welded crankshaft runout

[RifRafRacing]

Had my 1100 crank welded by very reputable source a couple of months ago.Im just getting around to assembling engine.This is the first time Ive done a complete teardown.When I set the crank in the upper case half and rotate it,the bearings are walking up and down.With an indicator on the worst one(right side second bearing in)Im seeing .025" runout.Now when you assemble the cases I suppose alot of this movement would be quenced,but I dont feel good about this when it sees 10k rpm.I wished I had checked the crank for runout before sending it out,it came out of my good running daily driver.Anyone seen this condition after/before welding?The service manual says no more than .004" runout.Is this crank now a fancy boat anchor?

[lecroy]

I assume your supporting in at the ends with blocks on a granite table, with the dial sitting on the table and not trying to do this in the cases. This isn't good. What did the reputable crank builder say?? If it really is bad and it's not something like your checking it in the cases where things may not be sitting flat and could move, it could very well still be repaired. If your just running it in a street bike, chances are real good. There is just not that much stress so you can get away with a lot more.

I don't think it is your job to take the crank to a machine shop to make sure things are good before sending it off. Some of the damage to an old crank like this you may not be able to see anyway. This is the crank builders job. Look at that eBay crank I bought for $180. Looked good for runout and side clearance. Bearing seemed nice and smooth. But once it was apart you could see the cage was cutting into the rods (just an old crank). Now had the crank guy just welded it, well we just don't do things like that to 20+ year old parts.

[RifRafRacing]

Its going in a dragbike,and cant be questionable.I did rotate it in the cases to get my readings,I can see how this may have given me some error. I will take it to the surface plate at work tomorrow.Do you set the outer bearings in the v blocks and then check each main bearing by holding the outer race stationery and rotating the crank?thanks,Steve

[lecroy]

Yes.

Ok, now for the important stuff, let's hear the details on your race bike???!!!

Turbo, spray, both or NA? Bars or no-bars? Extended swingarm, back halfed or the real deal? Car tire, or small tire? CCs? CR?

Stop holding out on us!! LOL. Good luck with the crank.

[rapidray]

It sounds like your crank has a slight bow to it. I won't say bend because it is so slight. A GOOD automotive machine shop can fix this for you. Preferably one that does race engines. Ray.

[RifRafRacing]

Im planning on going 1395-1428,had upper case bored for it.I have a 1260 flattop kit I could use with nitrous also.This is a stock helical crank that was welded,it wasnt disassembled.Ill see what it looks like today,and maybe it can be straightened if is bowed.

[RifRafRacing]

crank yanker

not quite as bad as what I was seeing before.still shows .015" bow at the 2 inside bearings and .006 and .008 at the next 2 working my way out.

[lecroy]

Lets see if I can put a positive twist on this for you.

This is a good thing!! If your really building a 1428cc engine with spray and your dragging it with a slick you really want to put some money into the crank, clutch and transmission. The engine can easilly put out more than the stock gear and basket can take.

By not putting this crank in you may have just saved yourself from the damage caused by an explosion, no to mention the possible health risks. The way I see it, the doctor bills alone could have been in the $100,000 range. So with all this extra money you now have, do it or have it done right!!


What I really don't understand is why would ANY crank builder take a 20+ year old crank and just weld it knowing it was for a big bore drag bike that had spray? Let alone telling you it would be ok to leave the stock gear on. I would love to hear the whole story and know who did the work.

[RifRafRacing]

tank da crank

you make a good point,Im giving GRC a call and see if they can rebuild this one or use it as a core,this has 1/4" welds at the pins.I need to go with the straight cut gear also.drop the coin and do it right.thanks,Steve

[lecroy]

If it is only a tack weld (1/4 long) this is great. Even if it was a full welded race crank they can rebuild them if the parts are good. Every crank builder is concerned with the press fit. Every time you pull a crank apart, you weaken the press fit. The welds do not provided the majority of the strength. All else, this decides what the crank can be used for. In my experience, normally it is not the crank parts that are a problem, it's the bearings and rods.

When Hill-billy-joe does a crank, he may not use the right rod. This can cause more harm than good. He may also over heat the parts (real bad). He may not get the right penetration. I have seen some cranks where the welds lay over the top of the fit.

The cost can be all over the map. Pearson did my last one for around $1000. This was a new MTC gear, 493 rods, bearings and full weld.

Figure a clutch basket will run in the 400 - 600 range. A multi-stage to go with it, in the 600 range. Pistons and block in the 1000 - 2000 range. Transmission in the 1000 range. The head work is all over the map. Friends T/G heads, around 3000.

If you want to go 9's, think Busa with a little shot. Very cheap fun. Getting into the 8's costs a little more. Not sure what the 7's are going to run.....

First born??

Have fun with it!!

[RifRafRacing]

I got an 81 1166 street/strip bike that ran 9.82 on a ratty dunlop.This weekend New England Dragway opens,Im runnin a small slick/bar should go 9.5-9.6.Yah,everybodys got a busa they all look the same.Stan Gardner set me straight,talked to me for about 20 minutes.He said the fact that this crank hasnt been apart before is a good thing.Im getting the full monty for around a G.......thanks,Steve

[lecroy]

That's moving right along, but I bet you want to go faster and that's why the new engine! Funny, like I read your mind or something?! LOL

Friends bikes are all in the 1500cc and up to run T/G class (8.20 index). Biggest was 1600, gas ported blah blah blah thing. The engines are built to run high 7's to make sure they can cover the number. No spray or turbo, just engine. These are 10" car tire bikes, which really sucks the juice to turn. You spray something that big with a small tire you should have some major fun!!! Videos when you get her out!!!!

I have never heard anything bad about his work. Did he do the first job?

Your right, I see a lot of Busa's at the track. They don't out number the old bikes around here yet, but moving up... Last guy I saw with one was running high 9's, no spray. Stock for the most part. Electric start and rides it. He was pretty small which helps. That is what is cool, they make some power with little changes and you can ride it to the track. I like the looks of the older 70's / 80's drag bikes myself.

[RifRafRacing]

no,it was APE but I cant say that it wasnt out of tolerance to begin with.I didnt ask them enough questions,I saw cranshaft welding for $100. and I went for it.Things happen for a reason sometime,now Im going in the right direction.

[rosco15]

I'm thinking the $100 price is the weld it without checking it price. I'll bet weld balance and true is much higher.

[lecroy]

I bet your right!

I just didn't understand the whole ... Oh, your cranks a bit out of wack, that's ok, we'll go ahead n welder up for you. Thatil be 100 bucks please.

To me, the whole point of using a well known shop is your getting their professional experience. They did a nice job with my pins, and all the aftermarket parts I have ever bought from them were top notch. I would have expected them to at least check the runout and side clearances, or to be very up front and warn the buyer. Just post a note on their website, warning, welding only includes welding, no support, no inspection.. Maybe make some recommendations as far as what to do. I don't know.

I'll stick with my man John.