1996 yz250

aiden
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aiden
Edited Date/Time 12/2/2021 8:07pm
Hello i have a 1996 yz250 the "tenth on the vin is a T" and the cylinder is bad i need to send it out to get redone. But i think the cylinder may be A 98... if so could this be a problem?. The power valves were getting hit by the piston in the previous setup and came very loose obviously. I just got the bike i dont know what to do here.


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sandman768
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sandman768 11/28/2021 11:44am
11/28/2021 11:44am Edited Date/Time 11/28/2021 11:48am
Powervalve parts likely worn out, causing over rotation of the drum into the piston. Show photos of the center drum left side end where it meets the cap/ stopper, if they are both showing wear, the drum over rotates…Pretty sure the 96-98 cylinders are interchangeable, may have slightly different porting but will still work. You will also want to surface those cases where the cylinder sits to remove the digs/ screwdriver marks, they will cause air leaks if not surfaced.
aiden
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aiden 11/28/2021 12:08pm
11/28/2021 12:08pm
Im saying Like the bottom of the cylinder ports dont match with the bottom end?
aiden
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aiden 11/28/2021 12:13pm
11/28/2021 12:13pm
sandman768 wrote:
Powervalve parts likely worn out, causing over rotation of the drum into the piston. Show photos of the center drum left side end where it meets...
Powervalve parts likely worn out, causing over rotation of the drum into the piston. Show photos of the center drum left side end where it meets the cap/ stopper, if they are both showing wear, the drum over rotates…Pretty sure the 96-98 cylinders are interchangeable, may have slightly different porting but will still work. You will also want to surface those cases where the cylinder sits to remove the digs/ screwdriver marks, they will cause air leaks if not surfaced.


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aiden
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aiden 12/1/2021 10:30am
12/1/2021 10:30am
450exc115 wrote:
Could be a 97 or 98 cylinder. There is a sleeved with PV 96 cylinder on ebay right now for about the price to get yours...
Could be a 97 or 98 cylinder.

There is a sleeved with PV 96 cylinder on ebay right now for about the price to get yours fixed.

[url=https://www.ebay.com/itm/363611177388?epid=1129575178&hash=item54a8ea41…]
Well my question then is can i get another 97 or 98 with the different bolt pattern so i dont need to get a new exaust and reed or do they not work right
450exc115
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450exc115 12/1/2021 11:12am
12/1/2021 11:12am
The 98 cylinder has the same reed valve and bolt pattern as the 99+ motors but it is different from the 94-97 reed valve pattern. If you switched to a 96 cylinder you would have to get a reed valve and intake boot. The exhaust should be fine as both were female spigots on the cylinders.

That said I've done this to a suzuki when swapping cylinders but if you get the 98 YZ250 base gasket and overlay it on 96 bottom end you might be able to remove material and take advantage of the boost ports on the 98 cylinder.

Personally if it was my motor I'd buy the ebay top end and grab a reed valve assembly for it.

When Jeremy McGrath raced the 98 YZ in supercross he actually used a 94 top end that PC ported for SX. When I talked with PC about doing this to my 98 engine they said the gains were really for bottom to mid range (needed in sx) but the 98 stock cylinder was better for outdoor MX as it had more mid top power. Jeremy was going to run the 99 YZ in outdoors but got hurt and then just had SX contracts after that.
aiden
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aiden 12/1/2021 12:00pm
12/1/2021 12:00pm
450exc115 wrote:
The 98 cylinder has the same reed valve and bolt pattern as the 99+ motors but it is different from the 94-97 reed valve pattern. If...
The 98 cylinder has the same reed valve and bolt pattern as the 99+ motors but it is different from the 94-97 reed valve pattern. If you switched to a 96 cylinder you would have to get a reed valve and intake boot. The exhaust should be fine as both were female spigots on the cylinders.

That said I've done this to a suzuki when swapping cylinders but if you get the 98 YZ250 base gasket and overlay it on 96 bottom end you might be able to remove material and take advantage of the boost ports on the 98 cylinder.

Personally if it was my motor I'd buy the ebay top end and grab a reed valve assembly for it.

When Jeremy McGrath raced the 98 YZ in supercross he actually used a 94 top end that PC ported for SX. When I talked with PC about doing this to my 98 engine they said the gains were really for bottom to mid range (needed in sx) but the 98 stock cylinder was better for outdoor MX as it had more mid top power. Jeremy was going to run the 99 YZ in outdoors but got hurt and then just had SX contracts after that.
I think id need a other pipe because my cylinders exaust port goes out... but the 98 or 97 cylinder that came with it does have different ports on the bottom where it mounts to the bottom end it doesnt line up like a 96 would. I dont even know what those ports are for i was thinking because they dont line up the engine could over heat and blow up...
450exc115
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450exc115 12/1/2021 12:50pm
12/1/2021 12:50pm
Then it isn't the 95-98 cylinder. Those were all female. Maybe it's a 94? What does the sides of it look like. The 95-98 have a big resonance chamber on the left side of the cylinder.

The ports are boost ports that help feed the bottom end during the intake stroke. It won't blow up if those are blocked it just won't get as much fuel and air as it could with those open. That said you might be able to remove material from the crank case to open those up, it all depends how the gaskets lay out over the crankcase. From the pictures it looks like you could do it.

So that said you either have to fix that cylinder and keep everything the same or get the right cylinder 95/96 and get a pipe to go with it.
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aiden 12/1/2021 1:55pm
12/1/2021 1:55pm
450exc115 wrote:
Then it isn't the 95-98 cylinder. Those were all female. Maybe it's a 94? What does the sides of it look like. The 95-98 have a...
Then it isn't the 95-98 cylinder. Those were all female. Maybe it's a 94? What does the sides of it look like. The 95-98 have a big resonance chamber on the left side of the cylinder.

The ports are boost ports that help feed the bottom end during the intake stroke. It won't blow up if those are blocked it just won't get as much fuel and air as it could with those open. That said you might be able to remove material from the crank case to open those up, it all depends how the gaskets lay out over the crankcase. From the pictures it looks like you could do it.

So that said you either have to fix that cylinder and keep everything the same or get the right cylinder 95/96 and get a pipe to go with it.
Oh i thought those holes in the bottom end were for coolant thats interesting to know ill send a better pic of the cylinder
aiden
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aiden 12/1/2021 2:07pm
12/1/2021 2:07pm
It is female
450exc115
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450exc115 12/1/2021 5:42pm
12/1/2021 5:42pm
4XL10 is a 98 cylinder.

I'd buy the eBay cylinder and find a used reed valve and intake boot and go from there. That will be cheaper than fixing that 98 cylinder.
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aiden 12/1/2021 7:42pm
12/1/2021 7:42pm
450exc115 wrote:
4XL10 is a 98 cylinder. I'd buy the eBay cylinder and find a used reed valve and intake boot and go from there. That will be...
4XL10 is a 98 cylinder.

I'd buy the eBay cylinder and find a used reed valve and intake boot and go from there. That will be cheaper than fixing that 98 cylinder.
Cool thank you!
aiden
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aiden 12/1/2021 7:53pm
12/1/2021 7:53pm
450exc115 wrote:
4XL10 is a 98 cylinder. I'd buy the eBay cylinder and find a used reed valve and intake boot and go from there. That will be...
4XL10 is a 98 cylinder.

I'd buy the eBay cylinder and find a used reed valve and intake boot and go from there. That will be cheaper than fixing that 98 cylinder.
aiden wrote:
Cool thank you!
Are the head and covers the same?
450exc115
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450exc115 12/1/2021 8:02pm
12/1/2021 8:02pm
Yes they should work fine. There should be a number on the head just like the cylinder. 4XL will be a 98 head. I
aiden
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aiden 12/1/2021 10:21pm
12/1/2021 10:21pm
450exc115 wrote:
Yes they should work fine. There should be a number on the head just like the cylinder. 4XL will be a 98 head. I
Cool ill pick up that 96 sleeved cylinder hopefully the bore is good
aiden
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aiden 12/1/2021 11:07pm
12/1/2021 11:07pm
450exc115 wrote:
Yes they should work fine. There should be a number on the head just like the cylinder. 4XL will be a 98 head. I
Cool ill pick up that 96 sleeved cylinder hopefully the bore is good
aiden
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aiden 12/2/2021 8:07pm
12/2/2021 8:07pm
Im gonna try to rig that 98 reed box in there mabye drill new holes

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