Petcock Rebuild

[DEEBS11]

Try installing your carbs without the airbox and feed carbs directly with fuel. You will see the offending carb(s) leaking soon after. Adjust the float until the carbs don't leak. If you are using Chinese carb parts you will most likely not be able to stop this breech.

[Supersport396]

The rotors appear to be well centered. I'll check the splooge hole.

The fuel overflow stopped during road test. I'll have to look further. Thanks for the replies, appreciate it!

[DEEBS11]

Just to give you the heads up on what's happening here, years ago, a work friend with an 86 GSXR1100 wanted to convert from DOT4 to DOT5 fluid (which I recommended he not do because it really buys nothing of any real value on the common street bike). So, he emptied and flushed with DOT5 and air bled the hydraulic system. He rode the bike to work the next day to show me. By quitting time (4:00PM) his entire brake system was locked up and he could not move the bike out of the parking space. I had to let air into the system just to release the calipers. I looked at him and said "Now do believe me?".

When most people do this conversion, they don't fully remove all DOT4 fluid which entails disassembling master cylinders and calipers and cleaning all rubber and metal parts with brake cleaner. Then you need to flush all the lines with brake cleaner as well. THEN you reassemble and flush the system with DOT5. I'm pretty sure your system is "swelling" under contamination.

[Supersport396]

The PO did the DOT5 upgrade. I've had my own experiences with DOT5. Presently on an old corvette I converted 10 years ago, one caliper started leaking. After several rebuilds & then a replacement it would not stop the leak. So presently I rebuilt everything, flushed all lines with denatured alcohol and went back to DOT3. This isn't from swelling though because all new seals leaked on the one caliper within days. There's something about DOT 5 like the molecules are smaller or something. Swelling is a longer term problem. I am not a fan and will likely do the same to this bike next winter. The DOT5 rebuild was done last year so hopefully I can get a year out of it.

[Supersport396]

OK so bike runs fine but on subsequent test drives, the octopus doesn't seem to work as it did before and I have to turn petcocks to prime. Is there anything wrong with running on prime if I always shut them off when not running? Does that use up reserve?

[DiverRay]

Running on prime is not a good idea. It's OK for the short time, but you need to "fix" the problem. I just bypassed the octy on my Special, and it runs well. I have a reserve, and put a "plug" in the location of the prime so no fuel can escape if the valve somehow ends up in the prime setting.
As far as the DOT5, I've run it for years in my older '79 Standard with no problems. I did do a COMPLETE rebuild with all new hoses, so know there was not any old fluid in the system.

[cajun31]

OK so bike runs fine but on subsequent test drives, the octopus doesn't seem to work as it did before and I have to turn petcocks to prime. Is there anything wrong with running on prime if I always shut them off when not running? Does that use up reserve?

Running on prime isn't your best choice. You need to find out why the octupus isn't working. Is it hooked up correctly? Was it rebuilt with newer parts? If so then there has been discussion concerning the newer part is too short and needs to be modified. Do a search of jetmechmarty and see where he has posted in the past about having to modify that part slightly to ensure it closes and opens properly. What you are describing as not working indicates you are not getting fuel flow under normal conditions? If that is the problem then it sounds like it is not hooked up properly or you have a vacuum hose leak. To answer your original question ... if you leave it on prime all the time then yes it will work and the flow of fuel is constant and if the floats fail you could experience flooding. Not safe on these old machines. Ideally the floats function properly and that won't occur but there is still the risk of flooding which can result in fire or flooding your crankcase with gas that can cause catastrophic failures. Many no longer have the center stand and park the bike on the side stands that can cause float sticking / flooding problems. Getting off on a tangent here but just want to make sure you realize the dangers involved. To answer the original question... when you run on prime you eliminate any reserve. When you run out of gas you are out. Prime is intended to bypass vacuum and get the bike started quicker. Ray beat me to the response but at least our theme is the same.

[Supersport396]

I did modify the diaphragm lengthening it and it seemed to work with a vacuum pump....guess I'll have to dig further. If I bypass the octy, isn't that the same as running on prime but for the reserve issue?

[cajun31]

I did modify the diaphragm lengthening it and it seemed to work with a vacuum pump....guess I'll have to dig further. If I bypass the octy, isn't that the same as running on prime but for the reserve issue?

Yes... you will be on or off, but bypassing the octy is basically bypassing the need for prime. Many have done it and you just need to remember to turn the petcocks off every time you stop and park the bike. I do that and still have my octy's. Just habit. The worst case is flooding. We actually had a member years ago that lost the bike and his shed to fire when he parked his bike and forgot to turn the petcocks off.

[Supersport396]

But still, if the floats fail, it would make no difference if it was running on prime or run with functioning octy and vacuum. Fuel would still flood. Am I missing something?

[cajun31]

But still, if the floats fail, it would make no difference if it was running on prime or run with functioning octy and vacuum. Fuel would still flood. Am I missing something?

Yamaha's solution ultimately was to have the carbs functioning correctly, meaning the floats, float needles and seats stop the flow of gas. Of course it is my belief that having the bike on a center stand helps in that because the carbs are parked level. As a safeguard they came up with the octy. Whether you have a standard or a special the octy concept is present in all of them. Of course the specials have the octy as a separate component and the standards have it built into the petcocks. Both work on the same concept. When the bike is running and a vacuum is being applied the middle valve is opened allowing fuel to flow. When the bike is turned off that vacuum is removed and the flow of fuel is stopped. When that component is not functioning correctly then the flow of fuel continues and if the carb floats or needles or seats...etc... are experiencing problems then flooding is the result. I have always believed that even those engineers understood the flooding issues or why put those octy devices on them to begin with? Folks will argue back and forth as to the usefulness of them. I have always believed if you can make them work ... then leave them on the bike because they are an added safety measure. Of course as I stated in a previous post, if you remove the octy or the function you have to ensure those carbs are spot on and you have to remember to turn the petcocks off. I mean even for short stop. Over the years I have always been in the habit of turning them off when I stop and turn the bike off. As I get older my biggest problem has been to remember to turn them back on when I take off. Can't count how many times I have been reminded a short distance down the road. Then I have to quickly get them turned back on while rolling down the road.

[Supersport396]

Strangely, I took the bike out for another test ride starting on prime, then after a short while, switched to run, I did get a little sputtering so I switched to prime and that cleared it up so back to run after a very short while and no further problem for the 10 or 12 miles I rode. Bike idles and runs great. Not sure why that would happen that way. I think I'll put a gauge on that port to see what vacuum reading I get.

Cases all polished up and ready to go. Last thing to do is pull the rear wheel & grease the shaft spline. Bike has less that 7k miles so don't expect any surprises.

[Supersport396]

So I have been using this bike only for short 20 miles or so trips with no problems. This past week I trailered the bike down to MD to do some riding with some friends. In 2 days we did around 300 miles. 2 problems surfaced. When I put the bike in the back of my pickup, I neglected to turn off the petcock when I shut it off. I realized this around an hour into the trip. Shut it off and continued. When I got to the point to transfer it into a trailer with the others, it started flooding white smoke coming out of the left pipe (unburnt fuel). **** it down immediately and fuel was coming from airbox. Pulled it and cleared it and it appeared to be the left outboard carb intake that was all wet. Oil was not overfilled and didn't smell. fired it up again, took for a spin, all is well. When we did our rides all was well for at least 90-100 miles. Stopped for lunch. afterwards, leaving to continue, I forgot to turn the petcocks back on and noticed it starving so quickly turned them on. pretty soon, sputtering and white smoke for the left pipe and gas leaking from airbox. quick shutdown, let the box drain. rapped on the carbs a few times with a tool to get the needle to seat and all was well for the rest of the 200 miles. Bike ran like a charm. I don't forget to shut off the petcock anymore but wondering if I can get the bowl off that carb to inspect without pulling them all? My suspicion is with the bike in motion, it doesn't allow the float to get stuck being jostled all the time.

ANyway, problem 2 was the forks seals leak a bit. I changed the oil over the winter and used the amount the manual recommend. Is it possible I overfilled?

Thanks for any help!

[Radioguylogs]

(1) I think you understand the finicky float problem in #1 carb. I don't think you can inspect it without removing the carbs.

(2) Maybe most of the fork oil had leaked out before you owned the bike. Then maybe you refilled it and now it leaks out? Regarding overfill, I see you measured how much oil to put back in. When you drained it, did you cycle the forks a few times to get our the trapped oil?

[jetmechmarty]

Once again, here is the link to fix the K&L diaphragm.

https://www.xs650.com/threads/vacuum-petcock-rebuild-kit-fail.65527/#post-823647