Topic: Need some advice from some of you Motor Gurus!!!!!

[mlinder]

The new rings for my 750 cost $160. Stuff ain't cheap.

Yea I'm finally realizing the costs on things!! lol Oh well nothing I can do about it now.

You can just dump the whole 650 engine in the 550 frame. That's easy. It's also a 10+ rwhp increase.... All you lose is the kickstart. Minor electrical things to deal with.

[Johnny-5]

Thats actually crossed my mind but still debating on it. Trying to figure out whats the advantages with modifying like what Paulages did with his 550/650 Hybrid compared to just dropping in the entire 650 into the 550 frame???

[/quote]
You can just dump the whole 650 engine in the 550 frame. That's easy. It's also a 10+ rwhp increase.... All you lose is the kickstart. Minor electrical things to deal with.
[/quote]

[mlinder]

He wanted to keep the 550 bottom end for the kickstart.

[Johnny-5]

He wanted to keep the 550 bottom end for the kickstart.

So other than that he would have done the full swap? Interesting.

[mlinder]

I think so, yes.

[Johnny-5]

Here's a question for some of you and maybe a simple one at that.....


Since I got this complete CB650 Motor should I just drop the entire motor onto my bike? Besides the point Ill probably pull the head and get everything ported and polished. Or should I mix a little bit of the CB650 internals into the CB550.

I will miss the kick start thats for sure but hey its something I can live without if its that much of a benefit of having the full 650 motor.

Any thoughts?

[mlinder]

650 head needs very little porting/polishing done. It's damned near close to a stage 2 porting of anything else in the sohc4 family I can think of. I'd just drop the #$%*er in the frame if the kickstart isn't a deal killer for you.

[Johnny-5]

650 head needs very little porting/polishing done. It's damned near close to a stage 2 porting of anything else in the sohc4 family I can think of. I'd just drop the #$%*er in the frame if the kickstart isn't a deal killer for you.

I wouldnt mind having it but I dont think its worth all the hassle for doing all that work just for that. Plus Ill be going with a little modern look with the bike as is going with a newer front end as well. Do you happen to know if the motor is extremely heavier or bigger compared to the 550? Is there any disadvantages of having that motor on the bike like effect handling or anything like that? Just curious? Oh and just out of curiousity as well....is there little upgrades you could think of with that motor and not going to extreme with it? Like new cams or carbs?

[mlinder]

It's slightly taller than the 550 engine. They weigh, more or less the same, and are the same dimensions otherwise.
A 650 is basically a factory bored and stroked 550 with a vastly improved head design.

[Johnny-5]

It's slightly taller than the 550 engine. They weigh, more or less the same, and are the same dimensions otherwise.
A 650 is basically a factory bored and stroked 550 with a vastly improved head design.

That works for me! Do you know of anything like cams or bigger carbs and things like that I can do with it? Or is this one of the engines thats good as is?

[mlinder]

Apparently, the early gs750 keihin slide piston carbs (not the VM) are almost a direct bolt on. They are an upgrade, in my opinion. Easily tunable, good flow. Any hot 550 cam will fit.
To be fair, someone like Mike Reick could improve the flow on the 650 head, but I just don't know how much improvement you'd see. Port matching may be the best thing to do here. Exhaust will help a bit, too.

Oh yeah, I've heard of cb750 carbs being put on these, too, can't remember what it took, though. Look for, I think, Soos posts on the subject.

[Johnny-5]

Apparently, the early gs750 keihin slide piston carbs (not the VM) are almost a direct bolt on. They are an upgrade, in my opinion. Easily tunable, good flow. Any hot 550 cam will fit.
To be fair, someone like Mike Reick could improve the flow on the 650 head, but I just don't know how much improvement you'd see. Port matching may be the best thing to do here. Exhaust will help a bit, too.

Oh yeah, I've heard of cb750 carbs being put on these, too, can't remember what it took, though. Look for, I think, Soos posts on the subject.

Thanks mlinder...you have been most helpful! Still learning these bikes and what modifications are doable and worth while! Great Forum!