Bike very hard to start and won't crank with choke on? urgent help needed!!

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ossagp

PD you say you checked the float, did you set it? The bikes you used to see on TV winning supercross races that were carbureted had theirs set before the event each time. So doing that to yours probably once in every 10 years might not be overkill. Sounds completely classic, and as I have stated before a very neglected part of a tuneup. For some reason people think those things stay where the factory put them.

I have seen people clean caburetors until they are "stony" from the fumes, and if you think about it, plugged jets cause your bike to run lean, and if yours is starting without the enrichenor circuit opened up, then yours is ANYTHING but LEAN.
 
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pdee4t

Yeah I reset it as per the manual seeing as I had the carby off the bike and all apart. 1 of the things I'll regularly check and keep an eye on now though.
It starts with out the enrichening circuit but doesn't run. Im able to use the choke after its started though.
 
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pdee4t

Yeah kinda. Previously I've had to use the choke to start it initially for 10 or so seconds then it idled fine without the choke.
With this issue it starts without the choke but doesn't run for very long til its warm then idles great without choke.
With this issue, I start it without choke then once it's started I turn the choke on for 10 seconds, then turn the choke back off and it idles fine
The only time time I am able to use the choke now is when the bikes already been started. But for initial start up, it won't start if I have the choke engaged. Very confusing.
 
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ossagp

yes, very confusing. have any of those symptoms changed since you started trying to correct the first problem? I had one carburetor on an early 426 yamaha get kind of stranged and it was oring related, at throttle closed positions it ran rich, but as soon as the throttle opened it made a lean situation. apperently robbing fuel from a fuel circuit and then losing the fuel once the vacuum dropped.
 
Mihylo33

Mihylo33

ossagp:
yes, very confusing. have any of those symptoms changed since you started trying to correct the first problem? I had one carburetor on an early 426 yamaha get kind of stranged and it was oring related, at throttle closed positions it ran rich, but as soon as the throttle opened it made a lean situation. apperently robbing fuel from a fuel circuit and then losing the fuel once the vacuum dropped.
Click to expand...


Winner winner chicken dinner!!!
Clean it twice then one more time just to make sure it's clean....
 
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ossagp

It would be nice if i was there. Did you catch the part in my other reply about orings? You seem to have a situation where at max vacuum (throttle closed) the bike runs rich, which is consistent with a float problem, then it sounds like you are saying you need the choke to make it run right off of idle. So we get back to orings that are designed and used to keep fuel in and air out. Did you take it down far enough to get the orings out and clean or replace? how about the ring seal under the throttle valve place? I have never seen one of the later cause what you are talking about exactly, but I am not sure I know "exactly" what is happening.
 
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pdee4t

I had a look at the o ring under the throttle valve piece but not far enough to get all the others out.
I did spray some plastic/sensor friendly carby cleaner in there though. Alot of it to clean it out.
It is normal for that bike to need the choke for 10 seconds upon initial start up until warm.
I've always needed to use the choke for 10 seconds to start the bike up and get it idling. But I've always been able to start it up with the choke and turn it back off after 10 seconds then the bike would run fine. Now the bike won't start or crank much with the choke on but since this issue, the choke seems to work only once the bike has already been started without it.
 
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pdee4t

i think it might be a float issue actually. i just re-tested the float and hooked the carby up to the fuel tank, unscrewed the bottom carby drain plug, turned the fuel switch on and only very little fuel came out the bottom of the carby. just little drops. it didn't pour out as such and stopped dripping out pretty quickly too. so i guess i just found my issue?
 
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Mihylo33

Mihylo33

Something within the fuel system is plugged. Like ossa said...a bad oring or just dirt. Start with the in tank fuel screen and work your way down. Once everything is broken down and cleaned it should be good to go.
 
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