Topic: Honda CB 750 Rear Shock Length/ Dimension

[Andy Downes]

Hi could someone please tell me the length/dimension from eye to eye for the Stock rear shock, on a stock CB750, thank you Andy

[Johnie]

K4 shock not mounted and the adjustment in the #2 position gets 13 inches.

[MCRider]

K4 shock not mounted and the adjustment in the #2 position gets 13 inches.

Just FYI: The adjustment (spring pre-load) won't change the length of the shock as the unloaded shock is topped out against its stops at every position.

I'm fairly certain 13" (at full extension) is correct. The popular Progressive brand shock replacement is 13 1/8 or more. But everyone uses them anyway. I don't think there are any after market shocks that are exactly the 13" we came with.

[Andy Downes]

Hi, thank you, Andy

[Bob750]

How about the width of the shocks?

I'm trying to figure out if Hagon "slimline" shocks will be required or if I can use their standard "wideline" shocks (same price and performance--it's purely a cosmetic difference). I'm measuring my shock springs at (about) 55.5mm. But the Hagon wides are "barrel shaped" with the Outer Diameter tapering from 53.5mm at the ends to 60mm through the middle section. [see: http://www.davequinnmotorcycles.com/cgi-bin/webc.cgi/HAGON_TWIN_SHOCKS.html] The slimline shocks are straight at 52.5mm OD. The only place this may be of concern is on the left shock, next to the chain guard.

The wides look cooler, but the slims may be the only way to get them to fit nest to the guard. Any one here know more than I do about what will work? Any one have the wides on a K4?

Lots of love.

Bob

[seanplarkin]

can you use a 16 inch shock, like the one being sold on parts n more?

[HondaMan]

Hi could someone please tell me the length/dimension from eye to eye for the Stock rear shock, on a stock CB750, thank you Andy

The sandcast K0 bikes had shocks 12.79" in length. This changed to 13.06" in length in early 1970. Hard to find, but Progressive makes some that are close: err to the short side for improved handling, like 12.75". I have some of these on mine now, like them a lot.

[Holden]

The sandcast K0 bikes had shocks 12.79" in length. This changed to 13.06" in length in early 1970. Hard to find, but Progressive makes some that are close: err to the short side for improved handling, like 12.75". I have some of these on mine now, like them a lot.

Wouldn't a slightly longer than stock shock improve handling as opposed to a shorter one?  Slightly raising the rear would put more weight on the front and improve steering, right?  Could you explain why I would be wrong on that?

Thanks.

[coma13]

I'd imagine any lowering of the center of gravity would help with the handling on these suckers.

[HondaMan]

The sandcast K0 bikes had shocks 12.79" in length. This changed to 13.06" in length in early 1970. Hard to find, but Progressive makes some that are close: err to the short side for improved handling, like 12.75". I have some of these on mine now, like them a lot.

Wouldn't a slightly longer than stock shock improve handling as opposed to a shorter one?  Slightly raising the rear would put more weight on the front and improve steering, right?  Could you explain why I would be wrong on that?

Thanks.

The CB750 has the shortest trail (up front) of all the superbikes ever built. It seems Honda's marketers could not decide if the bike would be used on Saturday nights to burn up the town, or cross-country to burn up the highway: longer trail is good for highway speeds, but adds a heavy feeling to the bike, while shorter trail speeds up handling, but lets tire and suspension wear issues cause erratic high-speed stability.

In the end, they settled on (mostly) 3.75" of trail for a lighter 'feel', while almost everyone else has 4.00" or more. If you raise the rear end, the trail shortens even more: using a 13.5" shock makes for 3.55" trail, for example (at 1/3 stroke on the rear springs). This is why softer or progressive springs on cafe' bikes make these chasses handle corners better, so long as you don't drag the passenger footpegs or centerstand. My own centerstand is seriously ground off, as are both passenger footpegs and mounts, from years of mountain riding with 13" rears and air forks up front to get some more trail (my wife used to beat on my back when I knocked her feet off the pegs, a built-in early-warning system...). More recently I went to the 12.75" rear length, stiffer springs with less preload, and a little less up-front air pressure in the forks, to soften the ride a bit while still maintaining the solid line in sweeping turns. She doesn't ride much with me, now, so the loads are lighter, and it better suits my aging back.

[lucky]

The sandcast K0 bikes had shocks 12.79" in length. This changed to 13.06" in length in early 1970. Hard to find, but Progressive makes some that are close: err to the short side for improved handling, like 12.75". I have some of these on mine now, like them a lot.

Wouldn't a slightly longer than stock shock improve handling as opposed to a shorter one?  Slightly raising the rear would put more weight on the front and improve steering, right?  Could you explain why I would be wrong on that?

Thanks.

The CB750 has the shortest trail (up front) of all the superbikes ever built. It seems Honda's marketers could not decide if the bike would be used on Saturday nights to burn up the town, or cross-country to burn up the highway: longer trail is good for highway speeds, but adds a heavy feeling to the bike, while shorter trail speeds up handling, but lets tire and suspension wear issues cause erratic high-speed stability.

In the end, they settled on (mostly) 3.75" of trail for a lighter 'feel', while almost everyone else has 4.00" or more. If you raise the rear end, the trail shortens even more: using a 13.5" shock makes for 3.55" trail, for example (at 1/3 stroke on the rear springs). This is why softer or progressive springs on cafe' bikes make these chasses handle corners better, so long as you don't drag the passenger footpegs or centerstand. My own centerstand is seriously ground off, as are both passenger footpegs and mounts, from years of mountain riding with 13" rears and air forks up front to get some more trail (my wife used to beat on my back when I knocked her feet off the pegs, a built-in early-warning system...). More recently I went to the 12.75" rear length, stiffer springs with less preload, and a little less up-front air pressure in the forks, to soften the ride a bit while still maintaining the solid line in sweeping turns. She doesn't ride much with me, now, so the loads are lighter, and it better suits my aging back.

If I was her I would have beat on your head.
No wonder she does not ride with you anymore.
It is very scary to be a passenger on a motorcycle,try it sometime.

[HondaMan]

The sandcast K0 bikes had shocks 12.79" in length. This changed to 13.06" in length in early 1970. Hard to find, but Progressive makes some that are close: err to the short side for improved handling, like 12.75". I have some of these on mine now, like them a lot.

Wouldn't a slightly longer than stock shock improve handling as opposed to a shorter one?  Slightly raising the rear would put more weight on the front and improve steering, right?  Could you explain why I would be wrong on that?

Thanks.

The CB750 has the shortest trail (up front) of all the superbikes ever built. It seems Honda's marketers could not decide if the bike would be used on Saturday nights to burn up the town, or cross-country to burn up the highway: longer trail is good for highway speeds, but adds a heavy feeling to the bike, while shorter trail speeds up handling, but lets tire and suspension wear issues cause erratic high-speed stability.

In the end, they settled on (mostly) 3.75" of trail for a lighter 'feel', while almost everyone else has 4.00" or more. If you raise the rear end, the trail shortens even more: using a 13.5" shock makes for 3.55" trail, for example (at 1/3 stroke on the rear springs). This is why softer or progressive springs on cafe' bikes make these chasses handle corners better, so long as you don't drag the passenger footpegs or centerstand. My own centerstand is seriously ground off, as are both passenger footpegs and mounts, from years of mountain riding with 13" rears and air forks up front to get some more trail (my wife used to beat on my back when I knocked her feet off the pegs, a built-in early-warning system...). More recently I went to the 12.75" rear length, stiffer springs with less preload, and a little less up-front air pressure in the forks, to soften the ride a bit while still maintaining the solid line in sweeping turns. She doesn't ride much with me, now, so the loads are lighter, and it better suits my aging back.

If I was her I would have beat on your head.
No wonder she does not ride with you anymore.
It is very scary to be a passenger on a motorcycle,try it sometime.

After she agreed to learn how to ride WITH me and not by herself back there, we could cover many miles of fast twisties and have a blast of it. Then, she would anticipate those corners deep enough to drag her pegs, and would gently lift her weight off of them, then press them gently back down after the corner. It's really hard to describe just how intimate that kind of riding can be together, unless you have someone that close to you who will learn to enjoy it as much. It took 3 years of practice, but it was worth the effort!

[Retro Rocket]

Hi Mark, what was the trail of the F models with the shorter 50mm offset on the clamps.? In your opinion, what is the ideal offset for one of these bikes ofr both, spirited riding and highway riding.? Trail number would probably do....  I used to ride hard with my wife on the back and she loved it, never used stock rear pegs on the Honda or the center stand, they scrape to easily....

[HondaMan]

Hi Mark, what was the trail of the F models with the shorter 50mm offset on the clamps.? In your opinion, what is the ideal offset for one of these bikes ofr both, spirited riding and highway riding.? Trail number would probably do....  I used to ride hard with my wife on the back and she loved it, never used stock rear pegs on the Honda or the center stand, they scrape to easily....

Roger that center stand, mine was almost gone at one point!

The trail I like best is about 3.80"-3.90". I control mine via air forks and estimation of weight on the rear, adjusting the spring notches to set the ride height for what I am about to do. Above 4.00", the handling feels heavy in the twisties, below 3.50" it feels twitchy above 50 MPH. At present, my fork bushings are severely worn (0.011" clearance!), so I am in the process of designing new ones from bearing bronze (which will one day appear on my website, for the rich...).

The published trail on the "F" bikes varied, depending on who was publishing the info, but the neck rake is supposed to be the same. Best way to know is to measure it: with bot wheels on the ground, strap a yardstick to the fork lowers to reach the ground on the centerline of the axle, then drop a plumb line down from the axle to the ground. Measure the distance between those 2 spots for your number. It's easy to repeat, later.

On my K2 (with Vetter fairing attached), I know that 3 PSI in the forks with top (softest) rear spring notch yields 3.75"-3.85" trail, with these new Avon Roadriders (110-90 rear, 100-90 front). At 7 PSI in the forks, this becomes nearly 4.00". With 150 lbs in the seat (me, dressed to ride), this 4.00" becomes 3.80", still on softest rear spring notch. This is my solo ride setting, usually. When I ride 2-up, people only, I use 10 PSI up front and middle notch in back, which takes it to about 3.75". With touring loads, I would run 12 PSI up front with 4th (or 5) notch in back, netting about 3.9" when on the road.

I should mention that I use a 1" preload tube in each fork, and the rear springs are 110 lbs./inch rate.

[01Thomas]

Bump (so I can find this topic again).

[MCRider]

Bump (so I can find this topic again).

You can save it as a favorite place (Internet Explorer) and go to it that way. I have many threads saved that way, in a folder uner Favorites.