Hi there
Is it possibe to replace a small end bush without splitting the crankcase and remove the conrod?

My piston melted due to the magneto coming apart and the timing shifted after riding through france bla bla (mag was not done by me)

I inspected the damage, I noticed the small end looks like it petrudes a fraction of a mm on one side, I'm wondering weather it shifted whilst being super hot or something or weather it was always like that (can't remember noticing it before)

anyway I'm wondering weather to replace it, and also can it be replaced without removing the conrod?

Hi Maxwell...Check the size of the gudgeon pin as well where it runs in the bush..it is not unusual for them to be undersize there when the engine has been 'cooked'. If you have doubts about the small end bush I would replace it. It can be extracted and a new one fitted without removing the engine from the frame by making up a simple tool. After the new bush is fitted you will need to ream it to finished size for the pin...for that you will need an adjustable hand reamer with 3/4" as its 'mid point' size....Ian

email (option): ian@wright52.plus.com

nice one.
that would save me a lot of work and money if i can do it with crank in tact
i notice there are 2 holes drilled in the small end bush too.

Hi Maxwell..Yes, the thing to do is fit the new bush, then drill one or two lubrication holes (put a wooden dowel or similar through the small end bush so that when you break through the bush with the drill you don't inadvertently hit the other side of the bush) and finally, ream to size for the pin....Ian

email (option): ian@wright52.plus.com

While pressing in the new you remove the old one.

Henk

email (option): ahum@quicknet.nl

I have found the hand reaming sometimes does not give a good result, the outer ends of the bushing get reamed a bit more then the centre. Ian what type reamer do you use??

Honing in a machine is far superior, but then the engine has to be stripped completely, so allways a toss up of what to do.

When the engine is apart, the conrod can be inspected for straightness too.

Cheers,

Lex

email (option): welbike@welbike.net

oof.

can it be reamed before installation?

No Maxwell. The act of pushing the bush in will squeeze it up. Reaming or honing is then done to give the gudgeon pin a nice silky slide fit. Clamp your con-rod between two wooden or metal blocks with G clamps to stop any undue stress and to stop it wobbling about before you start, and carefully cover the mouth of crankcase to avoid any fillings getting inside. I usually manage to make a bush remover with some studding and sockets. Just studding and washers needed to fit the new one. I then invite an engineer friend round to help me for an hour with one of his reamers if I'm doing it in the frame. Ron

email (option): ronpier@talk21.com

Thanks for the help
all i need now is that tool, and an engineering friend ha ha ha.

I use this tool:





I had it made by measures, on a lathe.
First, you need to screw the screw trough the bushing am into the “deep” side of the nut.
As you fasten the screw, the bushing enter into the free space in the nut, till it falls in.

Then you push the new bushing, but better use the “Shallow” side of the nut.
This prevent you from pushing the new bushing too deep to the other side.

When putting the new bushing, you usually have to start with the oiling hole a bit retarded anti-clock wise,
As it tends to rotate a bit while the screw pushes it in.

email (option): noam10@gmail.com

hi maxwell,heres a small hone,cheap enough at £5.00,but it is listed at starting at 19 mm which is just about 3/4'' so you may need to wear it down slightly in a piece of steel with a decent bore ( not any old bit of tubing ) this would prolly give you the best result.you would need to run this in a battery powered drill
and oscilate the tool back and forth in short bursts until the desired fit is achieved,taking care not to push or pull it too far through the bore and plenty of oil squirted on to lube it up.bear in mind there will only be a couple of thou
in the bush. ebay 140869847423
alternatively an adjustable reamer for £16.50 ebay 350475200663 then you will need a micrometer to set the thing initially and gradually increase the size as
required .these can be tricky and can also produce lots of interesting pattens in
your bush,these you dont want as its a one shot operation or another new bush
food for thought,hope this helps
cheers rick

email (option): richardholt@rocketmail.com

Tip, only turn the adjustable hand reamer in cutting direction .... never backwards at any time.
Small increments & many passes is how i approach them.

Harley Davidson do a wonderful tool for holding the con rod securely in place which is easily fabricated, I've not got a picture of one to hand, but I've done a sketch, they used the diagonally opposite studs to hold it down, and made the holes elongated so that it would fit all of the range, they are pretty easy to make from plate steel and just weld the uprights in and use little wing nuts to nip up the rod, with elongated holes you can make it to fit nearly all bikes with holding down studs, I think they designed it to use whilst fitting small end bushes and holding the rod whilst reaming it. You just have to wrap a little bit of shim round the rod to stop it from being scratched and ensure that the wing nuts are tightened up evenly to prevent the rod from bending.

email (option): davmax@ntlworld.com

My main concern would be if the piston melted now much of it ended up in the crankcase?

That's not too bad on the BSA, you can remove the sump plate and pump, check the pump and then flush it through, it won't guarantee to get all the bits out, but will certainly get nearly all of them out.

email (option): davmax@ntlworld.com

yea thanks for all the info and advice, yea i am going to split the cases and clean everything up to make sure no alloy is in there, just dont want to seperate the crank and con rod etc, so yea cool i can use this info and g from here. nice one

You may find it easier to replace and ream the little end bush before you split the cases,in case you drop any rubbish in the crankcase

yizzle fo shizzle
ill do it that way around, its all hood.

dont want no metal bits all up in yo stuff.

thanks for all the advice good help cheers!!

yizzle fo shizzle?
Have you been on the sauce Maxwell.

email (option): spacemonkeym@gmail.com

Not as much sauce as Henk by the looks of it there's just too many Yanks in the jeep on the forum picture, I thought you were issued a jeep when you enlisted!!!!

email (option): davmax@ntlworld.com