1976 Yamaha xs500 fuel/running problems

[Joee]

Just breaking out my bike finally to work on it since I can only work on it during the warmer weather and I noticed a couple problems. First was the petcocks were leaking. I bought new gaskets and the whole rebuild kit for them and that still didn’t work. I’ve always had problems with gas leaking either out of those or out of the fuel hose at any end. The current hoses have a fuel filter attached to it so I figured I’ll try and just get a new hoses and ditch the filter so that there’s no interruption of gas flow. So as far as the Petcocks go is there anything I can do or buy that just gets rid of the need of a damn petcock. I wish I could just attach my hose right to the gas tank without having the petcock anymore.

As well as that issue I managed to get the bike running for like two minutes before it died on me. Probably a carb problem but I did notice that the left side of the engine was a little cooler than the right side of the engine. What would this be and what would be the fix. Also I have a bunch of different jets for my carbs so should I change the jet sizes or adjust the idle or fuel air mixture screw to get it to stop dying like that.

One more thing to note would also be that with the petcock issue I noticed that maybe less gas was flowing out of the left side than the gas on the right side. So there was some restriction to gas on the left fuel line/path. (Gas tank was full and petcocks were all clean) this is why I wanna just ditch the petcocks and just go straight from the tank to hose.

 

[JJames]

If it ain't got petcocks, it ain't a motorcycle.

 

[Wingedwheel]

I guess my question would be is where are the petcocks leaking? Hose? Face? Fittings? Need pics and a little more info.

 

[Joee]

I guess my question would be is where are the petcocks leaking? Hose? Face? Fittings? Need pics and a little more info.

Can’t send you pictures today but I could try to get you some tomorrow. As of now the weird thing is they don’t leak when they’re in the off position but when I turn them on or on reserve they start leaking. Then I’ll turn them off and they will continue to drip for 5 minutes then stop while in the off position. They leak from the back of them. Like the side that is opposite of the petcock lever. That back plate that has the fuel line nipple connected to it. That’s where it leaks from.

 

[Wingedwheel]

It sounds like either the puck inside needs to be replaced or flipped or you have the compression ring on the lever cover not seated correctly.. probably need to redo those petcocks.

 

[nj1639]

There are plenty of simple on/off petcocks out there but there's no reserve and they require the proper spaced adapter plate that they screw in to - see NPT 1/4" in an internet search - petcocks/adapter plates.
Thinking "ifs"
IF a tank has two fuel outlets, one side could be rigged for reserve - maybe - and run that side until the engine tells you it needs juice and then turn on the other side.
You would need two "T's" , one to link the petcocks together and then another after that T to supply each carb. BS 34's already have that T but are designed for a single tank outlet. BS 38's have the dual output tank but will they run sufficiently being supplied by one petcock at a time? Probably no issue.
Downside? Cost and spaghetti of fuel line under the tank.
IF there was a fuel gauge a single on/off no reserve would suffice.

I need to address a leaking petcock (wtf is this now?) myself but the tank is most full and it stops dripping when riding. I'll run till reserve and then address it.

 

[Joee]

It sounds like either the puck inside needs to be replaced or flipped or you have the compression ring on the lever cover not seated correctly.. probably need to redo those petcocks.

Did some work on those and they don’t leak anymore and got rid of the fuel filters so the gas flows very well right now. I did start it up again and still noticed the left side of the engine was not as hot as the right. Any reason for this problem??

 

[5twins]

Carb sync (as in out of sync)?

 

[Joee]

Could be. I’m not sure how to sync them, I sync-ed the butterfly’s last summer and they shouldn’t have changed since then if that’s what you mean by sync. Other than that I’m not sure.

 

[Grimly]

Could be. I’m not sure how to sync them, I sync-ed the butterfly’s last summer and they shouldn’t have changed since then if that’s what you mean by sync. Other than that I’m not sure.

If you haven't vacuum synced or carefully did it by ear, then they're not adequately synced.
Some carb setups just like to go out of kilter to feck with your head.