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2001 cr250 tear down & top end rebuild. (lots of pics)

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Hello everyone. Winter is coming and I have a few months off from racing, so it is time for maintenance on the bike. I am the second owner of the bike, and I have put 90 hours on it over the last 2 seasons, previous owner about 20. I race hare scrambles in New England, so this is a moto bike turned woods bike. Here is what I have planned. Grease all the suspension bearings, stiffer fork springs, re-valve the shock, and re-lace a crf250x rear wheel so I will have an 18" rim. I also will be doing the top end, since it is the original honda piston with over 100 hours on it. It tested at 145 psi compression cold, so it was definitely time. I also took the right side cover off to fix a pretty good crack I found after a race. Bent the skid plate wing into the cover after hitting what I assume was a rock. It was a rough, muddy season so the bikes took a lot of abuse!

After taking the engine apart, everything looked to be in very good condition. It will be getting new piston, rings, gaskets, clean the power-valve (there's a lot of sludge in there). I've taken a few pictures along the way, if anyone has any questions about this feel free to ask. I have a couple questions for the CR gurus...

1) what is best to clean powervalve? gas, carb cleaner?

2) The ring gear on the back of the clutch basket has some play. maybe 1/8 inch rotational play. I know there are cushions back there, but should the be free play too? I can post video of what I mean if needed.

3) I'm going with a wiseco piston. Should I get the wiseco top end kit w/ gaskets, or just piston and use OEM gaskets?

Thanks for reading and hopefully the pictures can help someone else out.

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pile of parts growing

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here is the crack in the side cover. grinding was from removing the quicky jb weld job. Going to attempt to have it tig welded, not sure if you can weld that cast alum.

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crf250x wheel, not bad just needs new set of spokes.

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Edited by nate1590
wanted to say lots of pictures in title

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Ghetto clutch holding tool, just riveted together and used a sheet of brass to stop crank from turning. cheap but effective.

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engine out of the cradle

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head when I took it off

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top of piston

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stock piston after takign the jug off. Cylinder fought me hard, the dowels were corroded so it came off hard after being bolted on for ten years. rubber malet and some patience did the trick.

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inside of the cylinder. Ring gap was .023, so not quite out of spec but on their way.

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Powervalve all gooed up. Still works smooth, just a little slow to return.

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Head after a good cleaning. I think I can get the rest of the carbon off.

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Again if anyone has any questions about the procedure feel free to ask, I hope this will be a helpful thread!

Edited by nate1590
double picture

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1) IMO i like seafoam in a can then let it sit, if its really really bad aircraft paint remover and a paint brush

2) your rivets came loose and your cushions are worn out, get a new basket you'll be glad you did

3) i like OEM gaskets the best, if you want to be creative eric gorr talks about using different thickness's kn the base gaskets to change the power slightly, if you are a woods ridder there is a mod you can do to the boyssen ports to boost low to mid response ( i did this its not to hard and very easy to do just take your time ) there is a picture in his book of what you need to do

the 92-01 right side case cover will fir you can get them off ebay from $50-$85 id go that rout

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Berryman's B-12 Chemtool is an effective carbon eater too.

yup ! forgot about that:bonk: .... might try that before paint remover .... paint remover is for worst case scenario

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I haven't tried it myself, but I read somewhere that common oven-cleaner (easy-off) works well. And you may already have some laying around....

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I believe I can tell you what to expect when attempting to weld aluminum. Contrary to popular belief, Aluminum is very easy to weld if you follow the basics.

It most be extremely clean throughout - even inside a crack

Preheat the area with the tig torch just prior to laying the bead and this will also give you an idea how clean the surface is. = The surface will turn white if clean!

It most be free of any oxygen and contaminants when welding, and that's the problem when attempting to weld cast. cast aluminum is full of air pockets, so even thou a welder uses argon to displace the oxygen the little air pockets open up and the contamination rises to the surface and you end up with a big blob of contaminated mess. a good experienced aluminum welder could get it to stick but I personally would not be satisfied or trust the results.

There may be another procedure for a solid repair but I would not recommend welding

personally, I would look for a replacement

Edited by gitenold

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Plus, welding a casting like that will end up warping it a bit. Whether or not the gasket would compensate for the amount of warpage is something you'd need to tell us if it leaked afterwards.

OEM gaskets are always a safe bet and aren't too expensive.

The clutch basket cushions are available separately from Hinson but you have to drill or grind the old rivets off to replace them. Get a hard coated basket (Hinson or Moose) and replace the cushions when you install it. Check the inner hub friction surface for wear- same with the pressure plate friction surface. They can wear enough over the years to almost be the same as leaving a clutch plate out. Speaking of... I'd suggest all steel driven plates with either K&G or OEM fiber plates with stock springs.

When reassembling the top end, adjust the power valve linkage so there is no slop/free play with the valve in the rest position. It'll open completely, you want to insure it closes all the way when adjusting the pinch bolt. You may have to put a little preload on the spring to take out all the play in the linkage.

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I can get a used side cover for $40 or $60, i agree I would rather have a solid piece than on that has been welded. I had replaced the clutch plates and drive plates with an ebc kit with the steel plates about 5 hours ago, but didn't fix the basket because it was still race season. I like the look of the Hinson kit WPP3009, it comes with cushions and hardware, just need to switch the gear over. I am going to order a Wiseco piston and oem gaskets today. Hoping to pull the PV apart and clean it up this weekend. Thank you for the replies.

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its one metal and one fiber, riveted together to make it a solid unit. make sure to line it up in the clutch basket before drilling and riveting or the splines wont line up. Then use a piece of brass and jam the main gear and clutch basket gear to stop it from turning, and torque the clutch nut to 59 ft-lbs.

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I can get a used side cover for $40 or $60, i agree I would rather have a solid piece than on that has been welded. I had replaced the clutch plates and drive plates with an ebc kit with the steel plates about 5 hours ago, but didn't fix the basket because it was still race season. I like the look of the Hinson kit WPP3009, it comes with cushions and hardware, just need to switch the gear over. I am going to order a Wiseco piston and oem gaskets today. Hoping to pull the PV apart and clean it up this weekend. Thank you for the replies.

Dont forget to measure the ring end gap...

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to take the nut off you can use an air wrench, it will snap it off without anything holding it. to torque it is where I used this tool, and its 60 ftlbs so its not putting a ton of force with this tool since the loads on the whole basket and hub

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i need to do this tool. iv broke an in-good shape hub just coz i used the clutch tool similar that you buy at RM.

you probably had the angle of the arms wrong. I did the same thing and had to replace it. now I spend like a good 60 secs getting the clutch tool on there perfect.

I agree though that this is a case where the homemade tool is better than the aftermarket one. I saw someone do the same thing but he also welded a handle on it. thing looked bitchin.

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I have a question about clutch basket interchangeability. I found one on ebay listed for an 04 crf450, new in box oem basket, but the part number on the box is actually for a crf250. I know 02-07 crf450 baskets will fit my bike, but what about crf250 baskets? The auction ends in 2 days I'm hoping to snag it if it fits.

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Also have an original 01' cr250r what has never been apart. What is a good compression ratio and what is borderline? What kind of two stroke oil did you run?

Edited by greg-15
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I was told by my local shop when compression gets to 160 psi cold, its time to think about doing the top end. I have always run belray H1R at 40:1 with 93 octane pump gas. Stock jetting so its on the rich side.

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