carb

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Old 04-16-03, 05:15 PM
racer
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carb

I am cleaning the carb on a Yamaha Sno-scoot with a mikuni carb.I cleaned it and put it back on but it wouln't run unless I put fuel in the spark plug hole. So I took it back off and took it apart to find that I had cracked the rubber cap that plugs the hole where the low speed jet goes. Would this cause the problem of it not starting? What would that plug be for? What does it do? I never saw a plug like that in any other carbs that I have worked on 4 wheelers,snowmobiles or lawn mowers. Any help would be appreciated!!!!!
 
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Old 04-22-03, 07:28 PM
engine ear
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i am guessing it is some sort of seal that needs to be airtight in order for it to rin properly
 
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Old 04-22-03, 11:48 PM
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Hi Racer!

If the cap is cracked, it will allow air to enter through the hole it plugs, causing a lean mixture, possibly too lean for the engine to run. Why there is a plug instead of a needle valve is beyond me...these snowmobiles are not really my area. I do know that some 2stroke engines don't use a low speed screw....maybe this is one, and the carb is made for both applications, and just has the low screw hole plugged in your application.
 
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Old 04-24-03, 05:31 PM
racer
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I got the new rubber plug and installed it. I got it running ok at idle but when you go to open the throttle it will bog and die the engine. Then to get it to start again I have to squirt gas in the spark plug hole and it will fire right up again and idle until I open up the throttle again. It has a crack in the rubber boot that connects the carb to the engine. Would this cause this problem? Sometimes I feel like giving up the small engine work when you have problems like this. Does every mechanic run into problems like this and feel the same way sometimes?
 
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Old 04-24-03, 07:37 PM
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Yep...we all have "those days". They will get fewer and farther between with the more experience you get. The rubber boot from the carb to the engine will cause problems if it is cracked all the way through. Any place the engine can get air other than through the throat of the carb will cause problems. Your engine is leaning out. (more air than there should be in the air/fuel mixture). It could be carb related, or if the boot is cracked all the way through, that is a major contributor if not the entire problem.
 
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Old 04-25-03, 02:53 AM
racer
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It isn't cracked all the way through and I put some electrical tape around the boot where it is cracked to see if there is any difference but none at all. I can't get the main tube out of the carb it seems to be seized in and whoever worked on it before almost has the head stripped.
 
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Old 04-25-03, 11:24 PM
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One of those, huh? Somebody elses' failed attempt to fix the carb is causing you grief, lol. You may be able to soak the carb in a can of chemdip, but I think you'll be better off installing a new carb. It's not your fault that someone else stripped the thing out. You could wind up spending a heap of time on this thing, and still be back at square one, needing a new carb. Your call, but you know how valuable your time is and what you can charge the customer.
 
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Old 04-26-03, 05:54 PM
racer
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I cleaned the carb really good and then blew it out with compressed air and put it back on and it fired up right away. Runs like a top. Thanks for the advice guys.
 
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Old 04-27-03, 07:30 PM
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Good job! I'm glad this one went your way!
 
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