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1988 KTM Rebuild

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Hey guys,

I have been looking around for a winter project and was recently offered an older KTM 250 2 stroke project bike for less than $200. I figured what the hell, I basically have til June of next year so I went ahead and picked it up. The condition of the bike wasn't too terrible, and just about all the parts were there except for it needing a new front fender and left side plastic. The guy I bought it off of said it just needed new rings.

I got it home and started tearing into it. It was obvious to me that the bike had been sitting a good while so I'm figuring on just completely tearing the bike down and giving it a good cleaning, replacing the piston/rings, and seeing what else it needs.

From what I was able to gather after getting the jug off and looking at the bike:

1. The bike is actually a 240 instead of a 250. My measurements with a set of calipers read ~66.4mm instead of the 67.4mm that the 250 is. The cylinder is about immaculate and the piston isn't bad at all either.

2. Connecting rod bearing is good, no play up and down. Negligible wobble.

3. This bike sat for a LONG time. Lots of old stiff hoses and coolant in the lines.

4. The swing arm bolt is stuck...I mean...STUCK. We couldn't get it out on our own so I guess we're going to have to bring out the big guns. We thought about using an air chisel with a pencil bit to hopefully knock it out. If that doesn't work probably cut it where the frame meets the block, and press the pieces out.

5. Bike needs the pressure rod for the rear brake. Front brakes work awesome.

I did do a little research into the availability of parts (before buying) and found that André Horvath has a website that comes recommended for older KTM parts, well, as far as I can tell. I sent him a few emails with questions and so far they seem to be pretty quick to respond knowledgeable about the parts they're selling. Has anybody had any experience dealing with them?

I'm actually questioning the exact year of this bike at the moment. Unfortunately the manufacturer's tag on the frame doesn't show the year or such anymore, they seem to have faded off.

I'll get some of the pictures I have up tonight, I'm in college so I'm only able to work on the bike on the weekends, but I thought you guys would like to share in the experience.

So for now, does anyone have any experience with these bikes? Reliability? How do they ride/handle on the trails?

Edited by Milanak

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Sorry guys kinda slow getting back to this. School's been hell this week so far.

Yeah, I've been checking on ebay and found a lot of good used parts. Anyone know where I could get engine bearings?

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might be able to get them from ktm. simple phone call should get a answer. or write down the bearing numbers and check skf website or talk with a bearing house. bearings and seals are the least of your concearns when rebuilding a old bike

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Ok, finally got around to getting some pictures uploaded. More to come once I get back from class tonight.

Here's the bike once I got it home and took all the plastics off (excluding the busted front fender). Bars already have been replaced along with the clutch lever. Going to hope those rads hold coolant. There was some in the lines so I hope they do. Will test that next time I get to work on the bike.

111009_005.jpg

And here's the cylinder once I got it off and cleaned up. Poor bike was a mess. Seems it never really got cleaned.

111012_011.jpg

Once I get that swingarm bolt out I'll have to check out the bearings...might as well replace them while I'm in there right? And with regards to parts, for the most part it doesn't seem like I'll have a lot of issue finding them used, and I can get a good bit of parts new from Europe save some small miscellaneous stuff.

I guess we'll see what I can and cannot get when I find out what it actually needs.

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From the pic, it looks as though they got more than their money's worth out of that back tire... it looks like a drag racing slick... :thumbsup:

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Yeah its rough, but not THAT rough. :ride:

But yeah, it's a winter project, and I know I'll never get back what I put into it. It's more of a learning experience for me I guess, I've helped rebuild a couple Hondas before but never a KTM, or on my own.

I'm pretty excited to get into it, but I'm staying on campus this weekend. :thumbsup:

It's going to drive me nuts knowing I can't work on it.

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Yeah I've ridden my fair share of newer Honda bikes. 125s and 250s alike. Wondering how this will compare to them.

Got a question though. This bike was missing the part that connects the rear brake lever to the brake cylinder. Is this just going to be called the pressure rod? or something similar? I've been having troubles finding this part on its own. Might have to buy a used brake lever with it already attached.

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that rod may of been the same on may different models and years but i cant say for sure. do alittle investigative work. start with checking part numbers and go from there. just a guess but this might work. cross reference the part numbers to be sure

http://www.ebay.com/itm/1989-KTM-500-D-XC-REAR-BRAKE-LEVER-250-125-350-EXC-SX-/350396162902?pt=Motorcycles_Parts_Accessories&vxp=mtr&hash=item51953d2356

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Alright guys small update on what got done last weekend (hopefully I can get a ride home tomorrow to do some more):

Tried to remove the swing arm again. We tried beating it out with a hammer/punch, air-chisel, anything. We worked it back and forth, soaked it with penetrating oil. Nothing. It will move out about 1/4 inch then bind up. After about four hours of this I said the hell with it and started to cut it out. It seems I can easily get to all four of the places I would need to cut it. Got one part cut, burnt the blade up (no oil), and we couldn't find any other blades. So that's hopefully going to get finished this weekend so I can pull the engine/press out the leftover pieces of the swing arm bolt. I got a newer used bolt I'm going to polish up and use. Also going to have to order in some new bearings/bushings.

Pulled the stator side cover off. It's real dirty, I wish I took a picture to show you guys. What can cause corrosion in there? Water? Bad seal?

Pulled the clutch side off and all was good, still oily and all that. Didn't notice any problems in there that would cause binding so I'm thinking one of the crank bearings went (hopefully).

Probably going to need to replace the rear wheel bearings. A lot of play going on back there.

If the piston looks ok, do you think I should just re-ring it? Honestly it doesn't look too bad. When/if I get to work on it this weekend I'll take a ton of pictures for you guys to look at it.

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Here's a little picture of the clutch side. Sorry for the quality, my phone takes horrible pictures when the lighting isn't great.

111028_022.jpg

And a picture with the cylinder off when I first got it. As I said the thing was/is a mess.

111009_007.jpg

Also: Wanna mention about the piston. It looks like theres a lot of scoring on there, but it just seems to me like an oily residue.

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just some advice if your planing to take the motor completely apart. you want to loosen the crank gear nut, clutch hub nut and flywheel nut before removing the motor from the frame. makes it alot easier. motion pro has a wedge tool that goes between the gears of the crank gear, also motion pro tool for holding the clutch hub. might be able to undo the flywheel nut with a impact gun (make damn sure your turning the nut the correct way or you could damage the crank snout threads then youll really be fudged, actually i never use a impact on a dirt bike but you can use one with extreme caution) or use the motion pro tool to hold the front sprocket while you take the flywheel nut off or put the chain on and put a long bar between the rear sprocket to hold everything, then you need flywheel puller tool to get it off the crank. pain in the ballz to get them nuts off if the motor is out of the frame. do not break the clutch hub or any other parts for that matter. could get expensive and hard to find replacements. try to find a free manual online if you can. want to put everything back together with correct torque specs

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forgot to mention but after you take off the crank gear nut the crank gear may not just slide off. if it dont, there might be 2 threaded holes in the gear to use a some bolts and a puller. if you dont understand what im saying, the manual should show you how. do not beat it off with a hammer. and if the clutch hub is original and never taken off before it may have loctite on the splines from the factory. cant remember how i got mine off, some kind of puller i think. just look and you should see how to remove it.

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Yeah I have the clutch hub holder along with the flywheel puller, both tools I've used before. Usually for me it's easier to take the engine apart than it is to put it all back together. Do you think loosing everything attached to the crank would help? I figured if the air chisel/hammer whatever you wanna call it wouldn't get it out, nothing would. And honestly I am afraid that applying anymore force to it is going to break something where the bolt goes through the case, hence why we started cutting it out.

Really the only thing hanging me up is that swingarm bolt.

And yes, I've basically already decided just to get the whole piston kit, just didn't want anyone to start flipping saying the cylinder is ruined because of how the piston looks in the pictures. Just a shame it's going to cost me about $225 at a minimum to get it from Austria.

So yeah, I won't be around the bike this weekend (I think). Hopefully I'll try to get a buddy of mine to get some pictures for you guys anyway.

Also, I'm going to do some research tonight and try to find a manual to help with putting the engine back together...my real main issue is those mystery washers that seem to appear out of no where at times. I'll keep you guys updated!

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So I found out that I would be able to get a 1988-1989 engine service manual online for $24.95 shipped. I sent them an email just to make sure it's not all in German. Going to keep searching for a free one online until they get back to me and I make my decision.

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i believe this is the manual you want #20137 http://www.repairmanual.com/category/1988-ktm-250mxc/

seen people have to cut the swingarm bolt. take it slow and dont cut the frame or engine. might take a while but eventually youll get it out. loosening anything attached to the engine wont help. leave the engine together until you get the swingarm bolt dealt with.

might not hurt to have book #320278 also. well worth $1.69. basically its like a book microfish. shows all your parts and how they go together so you dont get washers etc in the wrong spot

all your older ktm manuals are printed in both languages. the manuals i have are austrian on the left side of the page and english on the right side. most likely yours will be the same.

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Yes thats actually the exact website & manual. They confirmed along with you that it was in English, so I'll get that along with the microfiche. Kinda bummed I won't be home to work on it this weekend but such is the life of a college student.

Going to look into some new tires also!

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Alright guys. Manual & microfiche hopefully shall be here this week. Gonna be home early on Friday so I can start ripping into it again.

What's everyone's opinion on painting an engine? I guess I should say, what brand of paint should I use? I know about using high temp., should I just go with a basic engine enamel?

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