Custom/Hybrid 650 bottom end/ 750 top end

[Joker]

Is it possible? Will it hold up? Do you get the same power?

 

[mydixiewrecked]

Never seen anyone do it

 

[Joker]

I remember some guy doing it but I can't member who. I was hoping he caught this and could respond. But I know pjs took the cases and modified them and put a 830 cc top end on or their viper motors.

 

[Austin]

My plan was to do that back when I started my project. But after I had talked to many engine builders it just doesn't work out as well as you would think. I know it would work but it would take some work. First you need to find 650 pistons that are 750 bore. then you have to machine the cylinders to go on the 650 cases.

It would work but from what I heard is a ported 650 (all 650 parts) would out perform a 650/750 engine. Alot of it has to do with intake ports and sizes. Your much better off just finding 750.

 

[Joker]

Ya I figured

 

[Austin]

It would work but I think it would be cheaper finding a nice 750 than paying for custom pistons and a ton of machine work to a Frankenstein engine that you dont know how well it will even run.

 

[Joker]

Pretty much I am already getting funds for a 750 now

 

[Austin]

Nice! You will be happy with the 750! I still cant wait to finish my hull so I can drop my 750 in

 

[Joker]

Ya in doing a 650sx up like people do a 300sx conversion.

 

[Austin]

sounds like it will be sick! you will have to keep everyone up todate withpictures of it.

 

[Joker]

I plan on making one big thread when I'm done I have a bunch of pictures. Probably 35 right now

 

[Vumad]

650 crank is lighter than the 750 crank. It's lighter because it's smaller and has a shorter stroke. Shorter stroke means less displacement, means less power, means wasted investment. Work a 650 or work a 750. Don't try to make them work together.

The 650 crank has 4mil less stroke. A 650 bottom (70mm) with a 750 top (80mm) yields 703.7cc. The stock 750 motor is 743.9cc. You'd be paying a butt ton of money for 40.2cc less than just buying a used 750 motor.

If you want a motor that performs well that's only 700cc, and you want to frankenstein 2 motors together, I would suggest you look into some Yamaha 62T cases and a 61x cylinder. That modification would make sense. The 650/750 Kawi though... waste all around.

 

[Joker]

Ya I'm going with a 750

 

[afraz1er]

wiseco made/makes at one time a kit for a 650 to 750. they are 750 diameter pistons with the wrist pin of a 650

 

[jetskijockey]

I have heard it was done with 750 cases 650 crank and cylinders.

 

[N2 H2O]

Yeah I have a motor with 750 small pin cases, 650 crank, 650 cylinder, and 650 electronics. My bore is only 1mm over, but the small pin cases have much bigger intake ports and a much better selection of intake manifolds. I'm not sure how much of a difference the 750 cases made though because I never rode it with 650 cases.

 

[jetskijockey]

Yeah I have a motor with 750 small pin cases, 650 crank, 650 cylinder, and 650 electronics. My bore is only 1mm over, but the small pin cases have much bigger intake ports and a much better selection of intake manifolds. I'm not sure how much of a difference the 750 cases made though because I never rode it with 650 cases.

post some pics of it.

 

[N2 H2O]

Here are the only pics I have on my computer. I'll get some better pics tomorrow.

 

[Joker]

I was looking for a 650 bottom and a 750 top