2003 Honda CR 250 - engine seizure

I've had this bike for about a year now, the previous owner had just put a new piston in the bike prior to my purchase. No more than 25 hours on the top end, but I'm not sure about the bottom end.

My friend was riding this bike when it just slowly died. He kicked it over many times without it starting (20 +). When he brought it back to me, I removed the spark plug and attempted to kick it over and check for spark. After 2 or 3 kicks, the kick starter seized.

I figured it was the piston, but upon removal of the cylinder, it became obvious that it was something in the lower end. I managed to break the crank free with a ratchet. It took quite a bit of force, at first it rotated with some hesitation but now it rotates smoothly.

I will post some pictures if necessary. This is my first engine seizure on the bike, and also the first time I'm attempting to do all the required repair work myself. I'd also like to know what to check for to ensure this doesn't happen again.

I've always mixed premium fuel at 32:1 with good oil, my air filter gets changed ever 3 hours. The flywheel shows no signs of a crank seal air leak. I'm thinking the crank bearings just finally wore out naturally.

The only two other issues that could have been hard on the engine were running it out of gas (accidentally forgot to open the fuel valve) and there was some 'popping' on closed throttle deceleration because my idle was set high. From what I understand however, this isn't detonation but rather fuel igniting in the pipe.

I'd love some advice, and I'm also not sure what parts to buy to rebuild the motor. I was set on the Hot Rod bottom end kit and a Wiseco piston kit. Now I'm not sure about the Hot Rod crank, seems that people have lots of problems. Should I have the cylinder checked out by a mechanic? Opinions on stuff like that would be great, like I said, this is my first serious bike problem!

upon dissasembly was the piston broken? what did it look like? the 03 cr250 have a poor intake seal and require some modification. take a look around the web for a updated sealing kit for youre bike. make sure youre piston has lubrication holes drilled for the exaust bridge. if it was bound up in the bottom end youre likly going to need to do some smoothing/polishing to the case as you probably gouged it. with out seeing it and only going by youre description it sounds like a heat seizure to the bearing. check the bearing surfaces for black or blue streaks. if youre feeling adventurouse and really want to find the cause cut the old bearing in half and check all the internal bearing for blue black spots/ streaks that will indicate a heat seized bearing.

1. if youre doing this rebuild on a budget get the kit below and polish youre case on the inside wear you made the gouge. when you install the crank bearing put them in the freezer for 24hrs. heat the case only wear the bearings are going to be installed carefully with a propane torch and drop them in straight out of the freezer. the temp difference will make life alot easyer and negate the need for bearing presses. DO NOT hit the bearings in with a hammer. with the above method they should drop right in. if u have to convince them to fit use a rubber mallet and be gentle.

2. if youre not on a budget send the case and top end without the piston/ crank assembly to pro circuit. have them do a case match and port an port polish squish mod on youre top end. the result is a much crisper more reliable engine. " knowing it was done 100% correctly" and with some improvements over the stock configuation. make sure you drill the new piston precisely for the lubrication holes for the exaust bridge.

if you can get the wiseco bottom end i have had better luck with them compared to the hot rods. but both are a decent product. " assuming you get the new wiseco bottom end as the old ones had a bearing tolerance issue and are prone to early failure. " = new wiseco bottom end kits are sometimes hard to find= and tend to be out of stock. i waited 6 weeks for mine.

PS: running it out of gas also runs it out of lubrication. if you did this and rolled for any amount of distance or did this on numerouse occassions it only deducts the life span of youre internal parts.


Edited by 03cr250works

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