Faster XBR

[guest1512]

Hi. I took my XBR's engine home for winter. And so this way I made some modification. And the others are in progress.
1. A cylinder and piston from NX650 has been mounted. This way I got more or less  XBR 600. Everything fits without modifications, excepts:
- two round holes for pins between a cylinder and it's head; drilling from 8 to 10 mm in cylinder head was necessary;
- original XBR washers has been used with NX cylinder bolts, so washers' holes might be enlarged from 8 to 9 mm.
2. Original camshaft bearings 6904 Z (with one metal sealing) was replaced with 6904 C3 R (with a gummy one) from one side and naked 6904 C3 from opposite one.
3. I have an idea of more km/h, less RPM by changing primary drive gear.  Furthermore of changing chain sprockets I have found another way. Our XBRs are the only Honda RFVC with 28 teeth primary drive sprocket. The rest have 34 teeth. Ofcourse there are also 2 kinds of clutch outer (different sprocket). But the rest of clutch parts are still the same. So the solution is changing these two pair of parts.
Originaly:
23121-MK4-600 GEAR (29T)
http://www.partzilla.com/parts/detail/honda/HP-23121-MK4-600.html
and
22100-KN8-000 CLUTCH (OUTER)
http://www.partzilla.com/parts/detail/honda/HP-22100-KN8-000.html
After change:
23121-MN9-000 GEAR (34T)
http://www.partzilla.com/parts/detail/honda/HP-23121-MN9-000.html
and
22100-MN9-000 CLUTCH OUTER
http://www.partzilla.com/parts/detail/honda/HP-22100-MN9-000.htmlhttp://www.partzilla.com/parts/detail/honda/HP-22100-MN9-000.html
And your motorcycle no longer sounds like lawn mower, when you want ride faster.
4. In the same move an oil pump gear will be changed (described in another topic):
http://www.thumperclub.com/smf/index.php?topic=4237.msg28315#msg28315

[guest564]

I ran my XBR600 engine with the XL600R primary drive gear and clutch basket, it gave me more options on gearing with a much lighter, faired race bike

[guest1512]

Thanks a lot,  now I know that it will work (with an XL600 primary drive gear). It will be less difference then using primary drive gear from NX. Tell me please, which size of chain sprockets do you use in a final gearing?

[guest564]

I ran a stock size sprocket. My engine would pull around 8K in top on the back straight at Snetterton (faired). Before that I used to run a 34-tooth sprocket but the 36-tooth gave me better clearance between the chain and the aftermarket ally swinging arm. The downside is, if I remember correctly, that the clutch basket is thinner on the XL, it does save a bit of weight though.

[guest1512]

Did you made any modifications in your oil hoses? I read a lot about insufficient oil supply at the top of engine, occurring over 3500 RPM. If you can ride constantly with high RPM you probably solved this problem.

[guest564]

I ran the stock hoses and tank, I didn't see any significant wear. I changed the oil (Silkolene Pro4) and put in a new filter after every race meeting.

[guest1512]

XL600R clutch is in delivery and cooperating sprocket too, however from a different source. And it's seller said that this sprocket had 33 teeth. In documentation I can see only 32. Do you remember how many teeth has your primary drive sprocket?

[guest564]

I don't recall how many teeth it had and my XBR stuff is stored a long way from here so, unfortunately, I can't check.