How easy is it to fit a new small end bush?

[shabashow]

Hi,
I'm fitting new pistons to my 52 A10 plunger and when I try the fit the gudeon pin in the small end on the right con rod, there is a bit of play, and I can rock the pin quite noticably.
Looks like I need a new bush, but would like to do it without tearing the bottom end apart to get the rod to a shop. How easy is it to do in situ? Getting the bush in looks straight forward, but then it comes to the reaming. Can it be done while the rod is still on the crank and in the case? If so, what precautions and advice would you advise? My biggest concern would be how to make sure the reamer is perfectly aligned so the piston sits square in the bore.
Has anyone tried it with success?
John

[muskrat]

G'day John.
Yep done it a few times. The old one gets pushed out with the new one. I then use a guide from the other L/end to get it all square.
Cheers

[shabashow]

Thanks Muskrat,

It's the squareness that I need to gen up about. How do you use the other bush as a guide? Can the tools and jigs required be sourced easily, or does it need specialist equipment?

John

[rocker21]

very simple if you have the right type of reamer with a long end to it and that fits into a machined tapered bush that locates into the other bush which keeps everything square, done it a few times with out problems over many years, you then need to put something into the crankcase so no swarf  can get in when you ream the bush.

[shabashow]

What kind of reamer would you recommend, and where would I get a machined tapered bush? Is that something I can buy along with a reamer, or does it need to made up to suit the other bush?

[rocker21]

i bought mine from a local tool shop some years ago, it is an expanding reamer and has a long spindle before the reamer part and that fits into a tapered bush in which the long spindle locates and keeps everything square, also used for doing camshaft bushes, but not the blind one, that has to be done by other means, but once that is done that can be used to locate this reamer and do the other 2.

[Dean]

I had an oversize small end bush turned up due to the previous one nipping up on the gudgeon pin and spinning in the small end. I did the job with the engine in the bike and hired an adjustable reamer to finish the bush bore. I had not joy at all, with the reamer either not cutting or jamming. I persevered and got the pin in and bike back together with a three-penny bit shaped bore to the bush. Its getting a bit tippy tappy now so, having suffered the joys of small end giving up under load I think I'll have to bite the bullet and strip it right down and get new rods and bushes set up professionally. Short cuts often aren't

[shabashow]

After all your useful advice, I've decided to stick the bike, minus barrels and petrol tank, on a trailer and take it to my local engineer to let him have a more professional try than I ever could. I'll update you when the job's done.

[rowan.bradley]

I then use a guide from the other L/end to get it all square.

If I've understood this correctly, it will ensure that the reaming is in line in one direction, but not the other surely, because the con rods may not be aligned exactly, but can rock backwards and forwards? Or do you have a way of clamping the con rods together so that they are in line? I guess I can imagine a way with a couple of bits of wood and a couple of nuts and bolts to hold them in line...

Thanks - Rowan

[shabashow]

Update on the small end (a year later!)
Got the bike, minus the head to the engineer. He lifted it onto his bench with a crane and did the bus in situ, ensuring all was square. I had sealed off the crank case with rags and gaffer tape so no swarf would get in. That was about 4000 miles ago. Running fine with no issues.

[a10 gf]

^^^ engine still on the bike! excellent job