| Author | Message | ||
     Reepicheep |
I get better kawasaki support here then on the Kawasaki forums!  So anyway, tore down kid #2's Christmas suprise tonight. It had issues, but I think it's salvageable. Remember when answering these questions that this is a $450 two stroke, 60cc, play bike. Stuff I wouldn't think of doing on a "real" bike will likely work pretty well on a 15 HP micro engine. And I can go from "running bike" to "complete top end tear down" in (literally) about an hours worth of work. It's moronically simple and insanely quick to tear down. So "rework" is no big deal... I can do a top end job on this bike in the time it would take me to change a tire on my 9sx. I could probably go from running bike through case split, rebuild, and reassemble on a single good saturday. And good cases are going complete on ebay for under $100. So you really can afford to take some chances on this kind of bike... So keep that in mind... Issue 1: New piston, idiot owner. The previous owner put in a new piston right before they sold it. But they cranked it over with a small bit of metal in the top end... very small, like maybe twice the diameter of a shirt pin and about as long as two pennies are thick. It embedded itself in the head, and put a matching detent in the piston surface. I dug it out, now it's just a matched set of holes. I'm tempted to take off the sharp edges with a file, run it for a season and see how it holds up. But A new piston would not be that expensive either. I don't mind taking the chance and risking another tear down after one season of riding... money is tight right now so one season would be a big help. Issue #2. Idiot previous owner and crank. The crank nut was loose and stripped. Who knows the chronology, maybe it was loose and chewed around in there, maybe they stripped it. The nut was by far the "most stripped" part, but the crank threads are significantly hurt as well. The roots of the thread are still there, but badly rounded. I have a bid on a used (good) crank on ebay, looks like if I am patient I can get a good used stock one for well under $50, and a new aftermarket performance crank and rod for under $150. So there will be a good crank in the garage for when this one fails. No big deal splitting the cases, I have all the tools. But again, when I do that it's all new seals and bearings, so if I could put that off for a season that would be goodness. So here is my kludge plan... Get a fresh nut with fresh threads, and use a die for the current size to freshen up the threads on the crank. Then carefully assemble with lock tite red, pucker as I turn, and go to the very low edge of the torque spec and hope it holds. If it torques, call it good. If it strips, then get a die for the next size down (maybe the next SAE size down if that leaves enough metal for threads, or just go to the next metric size down) and just cut new threads on the end of the crank (still in the bike) and go down one nut size. They won't be as strong as factory rolled threads (assuming thats how Kawasaki did them on the crank) but they will probably get me up to the right torque spec without splitting cases yet. Thoughts? Any tricks for the crank nut thing to get a better chance of the thing holding together? | ||
| Oldog |
Another possibility remove the crank from the engine have a good welder / machinist build up the threads and re thread it, I know one on the board, Contact J Ramsey He made some special spacer shields, If I have the X1 in Franklin next time ask me you gotta see these BTW he needs a good note book computer and some help seting it up New is not required, BUT he needs a working copy of ECM spy ( he has the cable )and a good browser with his e-mail set up ( he really needs a GURU and I am not qualified.) You probably could hook him up down side heat input and forces applied to the crank, Upside threads Other wise get a die IF you can find one MSC supply, Enco, McMaster Carr may be able to hook you up and chase the threads, I wonder what the rod bearings have been subjected to.. you are on the right track though any of the approaches will work, careful on the idiot thing we all have "our days" mine involved an exhaust flange nut remind me to tell you some time. | ||
| Dalton_gang |
Issue #1 I would be more worried about the bearings and the nikasil coating than the piston or head. I don't think you should worry too much, those engines are pretty forgiving. Since your not going to race it you could let it be a little sloppy. Just keep an eye on it. Issue #2 Damn that sucks. Good luck hopefully plan "A" works! Awesome x-mas gift! I also did that for my kids years ago | ||
| Damnut |
I just picked up an 84 CR60 not too long ago for my kid. Those 60's are cool little bikes.  | ||
| Gjwinaus |
You have given me useful advice before, this is my chance to repay you 1. "now it's just a matched set of holes. I'm tempted to take off the sharp edges with a file" That is a very practical solution, I have had spark plug cap (the little aluminium thingy) fall in the plug hole, was not paying attention and kicked it thru, crushed the cap, took the head off, did exactly what you described, and after a year it was not a problem. the holes will probably fill up with carbon anyhow. 2. "but the crank threads are significantly hurt as well. The roots of the thread are still there, but badly rounded." Replacing the crank for 50 bucks is the sensible way to go, BUT 1st cheater option. A custom made nut with an undersize thread would probably work also, maybe 0.3 mm undersize, but thats easy for me as I have friends who are toolmakers 2nd cheaters option , and this is absolutely last resort, my brother glued the clutch on a Canadien chainsaw with JB WELD ( or something like it) and he has worked the saw regularly for 2 or 3 years without is coming loose, He had stripped the nut as well. | ||
| Reepicheep |
Cool CR60! The KX 60 is very much like that, but water cooled. Rumor has it these things will hit close to 60 mph. I think I will gear it down to make it more of a woods bike for Jack... and so it'll wheelie better  And you are right Jim... when I say "idiot previous owner" to refer to the previous owner, I also say "idiot mechanic" to refer to the guy that works on *my* bikes... which is me The nut isn't left hand thread or anything, and since it's a 60 its a little thing. So I'll start with the thread chasing thing and see if it holds, then go down one size threads if it doesn't. I don't see how a smaller nut would be a problem... I bet it will hold just fine. That flywheel is held on by both an interference fit *and* a key... I think that nut is to push the stator bell on as much as anything else. | ||
| Bluzm2 |
Bill, Been there done that on both fronts! Don't worry about the piston and head. I used to race one of my old 250's with WAY worse.. If there are any burrs, feel free to knock them down with a file or what ever. As mentioned above, they will fill with carbon. I suspect the next time you do a teardown you won't see them as they will be filled! Regarding the crank threads. I just went through that last year on a fiends S1. The nut backed of and made a MESS of the threads. I considered using a die but was concerned about getting it started correctly (the end was that bad...). I instead did it by hand using a thread file. They are available in std. and metric. They have teeth spaced at for the standard thread spacing. They are square with different pitches on the 4 sides of each end for a total of 8 different thread pitches. I started on the inside where there was the lease damage and worked my way out to the end. Slow and deliberate is the name of the game. I even used a magnifying glass to make sure I was staying on track. End result? A new nut went on with red locker and torqued to 275 ft lbs. It ran all summer with no issues. Did I mention that the splines were hosed too? A little liquid steel before installation took care of that.. Good luck! Brad | ||
| Dalton_gang |
"Rumor has it these things will hit close to 60 mph. I think I will gear it down to make it more of a woods bike for Jack... and so it'll wheelie better" We used to flat track and motocross and had 3 65cc bikes 2 KTM and 1 Kaw for a while. they were all excellent machines and were very capable of pretty much types of riding at stock gearing. I think 60 mph should be just a gear change away. That bike should do 50 mph or better stock. As long as you keep the top end fresh it should wheelie very easy on the pipe in 1st 2nd and maybe 3rd. | ||
| Reepicheep |
Cool! Good news all around... 1) I re-tapped the stripped nut (that was *far* worse then the crank threads) just to make sure I had the right threads, and that nut by itself feels like it might be able to torque down pretty well. Thats before I attempt to refresh the threads on the crank. So I might not even have to downsize. 2) I got a good used crank on ebay for $19, plus $10 shipping. So the repairs of the one "in-situ" will be a lot less exciting 3) Somebody on the KDX forums did the "tap one size smaller" on a KDX-200, and it has held up great. If it'll hold there, it'll hold here. Hopefully I can salvage the existing 10mm 1.25 pitch threads. I don't have a 9mm die, and don't want to take it all the way down to 8mm. Though like you say, I could hand file the thing and cut my own threads for 9mm 1.25 pitch... basically just follow the existing threads but deepen them 1mm. Hmmmm.... | ||
| Reepicheep |
Oh, and my goal is to modify it so it *won't* hit 60. If my kid wants to loop it, much fun will be had by all. But I don't want him blowing into a ditch or tucking the front at 60 MPH. Maybe I'll tell him it's a 3 speed |
