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Is this stock 1996 yz250


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I dont know much of the history because previous owner bought it with these parts not sure what I have here but heres what I can see so far: FMF gold series pipe, pro circuit silencer, oversized fuel tank, rad valves and a stator cover that says boyesen, what is the purpose of the cover? and the biggest question is what is this spacer between the case and cylinder in the picture I do not see it in the parts catalog

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...what is this spacer between the case and cylinder in the picture I do not see it in the parts catalog
The spacer most likely means the motor has a long-rod kit, which was a real popular mod for the '96 (and maybe '97?). Nice! 👍

I think the spacer is supposed to be 4mm thick.

Or it could be just a spacer to change the port timing.🤣

http://www.surfnturfracing.com/customyz.htm

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That does look like the long rod kit. The spacer looks the perfect height! Nice going.

Remember, this was just a longer rod....not an actually change of stroke. If you think abotu it, the rod coudl be a mile long, yet only move up and down as far as the crank allowed it to. For whatever reason, this was very effective on this bike. Its a pretty hardcore mod for the bike as it would require a crank rebuild. Anyone going that far would do other hop ups as well. How does it run?

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It runs great lots of power, so if the length of the rod is extended and a spacer is needed for height of the cylinder would this affect the power valve arm i will go out later today and take a few pics of the bike

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...if the length of the rod is extended and a spacer is needed for height of the cylinder would this affect the power valve arm...
The long-rod kit included longer power valve linkage and linkage cover (I think the cover was from a 1988?).
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The long-rod kit included longer power valve linkage and linkage cover (I think the cover was from a 1988?).

I think it was from an 88. And the cover did not match perfectly. I think one of the bolt holes was off by a slight amount.

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The long-rod kit included longer power valve linkage and linkage cover (I think the cover was from a 1988?).

Correct, the 88 style power valve linkage is 4mm longer.

Was a great mod for that square displacement engine.

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here are a few pics I could get of the powervalve housing with the exhaust still on anyone able to tell if it is a differant housing, my biggest concern is if I ever have to replace the crank, rod, cylinder, head, bearings, powervalve components what parts I would have to get

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I can't see by the picture but if the lower bolt is missing it probably is the long rod kit,

if and when you go to rebuild it make sure you get an 88-89 connecting rod.

the stage 3 , yamaha long rod kit contained a spacer plate,130mm connecting rod,88-89 powervalve actuating rod,88-89 powervalve rod cover, longer studs and dowel pins for the cylinder.also came with a boyesen rad valve and a pro circuit pipe built for yamaha #yzr 4sr93 . I believe the pipe was nothing more than a regular P.C. pipe, just stamped with a yamaha part #. so it looks like someone did there homework and built it from available parts which I believe was a lot cheaper than buying the "kit"

The boyesen stator cover supposedly helped the clutch feel because it held the cable more securely and looking at how much flex I have in my cable especially after I spaced out the stock cover for a flywheel weight I believe it.

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I can't see by the picture but if the lower bolt is missing it probably is the long rod kit,

if and when you go to rebuild it make sure you get an 88-89 connecting rod.

the stage 3 , yamaha long rod kit contained a spacer plate,130mm connecting rod,88-89 powervalve actuating rod,88-89 powervalve rod cover, longer studs and dowel pins for the cylinder.also came with a boyesen rad valve and a pro circuit pipe built for yamaha #yzr 4sr93 . I believe the pipe was nothing more than a regular P.C. pipe, just stamped with a yamaha part #. so it looks like someone did there homework and built it from available parts which I believe was a lot cheaper than buying the "kit"

The boyesen stator cover supposedly helped the clutch feel because it held the cable more securely and looking at how much flex I have in my cable especially after I spaced out the stock cover for a flywheel weight I believe it.[/quote

Yes it is missing the lower right bolt you can barely see it in the pic just looks like a dark spot

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I can't see by the picture but if the lower bolt is missing it probably is the long rod kit,

if and when you go to rebuild it make sure you get an 88-89 connecting rod.

the stage 3 , yamaha long rod kit contained a spacer plate,130mm connecting rod,88-89 powervalve actuating rod,88-89 powervalve rod cover, longer studs and dowel pins for the cylinder.also came with a boyesen rad valve and a pro circuit pipe built for yamaha #yzr 4sr93 . I believe the pipe was nothing more than a regular P.C. pipe, just stamped with a yamaha part #. so it looks like someone did there homework and built it from available parts which I believe was a lot cheaper than buying the "kit"

The boyesen stator cover supposedly helped the clutch feel because it held the cable more securely and looking at how much flex I have in my cable especially after I spaced out the stock cover for a flywheel weight I believe it.[/quote

Yes it is missing the lower right bolt you can barely see it in the pic just looks like a dark spot

I did not remember the clutch cover until you mentioned it, but that is 100% correct.The boyesen clutch cover was a HUGE improvement with clutch pull. Especially after adding a 1/4" plastic spacer next to the mount to take up space in the too long cable .

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some thing that might help sorry couldn't scan so I just took pictures

j1i2m3_album

http://s1047.photobucket.com/albums/b471/j1i2m3_album/

you might want to copy those directions and keep them with your service manual.

I really can't tell you what the long rod kit feels like compared to stock, I had 94 yz's and WRs.. and this particular set up is with a 96 cylinder that I hogged out the exhaust subports. This bike was built from a lot of spare parts I had that I threw together and I have no real time on the bike or any testing/jetting. all I know is that it is a lot smoother than a stock 94 or any of my homemade modified 94 cylinders, deceptively fast / and revs to the moon to the point I don't think I have enough carburator for it. the engine will produces power with, hard to explain ,no sign off or overrev lack of power it just kinda hits an rpm ceiling while still being in the upper end of power. you can feel the power there just won't rev no further.

Edited by jsantapau
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heh just reread the instructions and a couple of things I remember that was funny, stage 1 pipe and silencer, stage 2 was the pipe, silencer, and spacer plate, stage 3 was pipe ,silencer,spacer plate, longrod etc etc.

so stage 2 was a 5mm spacer with no long rod? man that must of been some serious port timing and lack of compression.

also ignition timing one page states 0.0mm or 7degrees btdc @8600rpm with a timing light and another page states0.8mm btdc

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That is awesome man is that the actual instructions for the 96? I was just checking on replacement parts and was told the power valve arm for a 88-89 was discontinued however not sure if I will keep the bike or sell it for something newer if i kept it i would have to get rid of that oversized tank if i could find one cheap or someone to trade with, here are pics of the full bike.

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yes the arm is discontinued, but I have never seen one break and I always see an inner clutch cover case on fleabay that has the arm in it in case you ever needed one. Or you can take the 1990 to 97? arm and splice weld a section in.

According to Eric Gorr's Performance Handbook, the 89 yz250 was prone connecting rod failure when they started getting to the end of their service limit. I gather that is why Yamaha went to a 125mm length connecting rod in 1990. So it is with a grain of salt you should accept an old design "problem" with the "newer" hipo parts.

nice bike, if you like it keep it and just keep it fresh, most parts that are needed are readily available stock or aftermarket,brakes,pistons,connecting rods,bearings and such.My opinion is that it is a good solid built bike and if the connecting rod is an issue it should be easily noticable upon close scrutiny when you to a top end. Even if the bike is old and worn out you can smile, since you can rebuild it top to bottom cheaper than a valve job on a titanium valved 4stroke.

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yes the arm is discontinued, but I have never seen one break...

Or you can take the 1990 to 97? arm and splice weld a section in.

This is what MCR did when they built up a long-rod kit for my '96. 👍
According to Eric Gorr's Performance Handbook, the 89 yz250 was prone connecting rod failure when they started getting to the end of their service limit.
Hot Rods® offers a replacement connecting rod if you ever need one, and I imagine it is a stronger design as well.

http://shop.thumpertalk.com/catalogs/Tucker_Rocky_Offroad_2009/default.asp?p=461

nice bike, if you like it keep it and just keep it fresh, most parts that are needed are readily available stock or aftermarket...
Nice bike indeed. All the stock parts look real good.

The stock navy blue seat and tank tend to get darker as they age. You can 'brightened-up' your '96 with the royal blue tank, shrouds, and seat from the '98-'01 bikes.

yz2505.jpg

Then you can re-installed the stock pieces when it comes time to sell the bike.

1996YZ2501.jpg

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