trueing,welding, and balancing the crank

as some of you know, i twisted my crank and now im at the point i believe im going to try and save the old beast. some of you have said have the crank trued and welded. i understand the process of truing it up again, but where in gods name do you weld it, from looking at it in the case, i dont see any contact areas where it could be without interfering with the bearings. also, should i decide to have this done, how do they go about balanceing after the fact? i would think this would be a ngithmare with 4 rods hanging off. im probably going to try and find a replacement crank(81 j model -?) but what is to keep this one from twisting also? i can only assume the crank had a slight twist to it to begin with, I cant see how it happened with the popping from a lean condition. could the cyl have fired from risidual gas at the wrong time. im just curious how this can happen and how to prevent it short of sending any donor crank i find off the get welded also.

yes a detonation could have knocked the crank out of alignment. As for preventing it from happening again you can do a number of things. Make sure to clean the combustion chamber with a nylon brush or something (prevents hot carbon from igniting fuel prematurely), make sure you're jetted correctly, etc. As for welding the crank you can send it in to APE or Falicon or if you want to do a dangerously cheap way you can send it to a local welding/metal working shop and tell them where they need to weld it. I'm not entirely sure where to weld it on the J model engine but i can show you pics of the older model crank. Basically you're just welding the pressed piece to it's corresponding mate. Just know that it's rare for this to happen with an unmodified engine. If you go to "i think im going to be sick" thread i put some contacts for junk yards in your area if you're looking for a donor bike.

Funny thing;

I talked to my neighbor last night who has built a couple of performance (car) engines. I asked him about balancing and welding a cam for me because I thought about high compression pistons, aluminum rods, and bigger cams.

He said I could have anything done from:

1) Just crank balancing
2) Balancing the crank with the pistons
3) Full blueprinting which accounts for all of the components of the engine such as stroke, bore, and valve duration

He said there's a company in Minnesota that does this stuff, but it's not cheap. I figured I'd get a newer engine and shoehorn it in before I'd pay $1,000 for 'blueprinting.'

Oh yeah, on this vein I am an acoustics and signal processing specialist. I'm pretty sure I could pretty easily build a crank balancing jig with the software I'm running.

Maybe I'll try an old Tecumseh 5hp crank and let y'all know what happens.

i think my best bet would to get a used crank and if i get nervous with it, maybe heliarc it? that was the welding wouldnt be adding material to the crank, itd just fuse the two pieces together in a small area. im just leary about getting a crank off egay, had some total pieces of crap show up. anyone on here have a good straight one with all the bearings and rods still good? waitin for plummen to hollar in since hes only 35 miles away.

sully,the cranks are multiple pieces(lobes) that are pressed together.if you have ever seen the way a two stroke crank is built it is the same theory.you have one lobe with a hole in the center which is where the main pin presses through and a hole towards the edge that the rod pin presses through,then another lobe same deal hole inthe middle for the main pin and hole towards the edge for rod pin.so now we have two lobes with main pins pressed through the center and a rod pin with the rod on it through the holes in the edges.we will weld the areas where the pin and lobe come together.i believe that it is always done (or should be)with a tig.

follow the link and look at the picture.
www.babbittsonline.com/pages/parts/viewbybrand/default.aspx
hope that helps.okay you will have to enter make,motorcycle,kawasaki,find your model and check the drop down menu for crankshaft.then you will see your crankshaft.at least then you can tell whatcha workin with.

Sully,
From my information the newer J motors did have a lot of problems with cranks being out of true and a multitude of other things. If you talk to Larry Cavanaugh about it he will tell the straight dope as he was a mechanic for kaw back in the day. I also read many articles concerning the J motors.
As for building the engine balancing and blueprinting really would make the engine run completely different. If you are in to the low buck approach do what you have to do but if you have ridden a really well built engine before I think you probably wouldn't hesitate to do it again. The finer things cost the money. A grand spent on that crank balancing and blueprinting the pistons and welding the crank will be a huge improvement. Of course it would be cheaper to buy another complete bike and ride it and be totally happy.
If you don't like that then get another engine and put it in would be cheaper that way. The guy I talked to about engines was very informative and I have seen a well built engine vs. bargain basement rebuild. There is no comparison. If you love your bike and want it to run well you are gonna spend money to get it there. Nothing is cheap any more.

does anyone even actually balance these engines?if so not very often.i would not worry about balancing just tru and weld,you will be fine.my .02

I think before much more is said you should tell us
what you are trying to build.
Every day raider.
Caf bike
Drag bike/bracket
Pro stock
Each an every one will take a different amount of crank
durability or truing, balancing, welding. an so on.
Inquiring minds would like to know...
XENU

just wanting a daily rider, i dont need a10k motor thatll hold there all day and not burp. i bought the bike after hearing rave reviews from other ppl about the price i could get it at. i know the kz is a badass bike and has potential of incredible power. but i just want something i can ride back and forth to work and take the oldlady out on on sundays. if it has enuff nuts to get around those sunday drivers while passing in a blink of an eye, then so be it. but i just want a reliable daily driver that im not dumping a ton of money into every ten days. my avatar has a pic of the bike(cant figure out how to shrink them to post one), and its in great shape. im just pissed and dissapointed that i bought it and now have to dump some cash into it. as far a tig welding it, im certified in three states for industial welding through Valmont. so that being said, i know how to weld. the reason the heliarc would work better, is because it wont add additional wieght to the crank like mig or even tig welding will. thus not needing to balance the crank because nothing has really change, only that the two pieces have been melted together. tig would do about the same thing if done right, but im not as proficient as a tig(bout the same thing as heli)as i am with a heli. im just wanting a nice true crank with some rods that arent junk so i can start enjoying this bike that i know everyone loves so much. im just frustrated more than anything else because i bought this bike thinking it needed a carb cleaning and a batt.so PLEASE, someone crap a crank so i can get onto the more important things, like cutting it up to look cool, lol.

Anybody out there with knowlegde of American Turbo Pac kit install and set up?