2 stroke piston - questions

[tigertim20]

want to see what anyone can tell me about this piston.

Only markings on it are 'ART' - which I have been told is the supplier for oem pistons, to most japanese manufacturers, but dont know if that is correct or not?
one other marking says 18L00.

no other markings that I can find. pics are attached



Piston is out of a 1985 DT175. I know it isnt likely that a bike that old has a stock piston in it still, but it still has vin tags etc, it has been on the road in aussie, though I cant find a aussie version of carjam to confirm any more details on its history. The speedo is still all hooked up, and shows around 9K on the clock.

Pulled it apart as I just bought it, knowing it would "only run sometimes" and suspected rings. (and yep, rings need replaced).

also, if anyone has any info on these bikes, i.e. what material is the cylinder? I assume it is pre-nikasil era, and might be easier to rebore / hone later on?

[Banditbandit]

I'd be replacing that piston too if the score marks on the lower end are permenant. (If they are just oil marks then not a problem.) If they are permenant the marks indicate it's been scuffing against the barrel - have a look at that too.

[tigertim20]

since its apart, Ill replace piston and rings together regardless. might as well since I have it apart.
will have a closer look at the barrel this weekend.

[F5 Dave]

ART supplied pistons to Yam for virtually all of their bikes that era. There would be a 0.25, 0.5, 0.75, 1.0 on the crown if it was an oversize.

Get a bike shop to measure the bore for wear & rebore if required.

But also really clean the carb Pilot & choke bits to be sure.

Made those for years so after market or ebay NOS if YAM NZ get unreasonable. Stock ART are good quality.

Those marks are dirt getting past the filter at some stage, but aren't bad. A cheapo would measure the piston if the bore wasn't worn. 9000k on good oil and clean filters is no drama. On bad will be worn out. Always check for cracks.

[tigertim20]

ART supplied pistons to Yam for virtually all of their bikes that era. There would be a 0.25, 0.5, 0.75, 1.0 on the crown if it was an oversize.

Get a bike shop to measure the bore for wear & rebore if required.

But also really clean the carb Pilot & choke bits to be sure.

Made those for years so after market or ebay NOS if YAM NZ get unreasonable. Stock ART are good quality.

Those marks are dirt getting past the filter at some stage, but aren't bad. A cheapo would measure the piston if the bore wasn't worn. 9000k on good oil and clean filters is no drama. On bad will be worn out. Always check for cracks.

cheers mate. Will get it measured properly, hopd to get it done today to confirm bore size, but no dice, work was too busy.

bit f luck it will be going in a couple weeks when I get around to ordering bits. will strip the carb and do a bunch of other general maintenance stuff as well since its in bits now

[speedpro]

Like Dave said, that piston actually looks pretty good.

[Mike.Gayner]

I'd be replacing that piston too if the score marks on the lower end are permenant. (If they are just oil marks then not a problem.) If they are permenant the marks indicate it's been scuffing against the barrel - have a look at that too.

The fuck are you on? Visually that piston is fine. Obviously it needs to be measured against the bore.

At 9k there's no reason this couldn't be STD, and the lack of markings supports this. Personally, if the clearance was OK I'd just replace the rings - which is exactly what I did on my A7 with STD pistons, 12,000 miles on the clock, and the speedo disconnected.

[tigertim20]

I will wait till I have the bore measured before I spend any money then.

Been researching so I know where to go if I have any issues - but fuckin hell, I cant seem to find anywhere that can supply bits for the 1985 DT175. Parts galore available for the 84 and prior models, but having a cunt of a time finding suppliers for the '85.

any ideas?
even Ebay is pretty thin on '85

[george formby]

Yer bits are available. Wemoto

I got the engine bits for my DT 230 from JP parts. If you do need bits flick them the part numbers & get a quote. Prolly much cheaper than Wemoto.

[husaberg]

I know anything about them but it suggests they are the same as the era detailed
YAMAHA DT175 82-10 0.5mm O/S PISTON KIT 66.5mm RINGS PIN CLIPS
http://www.japbikespares.com/yamaha/...ings-pin-clips

[tigertim20]

ended up finding parts locally. bought the piston, took to the engine builder.
Engine builder called me the next day . . . reckoned the cylinder had slipped out of the vice = fucked cylinder.

He set it right though, and ordered me a brand new cylinder, so I swapped the o/s piston kit I bought for a std size.

Bike is all back together now, and running fine, along with new brake shoes front and rear.