Q Should I pol­ish out marks on my Blade’s bores?

Motorcycle News (UK) - - Garage -

My 954 Fire­blade has worn and scuffed bores at the bot­tom, plus sim­i­lar lines on the pis­tons’ skirt thrust faces. It’s a shame as the en­gine was al­ways ser­viced, but I hear it’s a com­mon prob­lem with 954s. I picked up a low-mileage set of pis­tons and crankcases with bet­ter bores, but still have very slight run­ning marks on the bot­tom of the bores that can just be felt with a finger nail, sim­i­lar slight marks on the pis­ton skirts too. Pre strip down it was run­ning fine, so should I at­tempt to hone or pol­ish th­ese marks out or leave well alone? Fred Skin­ner, email

A

An­swered by Steve Ham­mond, Mo­trac Race En­gi­neer­ing Ltd The CBR954 had an in­te­gral cylin­der block (i.e. it forms part of the top crank case) and this makes them more chal­leng­ing to re-plate. Scuffs and scor­ing was com­mon in Honda blocks at this time. Honda went through a phase of us­ing Alusil-type bores which used alu­minium with a con­cen­tra­tion of sil­i­con car­bide in the sur­face. Ef­fec­tively this ran alu­minium against alu­minium and the hard par­ti­cles pro­vided re­sis­tance to wear. This of­ten led to bore scuff­ing in the con­tact area of the pis­ton. The good news is that they can be im­proved by hav­ing a nickel ma­trix coat­ing ap­plied plus Honda used to of­fer a 0.25mm over­size pis­ton for some of the Alusil models. This gives the op­tion of pre­ci­sion-hon­ing the bores.

Your scored bores can be sorted with a nickel coat­ing

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