85 Interceptor Petcock issue?

I have had this problem on my 85 VF500F a couple of times, and it is a bit unnerving:

The bike runs fine when I start it up for the day and start riding to work. I get about a mile away and it starts running likes its out of gas and then finally dies. Running it with the choke on helps for a few seconds but then it wont even start with that. The petcock is in the on position there is gas in the tank. Is this most likely a petcock issue or a fuel pump issue? The bike normally runs fine and this has only happened a few times, which is kind of annoying and makes diagnosing the problem difficult. In all cases that it has happened, letting it sit for a half hour or so has remedied the problem. Any help? Thanks.

- Rick

 

Sounds like your fuel vent is bad. Next time it happens, pop your gas cap, start and ride it. See if that fixes your problem.

IIRC, the 500 has an external petcock.
Not that familiar with your bike - some ideas floating around in my head: does the vacuum line go to the motor? Is it plugged up? If your fuel cap is vented, clean the vent hole.

Does it happen when the bike is less than half full?

It is possible to clean the contacts on the fuel pump but I have never done it - just heard about it being done.

Do a fuel pump flow test - should be in the manual.

 

It does seem to happen when the fuel tank is less than half full - Or the couple of times that it has happened, that was the case. The petcock on the 500 is built into the tank just like the 700's however, and I have read about people having to rebuild the diaphragm in there - Any idea where to get a kit to do that? Just in case that is the problem.

 

The pet cock actually is attached to the bottom of the tank. If you take the tank off it should be attached with 2 bolts. You can take it out and clean it if you need to but be careful of the diaphrams. and if you are looking to get another there is a difference between years. My bike is an 85 and my parts bike is an 84 the petcocks look the same as far as the on/off/res switch go but the mounting is different. I had to switch tank and all.

 

I would verify the lines are clear before investing in a kit.

I couldn't find a specific kit for the Ceptor. But I did find one or a VF750S Sabre: https://www.partsnmore.com/item_index.php?part_unique=1833

I have read where a rider drilled out the rivets and replaced the o-ring inside then replaced the rivets with screws.

 

Yeah, I did check the lines and they look ok, it's probably the petcock. I think I may just remove the diaphragm assembly and make it manual. I am pretty sure that there is a page on how to do that somewhere. Seeming how there is a fuel pump anyway, it seems a bit silly to even need vacuum control of the fuel flow in addition. Thanks for all the advice.

 

Hey if you find that page post the link I would like to check it out.

 

http://www.daughertymotorsports.com/howto/tankvalve/tankvalve.html

 

My V-45 Sabre did the same thing. I removed the diaphram, and made it manual. Be SURE to disconnect the vacuum line and plug it. With the diaphram removed, gas could run into the engine through the vacuum line. Also, if you have a float needle valve that leaks a little, it will run gas into the engine when it is not running. You just have to turn it off when you're finished riding for the day. The diaphram system turns the gas off when the engine is off. With the diaphram removed, it will be on all of the time, unless you turn it off. Like Masonv45 said, be sure to check the tank vent. When it quits, pop the cap, then see if that fixes it.

 

can gas really run into the engine if you accidentally leave it on when the bike is off? On the interceptor there is a fuel pump. Wouldn't this stop that?

 

The fuel pump won't stop gas from flowing downhill, it might slow it down but won't prevent all flow. It will only leak into the engine if you have a leaky float needle valve. But on a 20+ year old bike, a leaky carb is not out of the question. My removal of the diaphram was a success, just make sure you don't get any gas in the oil. Gas could run through the vacuum line with or without a fuel pump. You just have to plug it off.

 

Another issue...

I think there may be another issue with my petcock. I seem to be able to run the tank dry on the "on" setting. I run out of gas with the switch on "on" and then switching to reserve I still can't start the bike and I can just barely here anything sloshing around (and I may just be hearing the suspension) when I tip the bike back and forth. Could this be some kind of seal issue in the petcock? It is not a clogged reserve because once I filled it I ran it on reserve to get home. Can you buy new gaskets for these? I am lucky this happened close to home... Thanks for the info.

 

My Sabre does the same thing. The tall straw on the petcock may have broken off, or the seals in the petcock gave up. I just reset the trip meter when I fill up, and get gas every 120 miles or so just to be safe. I'll go to "mrcycles.com" a Honda dealer, and look on the parts fiche to see if there is a seal kit available.

 

The Honda parts fiche shows all of the seals sold seprately for about 3.63 each. The entire petcock shows p/n 16950-MF2-005 for $164.42. It also shows the sizes for each seal. Just because it shows the parts doesn't mean they are available, only gives you the p/n. You'll have to call them to see if they can still get them. The breakdown will show you what the guts of the petcock look like.