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78 DT175 Heat seize


flyday58
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Wow, wow, and more wow, you guys are the bomb! Lots of good info, anyone else drilled oil holes in their pistons? Do OEM units have these, or are they correct from Yamaha in some other way?

Don't know the piston brand, OGOABINTHEUSA (he is 74)bought it from his supplier to save me some $$/££, will post a pic tomorrow. Size is laser-etched on the dome.

It was dark when this second seize occurred so I couldn't see the oil line going to the cylinder. But shortly after installing the clear line a few months back I had an issue at high revs where the oil appeared to get sucked out of the line. I asked but no one seemed to think this was possible, so maybe I had air in the system somehow. I will check this also.

I live in Missississississississippippippippippi, where it's been my experience that, if you wasn't born here then you ain't one of us. I have a damn hard time getting things done that my neighbor has people fighting over and supplying their own beer (yes, we have BOTH kinds of beer here, Bud AND Bud Light :offtopic: ). The guy who did my rebore was very hard to find, but he has a well-equipped shop with devices and machines dating from the late Cretaceous and I'm fairly sure his work is fine, but I will have the cylinder checked.

Garrowby Hill. Anywhere near the Hammersmith flyover? I know where THAT is. :thumb:

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Hi

I have been watching this post, having looked at the latest pictures of your piston all I can say is the 2 ports in your piston look smaller than the ports on the piston in my bike and I thought they shared the same pistons, the ports in my piston are bigger and are more of a square shape

$(KGrHqF,!lkE4lrfVIM(BORU58Izb!~~0_35.JPG

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I know whats over heating right now Flyday he is going to be pissed at the daft bugger who got him the wrong piston.

What type of piston is that nayruf? it's a beauty with the relife cut in for extra lubeing/weight saving.Just like most newer bikes use.

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I guess everone was right on this one.

lack of lube -- to small of ports

over heating---lack of lube

poor bore job-- lack of matching the piston port to clyinder to ports.

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Lol

I cannot show a picture of the piston that is in my bike ( as it is in my bike) but I know that the piston currently running has elongated ports and is recessed at the sides as shown in the picture, As the current piston has done well over 3000 miles and the bike will show an indicated 70 mph I am quite confident that it would of gone bang by now if it was drastically wrong, but I do appreciate any concerns shown,

I do also have the previous piston and that is also has the same characteristics

The only reason this piston was changed was because a crank brg broke up and part of the roller cage had slid up the side of the piston wall, I just wanted to show that I figure that Flyday has probably got a piston for a 5 port early DT/CT bike

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Lol

I cannot show a picture of the piston that is in my bike ( as it is in my bike) but I know that the piston currently running has elongated ports and is recessed at the sides as shown in the picture, As the current piston has done well over 3000 miles and the bike will show an indicated 70 mph I am quite confident that it would of gone bang by now if it was drastically wrong, but I do appreciate any concerns shown,

I do also have the previous piston and that is also has the same characteristics

The only reason this piston was changed was because a crank brg broke up and part of the roller cage had slid up the side of the piston wall, I just wanted to show that I figure that Flyday has probably got a piston for a 5 port early DT/CT bike

yeah I thought you'd laugh at that...however I thought all the twinshocks had the rounded intakes in the piston because the pistons are different part# and the model guide shows it to be so...Honest guvnor, I dont make stuff up

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yeah I thought you'd laugh at that...however I thought all the twinshocks had the rounded intakes in the piston because the pistons are different part# and the model guide shows it to be so...Honest guvnor, I dont make stuff up

Please don't get me wrong, I am not laughing at anyone as such, I am thankful for any input and always appreciate any advice,

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thats OK nayruf , this is what I meant, now this is the piston for a DT175C...clearly the holes arent as long as the 175MX...I know your bike runs well and I'm not suggesting for one minute (despite my little joke) that you shoud change it but just thought I'd point it out to you...food for thought as it were

For Twinshock

http://www.ebay.com/...6-/350456956387

and for DT175MX

http://www.ebay.com/itm/Yamaha-DT175-MX175-2n5-11635-00-PISTON-2n5-11610-10-ring-0-25-NOS-OEM-NEW-/370643961150?pt=Motorcycles_Parts_Accessories&hash=item564c1a053e&vxp=mtr

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I always use Yamaha or a good Japanese equivalent, these are more likely Chinese/Taiwan copies but thats why they're so cheap

Having said that..Because it's so hard to come by the good ones I wouldnt have any hesitation myself

It doesnt mean that it was the cause of the heat seize though...up the jet as well if it will run right

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fwiw, I put together all the parts in the piston kit you linked, but OEM and including a new bearing for $108 delivered. Looks like it would be about $112 for you so something went up a bit, but fair enough if you don't mind throwing in an extra 20 bucks for OEM. Shipped from U.S. (Georgia, I think) in a week + a few days.

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Thanks OBRH, I use Yamaha Sports Plaza in Oregon altho I use your guys, too. I think all of them get some of their parts from Japan as it can take inordinate amounts of time to get an order filled. Your site sometimes skips part numbers if they're no longer available, and I really need the cross-ref ability since I'm working on 3 diff bikes. I guess I could look them up on my site and order on yours to save a few $$ but I'm too lazy... :eusa_snooty:

I just wonder why some OEM pistons on fleabay are 150 bucks but the parts houses have them for 60 to 70. Just hope the piston I ordered are genuine OEM and not Chinese knock-offs.

Anyone remember when "Made in Japan" meant "junk"?

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