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Girl bought a bike, motor = shot. Rebuild thread.


LCW

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Did you make it right with the guy you sold a junk crank too ?

he absolutely did. He allowd me to return it and refunded my money, wich i actually didnt expect but was very thankful. Crank was still usable it wasnt completely shot but i was recommended not to do so as it did have some play in the rods. As LCW said, just a missunderstanding in the condition of it. I took it as a good usable crank wouldnt have rod play but i was wrong as it did but was still in spec to be usable.

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Not here to screw anyone out of their hard earned money. I'm a regular hard working joe like most here. I have been screwed before and it's shitty. I reside on this forum to contribute to the greater good of this community, as well as benefit from others contributions. Uman, thank you for posting in response, I apologize for not being more clear when I sold you that crank. I'm glad you contacted me to clear it up.

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  • 2 months later...

Finally have a couple updates on the rebuild. Got the crank back from crankworks. It looks good, but I'm not to sure about one of the bearings. I'll be calling them tomorrow to see what they think. Picked up a set of used cylinders and had them bored for some new pistons. Still have to chamfer the ports a little. Tore the bottom end apart and not so surprisingly found a bent rod on the other cylinder. The trans seems to still be in good shape, just had some wear on one fork. I spent a couple hours cleaning on the filthy cases and got them painted last night. Still need to clean up the chassis a little bit and deal with the harness routing. Had a carb acting up when the motor came out, but have yet to get to that. Could be a powerjet or something. It was running a bit lean and acted the same on both cylinders. Other than that small list, should be up and running within the week hopefully. Hope this crank doesn't hold me back any longer. Here are some pictures of the old crank, cases, cylinders, etc.

 

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  • 2 weeks later...

Got most of the motor built today. Hit a few snags along the way. I had a local shop do the bore job on the cylinders I picked up. The job looked good until I put the head on the motor and the pistons were kissing the edge of the domes on the exhaust side. I measured everything as far as squish and it's around .050. The issue seems to be the bore job being off center. I sanded the front edge of the domes down and got them to clear. I'm going to call the machine shop tomorrow and deal with that. I figure the only way to fix the issue now is to call Noss Machine and have them cut a dome with dome clearance.

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Nothing great about it. Only reason I sanded the front edge was to see if they would clear and they did. The machine shop can't do shit about it, because it's 66mm bore. I did some drawings in cad last night, a dome with .010 more inside diameter will give it plenty of room. Sometimes you have to play with the cards you've been dealt.

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i have seen wack bore jobs all the time from so called reputable shops.  i dont know whats going on but of center and to the front and to the back seems commonplace..  i dont know how thats ok>?  the guy i use has a dedicated boreing bar on a stand and a few jigs thats used when they get bored  the cyls are always straight and true, plus he wont do them unless i hand him the pistons.  he sets the clearance to the actual piston thats being used.  only time i have had a deff left and right wast mostly on cheaper budget rebuilds using namura pistons.  but they always seem to hold up just fine.  

 

hot rods in gold coloring?  must be new..  i really really really HOPE that they didnt farm the rod manu off to china... 

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i wouldnt automatically put blame on the machine shop. maybe they fuked up and maybe not. the problem you have on any head that doesnt use locater pins is they have alot of slop between the stud and hole in the head where the stud goes through so it lets the head move around. thats why you normally want to make sure the diameter of the head is just slightly larger than the cylinder bore. other wise you may end up with some of the head surface sticking into the bore. now if your head used locater pins like ktm and some hondas then you could machine the head diameter exactly the same as the bore and be ok because theres no movement between the two parts

 

also before you put the cylinders on the case, hold the cylinder with the head on and look up the bore. move the head around in all directions and notice if it protrudes into the bore at any point

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Yeah, I'll go take the cylinders off to confirm the issues that are already known. These were drag ported and @ 65.50. That means the ports were chamfered. When I got them back had to chamfer the exhaust ports and front transfer. Didn't really have to do intakes or anything past center on the intake side. I didn't think anything of it until I hit this issue. Sounds like bore job to me. How many guys have this issue with 4mil stock cylinders and cool heads?

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