Hello,

I recently acquired a 1978 DT175, and it has quickly become my favorite bike! Sold my 1985 Honda 700s, just don't have a desire to ride on the freeway anymore, and the DT is a perfect city bike.

Anyhow, the fellow I bought the bike from had tried rebuilding the petcock, but it still leaks considerably and so I'd like to just go ahead and fit a new one.. Is there a definitive way to determine which petcock I ought to order, short of taking it off and measuring the pitch, length etc? Seems like there are several varieties, and I'd rather not order the wrong one. My local vintage bike shop was not helpful. Thanks for any info!

If you look in the tech library (tabs on top of this page) there will probably be a parts list for your bike. If not look on here www.cmsnl.com/ once you have the part number :

I'm pretty sure your local Yamaha dealer will be able to order you a genuine one, or search ebay.
I am pretty sure all the monoshock DT175's used the same petcock.

Parts are still available to rebuild (#13, #19, #21 total $21.54). Not hard to do at all. And the whole petcock is still available as well (#17 is $48.76). I would bet the PO did not do it right, maybe by trying to reuse #19 or #21 gaskets. Always a good idea to replace everything in the petcocks and not try to reuse anything but the metal parts. And those can be cleaned in a carb cleaner soak.
www.partzilla.com/parts/search/Yamaha/Mo...FUEL+TANK/parts.html
Let us know what you decide to do and how it works out.

This question has been asked before... search and you'll find answers.

There are several threaded petcocks on ebay that fit bikes like the YG1 (same thread as the later DT175) that can be had for under $20

wow thanks for the quick and thorough replies!

I went ahead and ordered a clone, off ebay, will see how that works but may spring for the OEM or try the rebuild kit if I have issues. For the interim week before it arrives, would it be advisable to try some Teflon tape? or would that be a no-no?

this is the part I ordered, it does say it will fit my bike in the ad and the seller had a good rating:

Some of my experience...

The "new" factory Yamaha petcock is likely to look more like the "knockoff" than the original. The new Yamaha rebuild parts "should" fit your petcock if it's original. The rebuild parts may not fit the new Yamaha petcock.

I would just use the new one and save the original in case you or someone else ever wants one to restore a 1978 175 to "original". (If you don't use the original yourself the original could be valuable someday to a buyer on ebay? You never know.)

OK, so the $10 ebay petcock seems to be working fine! no more drips! although I made the replacement more difficult than it needed to be, took the seat/tank off for no reason and made a bit of a mess...

Anyhow, now the transmission oil is leaking! Any advice on which gaskets I ought to look into replacing first? Ebay my best bet again?

Thanks!

Finding out where the leak is would be your best bet.

Off the top of my head there is only one gasket and three seals. Yamaha should have them all. Ebay might. Just don't assume that ebay is cheaper. There are people buying new parts from Yamaha for the older bikes and selling them on ebay for a premium price because people don't know you can get them from Yamaha still.

First place I'd check is the shift lever shaft seal... if it's pushed out of the case check the transmission vent tube to make sure it's not plugged. I've seen that more than once.

The leak seems to be coming from the bottom of the cases, maybe around the drain plug? haven't investigated thoroughly.

Just ordered a gasket set from here: www.partsgiant.com/p325902-vesrah-complete-gasket-kit?f=115651

I'll check the shift lever seal and transmission vent tube when I get home, thinking I might just go ahead and order seals and bearings also, this set comes with the bearings and crankshaft seals but only those two:

www.partsgiant.com/p328939-msr-crankshaf...nd-seal-kit?f=115651

I'll check Yamaha also, thanks again

I recently replaced fuel petcock but the existing one had two fuel lines coming from the petcock to the carb, but the new one has only one, what is the purpose of the the second hose that connects to the front of the carby?