1974 300 jd

Deleted User · Post by **Deleted User** » Mon Jan 14, 2008 11:59 am

just purchased 1974 300 cleaned gas tank new fuel filter gas lines but bogs o ut at 3%4 had 'ski doo' mechanic look at carb 'walbro' he says just leave it . how can i clean it easy thanks cant type very slow

HoosierDeereMan · Post by **HoosierDeereMan** » Mon Jan 14, 2008 4:22 pm

The best way is to take the carb off and tear it down. Buy a complete Walbro brand rebuild kit. They cost around $30 to $35 depending where you look. Cleaning the carb can be done two ways. You can buy a gallon dip can with a basket and let it soak over night or you can buy 3 spray cans and clean up everything with them. It really depends on what the carb looks like after you tear it apart. If its fairly clean and all the passages and pin holes are open you might get lucky with the spray cans. If its pretty dirty or rusty looking inside I would buy the dip can and soak it over night at least. Scotch brite pads work good for cleaning the gasket surfaces. Don't use a screwdriver or putty knife as it will damage and mar the raised rim on the plates that seal the gaskets. Compressed air works best for cleaning the tiny ports and passages.

Some things to beware of: There are small indentions between the sandwich plates. Use them with a small O ring pick to pry the plates apart if stuck. Be careful with the very bottom plate at there is a screen in it you will have to reuse.
If the metering plate on the bottom of the main body is rusted chances are the 3 screws that hold it in place will twist off. At this point you are done. Also note that when you remove the choke shaft there is a detent ball about the size of a BB that will fly out because its spring loaded. So be prepared.

The reason I suggested a Walbro brand rebuild kit is because it's the most complete of any kit you can get. You also get a good set of instructions for rebuilding and setting up your carb.

Good Luck!

Deleted User · Post by **Deleted User** » Mon Jan 14, 2008 8:39 pm

Thanks for the info and help. Do you know who sells the kit and windshield?

Maj_hazard · Post by **Maj_hazard** » Tue Jan 15, 2008 12:10 pm

Ah....The good old WDB-31...

I swear at one point these Walbro carbs will be the cause of my next divorce..

After all my experience I would do the following..

Do a basic disassemble and see just what shape things are in.. If she's clean looking I'd replace the diafram (sp) do a general cleaning and stay away from disturbing the height of the metering valve...

If she's gumkie then tear it right down and a good over night or longer soak would be in order. A stiff haired brush, pipe cleaners (bend the end of the pipe cleaner 180 degress so it won't scratch anything.) wire) and compressed air is your best friend. You can never get things too clean so take your time.

If you find the interior rusted (white powder) then you may need to find another carb to rebuild.. Once they start to oxidize there is little that can be done to stop the process. A cleaning will work for a while then your problems will return.

On reassembly watch the order of thin and thick gaskets on the circuit plate and take your time setting the height of the metering valve.

If you take your time it's really not that bad but if you take any shorts cuts it will likely come back to haunt you..

Just my 2 cents worth.

Cheers
Mike

Danzig · Post by **Danzig** » Tue Jan 15, 2008 1:14 pm

When you get really good I can come over and we can race on tearing one of these down and putting in a new kit and re-assembling. I can do it in 7 minutes...

Danzig · Post by **Danzig** » Tue Jan 15, 2008 1:22 pm

JDFanPa · Post by **JDFanPa** » Tue Jan 15, 2008 11:50 pm

I agree with Todd on just replacing the diaphram and a good cleaning if the other components look good since it is actually working somewhat now. Changing everything in the complete kit and messing with the metering lever may give you some greif you dont need.