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My sons first bike/project


Reimbrandt

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Oh derp. I'm looking at the alternator rotor in the first pic aren't I? Lol. I'm not super familiar with these motors but why split the cases? Is the knock in the rod bearing or the wrist pin? Can you just pull the pan and UN-cap the rod and swap it out or is it a pressed together crank? If its just piston slap simply replace the wrist pin, circlips and rings, deglaze the jug and slap it back together.

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Ok so its def the rod bearing then? If you can access the crank thru the bottom of the motor via removing the oil pan you should be able to remove the rod and inspect the crank journal if you have a 1-piece crank/2-piece rod type motor. The skirts of those pistons look a bit cooked, like someone ran it out of oil or water, could just be a Shitty pic tho

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Ok, if that's the one with the rod knock it should be ok, if the knock is bad enough they slap around and scuff like that. Check the cyl walls, if they're torn up you may have to either eBay up a good stock jug or find a .030 over kit and a boring mill.

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Got it figured out...... Missed a bolt under the starter. Block popped right apart...... I beleive he found the problem....... :). The one spot on the cam needs ground down a little..... Has some scoring. Have to figure out where we could get that done and how much it will be. Time to shop for some engine parts.....

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Got it figured out...... Missed a bolt under the starter. Block popped right apart...... I beleive he found the problem....... :). The one spot on the cam needs ground down a little..... Has some scoring. Have to figure out where we could get that done and how much it will be. Time to shop for some engine parts.....

You mean crank, not cam? Pics aren't coming up for me so I assume you men crank. Idk if you want to grind down crank journals, those are bearing diameters and have very tight tolerances. The reason its knocking in the first place is there is too much clearance between the rod and the crank journal. New crank, new rod and new piston is more likely the proper fix.

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Schweeeettt.... I had noticed on the one quick search i had done that parts are very reasonable. That makes mama happy too...... Im gonna have him replace the timing chain while hes at it. That way when its back together its right the first time. (Hopefully)

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Hey might as well. I'd check the valve seating while you're in there. Put plugs in the head, flip over and fill combustion chambers with mineral spirits. Let sit for a day and see if any leaks out. If it does, valves need lapped. Cheap easy job.

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  • 3 months later...

Well the kid got the bike running...... Cost wise it was better to replace the engine than buy all the parts to rebuild it. Ecspecially since i was able to pick up a 99 250 engine with all the electronics and radiator for $175. So at the moment we have under $500 in the whole build. Now for paint........ :p. hes decided to go green motor and green exhaust (mufflers) with the body flat black with old skool green/white pin stripes. There are some cool head lights so its goin street fighter. Should be a cool little bike

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