1961 Mc Scotty 3.6 fuel problem

[twocyclemania]

I have a McCullough Scotty 3.6 with the tank on top. I added an in-line filter and the fuel flows to the carb with no problem with the hose disconnected. For some reason the fuel in the carb is quickly used up and it does not refill. There is a small pin that's attached to the float in the carb and this will rise up about an eight of an inch when the bowl is full. The gas is quickly used up as evidenced by the pin dropping and most of the time it does not refill without a lot of pampering. The bowl has been cleaned - the motor has had little use. I feel like I'm violating some law of physics as to why the fuel will not refill the bowl. Oh, yes I've even tried it with the cap to the tank removed so as not to create some kind of vacuum. This is a weird one. Thanks for any help!

 

[mrcrabs]

Re: 1961 Mc Scotty 3.6 fuel problem

I added an in-line filter and the fuel flows to the carb with no problem with the hose disconnected

you lost me here...what hose is disconnected? I want to say reconnect the hose but I'm sure there is more to the story. Please explain.

 

[twocyclemania]

Re: 1961 Mc Scotty 3.6 fuel problem

Yes, you're right there is more to the story. Sorry, I wasn't clear on that description. What I was trying to say was that the gas flows freely (as evidenced by the flow) from the tank on top and through the hose and filter. In other words, there's a good flow up to the carb with no restrictions.

 

[mrcrabs]

Re: 1961 Mc Scotty 3.6 fuel problem

you may have a restriction above the needle valve, Take the float and needle out and try compressed air down the hose nipple, there is also a atmospheric relief hole some place on that carb I would guess and that could be stopped up....maybe you need to strip the carb down and give it a good soak in 87 octan w/ethanol for a few days then take the air to it.

 

[twocyclemania]

Re: 1961 Mc Scotty 3.6 fuel problem

mrcrabs thanks! I believe you said the magic words 'atmospheric relief hole.' There is no logical reason for that fuel to not constantly fill the float/bowl other than something like that. I'll let you know how I make out. If anyone has a a diagram of this Tillotson carb AJ16A I would love to see it or an idea of where the relief hole is. thanks

 

[F_R]

Re: 1961 Mc Scotty 3.6 fuel problem

That hole where the float pin sticks through the bowl cover is a vent. There may or may not be another hole also. There slmost has to be an obstruction between the hose fitting and inlet valve. Have you looked carefully?

 

[twocyclemania]

Re: 1961 Mc Scotty 3.6 fuel problem

I had a feeling that where the pin sticks through the bowl cover that that should qualify as an atmospheric vent as it's not sealed. Any idea on how to remove the cork float without damaging it? Is it supposed to slide off of the pin? What holds the pin as I'm not able to lift it out when the cover is off. How do you get in there? The float fits tightly in the bowl with no way to pull on it (if that's what I need to do) without destroying it. Is the inlet valve below the float? I'm a Tillotson newby (especially this model). thanks for the help!

 

[mrcrabs]

Re: 1961 Mc Scotty 3.6 fuel problem

Try this link from Marshall public library, it covers your 3.6 carb
http://search.ebscohost.com/login.aspx?direct=true&db=s9h&AN=24327821&site=serrc-live

 

[F_R]

Re: 1961 Mc Scotty 3.6 fuel problem

Closest I can come to your carburetor is the 1956 version. Should be similar. Float pin comes out the bottom of the carb. Float is held on by a couple of hairpin clips.

 

[twocyclemania]

Re: 1961 Mc Scotty 3.6 fuel problem

Thanks F_R and mrcrabs: I printed out the diagram (looks like it) and I'm ready to go. I'll let you know what damage I've done and if it's working.

 

[twocyclemania]

Re: 1961 Mc Scotty 3.6 fuel problem

Just an update but I think I may have solved the mystery of why the fuel won't go into the carb. bowl. I think we can forget some kind of atmospheric vapor lock;especially since there's no tight seal where the float pin moves up and down through the top of the bowl cov er. Not having a tight seal would allow it to breath (thus negating that concern) and if you picture it fuel would leak out the top of this cover if the motor were inverted. For some it's probably hard to picture this carburetor and pin assembly (if interested take a look at the diagram F_R graciously posted). It's the only motor I have that has that setup.

Anyway, the clips (top and bottom) that hold the float in position on the pin (that allows fuel to enter the bowl) are missing. The float apparently would slide on the pin and not pull the pin up to allow fuel into the bowl. Once the float is secured to the pin via clips the problem should be solved. Now I've got to find clips or else use a dab of epoxy between the cork float and the pin. I also intend to re-shellac the cork float before assembly. Hopefully this will help someone else down the road. I'll let you know how it works out. Any additional advice is always appreciated. Just an FYI. thanks