Engine Rebuild - part 2

Last time we left off the crank bearings had been fitted ready for the rebuild. Next job was to fit the crank seals and assemble the casings.

From this point the internals were assembled, this includes fitting the crank to the RHD (clutch side) casing. Again gentle heat with the heat gun allows the bearing to ease onto the crank shaft.

IMPORTANT POINTS: Do not forget to fit the small gear pinion, Ensure the selector forks and rods are fitted correctly.

LHD casing fitted now - But don't forget the 1st gear pinion - (Its not yet fitted in this picture, bonus points if  you can see where it should be???)

Above -selector fitted and crank gears assembled 

NOTE FIT KICK START PINION AND CLUTCH WASHER NOW!!!

Clutch baskets assembled and ready to be bolted using another reaction tool (Home made)

Clutch plates fully fitted, note I use 4 rather than 6 springs. Makes the clutch lighter to operate.

If you do this remove opposite pair to maintain balance

Note the spring retaining collar must be located in its lug, get  it wrong and you'll spend hours trying to figure out why the clutch case does not fit. 

I use a syringe to give initial lube to crank and big end bearings

Piston and head all cleaned up and ready to go....Don't forget the c clip !!!

Soft solder ready to measure the squish band, measure in three or four places to be sure.

Measuring the solder, in this case 1.45mm - I adjusted this by removing a base gasket to get 1.25mm

Notes: - For a 250cc the min squish is 0.9mm heading up to 1.5mm for a softer power response.

The bike was then reunited with the motor, this took longer than I anticipated, but we got there in the end. Once filled with fluids and quick check all bolts were tight it was ready to start. It started maybe 3rd kick and settled to a nice idle on the choke. It sounded a little less "poppy" but until I knocked off the choke it was too early to detect any improvements. Being impatient of course I knocked the choke off quickly and found the motor to be fuelling OK, a very slight hesitation on the throttle but it was of course still cold. As it warmed I was able to dial back the tick over and tweaked the idle mixture screw to 3.75 turns out. This now meant the bike could idle on the verge of stalling, significantly lower idle rpm than before, a blip of the throttle resulted in a positive blat from the exhaust. I had a gentle ride round the garden and the bike showed much better throttle manners. Slow turns could be controlled with throttle and the slow idle running was making this much easier. A flick on the throttle gave instant response and resulted in a lightly lofted front wheel . Overall a huge improvement. I will tweak the carb settings on the next trial but for now I am just looking forward to riding it again.

Hope you found this useful and / or interesting.......

Bally