Hitchcocks Forum

I've just stripped a s/h 500 pre-unit engine I've bought and I find the crankpin nuts have been welded to both the crankpin and the flywheel on both sides. Is this a common thing to do or does it mean the big end was replaced by someone who perhaps is not familiar with these engines. The big end bearing seems fine so I don't think I have a reason to strip it further at the moment.

The crankshaft on one of my previous Enfield motorcycles broke into two pieces (shortly?) after one of those nuts came loose!
At least you wont have that problem...

The crank will be junk. Any one who welds on retaining nuts does so out of either ignorance or desperation. Ask your self; is a 2nd/3rd rate repair job acceptable to you?

Are they just tacked. Could be OK.

No they're not just tacked, the nuts are welded (very neatly actually) to both the crankpin and the flywheel on both sides. The big end seems absolutely sound and very smooth as are the main bearings so it's going back together as it is,with just new seals. What have I got to lose? Apart from my time (and a new barrel and piston) if something does let go. It doesn't seem to be unknown to weld built up cranks for reliability but I've never heard of it being done on an Enfield. Bit disappointed really, I was hoping I'd bought a tired engine with the original bottom end but someone's been there before me.

I have a Honda (sorry) 500 single engine with welded crankpin (there are no nuts,) which was built for me by Alf Hagon to racing spec. Remember the Japanese 500 singles racing formula back in the 80s? This was common practice then. I used it as a fast road bike so never gave it the stick it would get on the track.

REgards, Mark

Some people weld Harley crank pins on there racing motorcycles. I saw this on YouTube. They then use a dremmel tool to grind off the weld so they can re-use the crank fly wheels. The weld that they use is mainly just a very short weld to hold the pin. I have often wondered if there is a conrod, that would fit, the RE bullet 350 where the big end splits into 2 parts with bolts to hold them together and using simple half moon steel backed babbit faced bearings like in a car engine. The crank could be trued up then, and the crank pin welded into position making a solid crank that could have the conrod bearings replaced over and over with no need to have the crank rebuilt and trued up every time the crank pin needed a new bearing. It would make things a lot easier. Can any one see why this could not be done. The RE twins have conrod's like this. Perhaps there is not enough room in the bullet crank cases at the bottom to allow for the bolt heads in a split big end to rotate around with out hitting the crank case bottom. Hoping that some one can say why this could not be done.