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Carb Q.. Nothing out of drain screw?

11K views 8 replies 4 participants last post by  GarySeven 
#1 ·
Ok at work, had a few minutes this morning to tear into the bike. Going to be back at it tonight.



Short story. I am selling my firends 1991 Tw200. Its been stored at my place, and between some family illness and an engagement, both on his side, he will not have time to ride any longer.



It had only been ridden 1-2 times last year. I rebuilt the carb spring 2011. I went to start and its getting spark. I figured it was getting fuel, but when I opened the drain screw only a little fuel came out.



If I turn the petcock on and open the drain screw no more gas comes out.. When I remove the inlet hose from the carb, gas runs out of the hose, when the petcock is on. So I presume its a downstream problem on the carb.



I believe I should drop the bottom off the carb again and check it out, but what could have caused this, especially with the recent rebuild on the carb?



Any ideas given will help me get to it tonight. I want to make sure it runs correctly, and starts ok before listing it for sale.





I did remove the drain screw and tap on the side of the carb this morning, as that is how I got it to work before the rebuild... this time it didnt seem to allow any additional flow.





Thanks.
 
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#3 ·
I did replace parts.. here is a screenshot of the parts replaced. They were OEM from the local yamaha dealer.



Dropping the bowl I should be "possibly" able to diagnose, or should I pull the carb?



I am so weak when it comes to carbs, and bikes in general. Although I have read quite a bit in the past, I will read and investigate.







 
#4 ·
I was thinking you may have went with the after market carb kit. OEM should not cause you problems. I am not a 'tech' guy so I will defer to the opinions of those more knowledgeable. If I were faced with your situation, I would first see if I could solve the problem by loosening the carb and twisting it as to remove only the floatbowl. In my opinion, lots of testing and service can be done like this. Best of luck. Gerry
 
#5 ·
Open petcock to reserve. open carb drain screw a few turns. Tap on side of carb and see if fuel starts flowing out drain. Does sound like stuck needle/seat/float.
 
#7 ·
maybe apply some light air pressure to fuel inlet of carb? carb spray in inlet?
 
#8 ·
So I started and just ended up pulling the carb...



Green oxidation or substance on the bottom of the bowl, in the main jet hole and all over the needle valve.. to the point that the needle valve was stuck up (compressed), therefore when the float dropped it wouldnt allow gas to come in? At least that is how I believe it works.



So I am soaking that, and while I replaced the needle valve set last year, I may replace it again.. price seems to have jumped up to almost $20 from $13 last year.. so I may not given its not my bike and I am selling it, if I can get the bike to function fine once its cleaned up.



Anyway what might cause that oxidation or substance. It was geen, almost reminded me of algea. We used stabilizer as well as a little seafoam in the gas last year while riding.
 
#9 ·
Someone told me recently that gas now has a shelf life of about 15 days. You just don't want to leave it in anything. We ran old gas in our Troybuilt tiller and it caused a valve to stick, which then screwed up the cam. What happened was my wife started the tiller, but left the choke on. This dirty gas, along with the choke, caused a film to form on the intake valve, which after some minutes runtime stuck. When the valve stuck it caused the plastic gear on the cam shaft to shear. I ended up having to take the motor apart, replace the camshaft, get the valve free. It ran again, but cost me $80.



I've seen that green stuff in carbs. My tiller has similar stuff after sitting all winter. My TW200 did not have the green stuff, but it does have a stuck needled valve after sitting all winter.

My TW200 has the same carb problem, no gas in the bowl. Has to be a stuck needle valve. Earlier comments in this thread are correct, don't buy that expensive carb kit. Typically the problem with a carb will be the needle valve. My 1940 Ford 9N tractor had sit for about a year without being started. I had to clean the points and it was also not getting gas. It would start, run for just a few seconds to 30 seconds, then cut off. Start back up in a bit and do the same thing. The needle valve in the carb was sticking, but sometimes freeing up, hence it would run, then quit. I'm 53, so have seen changes to carb parts over the years. Really old carbs had solid brass needle valves. In my opinion they were more durable. Newer style needle valves have some type of rubber material on their tips. This tip seems to break down from the gas over time. They get sticky and the needle will start sticking when the float drops down. You can clean it all you want, but the needle will still stick. All you can do is replace it. Your typical carb 'rebuild' is to soak it to get all the trash out, then blow it out, replace the needle valve, adjust the float height and put it back together. For my Ford it was just that, replaced the needle valve, adjusted the float and it ran great.
 
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