I would like to see pictures.

I'm also wondering if you have a 1979 and not a 1978? What are the first three of the VIN?

I've never seen a DT175 with two hoses on the petcock... doesn't mean they didn't do it someplace in the world though... or someone could have installed a different petcock on the bike at some point.

As far as fittings on the carb, in 1979 they had a "vacuum" fitting near the front on the left side that had a rubber cap on it. It's about fuel line size. It was capped from the factory with a rubber cap and if I remember correctly was only on the 1979 and newer.

All the monoshock DT175's had a tiny fitting on the right side of the carb where the oil injection connects... it's almost exactly across from the capped fitting on the left side.

Hi, i'm guessing someone has fitted a vacuum auto shut of tap which would run a smaller hose to the engine side of the carb if there's a place there to draw vacuum from. Lots of bikes ran that sort of tap [petcock]. Maybe the previous owner had a fuel drip from the carb overnight & though he'd run this to fix it one way or other. I just bought two taps for very little off some Chinese site through out Trademe [NZ that is], mind you i'm still waiting for them but fingers crossed they'll turn up. If it's two fuel lines then sorry i'm lost as should both be Tee'd into the only way in for fuel & i did that once using a tap [petcock] of an RD200 twin. I'll find pics of what i bought--one of which is an auto shut off & has the diaphragm unit on the back.

Here's a link to one of what i bought. Easier for me than trying to sort a pic. Shows other views of it too. Not like yourse if it screws on to the tank by a single screw on thing & if it does mount like i think then yamaha V50 & bigger scooters ran that tap so yours could be one of those.

www.trademe.co.nz/motors/motorbikes/part...b0a8229a3a28138d-001

in answer to markt it is a 9/89 model vin - jya
it is at the front left of the carby, but it did run all the way up to the original petcock, i ran the primary line to what i thought was the fuel line into the carby and it runs, i put a large screw into the other hose to block it off, i can't get it to idle, have cleaned carby and all jets etc, have currently got it to idle using the adjustment on the throttle adjustment on the handle bars, cant seem to set the idle using the adjustment screw on the carby, seems to run fine when i'm riding it but doesn't semm to rev out as much as it should????

You've posted to a thread for a 1978 model. A 9/89 date is probably a 1990 model... last model in the US was 1981. The "JYA" is not useful on a model later than 1980/81... sounds like the prefix on a later 17 digit VIN. The prefix on the engine number "might" identify the model.

Probably would be best to start a new thread... pictures of your bike would be appreciated... we don't see many of the later models here.

Take a look at this document. I can’t find a YJA vin or engine code listed anywhere in the world.

yamaha-enduros.com/index.php/service-bul...des/viewdocument/171