Dirt Talk

Classic Dirtbike - - Contents - Tony Proc­tor Email

What’re you talk­ing about in the CDB world? We’ve a packed let­ters page this time.

I thor­oughly en­joyed is­sue 48 and your piece on the 3TA engine/bike project. I’ve spent most of my work­ing life in the auto and mo­tor­cy­cle busi­ness, so have amassed a rea­son­able amount of skills, tricks of the trade and spent time show­ing other ap­pren­tices how to do it.

Please don’t re­use those valve springs, they may look al­right and clean up lovely with your clean­ing tech­niques but they are old and most prob­a­bly get­ting to the brit­tle stage; the cost of new items and the peace of mind that you won’t drop a valve on your first fist­ful of revs will far out­weigh the un­cer­tainty.

Your valve com­pres­sor: neat as it is, is a real tid­dler com­pared to the chunky equip­ment used in the trade. Maybe a piece of steel bar welded or sif bronze welded to the out­side long edge? This should pre­vent bend­ing in fu­ture. When the spring com­pres­sor is in ten­sion a sharp tap with a small ball peen ham­mer on the tool at the top of the frame should see the col­let let go. Do you need a 3TA or any Tri­umph head for bits of fin? There might be suit­able finning to be had from many a scrap cylin­der head, most fins usu­ally be­ing very close in thick­ness. If it’s thicker then a dress­ing down with a suit­able abra­sive wheel is needed be­fore your ma­gi­cian ally welder gets work­ing.

You may have a spare Bul­taco head that could be the donor. Oth­er­wise a piece of alu­minium plate from a metal sup­pli­ers could be the an­swer, com­pat­i­bil­ity with the al­loy of the cylin­der head and alu­minium plate might be a stick­ing point but it’s worth a try. The metal sup­plier may be able to of­fer you ad­vice on this.

There will be some that say your orig­i­nal valve springs will be per­fectly al­right, but as so much of your engine is un­known and the thought of a valve hit­ting pis­ton and the po­ten­tial de­struc­tion, I’d go with other col­lets due to the rust.

Tony, a thought oc­curs as I read through your let­ter, surely some­one out there will know what spec alu­minium Tri­umph used for cast­ing cylin­der heads? Oh, thanks for the tip on the valve springs, I’ve or­dered new ones. Since the fea­ture was writ­ten I re­mem­bered where I got the spring com­pres­sor, it came from Nor­ton Com­mando spares spe­cial­ist RGM when they were in Gateshead. Tim

The sender of our Star Let­ter will re­ceive a prize from the Bel Ray cat­a­logue

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