Cafe Racer Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
189 Posts
Discussion Starter #1
Is there any way to stroke the engine with maybe a 450 crank or something for high compression and some more power??

Red
 

·
Registered
Joined
·
3,453 Posts
Are you sure strocking that engine is what you really want to do? Never heard of that, meself.
 

·
Registered
Joined
·
1,735 Posts
RondaD-

listen to these guys. evil's a short strocker and craig's a long strocker...but they both have very high compression pistons.
 

·
Registered
Joined
·
189 Posts
Discussion Starter #7
Well im going to run 12.5:1 Pistons and bored out to 362.

So Craig how did you do it?? And do u like it??
What are the pros and cons too?

Red
 

·
Registered
Joined
·
633 Posts
What it involves is: welding the crank pin holes up then re-boreing them farther away from the crank center, I dont know how much stroke you could actualy gain. It depends on how much clearence is left for the crank/ rod to clear the case as it rotates. also if you increase the stroke very much you will have piston to valve/ head clearence issues. This would probably cost mega bucks and would also probably require re-ballanceing too. I seriously don't think it would justify the cost, which would be a lot! Put bigger pistons and cams and sutch, you'll gain more bang for those bucks. Also better ignition and exaust.
 

·
Registered
Joined
·
4,508 Posts
I just said it could be done. I didn't say I did it. I don't really see the need. It'd be illegal for any of the classes I race in. And if it's just for the street there are better bikes that would make more hp for less money than trying to do this with a CB350. As oldhonda said, this would be megabucks real quick for not enough gain to make it worth it.

Craig
 

·
Registered
Joined
·
5,780 Posts
I think you guys are all a bunch of downers, trying to dampen any enthusiasm and creativity. I say go ahead and do it. Since the CB350 uses a built up crank, the way to do it has been done plenty of times. If I were going to do it with no regard to money, I would make up some new slightly bigger flywheels and move the crankpin out as far as I could. Then I would have Carillo make me up some shorter rods and Wiseco or JE make me up some shorter, bigger pistons. Then I would remachine the combustion chamber to match the bore and piston. Then I would port the head and put in some bigger titanium valves with smaller stems. I would top it all off with a hot cam and some giant flatslide carbs. That would make a really cool motor that would be close to 500cc and make almost 45 HP. I'll bet I could build that motor for under $5000.

Of course I guess I could just buy a nice GS500 or EX500 for $1500 and have a lot better bike all around.
Never mind, even if it can be done, there is absolutely no point in it. It is not worth the time money or aggravation.
Of course that is just my opinion, and I might be wrong.

Ken
 

·
Registered
Joined
·
1,413 Posts
i think it might breathe better by adding displacement side-wards... longer stroke puts more stress on the reciprocating mass too, if you can increase displacement without increasing the acceleration of reciprocating mass, you're doing yourself a favor... hence, bore it out, deck the head, etc, stroking probably won't be as much power for the money
 

·
Registered
Joined
·
681 Posts
I've no idea on fitments, just know they're out there for almost anything. You'll need to know the diameter and width of the OEM pins to look up offset replacements.
 

·
Registered
Joined
·
2,937 Posts
Or, you grind out the existing pin holes in the flywheels., offset outwards and go from there.

But who needs a long stroke. Much better with a shorter stroke and larger bore, which would need more valves, so think about say a 70mm CBR top end with a little welding and machining and you'd have half of a CBR1000 making about 75HP with EFI etc.

Or just get a pair of pistons from Les at Vintage ADvantage and do it the easy way.
 
1 - 20 of 22 Posts
Top