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sandman768 sandman768
12/17/2017 12:30 PM

Out of my 96 Cr 250 I build 2 years ago. 12.0 hrs on top end. gearbox locked up, cracked left side case... Finally getting around to tearing into it. This is the piston....any thoughts? Cylinder has original plating, just stating to show some wear on the upper exhaust port, nothing showing on the piston exhaust side. Some funny carbon buildup on top of piston, looks like some of the head gasket material, gasket shows signs of coating coming off around the closest edge of top of cylinder. Bike was running great before the trans locked up...Photo

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sandman768 sandman768
12/17/2017 12:56 PM
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rmoto003 rmoto003
12/17/2017 1:02 PM

Cant read it, theres no words on it

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BobPA BobPA
12/17/2017 2:03 PM

Looks fine to me. A touch on the rich side if anything. Do you have a picture of the plug?

Tomac and/or Anderson for 2020.....

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Paw Paw 271 Paw Paw 271
12/17/2017 2:07 PM

The underside of the piston shows that the clutch side crank seal was starting to leak. Piston look pretty good.
Cylinder may need replating.

Paw Paw

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sandman768 sandman768
12/17/2017 2:26 PM
BobPA wrote:

Looks fine to me. A touch ...more

Thanks for your input, I will take a photo of the plug, not sure if the plug reading Will be accurate, I had to idle back to the pits after the gearbox issue. Photo

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sandman768 sandman768
12/17/2017 2:35 PM
Paw Paw 271 wrote:

The underside of the ...more

Thanks Paw Paw 271. I thought the underside looked pretty dark & oily...agree on the cylinder also, 1 little spot starting to chip, but can be felt with finger nail, only going to get worse...cases have to be split anyway due to a gearbox issue, so I will replace crank seals...have learned a lot on this site in the last 4-5 years, still learning how to read Pistons...thanks for your input...

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sandman768 sandman768
12/17/2017 2:49 PM

Photo of cracked case, curious as to what caused this. 12.0 hrs on the meter, after full rebuild of engine. I did notice when the bike was on a stand, spinning the rear wheel I would always hear a click or clink coming from the countershaft bearing, just assumed it was ok...Photo

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pete24 pete24
12/17/2017 4:59 PM

looks to me like a wiseco piston , nothing wrong with it if the clearance is rite which i think your to loose, the flaking on the piston top is carbon that lifted over time id say that thing sat for a while before you took it apart and the carbon lifteted off the piston if you disasembled it within a week of ridding it would just show a tad rich

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sandman768 sandman768
12/17/2017 7:18 PM
pete24 wrote:

looks to me like a wiseco ...more

That's pretty good Pete, 10 of the 12 hrs on this bike were put on when I finished the build back in 2015. Fogged it, drained carb & did not ride it at all in 2016. This past August I prepped it & took it to a local practice track, after about 1 hr something in the gearbox let go & cracked the case...so I drained the fluids & parked it until today. The bike was running excellent before the gearbox went, I just thought the piston had some funny markings on it. It is a wiseco 1 ring flat top racers choice...this engine is a full Tom Morgan spec engine. I think I may use a dual ring piston this next time around.

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David934 David934
12/20/2017 12:16 AM

Nothing wrong with piston, looks fine to me. But cracked case, feel bad for you Sandman... not easy repair or you can still get new OEM one?

18 Yamaha YZ450F
94 Honda CR 500
90 Honda CR 500
81 Yamaha SR 500
68 BSA Thunderbolt
69 Triumph Tiger 100

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sandman768 sandman768
12/21/2017 2:01 PM
David934 wrote:

Nothing wrong with piston, ...more

Oem cases are NLA....I bought a set of eBay cases that are in decent condition, had the left case dye glowed for cracks, came back good. Need to match cases and correct all surface imperfections from previous hackers, otherwise should be ok. What I"m concerned about is what caused the case to crack...a lot of the tranny parts are NLA...

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sandman768 sandman768
12/21/2017 2:04 PM
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40 40
12/22/2017 8:09 AM

Rich Roy should be able to weld that case for you. Text if you need his number.
Also, (believe it or not), JAF actually has a good TIG welder that they subcontract some work out to. He did a subframe for me last year that got gouged out from airbox and number plate rubbing. Came out terrific for not a lot of money. On par with Rich's work. Definitely a pleasant surprise.
The grayish color on your piston crown with chunk type deposits looks like leaded fuel deposits. I get the same thing with Sunoco Supreme leaded fuel. You're probably using C12

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sandman768 sandman768
12/22/2017 8:33 AM
40 wrote:

Rich Roy should be able to ...more

Brother....Sunoco 110 leaded from exit 12 ...Tom Morgan said sunoco 110 leaded or c12 is fine. 40:1 amsoil dominator. The deposits don't look that bad in person, the photo kind of magnifies them. I was able to find a decent set of used cases, The crack is longer than the photo shows, I figured welding in this area would compromise/warp the bearing pocket & clutch actuation arm area...seeing how these cases are getting very hard to find especially the left side, Maybe I will bring it to Rich to see what he thinks.I just pulled the engine out this week, have not split cases to see what broke, I"m thinking the shift drum or fork? Something bound up the cases, hence the crack. ..I have not been to Jaf in a few years... I also have been using a great weld/ fab shop out of Clifton park, Dick Hicks. Dick is an awesome guy, builds a lot of dirt track car chassis & fabs up all kinds of aluminum stuff. He often welds small things while I wait. He has been doing all my vintage frames also. I"m trying to wind down all this bike work, did not want to be splitting cases on this bike back apart after 12.0hrs...really need to focus on finding some land to purchase for riding, something with sand!

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40 40
12/22/2017 12:33 PM

It's worth a shot at having that case welded. From the length of that crack, you'll probably have to do some machining to get the bearing pockets perfectly round and perpendicular afterward from the heat distortion, especially the clutch actuating arm pocket.
Can't blame you for wanting to wind down the amount of time spent working on bikes. Projects like these take a lot more time and effort than many people realize.

Your last sentence is important. I talked to the guy running ADK on the phone a few weeks ago. He says the Town of Ft Ann is continuing to give him a hard time. I would not be shocked to see him throw in the towel since he's already spent a lot of money on legal fights (sound familiar?). I didn't bother to ask him what his net profit was, but I would not be surprised if it's very low- if he even made money at all. After the devastating losses we've recently endured, this would be yet another big blow.

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sandman768 sandman768
12/25/2017 12:25 PM
pete24 wrote:

looks to me like a wiseco ...more

Pete, I sent you a pm... Let me know if you donot get it...I will send my email address..thanks...

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pete24 pete24
12/25/2017 4:01 PM

just looked got nothing

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sandman768 sandman768
12/25/2017 5:59 PM
pete24 wrote:

just looked got nothing

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sandman768 sandman768
12/1/2018 6:43 PM
pete24 wrote:

looks to me like a wiseco ...more

Just getting around to the top end on this bike, bottom end done....measuring everything, piston clearance is within spec...ring end gap not so much...measured .017-.018" ... Supposed to be .012"-.015"...I guess that explains the piston markings being setup too loose....I filed too much off the ring....where do you put the ring in the cylinder checking end gap? I put ring into cylinder from the top & pushed down with piston to square it up,then measured at 1 & 2 inches from the top...

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