Topic: CB750 Handling in a nutshell.

[eldar]

Depends on your size. The weight is about 100 pounds less but with good tires and tapered bearings for the neck, the 750 should not be to bad compared to the 550. There is more power to help offset the weight but it is a little harder to throw around the corners.

I think a lot depends on your size and strength and I suppose if you got a big ol beer gut and suffer from dunlap disease!

[HondaMan]

so let me ask, is the cb750 that much heavier & harder to handle than the cb550? I am building a bobber & I just always thought the 750 was too big for me & not light enough to zip around town like the cb550. What are your thoughts on this. Keep in mind we are dropping the engine in a softail frame with no stock parts. Also anyone know the weight & dimensions of cb550 & 750 engines?

In stock form, the CB750 feels very top-heavy, and it's a long way from the seat to the ground. These can combine to make the bike feel intimidating at first. Personally, I disliked the 500 I had in town driving, because the very low center of gravity always made the bike want to "stand up" from a turn, sort of like a BMW or British Twin. It also suffered, in stock form, from a slow clutch engagement and low-end torque like a 350. You have to "keep it wound" to keep power on tap, which is very different from the 750.

If the extra height of the 750 bothers you, lower the rear by installing 12" shocks, then slide the front fork tube down 1/2" on the tree. This will give the front a 3.5" trail instead of the stock 3.25" trail, making it feel less "twitchy", or quick-steering. It also "shortens" the bike. Also, a stepped seat can lower it as much as 2". Install a 17-tooth countersprocket in place of the often-found 18 tooth and the bike becomes a wonderful city machine as well as a spirited curve chaser. And, touring is it's really long suit, in great comfort. I've put back-to-back 1000 mile days on my "big four" and couldn't wait for the next one. My 500 would leave me feeling cramped and wishing for more zip during 2-lane passing events.

But, in the snow, the 500 WAS easier to muscle home...and the clutch made ice riding more predictable. 

[jaknight]

..... And, touring is it's really long suit, in great comfort. I've put back-to-back 1000 mile days on my "big four" and couldn't wait for the next one.

   Classy to the hilt, reliability, smoothness, more than enough power; these are some of the reasons I went for the Big 750 four............ (hmmmmmm........ that reminds me, my wife wants to talk to me about something...........)
   ~ ~ ~ jaknight ~ ~ ~

[BAZ]

Quick noob question here.  I am picking up a '73 cb750 in the next couple of weeks for next to nothing from the original owner ( family friend). It is getting shipped from Minnesota where it has been garage stored and run every couple of weeks to me. (AZ) I dont know much about the bike except it comes with some ugly windjammer, 4 into 2 pipes, taller handlebars, different seat, a 16"? rear wheel, different sprocket, and a '77 gas tank. It has 40,000 miles on it and apparently runs very well.

The windjammer will definately be coming off and next in line will be the handlebars. I would like to replace them with something a little lower and more aggressive looking. anyone have any suggestions? I am looking for low, but with a comfortable stance and something that enhances handling also.

Thanks guys :cheers:

[TwoTired]

Personally, I disliked the 500 I had in town driving, because the very low center of gravity always made the bike want to "stand up" from a turn, sort of like a BMW or British Twin. It also suffered, in stock form, from a slow clutch engagement and low-end torque like a 350. You have to "keep it wound" to keep power on tap, which is very different from the 750.

Having driven the Cb550 for 30 years, I guess a bike that wants to stand up by itself feels right to me.  It will turn nicely and predictably if you lean with the turn.    But, if you keep your own personal balance, it goes where it is pointed.  I recently got a cb700sc  It doesn't much care about personal balance or going in a straight line.  It falls off one way or the other and has no equilibrium of it's own.  If my Cb750's are going to behave this way, too, I can't imagine how they could be good touring machines (which is why I got them).  On a straight lane freeway, for example, staying in cage wheel track takes a great deal of concentration and attentiveness.  If I swivel head to check six, the thing wanders half a lane width by the time I look back forward!   Please tell me the Cb750F won't do this, too!

I understand the Cb500 got a clutch designed for a 350.  So, your comparison is apt!  The CB550 clutch is a different design.  The only ones I've had trouble with were aged Barnetts.

You're right about the power band, of course.  RPM is the CB550's friend, it is happy to oblige, and there is plenty of it.  If you want to pass, drop a couple of gears.  Zoom.  If you just want to twist throttle from low speed, some patience is required.  In traffic, I keep it no lower than 4K.  Nature of the beast.

Cheers,

[SteveD CB500F]

It's an interesting comparison 750 - 550 for handling. I've not ridden many 750s but I do have a 500 and a 550 and I think it may be more down to local setup than anything inherent in the design.

The 500 (Avon Roadrunners, Hagons on rear) is solid and "sits" into a bend as you power out (shame it jumps out of third gear - very embarrassing)

The 550 (Pirelli Phantoms, stock shocks) feel much taller, "falls" into bends and "fidgets" over every imperfection in the road surface.

I have never experimented with lowering or shortening but can see how it could help.

[Gordon]

Now that I've ridden the 550 to work for the past few days, I have a better idea of the difference between my 750 and 550.  I feel a little more confidant on the 750 in general, which I'm sure has a lot to do with the fact that I've ridden it pretty much every day for the last two years, but that extra weight and power just feels good.  On the other hand, the 550 is much easier to toss around in traffic and would probably be slightly easier to avoid an accident with. 

The 750 has that low-end torque that allows me to jump off the line when I want to (and I usually do), and makes passing a breeze.  To me, the 750 is more fun to ride because of the extra power, but I can definitely see where the 550 has its advantages.  If I know I'll be going somewhere that I'll be getting into tight situations, or parking may be iffy, or there will be a lot of heavy traffic, the 550 would be the better choice.  It's good for curb-jumping, making tight u-turns, and pushing backwards uphill if needed.   It's a great city bike.

[eldar]

Baz, check this topic for handlebars. There is a link to a very cheap site which sells good bars.

www.sohc4.us/forums/index.php?topic=7173.0

I cansee about getting rid of the fairing, but before you do, take it on a road trip.
You may find that you like it for that. So you could get the headlight and signal lights and put those on but if you go on a longtrip you can always put on the fairing in about 20 minutes.

[neilbron]

#2. Replace the rear swingarm bushings with tight-fitting, oil-impregnated bronze bushings. Change the oriental-style grease zerk fitting(s) with US-style zerks so the grease can actually be forced into the bushings. Lube those bushings generously when assembling them, and use new felt seals when you do.

#7. Use teflon-mixed oil in the front forks. Get teflon-coated seals that are slighty shorter in length (1/4" instead of the stock 5/16" to 3/8" stock units). These will "float" up and down slightly between the top of the fork retainer and the upper C-clip, which makes them seal better and respond to minor road irregularities MUCH better. Install the optional steel washer ABOVE the seal (good kits include these washers). Drill and tap the fork caps and install threaded Shraeder-type air valves (found at tires stores, used on mags), one in each fork. Run about 10 PSI pressure if riding single, 15-20 if carrying heavy loads.

If you do ALL of these things, you will not believe the difference the next time you hit a corner. It will feel like the bike lost 100 lbs somewhere... 

HondaMan that is a great post - as a newbie -  just what I have been looking for!
A couple of questions if you do't mind:

I've been told (not by anyone who actually owns a CB750 mind) that they need an extra fork brace due to fork wobble. Any comments?
Having just read the Duckworth CB750 book cover to cover (great book!) I see that some of the classic racers add aluminium braces to the frame swing arm pivot points. Make any difference on a road bike? worth doing if doing a complete frame strip down?

Thanks & cheers,

Neil.

[HondaMan]

I've been told (not by anyone who actually owns a CB750 mind) that they need an extra fork brace due to fork wobble. Any comments?
Having just read the Duckworth CB750 book cover to cover (great book!) I see that some of the classic racers add aluminium braces to the frame swing arm pivot points. Make any difference on a road bike? worth doing if doing a complete frame strip down?

Well, a lot of folks have tried to fix the "head shake" the later 750 had with things like frame braces and fork braces. The original front fenders came with a real stiff brace built into the fender, which often got removed for some sort of fiberglass fender. Then, suddenly, fork weakness appeared. The stock one was fine, but replace it with something stout if you change front fenders. With adequate bracing, the problem was actually caused elsewhere, by a wheel alignment issue (see my other posts about that). If you do add a different brace, try to make it light, but sturdy. Bikes gain approximately .25 HP of equivalent performance for every 10 lbs. of removed unsprung weight.

The rear wheel issues: I've never seen the rear frame to be inadequate, even over 135 MPH on high oval courses. What I HAVE seen is a lot of worn rear wheel bearings (all 3 of them) and tires, plus the swingarm bushing issues. Also, having tires out-of-balance introduces wobble above 50 MPH. It's strange how few bikers balance their tires, but it sure makes a difference.

Spokes and wheel trueness (and concentricity!) have MUCH to do with wobbles and irregular "wanderings". The top-hamper of the top-heavy CB750 actually minimizes this when compared to bikes with lower centers of gravity, but takes a little practice to master.

I seem to remember that Duckworth, or someone with a name like that, made racing frames in the 1970s. Is that what the book is about?

[seaweb11]

To: HondaMan.
There is a beautiful ocean water front,  1/2 acre lot for sale beside my property here on the West Coast of Canada/
Have you considered relocating?

Check it out, and my fridge always has beer in it

http://listings.coastrealty.com/details.asp?id=184070

[HondaMan]

Don't tell my wife...!

[neilbron]

I seem to remember that Duckworth, or someone with a name like that, made racing frames in the 1970s. Is that what the book is about?

Hi HondaMan,

Thanks for the reply - I aim to keep the stock fender so all should be fine. Will check all the other rear end issues for sure.

On a slightly different but related topic - did the fork mods from K1 to K2 really make a huge difference? Just wondering.

The Duckworth book is a Haynes CB750 book , a good read with a few pages on classic racing of CB's. They have some nice photos of a heritage racer which makes 90 hp! Plus the usual history and model differences etc.

Cheers,

Neil.

[chippyfive50]

is there a good source for the smaller teflon fork seals.....anyone...??

[HondaMan]

On a slightly different but related topic - did the fork mods from K1 to K2 really make a huge difference? Just wondering.

The Duckworth book is a Haynes CB750 book , a good read with a few pages on classic racing of CB's. They have some nice photos of a heritage racer which makes 90 hp! Plus the usual history and model differences etc.

Cheers,

Neil.

The late K2 , the K3 and K4 forks all had better damping. I think the late K4 and later forks were non-rebuildable, though. The earlier ones have individual parts and the damping can be changed with some minor welding and redrilling, plus they can be refurbished when the soft fork tubes wear....

[toycollector10]

I took your advice HondaMan and fitted a tt100 GP....it's handling like a new bike!!..Cheers  TC

[HondaMan]

Go get 'em, TC!

I'm just about to tear mine down for the 3rd rebuild. Makes me wonder what I'll change it into this time. It was a Production Racer and drive-to-work bike for 2 years, then a roadracer for 3 years (1st rebuild), then, with minor changes, a tourer in 5 different "flavors" since then. LOTS of miles, pretty tired. Last time I tried, it barely made the ton mark. 

Still took down a BMW R90S on the Million Dollar Highway in the San Juans, carrying a full touring load, though! Sometimes, it's not the HP, but the handling know-how. He was riding empty! Turned out to be a nice yuppie, though. When he caught up to me in Gunnison, CO about 30 minutes later he saw my bike at the MacDonalds and stopped in. He just wanted to check to "see if I had a turbo or something", and "where the hell did you learn to ride like that?" I showed him my load: a Tektronix oscilloscope, 40 lbs of hand tools and 2 week's clothing - I'd been out in the oilfiled for a while and was headed home. Bought him a hot chocolate and called it even.

I'll take pix of the rebuild along the way, maybe some of the RR mods I made (they're still inside), and, if I can figure out how, post some of them here.

Gonna be fun!

[Ted Nomura]

I remember when I got off my top heavy 1983 Kawasaki ZN1300 Voyager and got on my 1972 Honda CB750K2, the Honda felt like a dirt bike. Honda CB750 were never the best handlers, not like CB500/CB550 Fours or Triumph Trident/BSA Rocket III but it was good enough to capture the market.

[kaceyf2]

Yep, if you install air caps on the forks, you may as well go all the way and use a guage and an equalising tube between the two air caps, it equals out the pressure between front forks, and the gauge lets you see at a glance if you have a dodgey seal. I have this set up on mine.
Terry did the machine work on the caps for me as he had the gauges for sale...
One issue though, dropping the forks down a half inch or so in the top yoke looks #$%*e, better bet is to use cb650 fork tubes ( yep there just that shorter) thats what I got on my f2.
Be carefull buying phospher bronze swingarm bushes off a ebay, theres some badly made #$%*e with crappy tolerances floating around, go to mark at M3 racing.com, while your there,  check out good things he has for cb/cr 750's and drool!
if you really wanna go for handling what about a jmc or a dresda box section swing arm, braced and running tapered bearings or needle race? and a cbr600 front end...it all fits on...brembo calipers etc etc. These old girls are fun because they take real riders to ride them fast!

[cd811]

elcid...
i just curious...ya putting a sohc550 in softail frame ...did ya mean a regular swingarm or a softail...never seen a inline 4 in a softtail...now that would be cool...who made the frame?