marks pk50 engine .

[henri]

got a engine on the bench to be upgraded for mark ,a member on here .BILD2441 by henri briggs, on Flickr   .
damm filthy beast ,but came apart ok , an a hour or so sees the clutch side almost clean .BILD2443 by henri briggs, on Flickr    .
plan is to upgrade to 4 speed gearbox ,decent crank ,an a 130 kit an 19mm carb ,so i have a shopping list .
i wonder if any bodys got stuff lurking in there shed . i need a 19mm 3 stud pk manifold ,4 loose gears ,19mm carb , iron barrel 130 kit ,an a pk polini exhaust would be nice but failing that a 125cc sito+ maybe ,H.

[henri]

BILD2464 by henri briggs, on Flickr .
that took some doing ,but finally in a state were there not a embarrassment to have on the bench an can be worked on .
nxt step ,dry build with crank in dummy bearings an work out inlet times an adjustments ,then add the barrel an see whats what .H

[mark]

PH -Pre Henri

[henri]

BILD2465 by henri briggs, on Flickr .
time for some dummy bearings an a measure up now .H

[henri]

a chilly early morning session in the shed an this is what ive got.
exhaust opens at 92atdc = 176 duration
transfers open 116atdc = 128 duration an 24 degree blowdown .
inlet opens 130 btdc an closes 43atdc = 173 duration .
so not too bad a base to start with ,plan is raise exhaust roof to 87.5atdc to give a 185 duration an open/straighten the exhaust tract . leave transfers timings alone an have a 28.5 blowdown to help it rev higher .an extend inlet to give a closing at 50atdc to extend duration to 180 ,would like to have it open a bit earlier but theres no meat on the bone to carve there .
an the usual match transfers to case ,match inlet to cases ,etc .H

[spot66]

I hope Mark has invested in brown trousers.....

[henri]

Nov 23, 2021 11:46:21 GMT spot66 said:

I hope Mark has invested in brown trousers.....

but spot "brown is never worn in town" they say .

BILD2466 by henri briggs, on Flickr  .
made a start on the dremmel work ,inlet 1st .BILD2468 by henri briggs, on Flickr  .
needs some more opening an smoothing but its roughly there an matched to cases .funnily some person on another place had a idea ,rather than open manifold ,i should close up the case inlet to match with epoxy resin .i asked him to show his "working outs" but he's not got back to me yet ,so think i'll ignore for now .BILD2469 by henri briggs, on Flickr   .
on too cases ,an match transfers ,an lengthen inlet 10 degrees to close later .BILD2470 by henri briggs, on Flickr   .
a quick whizzer of exhaust port roof to raise the timing ,an thats the dremmel work done .polish some marks on piston out from a near seize ,hone the barrel an chamfer ports nxt .H

[henri]

then its on with the engine build .BILD2474 by henri briggs, on Flickr .
internals in ,new bearings and seals fitted ,an gears in to check the shimming .BILD2475 by henri briggs, on Flickr .
shimming checked ,gears back out for a final clean up ,then back in an cases together .BILD2478 by henri briggs, on Flickr .
had a pre-soaked clutch ,so cracked on with fitting it ,with the new polini "wave" spring .the old polini coil spring has been my go-too spring for a few years ,with decent plates they can hold upto 14-15bhp easily an not too heavy on the hand for me .not used a "wave" before ,so this is a trial .on with the inlet an left there for the day ,just top end and ignition to fit nxt .H

[henri]

another cold day with outside play cancelled ,raging lumbago/sciatica so only seated work on the cards ,so on with this one in the shed .top end fitted an ignition on an checked .a nice healthy spark ,an also a chance to check a flywheel i was given ,a dual key lightened one .unfortunately guy had attempted powder coating on it with a diy coating kit .magnets dont like heat ,so 20mins at 180 degrees an its as dead as a dodo ,doorstop anybody .BILD2481 by henri briggs, on Flickr .
not a problem ,plan always was too remove starter ring an use the electric start fly anyway .nxt run carb through carb cleaner ,adjust jetting an wait on exhaust/carb clamp/inlet sleeve to arrive from VE uk .hopefully today or tomorrow ,then its in the stand for a test run .H

[mark]

Hi H
Body work pretty good just tatty !

[henri]

the carb i got was a primmy one ,with the restrictive metal filter box ,these can cause space issues in pk frames .an ive found in past if a conversion rings made an fitted the pk clamp on filter sits forward an rubs on centre seam .so out with the tin snips an drill an alter the primmy filter .BILD2485 by henri briggs, on Flickr .
remove the boxy square inlet part ,keeping the 2 mesh inner walls that hold the old metal wire wool/mesh filter .fold them round in a circle an drill loads of holes in the lid/top cover .then rob the foam from a cheap pit-bike filter ,cut an shape ,an out with the 80's fave evo-stik .BILD2484 by henri briggs, on Flickr .
needs a tidy up an proper securing with a cable tie at carb end to be safe ,but viola a diy free-flow pod filter for a 19mm shb .new needle valve an main jets here ,an sleeve an clamp arrived 7-30 last night .so hopefully today its finished an ready to run in the stand .H

[henri]

an typically , all done ,rough timed n ready to rock , an weather goes rotten/wet ,so still sat on my bench ready to rock n roll .might break my rules today, sunday, an if it stays dry run it up in the stand .H57EBC895-EB72-4AA3-8860-EEF3ECEFF6D8 by henri briggs, on Flickr

[henri]

finally the weather dried up enough to get engine in the stand .97E2C606-17EA-44BE-B6DC-A773BA425032 by henri briggs, on Flickr .
click on picture to play vid .H