1972 Yamaha YR5

Practical Sportsbikes (UK) - - Ps World -

I’ve owned this YR5 since 2005 and had it on the road since 2007. It was al­ways des­tined to be a bit non-stan­dard as I had to cut the orig­i­nal cylin­ders off with a grinder and use RD ones. I ran it in mildly mod­i­fied trim (jet­ting/all­speeds) un­til the end of 2016 when I de­cided to re­verse the gen­tle cos­metic de­te­ri­o­ra­tion of the years and also make it into some­thing more suit­able for track­days.

Main mods are tuned cylin­ders, RD250B cases and gear­box, Vito crank­shaft, 28mm Mikuni rac­ing carbs, Pow­er­dy­namo gen­er­a­tor with Zeel­tronic pro­gram­mable DC ig­ni­tion, JL pipes and HVC rearsets.

I fin­ished the main build in sum­mer 2017 and man­aged to run it in, get it dyno tested (a very rea­son­able 51bhp at the wheel) and get out for a track­day at Cad­well which proved the con­cept.

How­ever, it also showed some flaws so I’ve been sort­ing these over win­ter. I used RD cases to solve the is­sue of crank seals blow­ing out and al­low the use of a closer­a­tio six-speed gear­box and did a few other mi­nor bits like fit­ting a bet­ter clock set-up. She’s back to­gether and just needs gear­ing to suit the new gear­box. Fin­gers crossed she’ll be spot on now.

“IT WAS AL­WAYS DES­TINED TO BE NON-STAN­DARD – I HAD TO CUT OFF THE ORIG­I­NAL CYLIN­DERS “

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