Topic: Need SOme DOHC Input, From Your Own Experience Or Knowledge

[bill440cars]

           Between the Honda 750 and 900 DOHC Engines, would there be enough difference in between the two, that the 900 would be a better choice of the two? If so, just what would it be besides the obvious? I've always heard that there's no substitute for cubic inches (or cubic centimeters). I HAVE seen the case where that just didn't hold up though. I'm just having some thoughts and wanted some input on this. BTW, I know that there are 2 DOHC forums but, I feel more comfortable here and I know that there is a lot of knowledge here as well.


                                                                                                     Thanks for the time, Bill  

[Caminokid]

You know Bill, I built a Yamaha 650 twin that would whip my F2 off the line even after it was built. And the Yamaha didnt have as many CC's as the F2. But at the 1/8 mile the 750 would catch it and pass it. It depends on how you build it...how light it is. I owned a 900 Z-1 Kawasaki. It had a 1205 kit in it and it would whoop everything off the line except that Yamaha I built. But at the 1/8 it would pass it like it was standing still. You just have to consider what you want to do and go from there.

[HavocTurbo]

I prefer the 900 only for the looks of the engine. The rest of it can go in the trash.

Are you looking at yet another bike Bill??

I need to move closer to you so we can swap parts!!!

[crazypj]

750 has shorter stroke and shorter cam chain so doesn't wear hole through cylinder as quick.
 Bored out 750 would be my choice

PJ

[bill440cars]

        I certainly appreciate the input. The point is, I've got an 80' CB750K that I want to get on the road and will probably make some changes to (not irreversible ones though). Plus, I've got a good part of a 79" CB750K and I've been seeing some CB900s and 1 1100F on ebay. And that has me wondering about the larger DOHC engine vs the 750 model (with some mods). Now, I'm not trying to see if I can duplicate the power of the GPZ with the Hondas. I'm just wondering what I can get out of the Honda DOHC engine without "breaking the bank"? Like take the 750, raise displacement, swap out the cams, ad some headwork, carb mods (or swap) and exhaust. Of course I know the basics of making an engine RUN! I'm loking for some pointers on making these Hondas go better. Thank you for your time,   Bill

[YogiBear]

        I certainly appreciate the input. The point is, I've got an 80' CB750K that I want to get on the road and will probably make some changes to (not irreversible ones though). Plus, I've got a good part of a 79" CB750K and I've been seeing some CB900s and 1 1100F on ebay. And that has me wondering about the larger DOHC engine vs the 750 model (with some mods). Now, I'm not trying to see if I can duplicate the power of the GPZ with the Hondas. I'm just wondering what I can get out of the Honda DOHC engine without "breaking the bank"? Like take the 750, raise displacement, swap out the cams, ad some headwork, carb mods (or swap) and exhaust. Of course I know the basics of making an engine RUN! I'm loking for some pointers on making these Hondas go better. Thank you for your time,   Bill

If you want to make a Rocket out of that 750K, then find a 900 motor and rebuild it with wiseco's 985cc big bore kit. I think going from a 750 motor to a 900 motor is damn near a direct swap. That thing will scream! If you really want to go balls out, get some CR carbs too. Myself, I wouldnt waste my time building a 750 DOHC motor, when theres a replacement as easy as the 900.

[crazypj]

The 900 is longer stroke and doesn't rev as well as 750 without breaking something.
The longer cam chain/guides wear faster, particularly if not adjusted correctly. (you wouldn't believe 2.5mm could make such a difference)
 Bore the hell out of a 750 block,probably get one cheap on eBay.
 I don't remember max bore (with liners) but believe you can easily get a 998 in there (I think 74mm XR250 pistons)
 Wouldn't use Wiseco unless your doing Carrillo rods though, they tend to be pretty heavy

PJ