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96 250 rebuild part 2... PIC HEAVY

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So I decided now was as good a time as any to build this motor up so it will run the way its supposed to. Ive dropped a crap load of money into this thing already, since Im in so deep I figured I might as well go all the way with it.

Now its time to send it off to Mr Gorr for some modding. Got the motor pulled, suspension on its way to FC and a spare set of forks on the way. Found a guy parting out a 98 Yz 250 so I grabbed the cylinder, head, rad valve, air box, and carb off him for a steal... paid 300 for all of it. Ordered a new piston kit, and full gasket and seal kit for the bike off egay, and ordered a jet kit from JD. Still waiting on the new black rims, spokes and red nipples to arrive, and when I get the current rims broken down my buddy is going to attempt to anodize the hubs red. He doesnt know if it will work because of the alloy they are made from, but if it wont he said he will just PC them for me at no additional cost. Started cleaning up the Noleen pipe that I will be running with this set up, which should really wake this motor up. Once I get the top end of this thing squared away it will be recieving a new hotrods crank, every bearing and seal will be replaced at the same time.

If anyone sees or notices anything in any of the pics (and there will be plenty more as I go) that needs attention or just have a suggestion about please let me know. I started on it and will probably work on it a little this week but its gonna be pretty much postponed until after the holidays. Gonna be a fun build for sure... Im hoping the new cylinder/ intake wont need any fab work to fit the 96 frame and motor but I believe they are identical.

And now for what you guys really wanna see.... THE PICS.:bonk:

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Starting canvas:

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Noleen... said to be the perfect pipe.

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One thing I noticed about this pipe is it seems quite a bit thicker than he FMF. Odd thing is that they weigh exactly the same when placed on the digital scale. Almost has the feel of a gnarly pipe as far as thickness of the sheet metal.

Who says mag. drain plugs dont work:

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Edited by ftball90

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that is some nastiness on that drain plug lol. the only thing i suggest is a new style tank lol.

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Next is the reed cage and petals... are these bad enough to hurt performance yet? Dont plan on running them any longer but Im gonna keep the 96 cylinder just incase so Im gonna hold onto the rad valve too.

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Cylinder... is worth getting this replated yet? Bore masurements are near perfect. Only off by .001.

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Head looks pretty good to me...

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that is some nastiness on that drain plug lol. the only thing i suggest is a new style tank lol.

Yea my clutch is pretty much shot... all but 3 of the plates and fibers measured out of spec.

Edited by ftball90

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Piston... has quite a bit of blow by for 25-26 hrs. I ride the bike hard, but I dont think I ride hard enough to create this much blow by. Anything abnormal for 26 hrs on this top end? One thing I noticed about this piston is it was extremely noisy compared to normal.

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Underside:

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took two without flash because the flash is decieving.

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what can you guys tell me about my jetting by looking at the plug and the piston. Seems like Im rich on one end and lean on the other??? Also IDK what those scuffs are from, not typical cold seize marks. At least none Ive seen.

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Thats all I got done today, other than pull the clutch but have to grab more batteries for the camera.

Anything you guys see that looks abnormal other than the fact that my jetting is whacked out, and the scuffs on the piston (which if anyone has any idea what those are from Id appreciate your input).

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Not sure if you remember my thread, but I had the similar scuffs on the corners. I looked at my old pistons, I think it's normal. Not sure about that one centered on the exhaust port. Maybe time for a replate.

That plug looks similar to mine when it comes out. I've always said I was going to mark how the plug was set in the head and see where those marks line up, but never have. I believe it's cleaned on that one side from the intake charge, but then the exhaust pulse coming back into the cylinder dirties up the other side. I'm not 100% on this, just a theory.

Jetting might be a tad lean for my taste, zero piston wash and a decent burn underneath, but no signs of detonation.

I think that cylinder looks dirty!!! hard to give much advice, clean it up and post some pics. If you've got a new cylinder already, I'd just keep that as a spare and get it replated later, use that cash to make it a sweet bike now!

I can't wait to see how those rims turn out. Did you end up going with the new style hubs?

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Great job,

The plug on the bike where I run a vortex ignition set up looks similar; one side grey one black and when putting the plug in with the head of the black part is the exhaust side so I figure it is kind of normal. The other bike with OEM CDI the plugs looks dark brown through and through. I run my bikes with the highest main I can use (sputter at 99% of throttle) The cylinder's head looks a tat browner and I got an even darker piston out each time. For me your piston shines like new. Pulling those pistons out at 50 hours they were almost entirely black, scary really. I went down to 40 hours now.

I figure that my using gear oil to oil the filter lets through some dirt and that could be the factor to blame for the scorching. With 40 hours the piston sports a 2cm ish dark brown-black rim; just below the ringland. The inside is dark brown. With 50 hours the inside of the piston is black with a brown rim the outside goes black over a third of the piston trailing out in brown.

When buying pistons I try to run D size pistons, OEM, Prox lite (lighter piston pin) and latest will be Woessner (forged piston in size D) So far I have not tried those. Hopefully this black and brown story doesn't confuse you :bonk:

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GMO... Yea the cylinder is dirty, I didnt wanna clean anything off so you guys could get a good idea of how everything came out of the bike. Ill post some pics of the cyinder cleaned up though. FWIW the cylinder was just replated when I got the bike last fall. Only 66 hours on this replate. I always put at least 120-160 hrs on a replate on my other Yz's which equates to 3 or 4 pistons (every winter durring the off season) the cylinder is replated. I still think that it had something to do with the piston, that was the noisiest piston I think Ive ever used. It was like that from day one. I inspected it very closely when I removed it to see if there was any stress cracks but there were none.

I didnt end up going with new hubs, I was going to but then backed out in fear of them not working out and losing a bunch of money. Plus at that time my buddy offered to do them for me, he can do it where he works, including spinning them on the lathe to get a polished finish.

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Great job,

The plug on the bike where I run a vortex ignition set up looks similar; one side grey one black and when putting the plug in with the head of the black part is the exhaust side so I figure it is kind of normal. The other bike with OEM CDI the plugs looks dark brown through and through. I run my bikes with the highest main I can use (sputter at 99% of throttle) The cylinder's head looks a tat browner and I got an even darker piston out each time. For me your piston shines like new. Pulling those pistons out at 50 hours they were almost entirely black, scary really. I went down to 40 hours now.

I figure that my using gear oil to oil the filter lets through some dirt and that could be the factor to blame for the scorching. With 40 hours the piston sports a 2cm ish dark brown-black rim; just below the ringland. The inside is dark brown. With 50 hours the inside of the piston is black with a brown rim the outside goes black over a third of the piston trailing out in brown.

When buying pistons I try to run D size pistons, OEM, Prox lite (lighter piston pin) and latest will be Woessner (forged piston in size D) So far I have not tried those. Hopefully this black and brown story doesn't confuse you :bonk:

No I get what you are saying... I usually run my pistons for 40 hrs. But since I wanted to replace reeds, bottom end bearings, shift shaft and rejet I figured I might as well replace it since I had to tear it apart. Glad Im not the only one with the plug problem, Ive never seen it before and was rather confused when I first saw it. Hopefully I can clean it up quite a bit with the JD kit.

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yea Im getting a JD jet kit. I guarentee I can clean it up with his kit. Ive had great results on all the bikes Ive purchased one for.

Be sure to write a review of the kit.

I can get pretty close with a bag of jets, but it's never ideal.

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JD had me buy a current (99-12) yz250 jet kit for my 97 and it worked well. As far as the exhaust port mark on the piston, make sure the powervalve is not touching it. Also, once your in this far, match the open powervalve to the exhaust port. Match it PERFECTLY in the fully open position. The top end power gain is huge. The metal is so soft that its really easy to hand file or emery cloth away the imperfections.

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