Silverguy80
XS650 Enthusiast
Ok first off I have read everything I can find searching Google on the subject of dual exact same time firing xs650 motors (twingle). Most Google searches turn up 270 and 277 rephased cam and crank stuff. Found one thread we're a guy found a dual firing cam on eBay.
So apparently they were banned in racing in the 1970's. They produce goobs of low end torque. (Torque is what got my attention. I love torque!!!) Have a lower RPM redline and the top end power is not very good. They also vibrate worse than a stock xs650. Kick starting them is practically impossible. You can use a decompression something or another off an early xs650. Not familiar with that and what it is or looks like.
My understanding is that all you need to do to achieve this is to rephase the cam to were the intake and exhaust valves open and close at the same time. The xs650 fires on both cylinders on each compression stroke anyways. One just dead fires. Which that part really makes my brain hurt as to why dead fire on a cylinder. Seems like such a waste of energy and spark plug wear. I could maybe talk Hugh into doing the rephased cam, where intake valves open simultaneously and then exhaust valves simultaneously.
I was thinking to make the Motorcycle streetable. I could play around with the sprockets till I find the right sizes. Bigger in the front smaller in the rear? Right? I get confused on sprockets. Would it be possible or even a good idea to somehow counter weight the crank? So to elevate some of the excessive vibration.
Also would a performance cam be possible to use? Shell #1? Oh were the heck do I get a shell #1 cam?!? Are they all gone? What cams are the same or similar or better?
I know just rephase it and be done with it. I helped a buddy build his rephased xs650 chopper already. So I kinda would like to do something different and something that I haven't seen done at all. Plus this seems fairly easy to do. For the most part...
Thanks in advance for any information or answers to my questions. If you have done this before. It would be awesome to pick your brain about this. If anyone knows of a cam that's rephased like this that's available it would be amazing!
So apparently they were banned in racing in the 1970's. They produce goobs of low end torque. (Torque is what got my attention. I love torque!!!) Have a lower RPM redline and the top end power is not very good. They also vibrate worse than a stock xs650. Kick starting them is practically impossible. You can use a decompression something or another off an early xs650. Not familiar with that and what it is or looks like.
My understanding is that all you need to do to achieve this is to rephase the cam to were the intake and exhaust valves open and close at the same time. The xs650 fires on both cylinders on each compression stroke anyways. One just dead fires. Which that part really makes my brain hurt as to why dead fire on a cylinder. Seems like such a waste of energy and spark plug wear. I could maybe talk Hugh into doing the rephased cam, where intake valves open simultaneously and then exhaust valves simultaneously.
I was thinking to make the Motorcycle streetable. I could play around with the sprockets till I find the right sizes. Bigger in the front smaller in the rear? Right? I get confused on sprockets. Would it be possible or even a good idea to somehow counter weight the crank? So to elevate some of the excessive vibration.
Also would a performance cam be possible to use? Shell #1? Oh were the heck do I get a shell #1 cam?!? Are they all gone? What cams are the same or similar or better?
I know just rephase it and be done with it. I helped a buddy build his rephased xs650 chopper already. So I kinda would like to do something different and something that I haven't seen done at all. Plus this seems fairly easy to do. For the most part...
Thanks in advance for any information or answers to my questions. If you have done this before. It would be awesome to pick your brain about this. If anyone knows of a cam that's rephased like this that's available it would be amazing!