Scoop with the lat­est on his KH250/500 project!

Classic Motorcycle Mechanics - - CONTENTS -

Wweld­ing’s cer­tainly com­ing on.” Nice to know my project’s im­prov­ing some­one else’s prac­ti­cal skills then. As might be hoped the chain line is bang on and dou­ble checked us­ing a rather rare and now ex­pen­sive ARE al­loy wheel with an old sprocket. In the­ory that should be the hard­est part done but as this is a gen­uine spe­cial and I’m be­ing a bit of diva here I want the bike to look sub­tly dif­fer­ent. The KH250 tail piece is ob­vi­ously the cor­rect one but I re­ally want the ear­li­est squarer and wider unit as used on the 72/73 bikes. A brief mug-up clearly demon­strates it’s not go­ing to be an easy job but when you set your heart on some­thing etc. As I’m ob­vi­ously now dig­ging my­self a fair sized hole here Ian cyn­i­cally goes on to sug­gest I run an early style three-sided rear light as well. Ap­par­ently I might as well solve two prob­lems rather than just the one! For­tu­nately I know of a man who should ell progress is be­ing made and if it’s not nec­es­sar­ily by me then it’s by my mate Ian Bird, who has been crack­ing on at a right old pace. The 500cc H1 en­gine is now housed within the con­fines of the 250cc KH250 chas­sis and if you didn’t know bet­ter you’d have to say it ac­tu­ally looks right. And when Ian then dropped in the H1’s air-box and car­bu­ret­tor rub­bers, two things were re­ally ob­vi­ous. Firstly, there’s re­ally not that much dif­fer­ence in terms of inches or cen­time­tres be­tween the 250 and 500 mo­tors and se­condly, the KH’S frame has more than enough space to house ev­ery­thing the 500 needs to make run hap­pily. Ian had fab­ri­cated then tack welded the new en­gine plates in place prior to pass­ing the frame onto a top notch welder who sub­se­quently com­mented: “Well that’s a re­ally neat job Ian, your

be able to ex­tri­cate me from this ever grow­ing abyss of in­san­ity. We need some de­cent brakes on this po­ten­tially ra­bid lit­tle mis­sile but the ques­tion is what to use? Ian’s own hy­brid uses a twin pis­ton slid­ing caliper that came off a Kawasaki GPX750R. Think­ing ahead for once I’d un­earthed some four pis­ton job­bies from my Yamaha FZR250 days, think­ing they’d be su­per ef­fi­ca­cious, but no. As Ian rather ably demon­strates, it’s sim­ply not pos­si­ble to use four pis­ton calipers on a wire spoked wheel be­cause the hous­ing for the in­ner pair of pis­tons touches the spokes. He also gives me a look straight from Dad’s Army that says ‘you stupid boy!’ The front forks are now stripped and the in­ners dropped off at A M Philpot of Lu­ton. They’ll give them a se­ri­ous talk­ing to, check they’re straight and ap­ply sub­stan­tially more hard chrome than Kawasaki ever did. Which just leaves the rear sus­pen­sion and here it’s go­ing to be hard to fol­low Ian’s ex­am­ple as his hy­brid runs Koni shocks from way back when. There’s also a clear­ance is­sue with the chain guard so for the in­terim the bike will get built up with what­ever comes to hand then we’ll take some care­ful mea­sure­ments. There had been a sketchy idea to also run an ear­lier style tank which has a sig­nif­i­cantly more box-like pro­file but, for this facet of the build at least, com­mon sense has pre­vailed. Look­ing at an early tank along­side the one ac­tu­ally in­tended for the KH’S frame it’s ob­vi­ous there’s a lot of dif­fer­ences and it wouldn’t be a sim­ple case of cut-and-shut. The ear­lier tank is sig­nif­i­cantly shorter than those used on ei­ther the S3s or the KH250/400 so

it’d have to be ex­tended but then its rear-end wouldn’t match up with the KH’S seat nose. Know­ing when I’m beaten I walk away from that par­tic­u­lar day­dream. At this juncture the newly welded chas­sis along with all of its pe­riph­eral com­po­nents, the gen­tly moul­der­ing wheels, a col­lect­ing of tail pieces and all of the alu­minium en­gine parts are gen­tly poured into the back of my car. Ian waves a fond farewell to a raft of parts that have been clut­ter­ing up his work­shop for weeks and I do a fair im­pres­sion of the lo­cal scrap man fer­ry­ing the lot back to my work­shop. The next few weeks see me mulling over what fin­ish to use on the cy­cle parts and how best to sort out the wheels. One hun­dred point per­fect orig­i­nal­ity is not what I’m af­ter so I can’t see the point in get­ting the old rims re-plated. It’s not a cheap op­tion any­way and if the bike is be­ing built as a spe­cial why not treat it as such? A joy­ful Satur­day morn­ing sees me out with the bolt cut­ters lib­er­at­ing the hubs from the spokes and some­time later but the same week­end the old rusty bear­ings are fi­nally evicted. With the al­loy be­ing so badly cor­roded the hubs are dropped off at T&L En­gi­neer­ing to be blasted (nuked?) clean so I can then fit new bear­ings. Af­ter some ju­di­cious pon­der­ing I’ve opted for stain­less spokes and al­loy rims but I’m avoid­ing the flanged type sim­ply be­cause they al­ways hold crud and are harder to clean. To be hon­est I could build the wheels my­self but with so much else go­ing on in my work­shop I’ve de­cided to flash the cash and ask Cen­tral Wheel Com­po­nents to do the job. They come with a fine rep­u­ta­tion and hold the al­loy Mo­rad rims I want in stock. I’ve fi­nally de­cided to have the cy­cle parts ce­ramic coated which should give both a de­cent fin­ish and also be harder wear­ing than ei­ther two pack or pow­der-coat. Al­loy rims, stain­less spokes, ce­ramic coat­ings? I told you I was hav­ing a diva mo­ment!

Koni in the rear.

Here be the calipers. Early rear light: thoughts? Here’s the hub of the is­sue! H2 tail piece looks cool. Or maybe the KH rear?

Com­par­i­son of the two tanks.

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