270/90 crank pins? 2022

Oldnwiser

XS650 Enthusiast
Messages
82
Reaction score
64
Points
18
Location
Desloge,MO
Gentlemen,

Is there anyone making the 270/90 pins for the XS in 2022? I heard one on U-tube with some nice pipes built at Hugh’s and it really sounded good?

Is there a big difference between the 270 and the 277 as far as balance and power? And can a 256 cam be cut and welded to put into a 447 engine? I still want to do a rephrase 750-800cc engine for a light Cafe Racer style bike. Just wondering, there was a guy making splined pins for it. I have a good. port design for intake and exhaust to develop. That would be lotsa grunt .
 
Gentlemen,

Is there anyone making the 270/90 pins for the XS in 2022? I heard one on U-tube with some nice pipes built at Hugh’s and it really sounded good?

Is there a big difference between the 270 and the 277 as far as balance and power? And can a 256 cam be cut and welded to put into a 447 engine? I still want to do a rephrase 750-800cc engine for a light Cafe Racer style bike. Just wondering, there was a guy making splined pins for it. I have a good. port design for intake and exhaust to develop. That would be lotsa grunt .
Ask Gary Hoos @Hoos Racing
 
Yes Ivan Hoey makes them in batches, But you need two cranks to make one 270 as pins are splined on each end.
https://old.xs650.org.au/Racers.htm

I have never been able to compare the 277 to a 270 so can't comment on question 2.

With swapping cams you need to ensure the crank sprocket has half the number of teeth as the cam. It did change from 17/34 to 18 /36. I think it was when the rod length changed but not 100% on that.
The cam sprocket can be pressed off and altered. If you are going all out you will probably want an adjustable boss for the cam so you can dial it in to your liking.
You can buy adjustable sprockets or make one if you have the machines.
 
Well actually not two whole shafts but 2 inner wheels that carry the female spline. Have a look at the pins in the link and you will see.
Thank you, I can picture it now! I may have a couple of flywheels in the boxes in the loft. I appreciate it!
 
I doubt there is much difference between identically built 270 and 277's. I have been running a 700cc 277 since 2008 and have been very happy with it. BTW I don't see how a rephase can increase hp unless there is a tiny gain from not putting as much energy into vibrating the bike and the rider.
 
An XS650 is a wonderful blank slate for lots of ideas and exercises.

I haven’t heard of or seen an old Triumph rephrased. I’m sure it’s been done, just not lately.
 
Here are some screen captures from a program I wrote that shows the relative vibration in the vertical plane in the form of an animation. I included 360, 277 and 270 degree configurations at a 60% balance factor and the 277 at 53% and the 270 at 50% both which have the least vibration in the vertical plane. Note that the rephased engines would also include a rocking couple which I never attempted to model. So the 270 appears to be a little better than the 277 but not by a lot. Personally I didn't like the idea of replacing the center shaft with something non-OEM.
 

Attachments

  • 50 - 270.GIF
    50 - 270.GIF
    18.4 KB · Views: 56
  • 53 - 277.GIF
    53 - 277.GIF
    18.2 KB · Views: 53
  • 60 - 270.GIF
    60 - 270.GIF
    18.1 KB · Views: 52
  • 60 - 277.GIF
    60 - 277.GIF
    18.1 KB · Views: 58
  • 60 - 360.GIF
    60 - 360.GIF
    18.4 KB · Views: 55
Jetmech a local(ish) tuner here has had his son racing a rephased classic triumph he has completed last year. It is very fast I don't know the rephase angle.
His son jokes that he wore a set of tyres out wheeling the bike on and off his dyno.

Another thing to consider is that as far as I know there are no off the shelf 270 ignition systems, with 277 there are some of the shelf units.
 
Back in the 70's there was a mechanic/racer/builder that worked out of Free State Honda in Bladensburg MD, Greg Edmonds, who built a re-phased Triumph twin with a fabricated crank.
For dirt trackers it was mainly to get the better firing impulses to hook up in the dirt, more like the Harley's, and even the Harley's, with their individual cam layout could take it one step further and reposition the cams to get firing impulses 45° apart then 675° before the next two firings.
 
Back
Top