ON OUR BENCH

1977 Kawasaki KH/H1F Hy­brid

Practical Sportsbikes (UK) - - Contents -

MG’S KH/H1F, Jim’s new YZF750 and Tyler’s YPVS

In­va­sive surgery re­quired to re­move old 250/400 mounts and line-up the 500 en­gine

The time has come to be­gin the real work and go be­yond the point of no re­turn: grind­ing off the KH en­gine mounts to fit the new H1 mounts. A lot of metal has to be ground away. The H1 plant is a tight fit. Af­ter a bout of “Are you ab­so­lutely sure?” “Yes.” “Re­ally?” we set to with the an­gle grinder.

It’s vi­tal not to ac­ci­den­tally gouge parts of the frame tub­ing with grind­ing wheel, which we al­most avoided dur­ing the process of re­mov­ing enough metal to get the en­gine sit­ting in the right spot (the fine fin­ish­ing will be done with the frame shorn of front and back ends). For now it’s a case of rough re­moval of the front lower mounts and swingarm gus­sets so the en­gine can be of­fered up with the trans­mis­sion out­put shaft and gear­box sprocket to de­ter­mine chain line and bar­rel and cylin­der head to frame clear­ance. We also had to grid away the top por­tions of the up­per front gus­sets to clear the front ex­trem­ity of the crankcases.

In goes the en­gine with the front mounts in po­si­tion. The chain line is per­fect, but the en­gine seems to be sit­ting 5mm to the right and the rear mounts do not line up. Odd. We won­der if there’s

sup­posed to be a lit­tle amount of off­set. No. The cen­tre cylin­der should sit dead cen­tre in the frame.

We knock out the rub­ber mounts and in­spect them. The fronts are dif­fer­ent: one has a spigot, one doesn’t. Nei­ther should have spig­ots. The rub­bers are moulded el­lip­ti­cally on the fronts too. All the oth­ers are con­cen­tric. It seems a pre­vi­ous owner has bodged a lower mount into be­com­ing a front mount and the 5mm of spigot is push­ing the en­gine 5mm to the right so the rear mounts don’t line up.

Tem­po­rar­ily fit­ting two non-spig­oted front mounts re­veals the en­gine will line up and the gear­box sprocket will need to be off­set 5mm to the right. Not a prob­lem. The prob­lem, or rather the op­por­tu­nity pre­sent­ing it­self, is now we need to make new en­gine rub­bers.

The mis­placed op­ti­mism of last month has

THE PROB­LEM, OR RATHER THE OP­POR­TU­NITY PRE­SENT­ING IT­SELF, IS NOW WE NEED TO MAKE NEW EN­GINE RUB­BERS

now been re­placed by the cold re­al­ity of just how knack­ered the H1’s rub­ber en­gine mounts are. They’re crit­i­cal to get­ting the en­gine mounted and lined-up in the KH frame – and they’re not only be­yond hope, but mis­matched too – that’s what you get with un­known quan­tity en­gines.

The en­gine is oth­er­wise in good shape so one curve­ball is not the end of the world. The trou­ble is the mounts (in de­cent nick, or new) are very hard to find. There’s a man in Ger­many (Volker Shulz) who makes batches of new ones – but typ­i­cally he’s just sold out the lat­est lot and won’t be mak­ing any oth­ers un­til next year. The plan now is for us to make our own.

We have op­tions: (1) hard mount the en­gine with ally plugs, (2) buy some 1-inch nitrile rub­ber and drill to fit the steel in­serts, or (3) mould some polyurethane bushes around the in­serts. The hard mount­ing op­tion would give the best tor­sional stiff­ness but the nig­gly sec­ondary vi­bra­tions from the triple might prove to be hor­rific to live with (al­though the orig­i­nal 1969 H1, not this 1975 H1F, had a hard-mounted en­gine).

Op­tions two and three would both work, with two be­ing per­haps the eas­ier of them. We’re cer­tainly not wait­ing un­til next year and the new batch of Volker’s items – good though they’re re­ported to be. We’ll also have to re­pur­pose the in­cor­rect front mount to its re­quired spec (with­out spigot), which is easy enough. Then it’s a case of grind­ing off the old de­cayed rub­ber and fit­ting the new harder stuff, mak­ing sure the front mounts have the cor­rect amount of off-cen­tre.

We can only as­sume the front mounts are ec­cen­tric to po­si­tion the most part of the rub­ber on the bot­tom to damp torque re­ac­tion that forces the front of the en­gine down un­der ac­cel­er­a­tion.

As ever, what looked like a straight­for­ward fit­ting job turned out to be so much more. We stood around scratch­ing heads and drink­ing tea quite a bit. What’s cer­tain from this lit­tle episode is that the en­gine fit is crit­i­cal to keep­ing the heads and bar­rels away from the front down tubes. The in­stal­la­tion is cosy to say the very least. It’s also en­tirely worth­while, and al­ready the lit­tle KH looks ex­cit­ingly dwarfed by the sub­stan­tial H1 en­gine. And thanks to An­drew Walm­s­ley of 3cyl.com for the ex­cel­lent en­gine mount draw­ings which have proved to be ab­so­lutely spot-on.

Next month we will bring you all the fun and games of pour­ing polyurethane into moulds and mess­ing about with more grind­ing and fin­ish­ing. When the mounts are done, the cy­cle parts await. The prospect of an early sum­mer fin­ish though is look­ing more and more re­mote.

Out­put shaft in­stalled with drive sprocket to de­ter­mine chain­line

This is the sort of un­us­able con­di­tion the rub­bers were in

Rear gus­sets chopped back, will be re­placed any­way

New front up­per mounts all good, rub­bers less so

Front lower mounts have to go – and they went

There’s no go­ing back once the cut­ting disc is spin­ning

Orig­i­nal metal won’t give up eas­ily. Not in its na­ture

It’s a tight squeeze, but it works

It’s wide in the frame too

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.