Dirtbike forks on Dohc CB750


CB750 Member
Reaction score
Hey guys, i'm sitting here going through my head the different front end options i have for my cb750c and one came into my head I hadn't seen before.

Has anyone ever put a lowered set of dirtbike forks (preferably cr250r or crf 450r) forks on their bike? I really want to use a set of 17"supermoto rims for 1. The 320mm rotor, 2. The tire width and choices and 3. They look sick. Plus there is a lot of after market for these forks and they typically are cheaper than gsxr or cbrr forks. Figured then i wouldnt have to play guessing game with centering the wheel with the forks
Forks that hold up a 200 lb. bike can fail on a 500 lb. one. May be big enough on OD but VERY likely to be much thinner wall there. The weight will likely sag the springs solid too.
I think they would work fine but dont know for sure. When see the pounding that is put on these modern motocross bikes with the huge hits they take coming off of triple jumps etc they take far more abuse then any street bike. I know first hand accidently hitting a jump too hard and when landing broke two spokes but rest of bike unfastened by the incident. On another note...professional hill climbers use dirtbike chassis and stuff nitro burning 4 cylinder street bike motors into the dirt bike bike frame and just use revalved and resprung otherwise stock forks and shock. So I would say they would be strong enough but you will need to have them resprung and have the valving changed to deal with the extra weight and constant higher speed.....this would make the cost more then likely higher then going with the usual sport bike setup....valving isnt cheap. Remember dirt bike suspension isnt made for the weight or the speed of a street bike, they are made to control and use all of the 12 to 13" or so of travel, they have to be stiff yet take an abrupt hit from the edge of the jump, they dont care how they handle at highway speeds because they rarely get up to highway speed......kind of scary when you do take them there! So some things to think about.
Now you're making me think about it and you are likely dead right...............the dirt forks are intended to damp over a very long range of travel and likely the damping will have to be altered to get stiffness at the very short stroking amounts like street stuff uses. I'm full of crap probably when it comes to the overall fork strength. Thinking of how the very earth shakes when those bikes touch down after a 30 foot travel in the air, you feel the contact when they hit.

The issue will be getting the spring to stabilize at the needed ride height and then getting damping on for the 2-3 inches street normally uses, simply driving a dirt fork not hard will have the fork using 5-6 inches easily, that kind of rocking horse will get you in trouble fast with the heavy weight of a street bike and you doing a panic brake move, you'll lose control of the bike. Maybe stabilize deeper into the travel to also get more fork tube overlap, which greatly strengthens them too.

Also thinking now about my first ride on a Yamaha 1200 V-Max, the first impression I got of the wild suspension performance tied to that engine was that I was riding a dirt bike with 130 hp. The bike under hard power felt exactly the same as an unbelievably powerful dirt bike, it was using up every bit of suspension it had. You know you are really travelling when the level street feels like you are off-road......................
Last edited: