Welding crankshaft journal- I am crazy!

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Hi,I have a gx200 clone 6.5hp when stock. I have been modifying it. One of the modifications include an arc billet aluminium rod with bearing inserts and forced oil dipper, because I plan to rev to 6500rpmUnfortunately, after measuring my crank, the clearance between bearing and crank is around .009. It is meant to be around .004. If I run it with current clearance it will knock and die quickly. Arc do not manufacture undersized bearings for their rods. Therefore they reccomend to buy a new crank. I would have done if I had not spent hours fixing it- here. I can buy an undersized clone rod, but it would be far weaker than the arc, preparing myself for a free hole in my block!I wondered if there was an easy and free or very cheap way to increase the crankshaft diameter by around .005-.007, or modifying the rod bearings? I was considering welding after evenly heating the crank. I would then evenly heat the crank and slowly cool it, and lathe it back to size. I could also increase the stroke and make one of these (first one) or maybe increase by more, up to .080Am I crazy? Are there any other methods?PLEASE help! I would have bought a new crank before fixing this one earlier if I had known this issue!CheersRobLast edited by r_chez_08; 06-03-2012 at 03:45 PM.
Reply:Crankshaft welding is a very common practice.
Reply:Originally Posted by 76GMC1500Crankshaft welding is a very common practice.
Reply:Persoanlly I'd try it lol. You'd probably need to weld it up with TIG and stainless filler.Doing it just to justify all the time you spent on a bad crank is kinda dumb, but if you're just doing it for a fun little project or to see if you can pull it off then sure why not.Welding/Fab Pics: www.UtahWeld.com
Reply:OK thanks. You guys are really quick at replying! I would like to give it a go, one of my many projects. I doubt many 16 year olds are making their own stroker cranks! :PI have arc welded and machined stuff before. It machined nicely.I have mig welded and machined stuff before. It was horrible!Is there a problem with arc welding it? I would rather not try a new technique if it is going to be impossible to machine with normal tools.ThanksRob
Reply:How about using a piece of shim stock under the bearing? If its otherwise unuseable that would be something to try. A piece of brass shim in .002 or .003 shouldn't be too hard to find and will give you a .005 or .003 clearance.Last edited by Coupebuilder; 06-03-2012 at 05:33 PM.Reason: speeling "Anybody can talk $h!t behind a monitor, I let the quality of my work speak for itself"Lincoln Square Wave 255 and 355 Tig Lincoln 255 Power-Mig w/ spool gun Koike 5 x 10 CNC plasma Hyd-Mech DM-10 bandsaw Ineco QB-76 NC tube bender
Reply:Opposite end from locking tab of each beaing shell would have to be trimmed to maintain proper crush and prevent deformation if using shims.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Yeah but a file would take care of that in two strokes if it was even necessary...only talking .002. Never would recommend for a good motor but his crank is scrap otherwise and much easier and more likely to have a  positive outcome than trying to stick weld it and locate it in a 4 jaw to turn. I have seen it work in v-8's and last for years. Try it and plastigage it to see. Hell could probably use aluminum foil for the shim lol. "Anybody can talk $h!t behind a monitor, I let the quality of my work speak for itself"Lincoln Square Wave 255 and 355 Tig Lincoln 255 Power-Mig w/ spool gun Koike 5 x 10 CNC plasma Hyd-Mech DM-10 bandsaw Ineco QB-76 NC tube bender
Reply:Coupebuilder, I was thinking the same thing, and was told it wouldn't work. This will be a good motor, I am not wrecking a $60 rod for nothing!Would this honestly work? I personally did not see why not.I need to get some plastigauge...Edit: where can I find some shim that thin, except from foil?
Reply:Hack up an old feeler guage. Nice and precise like
Reply:Lol, not a bad idea but they are not really wide enough, the bearing is between 20 and 25mm thick by memory. A feeler gauge is only 12mm or so thick. I would need a few gauges too.
Reply:Originally Posted by r_chez_08Edit: where can I find some shim that thin, except from foil?
Reply:I have come across shims that were made from beer cans in old motors before. I don't have a beer can or a micrometer right handy at the moment. My advise as a mechanic would be to do it once and do it right. Buy a new crank.Miller millermatic 251Miller aircrafter 330st, wp201961 Lincoln SA200Ellis 1600 bandsawLogan 820 latheSouth Bend 13"Bridgeport M Head
Reply:It seems to me that your problem is that you're putting parts inteded for a Honda engine onto a Chinese Honda knock-off.You're gonna run into the same issues putting expensive parts on a cheap motor as you would putting cheap parts on an expensive motor.
Reply:Well if you want the voice of reason I will be it. If you needed to get some time out of a POS than patch her up BUT if you are putting money into it then do it right . Perhaps find another motor for doner parts, but dont mickey mouse it if you want it to last turn fast and are putting money into it. Do it right.Miller thunderbolt 250Decastar 135ERecovering tool-o-holic ESAB OAI have been interested or involved in Electrical, Fire Alarm, Auto, Marine, Welding, Electronics ETC to name a just a few. So YES you can own too many tools.
Reply:Call around and find the closest crank grinder that does all the local odd jobs. Chances are he can do it for you. The guy that does mine always has odd small engine jobs in his shop. He uses sub-arc and tig to weld up his crankshaft's.
Reply:I don't know what they use today to weld up cranks for off-center grinding (stroking the crank), but in the old days (the 70's) the crank guys welded the journals on a forged steel crank with a stick welder, and they weren't that finicky about it.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:Ok, so the shimming idea won't work well then?I can try and weld and grind it, has anyone got some tips on how to get the crank set up correctly?ThanksRob
Reply:Note....Irickdante is a spammer.
Reply:If you try some halfassed weirdness, just assume you will ruin your billet rod, it would be stupid not to.Welding/Fab Pics: www.UtahWeld.com
Reply:So many helpful replies!I can understand the possibility of damaging my rod with a shim, but surely the worst could happen with a welded crank is the bearing shells getting scored, and $5 for some new ones?
Reply:Originally Posted by r_chez_08So could this be easily done, and turned down with a 4 jaw chuck? Could I use my arc welder?Thanks for your reply.
Reply:Originally Posted by r_chez_08Ok, so the shimming idea won't work well then?
Reply:I assumed it would be weldable and turnable, since they make .060 stroker cranks from these clone cores. Just didn't know the correct technique.I do not have access to a spray welder.No I have never welded or ground the journal of a crank, but there's a first time for everything. I consider this and most of my projects a learning curve. If it works, I have learnt. If it fails, I have still learnt!I can talk to my local machine shop about welding. I say cheap or free because the crank is cheap. Arguably adisposable part, however I do not have disposable income.Last edited by r_chez_08; 06-04-2012 at 08:35 AM.
Reply:Machine the rod cap mating surfaces - if it's a split cap.  If it's a solid cap with a press fit crank, it's time for a new crank.  Shims work ok for a low rpm motor, but you are planning on turning this to 6500.  It will spit the shim out.Welding, grinding and polishing is an option, but I bet you will have more money into it than a new crank will cost.MarkI haven't always been a nurse........Craftsman 12"x36" LatheEnco G-30B MillHobart Handler 175Lincoln WeldandPower 225 AC/DC G-7 CV/CCAdd a Foot Pedal to a Harbor Freight Chicago Electric 165A DC TIG PapaLion's Gate BuildOriginally Posted by r_chez_08So many helpful replies!I can understand the possibility of damaging my rod with a shim, but surely the worst could happen with a welded crank is the bearing shells getting scored, and $5 for some new ones?
Reply:..,mnbbhnjgvchWelding/Fab Pics: www.UtahWeld.com
Reply:I mean the babbitt bearing shells in the con rod. The crankshaft has ball bearings on both ends, and a cast iron cylinder. Honda didn't design it as a crappy throw away block, despite the $35 price for a new clone block!What do you mean by a split cap or solid cap?ThanksRob
Reply:Split cap is one that separates like a rod cap on a V-8 engine.  A solid cap is one that is machined with the crank hole, then the crank is pressed together through the rod.  I forgot to add, if the rod cap mating surfaces are machined down, you end up with an oval opening.  Machine it down to "0" clearance, then have the big end bored to the correct size for the clearances you want.  Doing it this way would be easier & less expensive than welding/grinding/polishing the crank.MarkI haven't always been a nurse........Craftsman 12"x36" LatheEnco G-30B MillHobart Handler 175Lincoln WeldandPower 225 AC/DC G-7 CV/CCAdd a Foot Pedal to a Harbor Freight Chicago Electric 165A DC TIG PapaLion's Gate Build
Reply:OK I understand now (I think!!!)Pretty sure it's a split cap, as the cap is a separate piece. However, machining would not really be an option. The rod has some crazy machining between the cap and the rest of the rod. It is zigzagged to fit and stop any movement. I could not replicate this.What is the difficulty of welding and machining the crank?Here are some pics of my rod and crank- Attached Images
Reply:Originally Posted by WinmacThe correct process would be to turn the journal undersize leaving a rough finish, then it would be built up with spray weld, to follow by grinding and polishing to give a surface finish that will maintain lubrication.
Reply:Fair enough, I can understand the bearing spinning idea, would destroy the rod. What would a machine shop be likely to charge to do the spray welding, and how would the strength differ from arc or tig welding?ThanksEdit: Another thing I could do is nickel plate the crankshaft, which would bring the diameter up a little, and polish up nicely to reduce friction. Does this sound feesable?Last edited by r_chez_08; 06-04-2012 at 02:15 PM.
Reply:as far as what a shop would charge for this process I cant say, each shop has their own hourly rates and so on,    dont know about the nickel plating,  to understand the way a crank and bearing work isnt just the bearing runs on the crank with a layer of oil in between, the bearing is made out of a specific soft mixture of materials and the crank is hardened to a specific "brinell" hardness, (or some may say "rockwell" hardness) to a certain depth, the purpose of this is so the bearing may absorb any foreign material that may travel in between the bearing and crank and not damage the crankshaft itself, so as I dont think I would be fooling with the idea of coating the crank with anything other than the spray,    Now, as far as the advantage of spray over welding, a crank shaft is not "turned down" with a typical hardened steel or carbide tooling bit, it is turned down with a large stone, this stone has a flat surface, the welds would ruin the surface of the stone, the machine to weld a crank shaft can be seen here , the process can build up a crank to just over the desired ID and then turned down on a crank grinder to the specific diameter you are looking for, many good videos on turning cranks on youtube also, check them out,   you would probably be money ahead to buy a new crank, but to just "mig" up an old crank and then go turn it down probably wouldnt work, it would just "muk" up the rest the engine, hope this helps,
Reply:Grind the ends of the rod and put the cap back on and recondition the rod with a sunnen hone.....Bring it back to your crank spec.....  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Most crank welding is "Spray welded"  Miller Dynasty 350Twenty Six HammersThree Crow BarsBig Rock
Reply:Most crankshaft buildup ive seen has been done with sub arc welding.
Reply:Originally Posted by B_CGrind the ends of the rod and put the cap back on and recondition the rod with a sunnen hone.....Bring it back to your crank spec.....
Reply:I see your con rod has a serated parting line, it cannot be resized by the method mentioned earlier.Dam you barely beat me to it , duaneLast edited by Winmac; 06-04-2012 at 10:13 PM.Briggs weldnpower 225/210/cvLn-25 suitcaseMillermatic 130
Reply:Sorry I posted the wrong video link, I am with B_C on the spray as I said before, here the correct link to the spray welding
Reply:why are the bearings rod specific? if you take the connecting rod bore dimensions and bearing width you can probably find bearings that will work with what you have or maybe some that will work if the crank is ground undersized. as long as the OD of the bearings will fit the rod (you do need some crush) the width can vary some. if the bearing is a little narrower that's fine, if it's a little wider it can be narrowed.not that it matters but that rod can be resized but only with the equipment that was used to make it. the serrated faces would have to be recut. serrated faces are very common on aluminum rods and many also have dowel pins for the bearing inserts
Reply:Thanks for the replies. Spray welding looks good, but it would be too expensive.I am trying to look into rod bearings from another engine, but I don't know where to start! What would be the issue with nickel plating? The hardness would be similar to the original cast iron.
Reply:Remember one thing here..If you do weld it OR send it out for plating for build up those crank throws are re-machined on a CRANK GRINDER.Without one you are screwed.You will NOT get the proper finish by turning it in a lathe..If you could at all....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I have access to a toolpost grinder for a lathe, would this do? Then use crocus or emery cloth to polish the last .00025 or so.Is there a problem with nickel plating? I can plate at school for free.
Reply:Oh no...Let's just put it this way...Whatever you do to the CRANK is NOT going to work.I can run a engine lathe with the best of them and you nor I will ever turn crank journals on a lathe.Main bearing surfaces maybe but not the throws.You need to go to plan "B" if you have one.Your best option is to resize the rod but that will shorten the stroke by "That Much".....zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:But after looking at the pics of the rod again..Nope.That won't work either..Resizing.Oh well..Now what?...zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:Originally Posted by zapsterNow what?...zap!
Reply:You could easily offset the snout of the crank in a 4 jaw but what do you do with the center on the other end?There are no centerholes in the ends of the throws..How are you going to indicate the throw in to zero with weld all over it?..zap!I am not completely insane..Some parts are missing Professional Driver on a closed course....Do not attempt.Just because I'm a  dumbass don't mean that you can be too.So DON'T try any of this **** l do at home.
Reply:I was planning to nickel plate, I assumed the coating would be uniform. I wouldn't mind if the stroke was a few thou out.There is a hole going right through the throw but it's cast and I wouldn't count on it being central!Anyway, I have some good news!Here is a message I got from ARC, the manufacturer of the rod-Me:Quote:Originally Posted by R_chez_08Hi,I have one of your gx200 std. length billet rods. Do you or will you soon do undersize bearings for these rods, because my crank measures 1.174 and is still round.ThanksRobArc:We may do some .002 under and .005 under. Watch our website under "Newly Listed"arcracing.comOMG!!! What is really annoying is I can buy a new crankshaft for $17, but I live in the Uk! Shipping on bearings would be far cheaper.