Honda CX 500 Forum banner

21 - 40 of 42 Posts

·
Super Moderator
'84 CX650E that is evolving into a GL500
Joined
·
16,263 Posts
Rap the side of the float bowl with the handle of a screwdriver a couple of times and see if that dislodges whatever is keeping the float vlave from closing. If that doesn't work turn the petcock off, remove the float bowl, hold the float up and a container under the carb, turn the petcock on and let the float down & push it gently back up a few times to see if that flushes it out of the valve.
 

·
Registered
1979 Honda CX500 Custom, 45,000.
Joined
·
22 Posts
Discussion Starter · #22 ·
I will try it here in a bit, thank you Bob. It stopped on the way home we'll see if it happens again after sitting for a little while, I suspect it will after running that that other tank and all the shit that was in it. And who knows how many decades it has been since they were touched. I think I am going to flush this new tank too just to make sure, I am not running an inline filter anymore, new tank had an intact tank filter. Doing some carb research at the moment. Debating whether to take it to someone or not, all my other bikes and vehicles were injected, if I had another vehicle I wouldn't care about taking my time with it and learning, the bus really sucks.
 

·
Registered
Joined
·
1,299 Posts
I never do. I figure that way I can tell if there is a problem with the float valves from the smell of the garage ;-)
That really surprises me you don’t. Every experienced motorcycle owner/rider I have ever met practices the routine of closing the petcock when parking. Most I know will close it when parked for just a short time. Over on the bmw airhead forum someone always points out an open petcock if posted in a picture. Granted with an old bmw the fuel most likely finds its way to the crankcase if the needle valve doesn’t seal.
 

·
Super Moderator
'84 CX650E that is evolving into a GL500
Joined
·
16,263 Posts
What can I say? Some people are in the habit of turning the kill switch of every time they park too but to me that just seems like a way to wear the switch out sooner.
Most of the bikes I've had have had either vacuum petcocks or fuel pumps so shutting the petcock off wasn't necessary and I never developed the habit. I currently have a non-vacuum petcock on Eccles (I experimented with a separate vacuum valve but removed it) but the only time I turn it off is if I need to take the tank off.
IF the float valves are working right and the tank is clean you shouldn't need to turn the fuel off. I guess I've been lucky because I've only had a float valve not seal a few times over the years and usually noticed it when I was out so I knew to turn the petcock off when I got home.
I do always park in gear but that's a sidecar thing (they can roll away when parked in neutral ;-)
 

·
Registered
1978 CX500 "The Grub", '83 GL650, '82 GL500 Project "AdventureWing", '79 CX500C, '78 CX500 Scrambler
Joined
·
10,408 Posts
The Grub pees on the floor if I haven't taken it out to play for a couple days. (Bad dog!) I'd much rather have days worth of leaked gas in the tank than on the floor.
Hopefully, I've fixed that by buffing the float needle seats when I had the carbs off last weekend. I'll find out next time I have an excuse to ride.
 

·
Super Moderator
'84 CX650E that is evolving into a GL500
Joined
·
16,263 Posts
I don't even shut the petcock off for storage. I drain the tank, run the carbs dry and then drain them so there is no fuel left anywhere to turn to varnish.
That's another time I turn it off though, because I have to while I switch to a length of fuel line long enough to reach into the gas can when I drain the tank.
 

·
Registered
1979 Honda CX500 Custom, 45,000.
Joined
·
22 Posts
Discussion Starter · #31 ·
Rode her into work today, wasn't dumping anywhere. Next paycheck in a week and half I am either getting them cleaned, or re-jetting them and cleaning them myself. The airbox boots are shredded, might just run pods. I think my choke may have been stuck yesterday when it happened too, I had to manually push it down at the carbs this morning.
 

·
Registered
Joined
·
3,677 Posts
Petcocks on old Japanese bikes are all poorly designed pieces of crap. I hate them all. Some are model specific and impossible to replace like on the Interceptors so you have no choice but attempt to rebuild them over and over again until you get them just right. By the way, I always put an inline fuel filter between the petcock and carbs but that's another story. As for fuel leaks, if the petcock drips it has to be dealt with. But there is another failure mode to consider and that is when the petcock doesn't drip but rather allows fuel to flow to the carbs when you don't want it to, which in some cases can be disastrous if it floods the cylinders. This is more common on old Kawasakis and can lead to hydraulic lock and bent valve stems and / or gas in the crankcase. On that kind of bike I have installed manual fuel line cutoff valves just downhill from the petcock. Good insurance. I really do hate petcocks. You would think some company would have designed and marketed a much better alternative by now.
 

·
Super Moderator
'84 CX650E that is evolving into a GL500
Joined
·
16,263 Posts
When you consider that these bikes were only expected to last 5 or 6 years I think their petcocks held up pretty well. There are companies that make better petcocks (Pingel comes to mind) but I have no idea whether they have them to fit these bikes.
 

·
Premium Member
1978 CX500, 1982 GL500 Silverwing Interstate, 1980 CX500 Custom
Joined
·
130 Posts
Petcocks on old Japanese bikes are all poorly designed pieces of crap. I hate them all. Some are model specific and impossible to replace like on the Interceptors so you have no choice but attempt to rebuild them over and over again until you get them just right. By the way, I always put an inline fuel filter between the petcock and carbs but that's another story. As for fuel leaks, if the petcock drips it has to be dealt with. But there is another failure mode to consider and that is when the petcock doesn't drip but rather allows fuel to flow to the carbs when you don't want it to, which in some cases can be disastrous if it floods the cylinders. This is more common on old Kawasakis and can lead to hydraulic lock and bent valve stems and / or gas in the crankcase. On that kind of bike I have installed manual fuel line cutoff valves just downhill from the petcock. Good insurance. I really do hate petcocks. You would think some company would have designed and marketed a much better alternative by now.
Reminds me of the stories about the "Pre-Fab" (fabricated) houses built ion post-war Europe, also designed as temporary structures to last a few years, and... With constant upgrades they are still lived in and worth a small fortune (based on location !!).

Sound familiar? Cheers, Adrian
.
 
  • Like
Reactions: nolimitz

·
Super Moderator
'84 CX650E that is evolving into a GL500
Joined
·
16,263 Posts
I'm not sticking up for them, just reminding you that they were more than good enough to last as long as the bikes they were installed on did.
The parts that fail in them are all rubber and that doesn't last forever, especially in contact with gasoline for prolonged periods. Better ones might have held up better but they also would have cost a lot more; If they had adopted the philosophy of using only the best of everything the price would have been so high that they wouldn't have been able to sell them.
 

·
Registered
Joined
·
380 Posts
If the overflow tube inside the float bowl and the attached drain tubes are clear there is no reason why a stuck float or a jammed-open needle will allow gas into the engine.
For fuel to leak into the engine three events have to line up: the needle not seating or a sticky float, the overflow tube being blocked, and then the fuel has to find it`s way past an open inlet valve.
Pretty unlikely, really.....
All the times i have had issues i`ve always seen fuel dribbling out of the float bowl overflow tubes underneath the bike.
(waits for responses from dozens of CX folk who have experienced the phenomina......)
 

·
Registered
1979 Honda CX500 Custom, 45,000.
Joined
·
22 Posts
Discussion Starter · #40 ·
Been riding her the last couple days, running the best she has since I got her, but still cutting between 7-8k. Can't wait to get the carbs done and see the difference. Weeping a bit of coolant too, time to replace the seal. A lot of work needs to be done but overall for $800 initial purchase, great buy. And yes my petcock does drip every now and then (probably a joke somewhere in there), but it is still functioning as it should. FYI this does not work, wrong size outlet, I did use the straw and gasket though:
207674
 
21 - 40 of 42 Posts
Top