Knackered's Project - Highly Modded Mk1

Post by **knackeredMk1** » 13 Mar 2008, 14:02

Interesting this

As far as I can tell (measuring cylinder head dimensions is not easy), the profile of a Mk1 and AR heads are the same

The AR is much smoother (the one in the picture has been rubbed down with 1500 W&D) but the shape is the same apart from where the spark plug sits, which is much tidier on the AR.

The squish band on the Mk1/AR is much larger than the Mk2 (which has 2 domes in the head). This is much better for torque at low/mid range from what I have been reading. As I'm tuning my engine for torque I will be using the AR head.

Quote from Eric Gorr 'Basic 2 Stroke Tuning' - 'Cylinder heads can be reshaped to change the power band. Generally speaking, a cylinder head with a small diameter and deep combustion chamber, and a wide squish band (60% of the bore area). Combined with a compression ratio of 9 to 1 is ideally suited for low to mid range power. A cylinder head with a wide shallow chamber and a narrow squish band (35-45% of bore area) and a compression ratio of 8 to 1, is ideally suited for high rpm power.'

Squish band on AR/Mk1 = As near as I can tell 54% of bore area. Mk2 = 47%.
Compression Ratio - Mk1 = 6.2, Mk2/3 = 6.4, AR = 6.7.

Mk1, Mk2 & AR -

Post by **knackeredMk1** » 15 Mar 2008, 19:28

The front wheel fits straight on. Mk1 fitting would have required new bearings & spacers as Mk1 has smaller (15mm) axle but I now have a bigger (17mm) CR125 axle so it fits straight on.

XR650 rear has 20mm axle rather than 17mm of all Mks CRM. This needed new bearings to get down to 17mm, one of which is a 'Special'. Also the brake disk was too large and needs smaller one to fit CRM caliper. XR650 disc bolts are M6 but CRM are M8 with an 4mmxM10 recess. Quick and very easily done but needs to be done correctly.

XR650 wheels are cheaper than XR400 and the bearing surfaces are much larger which probably translates to fewer bearing replacements

Post by **knackeredMk1** » 19 Mar 2008, 18:29

Started making some carbon fibre bits over the last few weeks. First part out of the mould today - Generator cover. It's the most complex piece I'm attemping and I'm quite pleased. Got a lot to do - filling air bubbles, T cutting, polishing & last but not least - fitting

.

Cover & Mould below - have polished a little of the surface to see how it could look.

Post by **knackeredMk1** » 19 Mar 2008, 20:52

I took every paintable part except the engine (and the ones I have already done) to the powder coater today. Should be on target to start rebuilding in about two weeks

Colour scheme -
Satin black frame and subframe. (+ shock spring if I can get it off

)
Silver fork legs, yokes, sidestand, swinging arm and suspension linkage
Dark silver (smokey silver) crankcases, barrel & head
Original red & white plastics plus the tank and shroud graphics seen earlier
Black bars

Also replacing all non-suspension bolts with stainless steel.

Post by **knackeredMk1** » 21 Mar 2008, 16:09

Rear Disk Guard

Post by **knackeredMk1** » 22 Mar 2008, 15:34

I've had these for some time but just getting round to sorting. Original swingarm bearings are 12mm wide, unsealed and prone to seizing. Leisure Trail supplied me with these. They are 18mm wide and have a seal on one end - 40% more bearing surface and less crap in 8) .

Post by **knackeredMk1** » 27 Mar 2008, 18:39

These are for a CRF; they fit perfectly. I will use a pressure switch to operate the brake light. Bought new on US eBay.

Post by **knackeredMk1** » 28 Mar 2008, 18:29

Frame and rear suspension back from Redditch Shotblasting

. Just a bit of tidying and then start rebuilding

Post by **knackeredMk1** » 02 Apr 2008, 17:09

Started rebuild. Not really smooth going to now as had to refit both tyres over the weekend due to pinching

and rethread part of steering head.

Post by **knackeredMk1** » 03 Apr 2008, 11:15

Got a rolling chassis

Seems a touch tall, in fact very tall - like my old Husky 125

I hope the engine gives 2 inches of sag to help me climb on.
Now the electrical work begins

Post by **knackeredMk1** » 09 Apr 2008, 19:23

The original kickstart was shot so I bought an AR one. Although this was much lighter and in much better condition, I'm sure it was too long as the new tank comes a lot lower down the engine. I sold this as there seems to be a particular demand for kickstarts at the moment

and have spent a few weeks looking around for alternatives.

I think I have found one - CR250 2003. It's in good condition, the splines fit and I think it's the right shape.

Post by **knackeredMk1** » 09 Apr 2008, 19:35

I knew someone would want a side view

It's pretty well built

Post by **knackeredMk1** » 12 Apr 2008, 20:47

Having a real game with this. Took me 4 goes to get the glass fibre mould right and I've had 3 with carbon fibre

Struggling

One is straight out the mould the others have been heavily worked on but nowhere near acceptable

Post by **knackeredMk1** » 17 Apr 2008, 10:08

Laid out the wiring loom so as to get some reference points before I start chopping.

No carpet jokes please

Post by **knackeredMk1** » 17 Apr 2008, 19:46

I have had a few rants before about the previous owners of this bike and I regret not taking photos before I stripped off the trully horrific stuff. This is the only remnant of the quality of workmanship. Rear light and number plate holder - cut shorter and drilled so it could be mounted on the bent subframe. The plastic burrs are still there but come away easily if you are so inclined. This was attached with a/f bolts (to knacker the threads) and cut with jagged ends (to knacker your hands).

Knackered's Project - Highly Modded Mk1

Cylinder Heads

XR650 Wheels

Carbon Fibre Bits

Colour Scheme

Rear Disk Guard

Swingarm Bearings

Front Brake

Powder Coating

Rebuild 1

Rolling Chassis

Kickstart

Re: New Knackered's Project

Oil Pump Cover

Wiring Loom

Workmanship!