TOPIC:

I mentioned this briefly in my build thread, but I think there is more to be said.

Sometime ago I found the info below. I don't remember where I got it. Do you agree? Does this look correct? I want to be sure I tell the welder the right thing to do.

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Crankshaft Welding

Welding the crankshaft is a must if you are going to race even occasionally.
Just take the crankshaft to the best welder in your area.
The crankshaft is made up of a total of nine separate sections.
There are eight counterbalance throw sections and one center piece with the cam chain drive sprocket. The sections are pressed together using either connecting rod pins or main bearing pins. It is these pins that require welding. Each counterbalance throw section will have one pin (either connecting rod or main bearing) which requires welding, for a total of eight welds per crankshaft. The pin needs to be securely welded to the counterbalance throw. One half to three quarters of an inch of solid weld bead should do the job.
This is no easy task for the welder.
The area in question is very difficult to reach with a welding torch.
Your welder should have grey hair and patience.

That looks like how mine was welded. I didn't have mine done. I bought it that way. Looks like some of the welds would be quite difficult to get to. Definitely a job for a pro welder.

Will welding throw the crank out of balance? Should the welder use a torch with NO rod in order to avoid adding weight?

I have welded a few of them over the years, What I do is get a new polished peice of o-1 drill rod 17mm make sure it goes threw all the wrist pin holes on the connecting rods smoothly with little effort. This will help keep them from moving. Then you need to grind a small champer (2 half moons) on each counterbalance pins, clamp the crank down to a flat welding table. Then you can weld it but only do half of a pin and move to the same one on the other side of the crank then go back etc etc use very little filler rod just enough to fill the champer that you ground in flush again.

I've never done it. But each of those crank sections need to be aligned correctly for a straight crank. Also a rebuild would be best before welding it together. V blocks and dial indicators, or held in a lathe checking for run-out. Seems like the links have been posted in the past for Falicon. They would be my choice, and on the cost of a race motor quite reasonable. Balance and straight, with a rebuild that's what I would want

Be sure the crank is not twisted before you weld it

Your best bet is to send it out to a shop that specializes in building press fit crankshafts. I've been welding for a living for 15 years and I sent mine out because I wanted it done right. Pearson racing tore mine completely down, chamfered the pins and throws, shot peened the rods, replaced the thrust assembly with a roller bearing to reduce friction, put it back together, welded it, and trued it for $415.

Like andy, I've been welding, fabricating, machining for almost 30 yrs for a living and I sent mine to pearson also. I believe it was a little over 500 but he basically done a top gas crank with the thrust upgrades and extra large chamfers before welding. I do weld exotic steels almost daily and part of doing it well is to know what the parent mat'l is your welding and the prep involved. Do you preheat and if so to what temp, What bonding rod do you use? What I'm saying is I could have done my homework and figured it out but why. Pearson has one of the best reputations out there and I have too much time and money invested to risk it on trying to save a few bucks. Now for the other side of the coin, If I were building a budget street/strip e.t. type bike I would do it in a heartbeat. Just for the leaning curve if nothing else. If your confident I say go for it! I don't want anybody to shy away from learning or trying anything new but first do your homework, it will pay in the end.
I hope this helped
Les

What les said x2. He said basically what I was trying to get across. If you are willing to risk it not being right when you're done for the sake of trying to do it yourself, go for it. If you're going to farm it out to be done spend the money on one of the best guys doing it, not on the local guy that is willing to give it a shot. I wish I had a picture of Johns work to post up on here because it would truly be worth a thousand words.

Heres a quick pic for you.

Lots of good info, thanks! Actually I was not considering doing it myself. I just want to learn about it and know what to ask a welder to do.

My crank is from a very smooth, good running engine and the bearings are excellent, so I'm confident it's not twisted.

I'm thinking of taking it to a local welder and have it welded ONLY. Meaning no fancy rebuild, balancing, or anything else.

So welding is not enough to throw it out of balance and cause a vibration?

YES! welding can and probably will cause the crank to not be straight when done. That is why it gets trued after welding to make sure it's not banana shaped when you bolt it back in. Unless your welder has a set of vee blocks and knows how to check the run out properly it's a risk you take.