yep those are probably trash but this is the parts bike and 750 cams aren't as desirable as the 900.

As you said I do need to pick up 2 sets of 900 cams. one for each bike.
 
Hey DOHC riders/builders/posse,

I'm rebuilding and cafe'ing an 82 CB750K. I've been agonizing over the right seat style to slap on this beast. The K model has that stupid step up on the frame, and I'm sending out a feeler for the learned and experienced readers of DTT. What did you purchase that worked well-- I'm looking for basically an 'off the rack' seatpan or seat. I've looked at a number of different pans or seats, and well, I just can't seem to pull the trigger.

Any input you may have on what you bought that worked well for you would be greatly appreciated.

Thanks,

loudest143
 
rocketritch said:
Yep those are probably trash but this is the parts bike and 750 cams aren't as desirable as the 900.

As you said I do need to pick up 2 sets of 900 cams. one for each bike.
Click to expand...

You may know this already if you do just ignore me,
The 900 cams are not always a straight drop in, sometimes due to quality (not) of the honda castings, you may need to grind the tops of the cam follower tunnel and the underneath of the cam cover to get clearance. Some need work and some dont its luck of the draw.
 
loudest143 said:
Hey DOHC riders/builders/posse,

I'm rebuilding and cafe'ing an 82 CB750K. I've been agonizing over the right seat style to slap on this beast. The K model has that stupid step up on the frame, and I'm sending out a feeler for the learned and experienced readers of DTT. What did you purchase that worked well-- I'm looking for basically an 'off the rack' seatpan or seat. I've looked at a number of different pans or seats, and well, I just can't seem to pull the trigger.

Any input you may have on what you bought that worked well for you would be greatly appreciated.

Thanks,

loudest143
Click to expand...
I'm building my seat at this very moment, but if you want something off the shelf, check Benji's. http://www.benjiescaferacer.com/parts.php I just get opti-rectalitis when I see his prices...
"Can't see my ass doin that!"
::)
 
Thanks for the advice on the cams, lob. I plan on doing that swap a bit later this year.

I have to agree with others in that forums such as CB1100f and CB750C don't care much for cafe builders or users of indiv filters... I made accounts there just to browse because posting seemed daunting. Some good knowledge is being accrued on this site, especially this thread, for our DOHCs. Makes me want to write shit up better for posterity!
 
loudest143 said:
Hey DOHC riders/builders/posse,

I'm rebuilding and cafe'ing an 82 CB750K. I've been agonizing over the right seat style to slap on this beast. The K model has that stupid step up on the frame, and I'm sending out a feeler for the learned and experienced readers of DTT. What did you purchase that worked well-- I'm looking for basically an 'off the rack' seatpan or seat. I've looked at a number of different pans or seats, and well, I just can't seem to pull the trigger.

Any input you may have on what you bought that worked well for you would be greatly appreciated.

Thanks,

loudest143
Click to expand...

im just getting ready to cut the back of the frame off of my '79
plan is to weld in a new hoop that will be the entire base for the seat. this will also allow me to adjust the rear shock mounts so i can get a little more height out of the back end.
ive only found a couple options for seats on the dohc bikes and they are ridiculously expensive. if you get rid of that bump in the frame you can run any seat pan you want!
 
Careful with moving your shocks to get more height out of the rear end. My 900F got a bit twitchy in the front end when I adjusted the shocks to get more ground clearance. I am just referring to the spring preload. I am not sure if the 750 would act differently or even if this was just an anomaly with my particular bike.

Brian
 
Hoosier Daddy said:
Notlob and I been talking about this mod. He knows more of the history as it is PDF of a long ago document. Maybe we should share that here, unless it already is somewhere and I missed it.
Click to expand...


You lost me on this. What is the RSC kit manual? I've googled and it turns up a thousand things not related to moto carbs.
 
canyoncarver said:
You lost me on this. What is the RSC kit manual? I've googled and it turns up a thousand things not related to moto carbs.
Click to expand...

Its a manual you got when you bought performance upgrade kits from RSC who were the predecessors to Honda HRC. There is a section in it that explains what modifications you have to do to the stock CV carbs to get them to run with velocity stacks or pods. They had to use stock carbs to qualify for F1 (now WSBK)and American Superbikes series so had to make them work without the airbox.
 
notlob said:
Its a manual you got when you bought performance upgrade kits from RSC who were the predecessors to Honda HRC. There is a section in it that explains what modifications you have to do to the stock CV carbs to get them to run with velocity stacks or pods. They had to use stock carbs to qualify for F1 (now WSBK)and American Superbikes series so had to make them work without the airbox.
Click to expand...


Thanks for the explanation notlob. Anybody have a digital version?
 
Thanks for the reply on the seat options. I really don't want to get into cutting the frame. I guess perhaps at some point I'll consider it, but I'm gonna look at my options for seats. Here are a couple that are my top two choices. **at the moment.**

http://www.motorcycleseatsdirect.com/1979-1981-Honda-cb750k-cb750-k-cafe-motorcycle-seat-metal-pan/

http://www.hotwingglass.com/seats/dark-wing.shtml

By measurement, they are both viable options. I'm leaning toward the first seat, if they can do a couple of small things to it-- shortening the tail length so it doesn't stick out so far over the rear fender, like the stock seatpan does.

The second seat is pretty easy to work with, and I could see that working just fine on that frame. The measurements are darned near perfect for an off the rack seat pan.

Just sharing. Perhaps some of you hadn't had the chance to see those two vendors before.

Loudest143
 
canyoncarver said:
Thanks for the explanation notlob. Anybody have a digital version?
Click to expand...

notlob said:
Its a manual you got when you bought performance upgrade kits from RSC who were the predecessors to Honda HRC. There is a section in it that explains what modifications you have to do to the stock CV carbs to get them to run with velocity stacks or pods. They had to use stock carbs to qualify for F1 (now WSBK)and American Superbikes series so had to make them work without the airbox.
Click to expand...

Same problem here doing a search on this manual.
 
loudest143 said:
Thanks for the reply on the seat options. I really don't want to get into cutting the frame. I guess perhaps at some point I'll consider it, but I'm gonna look at my options for seats. Here are a couple that are my top two choices. **at the moment.**

http://www.motorcycleseatsdirect.com/1979-1981-Honda-cb750k-cb750-k-cafe-motorcycle-seat-metal-pan/

http://www.hotwingglass.com/seats/dark-wing.shtml

By measurement, they are both viable options. I'm leaning toward the first seat, if they can do a couple of small things to it-- shortening the tail length so it doesn't stick out so far over the rear fender, like the stock seatpan does.

The second seat is pretty easy to work with, and I could see that working just fine on that frame. The measurements are darned near perfect for an off the rack seat pan.

Just sharing. Perhaps some of you hadn't had the chance to see those two vendors before.

Loudest143
Click to expand...


Did you notice that the motorcycleseatsdirect guys charge 99$ for shipping?
 
Yeah, that shipping charge is darned high, but I figure it's coming from Vietnam, so that might have alot to do with it. Still a nice product, and not insanely expensive with the shipping charge, IMHO. ;D
 
HD beat me to it

The modification should enable you to run either velocity stacks or pods (don't use the cheapo lipped ones). I know of two guys who race CBs in Classic racing and have used the mods to great effect. Just remember the jetting will have to be specific to your situation ie, state of tune and location relative to sea level, the jets they stated in the manual are for the minimum "Kit A" of a bored out capacity of 996cc.
 
I'll give this a good read through. My 81' CB750F is currently still waiting on me fixing a bunch of electrical harness stuff. Then, it's on to the carbs.
 
so let me see if I'm getting this correctly, by sealing up the secondary air jet and air cutoff valve.... this will allow the vacuum slides to work properly with stacks/pods? this is my first go with carbs, so im learning
 
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