Fuel in oil, leaking overnight - Manual Petcock

Kickflippin

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I replaced the vacuum petcocks with manual ones from MikesXS to solve an issue with gas backing up into the engine and mixing with the oil then leaking out.

After riding around yesterday trouble-free it is doing the same with the new petcocks.

Carbs are rebuilt and clean as a whistle

It seems similar to this thread but I didn't see any concrete resolution. I've done what I can to troubleshoot, including: http://www.xs650.com/forum/showthread.php?t=9663

- pulling carbs and verifying float height, float needle operation and float integrity
- float valves are brand new from MikesXS
- made sure fuel line was tight and obstruction-free
- replaced needle jet o-ring (1mmx4mm)

Parking it for several hours yesterday there were no leaks visible but somehow sitting overnight draws enough gas out to make my oil smell quite strong and leak a couple ounces on the ground:
5o73IFX.png

I can't really identify where it's coming out either. The carb boots don't appear to be the culprit.

This is happening equally with new petcocks in on or off position. I've drained the oil and replaced twice now thinking it was solved with new parts but no luck.

The float pins seem to move well but they do feel pretty loose, I'm not sure how tightly they are supposed to fit between the posts. Everytime I pull them they seam to be seated fine.

Any suggestions on where to look next? Thanks. Below is my carb setup where it is giving trouble
D4PNhSP.png


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dInGrMo.png
 
I recall some older posts where members questioned the relationship of the float tang to the float valve spring-pin. When seated at the correct float height, they should be perpendicular. Any angling here can make the tang push the valve to the side. I believe this was related to some questionable aftermarket floats. Might be worth investigating...
 
I'd say the root cause of your problem is the petcocks. Float valves are always considered to leak slightly, which is why bikes use petcocks. Petcocks are supposed to be 100% leak proof, and usually are.

Even though the petcocks are new, doesn't mean they are 100% leak proof. The quality of parts coming from Mikesxs is always suspect.

You should route some fuel line from both petcocks down to an empty dish and then monitor for a period of time. Its the best way to know if the petcocks are passing.
 
agree...the first thing is to check the petcock. In the off position, it shouldn't leak any fuel. If it does, there's the problem. Do as above, route two lines from petcock to empty containers and see if fuel collects with the petcocks in the off position. I suspect that's the issue...perhaps bad seals?
 
UPDATE: I was able to stop the flow by turning the petcocks beyond the OFF mark, about halfway to the reserve mark. That seems odd, maybe just low quality parts or is it worth taking them apart and reassembling to try and make the marks more accurate?

I'm still concerned about how easy it is to leak fuel back into the case. All other bikes I've owned it wasn't ever an issue if the petcock was left on occasionally by accident. It seems to be a mixed bag with the BS38's but I would like to have that extra assurance that a forgetful night doesn't always have to lead to an oil change!
 
agree...the first thing is to check the petcock. In the off position, it shouldn't leak any fuel. If it does, there's the problem. Do as above, route two lines from petcock to empty containers and see if fuel collects with the petcocks in the off position. I suspect that's the issue...perhaps bad seals?

Man I love that cafe build with the Norton vibe! I'm in Olympia, we should stay in touch I have a bunch of '78 parts and another nearly complete parts motor I picked up from a guy at the One Show.
 
UPDATE: I was able to stop the flow by turning the petcocks beyond the OFF mark, about halfway to the reserve mark. That seems odd, maybe just low quality parts or is it worth taking them apart and reassembling to try and make the marks more accurate?

I'm still concerned about how easy it is to leak fuel back into the case. All other bikes I've owned it wasn't ever an issue if the petcock was left on occasionally by accident. It seems to be a mixed bag with the BS38's but I would like to have that extra assurance that a forgetful night doesn't always have to lead to an oil change!

As I mentioned earlier, the quality of parts from Mikesxs is always suspect.

I use those same petcocks, and mine are always totally shut off when they are horizontal. Its another example of poor manufacturing in Taiwan or whereever they source their parts.
Mikesxs is infamous for such things, and the tradition continues.

Its not BS38 specific, all carbs with float valves are totally expected to leak fuel even when the float bowl is full. That's because they are a control valve, not an isolation valve. Isolation valves such as petcocks are designed to be 100% leak proof. Its a random thing, one day the float valve will be totally closed, and the next day it will leak fuel. That's just the nature of the beast.

There is no extra assurance. Part of owning a bike with manual petcocks, is the duty of the owner to shut the petcocks off when the engine is shut down.

You could always go back to vacuum petcocks, but personally I would never trust those things.
 
retiredgentleman - thanks for the advice. I'll just have to be extra diligent with these petcocks I guess, maybe even put a sharpie reminder on my forehead!

No way on those vacuum devils; the problem was much worse when I had them on.

I'm guessing then my other bikes have been isolation valve equipped in the carb. I once left my Suzuki VS1400 petcock on an entire winter like an idiot. Luckily the gas stayed in place.
 
Man I love that cafe build with the Norton vibe! I'm in Olympia, we should stay in touch I have a bunch of '78 parts and another nearly complete parts motor I picked up from a guy at the One Show.

Thanks! the bike was a fun build and I'm still tinkering with a few things, but overall it's just what I wanted. :)

Now onto the next build...lol.

Yes, definitely keep in touch. ..there are a few of us in the WA area. (BTW, I was at the One show this year...pretty good turn out I thought.)

Glad you got the petcocks sorted...you may want to Crack them open and see what's going on with them...perhaps just a gasket issue? But then again , if you got them to shut off...maybe just live with it for a while? Why mess with it if it works. :)
 
I've read several comments about the manual petcocks from Mikes being suspect. I had two different 81 vacuum type petcocks that i have rebuilt. Both worked for a short time and then started leaking. Rebuild kits from Mikes and followed the detailed instructions from this forum. Ready to just go manual. Does anyone have a better source then Mikes for a manual petcock that will fit the stock tank for an 81 special ll?
 
You could try ebay?

Not sure on fitment for the 81, but guessing these may work. (For what it's worth, I have a set of Mike's on mine--I only use one side as the carbs are connected, so the other I just keep closed at all times. Anyways, mine haven't leaked or had any problems really...although I did get OEM sealing washers and tossed the ones that came with the petcocks...those are garbage and have not shown to be effective at sealing the two bolts that mount the petcock. They leaked the first time I tried them...so with the OEM washers no leaks yet with +3 yrs of use).

This looks just like the one's from MikesXS: https://www.ebay.com/itm/Yamaha-Pet...KQAAOSwYxBZ7elR:sc:USPSFirstClass!98155!US!-1

This one is an adapter that lets you use a more straight forward petcock (like harley, etc): https://www.ebay.com/itm/YAMAHA-SR5...558238?hash=item33e07c0cde:g:K1QAAOSwN6NbTkFj

This looks like a vacuum style OEM version that I've never seen, or tried. Maybe it works better? : https://www.ebay.com/itm/Fuel-Valve...:XS650&hash=item2f1c736a92:g:4MMAAOSwkcFbITlP
 
you can buy Pingel petcocks and adapters to fit the vacuum centers on a late gas tank, but somewhere north of $200 per. I had one that was on a bike I bought, it leaked. :shrug:.
 
Glad you found out it was the petcocks. I only run Pingel on my bikes. Ditched the Vacuum one on the Harley and never looked back. Just got one for the XS build had to move a bung in the gas tank so I still have to pressure test but I have a Pengel for my build. And if your ever in Central Wa and need help let me know.
 
No i haven't Jim, I came across these guys from a bookmarked link from Cruzinimage. .......Criuzinimage changed have changed their store set up .....Bit weird, maybe they are connected some how????
 
Well, I've read nothing but bad things about Mikes petcock seals... and OEM from Partzilla is over 40 bucks counting shipping. I might just take a chance on it.
 
I might just take a chance on it.

Jim, you may well have seen this but if not you might want to read through Yamadude's thread regarding installing Mikes petcocks. Some talk in there about using safety wire to keep the filters on. Looks like the same type of in tank filters on these.
 
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