Boxerworks.com

Some of this is cross posted from ADV rider.

As part of my usual winter therapy, I've decided to experiment by fitting a new cam to my R90/6. The engine is in very good condition having been rebuilt by Jim Cray 2 years ago. The build spec was to to create a smooth touring machine with good low and midranger performance. Modifications included full balancing, 9.5 lieghtweight pistons, dual plugs, lightened flywheel and very lightly ported heads and a sachse ignition. The bike works well and will get up to 60 mpg (imperial).

I have decided to fit a 320 degree cam from motoren Israel, these are available in small seal versions suitable for this bike.

I took the bike to the Dyno just before Christmas, just to get some base line figures, and the dyno charts are below, I think that the charts show that Jim's build fulfilled the spec, I'm hopefully that the new cam will give me a bit more pep on the top end, without losing too much low and midrange tracterbility and power.

The work will start sometime next week and will post the results, once the bike is complete and has a few miles on the new cam.






Both the images are cutoff. But you can see the full charts here. http://s46.beta.photobucket.com/user/ch ... o%20charts

chasbmw wrote: The build spec was to to create a smooth touring machine with good low and midranger performance.

I'm presuming a Ranger in Middle-Earth would be a "MidRanger." So, if this means the performance of Aragorn, that sounds pretty cool.


If you can keep that torque curve flat or climbing up through 6000, sure that would be cool, but I'd hate to give up anything down around 4000 to get it, and I suspect that's likely.

On my Oilhead, I actually made the opposite choice. I did the switch on RS to GS intake tubes. The oilhead can comfortably turn a bit faster, but I gave up 6 hp on top to gain 5 hp at 4000 and at 6000. As you can see, in stock tune the RS has a nasty dip in the torque curve at 4k, but with the change is WAY nicer everywhere except peak hp from 6500 - 7500.

I find this to be far more fun 98% of the time. I can live with the slightly less awe inspiring 2%.

Major,

I suppose that the difference between the R1100 and the R90 is that the R1100 has twice as much HP

My other bike makes just just over 72 BHP, and it also has retained very good low speed performance, together with a kick at around 5000 rpm. This bike is fitted with the Seibenrock supplied assymetrical cam, which is not that dissimilar to the 320 cam I'm fitting, so I'm hopeful that I will get the results I'm looking for.