Deep in­side my Martin­syde

With ma­jor progress on this ec­cen­tric mo­tor­cy­cle’s engine im­mi­nent, Rick re­flects on its in­nards

Classic Bike (UK) - - Classic Workshop - IL­LUS­TRA­TION: IAIN@1000WORDS.FI

My last men­tion of the Martin­syde was to own up to fail­ing mis­er­ably in my at­tempts to weld the cracked crank­case. Well, just be­fore Christ­mas word reached me that the new and im­proved cast­ing is ready for col­lec­tion at the foundry. Of course, that’s only the be­gin­ning of the story, the next step is ma­chin­ing it to fit and I hope to cover what goes into that in the near fu­ture but in the mean­time, I have been marvelling at the work in­side that gave a dear old vin­tage side­car twin the power to de­stroy it­self.

Orig­i­nally my bike had been a ‘Quick Six’, the 736cc big brother to the stan­dard 680 twin, the ex­tra ca­pac­ity com­ing from a longer stroke (96mm) crank. Since only one of th­ese cranks sur­vives, when spe­cial­ist Chris Tait built my engine he had to find an al­ter­na­tive. By get­ting Al­pha Bear­ings to make cus­tom main­shafts to suit the Martin­syde crank­case, he was able to adapt a (97mm stroke) Har­leydavid­son 45 crank to fit, co­in­ci­den­tally side-step­ping an­other Martin­syde is­sue – the high and tiny di­am­e­ter gud­geon pin that hin­dered fit­ting al­ter­na­tive pis­tons. The Har­ley crank has a stronger big end and shorter rods with larger small ends that ac­com­mo­date var­i­ous pis­tons – mine are from a 250cc Tri­umph, giv­ing 767cc.

To me, half the ap­peal of the Martin­syde is Chris Tait’s 70 years of ded­i­ca­tion to pro­mot­ing and im­prov­ing this ob­scure and ec­cen­tric mo­tor­cy­cle and it’s a great hon­our to take up the chal­lenge in his ab­sence. Yes, I screwed up try­ing to re­pair that crank­case, but Chris did things he re­gret­ted – like chop­ping up the last sur­viv­ing Quick Six to make a sprinter. I just wish he were alive to see us cast­ing stronger crankcases, I don’t think he’d have dreamed this day would ever come.


Rick’s Martin­syde engine has had a crank­shaft swap which al­lows al­ter­na­tive pis­tons to be fit­ted

WHO IS RICK? Rick Park­ing­ton has been rid­ing and fix­ing clas­sic bikes for decades. He lives and fet­tles in a fully tooled up shed in his back gar­den.

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