yamaha carb

[jwilkey84]

This is a little off subject, but I have an old yamaha scooter/motorcycle thing and I have a question about the carb. I was haveing trouble with it running right(sputtering), then I found a hole on the side of the carb and when I plug it, this thing runs awesome. What am I doing, any ideas? I figure the principle would be the same for a boat motor since this is an old two stroke yamaha chappy. thanks for any info as I am haveing a hard time finding an explanation.

 

[Whoopbass]

Re: yamaha carb

Is the hole for the lean/rich mixture screw?

Plugging that hole might cause a lean mixture and will quickly lead to seizure.

When I was younger I put a new piston in a Husky chainsaw and set the carb way to lean because I didn't know squat back then (barely do now). Well, that chainsaw buzzed through wood like one of those "hot saws" on Espn. It lasted maybe two outings before it seized again.

 

[jwilkey84]

Re: yamaha carb

no it is not a hole for a lean/rich screw. It is just a little aluminum nipple that comes off the carb, previously it had a hose on it, but I dont think it went anywhere, it was just kind of an overflow hole or something. When I went through the carb I just left the hose off since it went nowhere. There is another nipple on the carb that has a hose to nowhere, but it comes off the bottom of the bowl, I just figured it was like a drain hole for the bowl. so basically from what I can tell i just have one hose on the carb that does anything, the hose that brings fuel from the petcock to the bowl of the carb. The other two "nipples" dont really lead to anywhere, but when I plug the one it runs good. I ran it around the block this way, hope I didnt hurt anything. This particular motor has an "oil injection" automatic oiling system, so could I still run it too lean and hurt something. I am not for sure how the oiling system works, but it looks like it puts oil in the cylinder after gas has entered the carb.

 

[Whoopbass]

Re: yamaha carb

I have no idea what the hole is for. Try looking up that model of scooter on the internet and maybe you will get some info.
Since you have oil injection you will always get the right mixture (as long as its working) but that has nothing to do with the lean/rich settings.
If the motor is idling fine the mixture screw is probably set right. If the rpms are high at idle it could be too lean or if its idling rough it could be too rich.

Sounds like a neat scooter so you should try and find a maintenance/repair manual for it.

 

[blared]

Re: yamaha carb

I don't know what year or model is your scooter, it can be bowl went, fuel in, idle air, or main air or even a oil inlet. I would tell you if you had a picture.

 

[jwilkey84]

Re: yamaha carb

ill get a picture tonight

 

[jwilkey84]

Re: yamaha carb

here is a picture of the carb, if you can identify this hole just above the main fuel inlet and tell me if it is ok to plug it that would be helpful. when I plug it, the bike runs better. Thanks for the help even though this is a boating forum! http://s281.photobucket.com/albums/kk205/ownerator84/chapy/

 

[blared]

Re: yamaha carb

From what i see in the pictures it's your idle air, main air or bowl vent but since i cant see the other side I can't tell ... if it had a hose going nowhere it is probably a vent.

 

[jwilkey84]

Re: yamaha carb

so if it's a vent, is it ok to plug? Some people have told me to just plug it off. I am getting mixed signals.

 

[cousinabe]

Re: yamaha carb

post the year, make and model number of the scooter.
you can possibly get a diagram here.
http://www.boats.net/parts/search/Yamaha/Scooter/parts.html

 

[jwilkey84]

Re: yamaha carb

it is a 1976 yamaha chappy LB80

 

[cousinabe]

Re: yamaha carb

i found some parts diagrams which may help.

http://www.cmsnl.com/yamaha-lb80-scooter_model16970/