Help me not put holes in my wall! '81 won't start

[Pattymatts]

First off, hey dudes, I'm new to the site. Did a bunch of research and read a bunch of the tech guides and still can't seem to figure out the problem with my bike.

I'm going to try to give as much information about what is going on, but bear with me I'm no motorcycle tech haha. So a few days ago I finally got my '81 running, after maybe a minute of idle I would blip the throttle and she would just take off and the idle would NOT go down and then fuel would piss from the intake of the left carb and only left(I'm thinking that was gravity's work though). So I explained what was going on to a buddy who knows more than I, and he said the carb floats were most likely stuck. I then took the carbs to a shop who cleaned them. Put them back on yesterday and she sounded great, took it for about a 15 minute ride and it stalled twice and when I rode into my garage fuel was dripping from the left intake, not pissing like it was, but dripping. So I go to mess with her today and she won't start, full choke nothing, after about 30 kicks(it's kick only btw) she starts with the choke off, is idling like crap and when I would try and open the throttle it would die. So I then decided to mess with the mixture screws on the carb, the right was at 2 turns and the left was at 3.5(never have I touched these before), so I set them both to 2 and eventually 2.5 and she started, sounded better than before and then died. So after about 45 mins and dripping sweat in the Vegas sun I threw my hands up, said fuck it, pushed her inside and now I'm going to you fellas for help. Hopefully I was descriptive enough for you. Please help!

 

[NONclow]

First off welcome to the site! If you have the vacuum petcocks it sounds like the left has a hole in the diapragm and is flooding into the left intake via the barb on the carb boot. Has your oil level increased? Does it smells like gas?

 

[Pattymatts]

Thanks! We'll I don't believe I have vacuum petcocks, they're aftermarket(2 feeding into one t-line,but I only open one petcock) I just did an oil change yesterday. And yes it does smell like fuel while I'm trying to kick it over.

 

[NONclow]

Me thinks the carbs need rebuilt, not just a cleaning, the LH float could be compromised, or the float needle and seat. The BS34's also have a small black plug that isolates the pilot circiut (the tower adjoining the main jet). If it's left out, or in need of repacement, you'll get way too much fuel.

 

[Grinder]

Does your battery have a full charge? Was the charging system working?

 

[I am Carbon]

Well if your carb or carbs are screwed up you will have problems like you are having.
CV Carbs - one of the best how-to manuals ive found for the original carbs
http://www.amckayltd.com/carbguide.pdf
this will help you understand your carbs.
Your carbs should be the bs34s
there are good pix in there that will identify them.
or post a photo and we will identity them.

 

[Pattymatts]

Took it to the shop that cleaned the carbs in the first place, told them it was fucked up. I guess something was tweaked and was making the float catch on something, couldn't really understand the tech because he was deaf. Him red-lining the bike with my Ya Mama exhaust while I was right behind the pipes didn't help me hear any better either haha. Another guy at the shop said something along the lines of my tank being more upright than stock there was more pressure feeding the gas through the petcocks so I don't really know haha. But it's back to working now and I'm happy. Thanks for all of your inputs fellas! I'll understand more about them through trial and error and studying these carb guides more and eventually get the hang of it!

 

[XSLeo]

I might suggest you tell us a bit more info. Like what mods you have done. Any mods to the air intake and exhaust have a very strong effect on how a bike runs.
If a guy tried to tell me that how level a tank sets on a bike can cause a bike to act like yours does, I would find another shop. No, I wouldn't I'd fix it myself.
Read the carb guide. Take off your carb's off, tear them down, clean them, inspect them.
As far as the position of a tank the only effect it has on fuel pressure at the carb is the height of the tank above the carbs. Higher makes more pressure. It would have to be several feet above the carbs to have much effect on the carbs.
Leo

 

[joebgd]

Idk why when i put my vacume petcock on prime my carbs leak, why on just strate on n off petcocks that doesnt happen? Or is thhere something wrong w my carb? Figure its somewat related,

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[XSLeo]

With vacuum petcocks, no fuel flows in the on or res position. unless the engine is running.
When you put it in prime, you are bypassing the vacuum control. So you get fuel flow even when not running.
The same over flow will happen with regular petcocks. Over flow happens when the float valve won't seat properly or on some years a bad o-ring on the float valve.
Taking the carbs off and cleaning them, adjusting the float level, should fix things.
Leo

 

[joebgd]

So am i corect in saying fuel should not b leaking from my intake when my petckoc is on prime?

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[NONclow]

If the float needle and needle seat have an acceptable seal, then NO fuel enters the carb. No matter what the petcock is doing.

 

[XSLeo]

Anytime fuel leaks out of a carb then yes, you have trouble. It doesn't matter what petcock or position.
A leaky pet cock can contribute to a leaky carb but if your petcock is functioning then no fuel gets to the carb to leak.
NONclow, you are talking like the float valve is a shut off, it's not, it's a metering device to control the fuel level in the float bowl. If it was a shut off then they wouldn't waste the time and money adding a petcock.
Leo

 

[NONclow]

it's a metering device to control the fuel level in the float bowl

Yup. If the bowl is full, it shouldn't get any more!

What I meant was it shouldn't be flowing exsessively, or puking out. I also prefer the positive function of manual petcocks, not lackadaisically trusting an aged rubber (or not if it's new) diaphragm to stop the flow untill the motor starts producing a vacuum pulse. I use those barbs for tuning purposes... when present

 

[weekendrider]

So am i corect in saying fuel should not b leaking from my intake when my petckoc is on prime?

Posted via Mobile

Yes you are correct. If the float valve is working correctly it should stop the flow.
I don't care if that float valve is in your carbs, your toilet tank, a stock tank, a heater treater or any of the other many uses for float valves. That is what they are designed and used for. To stop flow after a certain preset level is attained.

As for the purpose of petcocks. They hold fluid in the tank any time the fuel line is unhooked from the carbs. Think about what a pita it would be if they weren't there.
You would have to drain the tank each time or add line to get above the pressure.

Yes I use my tank valve.
Yes I shut if off before I actually stop to keep from leaving the carbs full.
But I also turn them on and let it sit sometimes to make the float valve is doing it's job.
Stopping the fuel when the bowl is full.

 

[Pattymatts]

Well it's doing the same thing again. Wouldn't start, fuel pissing from holes in back of carb, etc. taking the carbs apart while reading the carb guide. Hopefully I find a problem.

 

[Pattymatts]

And being more specific the fuel is coming out of the pilot air jets

 

[Pattymatts]

And being even more specific it doesn't do it when I back my petcock off to a certain point.

 

[nj1639]

On the fuel line from the petcock to the carbs.....
I run my line on the outside of the left carb into a fuel filter and then sweep it up between the two carbs into the 'T' that has been turned down. Yeah, it's in the open but I can see the filter and any debris in it and it makes taking the tank off and on a two minute job.

You could disconnect the fuel line into the carbs and see if the petcock is allowing gas through.
I'd be checking the float height and the little rubber tips on them needle valves or whatever the hell they call them.....make sure they're pliable......get in there and clean their seating too.

I see you were posting whilst I was busy writing a book......