Thumbs up for the Boyesen Rad Valve. Seems to have smoothed up power delivery and maybe a little more power . Can open the throttle wide at 3000rpm and the bike will accelerate smoothly all the way through to 9,600rpm. No hiccups or misses .

Doesn't seem to need leaner jetting as is suggested in the leaflet - virtually no smoke once warmed up.

Also found the answer to why it was hard to start after it had been standing for a few weeks and was very smokey on startup. - I changed oil pump to a newer version (Mk3). I think the old pump was allowing oil to seep into the intake over a period of time due to gravity. I think Skidmark first suggested this elsewhere .

Fitted PowerNow Plus - Other side of carb from PowerNow. I know its a bit of a gadget but I think it does work (but not for THE ULTIMATE POWER GAIN ) and the theory is sound. Definitely improved throttle response and maybe a little more torque at low/mid throttle openings. Boyesen make something very similar but not for this carb.



PowerNow + PowerNow Plus

I've always been a bit dissatisfied with my clutch especially since completing the Mk3 project. It has always been stiff despite the new parts and I was thinking about getting an hydraulic clutch. So I checked into what variance there is between different models amongst the parts I've got lying around.

Starting with the lever and perch. My perch and lever are the ones used on the Mk3/AR and they are the only parts that I can find that go under a CRM product code that were fitted to the CR range - so they must be pretty good.

I then found that the push rods for the Mk1 & 2 are the same (with different part codes ) but the Mk3 rod is ~ 0.8mm longer. This gives the actuating arm (the one where the cable attaches to) a more efficient position to pull. In addition the Mk1/2 actuation arm is longer than the Mk3 so requires less pull to move. I also noticed that the angle ground into the actuation arm where it contacts the push rod is slightly different Mk1/2 v Mk3. So I reground my Mk1 arm to approximately the Mk3 angle. Finally the Mk2 springs are thinner than the Mk1 springs and so less effort required to the pull lever.

What I've ended up with is a Mk1 actuating arm, ground to roughly the same angle as a Mk3. With a Mk3 push rod and Mk2 springs. Boy does it make a difference .

Keep getting questions about this -

For the record this bike is significantly more powerful across the range than a standard Mk1 and also a standard Mk3. Both of which it has been tried against. Other than that I can't tell you.

Passed MOT yesterday but had blown a bulb. Headlight has two standard H3 halogen 35w bulbs.

Replaced with PIAA H3 35w D96 bulbs. Vibration resistant and apparently give the light of a 55w without the heat. They are significantly brighter - getting more like an HID setup .

Current setup -

New smaller stainless steel ignition key and barrel to fit on new speedo bracket as have fitted XR400 yokes with the forks. I had to install the old Mk1 steering post on the new yokes as the XR post is slightly longer and doesn't fit. Much better length, sprung and damped than the CR forks.

Decided to revisit a Mugen head for my Mk1. So I have got the head modified to take the larger piston diameter and worked the head gasket so as not to get any 'hot spots' using the higher compression ratio. You can see the enlarged head capacity matching the head profile as a ring around the edge.



Works fine after changing the thermostat (which was no longer working ). Can't say there is any noticable gain in power but there should be a little at the bottom end at least.

Made a carbon fibre clutch cover -

I've changed the gearing by swapping some gears and the final drive shaft from a Mk3. Original Mk1 gearbox on the road with 17 inch wheels, 15 tooth front and 42 rear, 65 mph is ~6,5000 rpm (peak torque) and just a whiff of throttle. Not comfortable cruising or good for engine oil supply. Changing the top two gears to those from a Mk3 gives ~74mph at 6,500rpm.

I've actually swapped 3rd, 4th, 5th and 6th cogs together with the selector forks and final drive shaft but kept the 1st and 2nd from the Mk1 with the clutch shaft. I had to take 1.0mm thickness off the 6th gear cog on the clutch shaft and 0.5mm off one of the diameters on the final drive shaft to be able to fit the gears.

Wiseco TRX clutch basket fitted (work done by S. E. P. Kegworth) and 68.25mm rebore (264cc - 7.3% increased capacity from original) and Wiseco TRX 'Racer's' piston fitted.

Thanks, that was a good read.

Its a shame the photos don't work anymore, but I assume you still have them stored somewhere.

I think I'll start a rebuild thread for my mk3 soon, not a lot of action on here recently.