Need help with 1948 NH big end side play

[Gary Inglis]

I'm rebuilding a 1948 350. I've disassembled the crank to install a new big end pin and bearing (Draganfly). I've found that there is a lot of wear on the flywheel "cheeks" next to the big end pin where the con rod big end has rubbed the flywheels. So much so that there is about 2mm of side play at the big end when the crank is assembled. Recommended side play is 8-12 thou (0.2-0.3mm)
I've read through this forum looking for ways to fix the problem. One gentleman was able to machine up and install new steel washers onto his flywheels, but thats beyond my skills.
Ariel manuals mention using bronze washers riveted to the flywheels as another way to repair the damage.
I've seen members here say that later model Ariels used shims between the con rod and the flywheels to set the side play. I've not been able to see anything in the parts listings I have access to showing such shims. There are shims for centering the crank assembly inside the crankcases and setting crank side play, though.
I note that most modern 2 strokes use bronze shims between the conrod and the crank wheels.
I need advice on how to proceed with this repair!
Thanks in advance
Gary

Here's photos of the worn flywheels..

[Roger Gwynn]

I think you will find that the .008/.012" end float that you refer to is for end float of the crank in the cases not con-rod in wheels. I have never seen a figure for the side play and I don't think that it is anything to worry about as long as your con-rod is straight the rod should not be sliding about across the big-end. I would say that .080" is not excessive and most wheels exhibit marks in that area. The 1956-58 500cc models were fitted with washers either side of the big-end that fitted into recesses machined into the flywheels, part number 1180-56 but they won't fit your crank.

[will_curry]

Welcome to the forum.

The other question to ask about the engine is what state is the con
rod in?

What damage has been done to the side bearing on the flywheel?

Sometimes a worn bearing will cause the rod to bear on one side
of the flywheel but more often the cause is that the rod is bent.

[chris.shearwood]

I think you will find that the .008/.012" end float that you refer to is for end float of the crank in the cases not con-rod in wheels. I have never seen a figure for the side play

Hello Roger, It looks like Gary is correct about the side play specification. This is from Section B, Page 4 of the WNG manual:

[Roger Gwynn]

They say you learn something new every day and after 47 years I still lernin. Never seen that before.

[Gary Inglis]

The 1956-58 500cc models were fitted with washers either side of the big-end that fitted into recesses machined into the flywheels, part number 1180-56 but they won't fit your crank.

Thanks Roger - thats good to know.
Are those washers 1180-56 available? These flywheels are going to be machined to smooth out those "cheeks" , and it might be possible to also machine recesses to fit the washers.....

Will, I am checking the conrod for twist and bend at the moment. All the crank bearings are being replaced as part of this rebuild- the original bearings were okay for a couple of short rides after I bought the bike, before they made nasty rumbling noises. I didnt think to check the crank for clearance or for centreing before I dismantled it, so there are lots of possible causes for the flywheel wear.
...but I do want to get the engine back to something close to the original specifications if possible. I hope this engine will be running for many years into the future.
Gary