Honing motor cycle small ends

[Tim StevensParticipant @timstevens64731]

Bending the rod to get it as near as possible was standard practice when I was in the business. Almost my last job at BSA was aligning the little-end on one of the first B50s – then I finished the assembly and put it on the brake.

And if you know anyone who could use a complete Hennan and Froude brake, do let me know. I know of one in the UK which needs a new home for not too much dosh.

Cheers, Tim

[Oily RagParticipant @oilyrag]

Hi Tim,

You may recognise the bike in my avatar photo then?!

Edited By Oily Rag on 11/05/2019 15:44:18

Edited By Oily Rag on 11/05/2019 15:46:07

[Tim StevensParticipant @timstevens64731]

Goodness, it was 50 years ago, and I can't see through the fairing …

But if the bike was used in the TT between 1974 and 1980 I expect I scrutineered it at least once.

Cheers, Tim

[I.M. OUTAHEREParticipant @i-m-outahere]

Posted by Hopper on 11/05/2019 08:38:13:

Posted by John MC on 11/05/2019 08:18:24:

Posted by sparky mike on 10/05/2019 08:36:20:

The reamer will not produce a good enough finish and chance of getting it off square to the cylinder barrel.

Mike.

Totally agree. The small ends really need to be bored parallel to the big ends. While a good (sharp) reamer will produce a size/plus hole with good repeatability it may not be the right size for the pin or a good enough finish. My preferred method is to bore a small end bush to within a couple of thou and then on to the (Delapena) hone to finish.

Velocette made some of their small ends neither metric or imperial in diameter to discourage the use of a reamer to finish the bore of the bush. Problem was that it was easy enough to get a reamer ground to the size required……

I good attempt to encourage getting the job done properly.

John

Dunno about that. A lot of Harley small end bushes are an odd ID, something like .792". But the factory workshop manual specifies to use the factory service tool – a reamer, which was avialable only from them!

Then the factory manual recommends checking the wrist pin for square with the crankcase mouth and if it isnt, to use a big long lever special tool to BEND THE CON ROD to bring the pin back to square.

Go figure.

I have never had to go the last step. With careful reaming of a bushing not too far undersize to start with they always seem to come out square when checked. Of course with engine disassembled it's best to do it in a drill press or mill to ensure squareness. Thing is, I found the drill press my old man used for rebuilding Harley rod sets for years had 20 thou droop on the table front to rear. Yet those rods and small end bushes worked just fine and are still running today. Must have by luck (or maybe he knew?) had the rods oriented the right way so the error was radial and not axial when reamed.

I used to fit and ream the pin bushes on victa engines and used an old piston as a guide for the reamer to help keep it square , i used to have a piece of plate that fitted over the cylinder mounting studs and it had a slot cut for the conrod so i could sit the piston skirt on it and and line the whole lot up and slide the expanding reamer in .

[HopperParticipant @hopper]

There is, apparently, a bit of an art to bending con rods. S&S, suppliers of high performance Harley parts (yes there is such a thing!) sell a special F -shaped tool with long handle that is put on the rod slightly below the small end and used to bend the main beam of the rod, not the point where rod joins the small end boss. This, apparently, puts less stress on the rod than just putting a long bar through the small end bushing and bending away.

Tim – running B50s on the dyno all day and they paid you for it! Tops.

XD 351 – Now that's using your loaf.I'll have to store that one away for next time I do a rod bushing.

[Michael HornerParticipant @michaelhorner54327]

"I used to fit and ream the pin bushes on victa engines and used an old piston as a guide for the reamer to help keep it square , i used to have a piece of plate that fitted over the cylinder mounting studs and it had a slot cut for the conrod so i could sit the piston skirt on it and line the whole lot up and slide the expanding reamer in".

XD 351

You should win the John Stevenson Bodger award with that one.

Impressed!

Cheers Michael.

[I.M. OUTAHEREParticipant @i-m-outahere]

You don’t want to know how i sorted a bent rod !

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