Topic: CB 750 Brat Style - Shock Lenght

[Bacchus]

I am searching for shocks for my 74 CB750 which I am making into a Brat (rear hoop and flat seat). I also installed a custom oil tank....  Both mods restrict the travel length of the shocks. Per David Quinn the fully compressed length of the 13"  Hagon shock is 10", which unfortunately is just a bit more than the space I have to play with. The 14"  shock's fully compressed length if 11" which works with my application. My question is, for casual riding around town,  could the travel distance of a shock be maxed out and would jumping to a 14" shock affect the center of gravity of the bike?.
I prefer the lower stance. Any advise or suggestions are greatly appreciated. I have searched but have not found anything on this topic. Cheers

[Yamahawk]

It would be nice to see a few pictures of your current set up with the rear loop and seat, and oil tank. The measurements you have taken have your rear tire within 3" of the bottom of your frame loop and flat seat? That's pretty close I would say... Now if you add longer shocks, that will affect your rake and trail, which for a race bike will give you a bike that will turn in quicker, but on the street may translate into 'twitchy' handling. Whenever you change one end, it is always good to change the other as well. This means raising the front end, by either lowering the forks in the triple tree(which you probably don't have any 'extra' above the top triple tree to do this with), or by adding a lower profile rear tire... you won't find an inch lower rear without changing rim sizes, and even then the 16" rim will have about the same tire height if you go with the fatter/taller 16" tires out there.
So, what you have is a compromise, in what you are able to end up with. The least hassle is to add the 14" shocks, and put up with the modified rake/trail, and try to get used to the handling... or, do the shocks and install longer fork tubes to balance out your bike. It will end up 1" taller front and back, but your rake/trail will be close to stock. Let's see what you have, first! Post those pics!!
Charlie

[Bacchus]

Is this a common compromise with these types of builds?.I do not want to compromise the ride and would rather keep the stock shock length (13").
I see a lot of brat style CB750 with similar set ups; not sure what length shocks they are using,but they look standard.

[Yamahawk]

The rear looks very nice, and if you feel the shock will compress into the seat area, then you should get a longer shock. Have you looked for a 340mm length? This would give you 13.5" approximately and may give the clearance you need without having too much of a problem with height. Most shocks won't bottom out, if you set the preload up a little. So with the 1/2" longer shock, you might be ok.
That will be your call on that. I like the Excel rim!
Charlie

[DV Red Herring]

I would ride it first. It looks like you have quite a bit of room to work with. Mine only has about 4 inches between the tire and the rear fender and I have yet to bottom it out and I'm 200lbs.

[seanbarney41]

I have ran 14" cb900f shocks on an otherwise stock suspended and geometried (is that a word) 750k5.  It was twitchy.  I can think of at least a few situations where I got some chilling amounts of head shake.  Riding above about 70 mph was kinda like, "Ohhh Kayy, now I must hold my body verrrry stilllll."

The correct way to check how much travel you need is to remove the springs from the shocks you intend to use, mount the shocks on the bike and compress the shocks to the stops...or does the tire contact the frame first?

[Bacchus]

The 13" shocks fully compressed are 10"; this made the tire rub the oil tank. I could either offset the tank or order the 14" shocks. Did not want to change my intended design, so I ended up ordering the 14" shocks.  I appreciate the responses and promise to post and update on how the bike rides.