Rebuilt carbs - replaced petcock - now petcock issue?

jummpr20

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Los Angeles, California
Working on a '73 CB350

Rebuilt the carbs - drained, cleaned and flushed tank with "Metal Rescue" - installed new petcock valve.

Bike started and idled for about a minute or so at about 1500 rpm.

Was running on both cylinders - hot exhaust from both pipes.

Carbs responded to increases in throttle.

Gradually lost power and now will not start.

Disconnected fuel tank and placed on bench. Petcock only drains from right hose (the one towards the front of the bike) regardless of being in "on" or "reserve" position.

Suggestions?

Process of elimination?

Many thanks to all.

Jim
 
actually, if you have inline fuel filters, start there - and consider very high flow, or removing them.

take the bowl off the bottom of the petcock clean out the filter/screen. remove the hoses from petcock if you haven't already, and check the drain directly from the petcock. if you have in line fuel filters in the fuel line, it doesn't take much for them to restrict/stop flow. I just pulled them off my CB350, and went with just the screen in the tank for now. also, remove petcock from tank and check to see if the base area where it draws for reserve is gunked or plugged with anything. blow compressed air through the petcock, rinse and wash out with clean gas. I like the canned compressed air like they use to clean keyboards and such for this.
 
Dear film495,

Will do all this tomorrow - thanks for your advice.

Also - when I remove the hoses - should fuel flow through both spigots at the bottom of the petcock - right and left - regardless of being in either the "on" or "reserve" position?

Many thanks,

Jim
 
jummpr20 said:
Dear film495,

Will do all this tomorrow - thanks for your advice.

Also - when I remove the hoses - should fuel flow through both spigots at the bottom of the petcock - right and left - regardless of being in either the "on" or "reserve" position?

Many thanks,

Jim
Click to expand...

I'm no expert, but my understanding is both spigots should flow fuel the same. I just checked out my tank petcock yesterday, so this is fresh in my mind. I used a cleaned out and dried 2 liter coke bottle with a large fuel funnel as a gas catch, and just returned it to the tank. I had the exact problem you're describing. I checked the petcock to make sure there was a screen filter in it and ran new fuel lines with no inline filters. I don't know if that is my permanent solution, but - sure did it work and the motor runs and rides now.

-Mike
 
You’ll rarely get it to flow evenly out of both petcock outlets when testing it. That is normal. Just take turns plugging one and making sure it flows out the other. Yes, reserve and on should flow the same.
 
film495 said:
I'm no expert, but my understanding is both spigots should flow fuel the same.
Click to expand...

Middletons above is correct - the petcock will flow out of one or the other at times, but still flow as needed when the carbs ask for fuel. It happens because the "general" feed divides into the 2 spigots and the amount of fuel flowing isn't enough total volume to flow through both at the same time, but as one carb fills the other will fill when the float needle shuts off the one that is full first
 
Thanks ALL for your help!

As suggested - I disassembled the petcock, soaked in gas and cleaned out with compressed air.

Reassembled and reattached.

Then bench tested for flow.

At first, gas only flowed from one spigot, but, as Middletons suggested, once I plugged up "flowing" spigot with my finger, gas flow shifted to the other spigot - then - upon releasing my finger, flowed steadily and evenly from both spigots both in "on" and "reserve" settings.

Before putting tank back on bike - plan on leaving tank on the bench and running longer "test hoses" to both carbs to see if bike will idle/run.

If not - I suspect the problem will be with my attempted carb rebuild.

Any potential problems with this plan on leaving the tank off the bike for this test?

Many thanks for all the help and suggestions thus far.

Jim
 
Just don't knock the hoses and pull the tank off whatever you're setting it on. My guess is if you approximate the same elevation the tank sits on the bike, the test is valid, but - my guess is you've tested the tank, so - just put it back on the bike, you're pretty much done with it, install it and move onto the next thing.
 
Put the tank back on the bike as suggested.

Fuel running to both carbs - but bike will not start.

Here's a recap of my process...

Working on a '73 CB350

Rebuilt the carbs - drained, cleaned and flushed tank with "Metal Rescue" - installed new petcock valve.

Bike started and idled for about a minute or so at about 1500 rpm.

Was running on both cylinders - hot exhaust from both pipes.

Carbs responded to increases in throttle. Was able to rev it up and down.

Gradually lost power - became unresponsive to throttle and now will not start.

Any suggestions on process of elimination addressing the "rebuilt by me" carbs? (New jets - gaskets - floats).

Thanks to all for your time and attention.

Jim
 
pull a plug cap and put it on a loose plug and check to see if you have spark; then do the other side. if spark on both sides, crack drains on carbs to see if they are filling with fuel, can't see why they wouldn't be, but - got to check to see. check your oil level, basically - go through a pre start checklist, the rest of your bike will like you, air pressure, lights, go over the whole thing - then, get back to it not starting, it is what I would do, but that's just me. You might find your problem by looking at other systems.

if you have spark and fuel in the carbs, just a guess would be - pull a plug and my guess would be it will be wet with fuel, and the float level in the carb is off and you're flooding - if it is dry, your pilot jets are plugged; try starting it will more throttle applied, but do this on the center stand just in case. I played this game with my CB350 last week and don't recommend it, but did spritz a little starter fluid into the air intakes to see if it would kick over. It helped me track down my fuel supply issue, so - it was worth it IMHO.
 
Dear film495,

Thanks SO much for your checklist.

Removed plugs from both sides and no spark on either when turning the bike over.

Obviously had spark before when bike ran for about a minute and eventually died out.

Both coils get warm when turning bike over.

Some background on bike's electrical history:

Old wiring kept blowing fuses - but only when headlight was on and handlebars got turned to the right. Tracked down short to control box and/or wires for high/low beam - starter button - kill switch. Replaced entire setup with new control box and attached new wires.

Also - prior to this had electrical system meltdown (had 20 amp fuse in fuse box at the time instead of recommended 15 amp). At the time my ignition switch was in my hand (not grounded to bike - not sure if that matters). Turned switch on - smelled melting plastic - and before I could turn switch off round connection where ignition switch wires connected to wiring harness melted together.

Replaced entire setup with completely new wiring harness and started from scratch.

Voltage meter indicates that kill switch is working properly (black wire with white stripe) - at connection inside headlight bucket and further down harness at connections to coils. (measures 12 volts)

There are two solid black wires from control box I connected to a double black wire input inside headlight bucket - when I connected this with key in "on" position, I got sparks. Not sure if this indicates a short somewhere?

Headlight (high/low beam), starter switch, horn and all indicator lights (neutral, turn signal, hight beam between tach and speedometer) and lights inside tach and speedo all work.

Also got rid of original regulator/regulator setup and replaced with combination regulator/rectifier.

Where to go from here in process of elimination?

Many thanks!

Jim
 
If coils are getting warm, you are getting power TO ground (presumably at the points).......Plugs ONLY fire as points break open, so perhaps the points have become loose enough on the plate to back away from the breaker cam of the advance unit and are remaining closed....OR, you could have shorted condensers....Or the drive pin for the advance unit fell out....Or shorted point wires....OR fouled plugs......
You may phone...************
Steve
 
I'm no electrician, but you'll need spark to run. Strange it would run for a few minutes and then go dark. Could have been a coil on its last leg? Do you get a voltage reading at the connections leading to the points under the tank? Usually you can sneak a volt meter up there - should read about same as battery voltage with ignition on. Just follow the wires up from the point - should be 2 connectors, each should have voltage with the ignition on.

Call Steve, think I'm gonna call him tomorrow about electrical on my bike too... hot topic lately.
 
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