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Dry plugs after carb rebuild!

  • Thread starter Thread starter oblique
  • Start date Start date
O

oblique

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Bike is a 1980 750L. Ive got a new OEM petcock on there set to 'PRI'. Carbs were torn down and dipped then boiled in the Yamalube stuff and put back together with new gaskets and orings.

I have spark and after each session of cranking Ill pull 1 or 4 and they are dry. No fuel smell at all.

This petcock has me confused though: its the slotted plastic screw kind and it has no stops: it just keeps revolving round and round when I turn it so I dont know if Ive already managed to mess up a new petcock and hence getting no fuel.
 
Apply suction to the vacuum line. Fuel will flow no matter what position it's in. On yours even the Prime position takes a little suck to get it going.
 
Haha 'apply suction'. Without using my own mouth I dont know how else Im going to make that happen!
 
FYI horizontal is "run" and
Vertical is "prime".
Those are the only two settings.
Pull the small hose from the #2 carb and suck. You should feel the diaphragm in the petcock pop open. Don't worry, the fuel comes out the other hose. Suck the small hose and maintain suction for say 20 seconds and the bowls should be full.
Re attach the small line to the carb nipple and leave it on prime.
Crank the bike. Once it attempts to fire.....switch back to horizintal and your bowls should be full and good to go.
I think u just panicked.
 
just to be sure we're talking about the same petcock: mines says 'fuel' on top with an arrow pointing down so as to make one think that the slot being vertical would deliver fuel. 'PRI' is at 10:30 and a little dot is at 9 o'clock.

 
oblique said:
just to be sure we're talking about the same petcock: mines says 'fuel' on top with an arrow pointing down so as to make one think that the slot being vertical would deliver fuel. 'PRI' is at 10:30 and a little dot is at 9 o'clock.

Click to expand...
prime up
run horizontal.
its in the service manual available for free on Bikecliffs site.
 
section 8-2 in the 80-83 1100E manual. The leverless petcocks are all the same.
 
loud et said:
Suck the small hose and maintain suction for say 20 seconds and the bowls should be full.
Click to expand...
Yes, it may take 20-30 seconds to fill the bowls, but there is no need to maintain suction for the full time, if the petcock is on PRIme.

As mentioned by tkent in the first reply, your petock takes a brief "suck" to get fuel flowing in PRIme, then will keep flowing until the selector is turned or the tank runs out.

That "brief suck" can also be provided by cranking the engine, then letting it sit for a minute or so.

.
 
There is another quirk with that valve. When you turn it to horizontal for the run position, it might still act like it is on prime. I have had to pull the fuel line and tweak it until fuel stops flowing. It kind of defeats the purpose of the valve and they could have easily designed it with a stop but there you go. If you don't pull the line and check, you might end up with crankcase full of gas.
 
I will try sucking this evening.

This is the first time the bike will be started in 14 years.
 
VROOOOOMMMM!!!!

She roared to life....for about 5 seconds until hit the killswitch...the idle was at 5.5k and climbing.

Im thinking possible vacuum leak. The engine side intake boots were soft so I reused them and Ive got brand new airbox side boots. I noticed that the foam around the air filter cover was rotten..is that it? Also Im missing one of the carb vent hoses.
 
Update.

I've just returned from a trip and started to address possible vaccum leaks to explain the 5500rpm idle.

Changes made:
-added a missing carb vent line,
-replaced the hard breather hose leading to the cylinder head and sealed a crack in the airbox nipple.
-Replaced foam around air filter box cover.

I have new boots between [freshly rebuilt] carbs & airbox and I've cleaned the ones between motor & carbs which were still soft.

I've got fresh gas and the bike refuses to start. I only ran it for a few seconds last month the first time in 12 years because it idled so high. Could that have fouled something?
 
Did you remember to use "prime" spot on petcock and initiate flow by sucking on vacuum fitting or brief cranking ? After a month the gas in bowls is long gone.
 
I drained the old stuff (didnt smell like gas anymore) and made sure I had fuel flow to the carbs. I will check for spark tonight...I dont know what could've happened.
 
Gas turning to varnish can ruin your carburetor rebuild real fast. I would look for a better ventilated shaded spot to park it in.
 
Last edited:
The old gas was only 5 weeks old and when I pulled one of the bowls and it was discoloured and smelled foul but it was definitely liquidy and consistent. Bike sat indoors while I was gone.

This evening, with fresh gas, I got one little grunt out of the engine and thought it would fire but nothing else after that. I cleaned around the spark plug holes as there was a lot of grime for a good ground. The plugs themselves look new and they are Champion RS6HC.

What does 'good spark' look like? I checked it on 1 and 2 and got a thin but fairly bright little lightning bolt that danced around the gap. After all that cranking, the plugs had a very light gas smell to them.
 
You will have a lot better luck if you get rid of the Champion plugs and use the proper NKG B-8ES plugs.
 
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