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Petcock troubleshooting advice

08 Apr 2020 21:39
Yamahamadingdong
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Petcock troubleshooting advice #1
Heyo.

I don't have a leaky petcock, but I THINK it might just not be shutting off. When in use, it's dry and seems normal. No leaks. It sat in the garage switched to what I thought was off, and I would switch it to on when riding.

For anyone who was following my 6 to 12v misadventures, I switched it to the off side, but when I popped the fuel line off, gas went woooooooooooosh. Didn't seem to matter how i turned the petcock valve. It kept coming and i had to sit with my finger over the opening and stretch across the garage to get a gas tank to drain into.

Maybe I am just doing it wrong? It is a 1975 DT175B, and Reserve is turned all the way to the right (lever points up, at 12 o clock), off is turned counter clockwise to about 9 o ' clock, and on is 6 o clock?

I'm wondering if it is just stuck open or something since it's so old and wasn't ridden. The petcock itself is not rusty, and it all seems to turn really well, but I don't want to start opening it and dicking around unless I really need to.

The mounting plate up onto the tank looks a bit rough like the screws may be a real adventure to get out of there.

Is there some good troubleshooting steps for this problem? Maybe it is just user error and I am a moron?

I saw there is a cheaper aftermarket petcock on partzilla (from a post on this forum), or I can get an OEM 1975 DT175B one for like 40$ more.

I assume I then need to buy gaskets and some other stuff to complete the swap out.....

I'd like to avoid that, but wanted to figure it out before I pull the trigger on some lightbulbs and stuff, since buying the petcock if I really need it will get me free shipping!

maybe this isn't a huge concern. I was told you absolutely MUST put the fuel line into OFF mode. If it's not been working right this whole time, that sounds bad.


Side question while I am thinking about it. There is a tiny white plastic thing on the fuel line. I'm assuming it's a fuel filter, and because of how white and shiny it is, I am guessing it was something added aftermarket by the previous owner.

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08 Apr 2020 22:16
Mothersbaugh
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Petcock troubleshooting advice #2
There are internal rubber parts which get hard and break, or flatten over the years and no longer make a good seal. The oarts are available from Yamaha still.
www.partzilla.com/catalog/yamaha/motorcy...975/dt175b/fuel-tank
#35, #38, and #29 are still available. #30 is not, but it's not usually a problem. #29 is usually the problem. Yes, you can replace the whole thing with the new model petcock, #28 (498-24500-01-00), but replacing #38 would still be a good idea. #40 as well, the pair of sealing washers on the mounting screws.
Unless you want leaking gas onto a hot engine while you ride, you need to do this work. Drain the tank, remove the tank, and the work is much easier to do. While you have it all apart, you can clean it by setting it in a can of carb cleaner like Berryman's. Just the metal parts, though.

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08 Apr 2020 22:33
Yamahamadingdong
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Petcock troubleshooting advice #3
On a scale of 1 to 10, how hard is this work usually? Looking at the diagram, it looks pretty straight forward.

My petcock looks great minus the mounting point on the tank, so I don't think I need to replace the whole thing and would prefer to leave the original and just swap out all the goony parts inside that went bad.

So: Valve, Gaskets, New Screws for all the spots I am going to touch, and new washers?

Like I said before it doesn't seem to be leaking at the moment, but it doesn't seem to close. I might go pour some gas in it tomorrow and wiggle the lever around and see if I am just really stupid, but will order these parts anyways since if I don't end up needing them now.... I probably will soon.

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08 Apr 2020 22:41
MarkT
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Petcock troubleshooting advice #4
I can't remember ever seeing a petcock where straight down is not "on".

Sometimes "reserve" and "off" positions are swapped on an aftermarket petcock but here is a picture from a Yamaha Manual










.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

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08 Apr 2020 22:53
Yamahamadingdong
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Petcock troubleshooting advice #5
Straight down is on for me. that's what I meant by 6 o clock. I might just be a total dumbass and everything is actually fine and I've been turning things the wrong way.

I went out and got some pics and attached them. It only turns between 12 and 6 o clock. if I turn it to around 9 o clock and jiggle it around to get some gas going (its mostly empty at the moment), gas still comes out of the opening.

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08 Apr 2020 23:21
MarkT
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Petcock troubleshooting advice #6
Petcock looks original style... looks like someone mickey-moused it or it's a cheap copy. Maybe just put together wrong.

Long end of lever should not be able to rotate up like that.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

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08 Apr 2020 23:30
Yamahamadingdong
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Petcock troubleshooting advice #7

MarkT wrote: Petcock looks original style... looks like someone mickey-moused it or it's a cheap copy. Maybe just put together wrong.

Long end of lever should not be able to rotate up like that.


The top area where it's rotated to pointing upwards is the "reserve" stamped area. Is it not normal for the "RES" to be stamped up top there?

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08 Apr 2020 23:39
MarkT
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Petcock troubleshooting advice #8
See picture I posted, shows range of lever travel.

Someone probably put a $5 petcock on it and it's not made right. There's a whole thread on inexpensive quality Yamaha petcocks that fit. It's important that it shuts off.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

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08 Apr 2020 23:49 09 Apr 2020 00:03 by Yamahamadingdong.
Yamahamadingdong
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Petcock troubleshooting advice #9

MarkT wrote: See picture I posted, shows range of lever travel.

Someone probably put a $5 petcock on it and it's not made right. There's a whole thread on inexpensive quality Yamaha petcocks that fit. It's important that it shuts off.


Yep. I looked through that thread and at the more expensive OEM one specific to the DT175B.

I'm not exactly sure what "mickey mousing" it means, but it has me cracking up.

it's weird since it looks like the range of motion on mine, and the way it's expecting to turn is rotated compared to what is expected from your photo.

Instead of RES ON OFF, mine is

----RES
OFF
----ON

I guess I should definitely order that stuff (gaskets, screws, washers) AND a new Petcock while I am at it?


EDIT:
www.ebay.com/i/222597000404?chn=ps&norov...fEAQYASABEgJ-uvD_BwE

Looks like this one!

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09 Apr 2020 00:17
Yamahamadingdong
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Petcock troubleshooting advice #10
Actually, if you check the DT175B partzilla Petcock image and rotate it to match how you'd look at it as installed, it seems to match what I've got on my bike now.

Same orientation of the Res/Off/On, and the lever points upward.

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