Carburetor Leak and Air Cleaner Clean Up   Leave a comment


When I was originally looking at JP, the evangelist told me the carburetor was leaking. “It’s easy to fix with a $5 part from NAPA,” he told me. Since he was an evangelist and seemed like the real deal, I took him at his word. Once home, I could see it was the diaphragm connected to the throttle linkage that was causing the problem. Four loosened screws later I was holding the diaphragm in my hand. The problem I found was that not one of the parts stores in my town stocked a “$5 part” in this size. And since there was no label or tag on the carb telling me what kind it was, and I obviously had no idea, nobody could even order it for me.

To avoid any more wild goose chases, I decided to take the whole carb off and bring it around with me to see if I could get the right part. Besides, it would give me an excuse to turn a wrench and learn a little more about this stuff. I was a little nervous considering I had never done this before (which will be a recurring theme on this blog) but it came off very easily even for me. Once the carb was off, I found the real reason for the leak was a broken screw hole but figured I would replace the diaphragm anyway. Before I took the carb around looking for the part, a guy I go to church with told me about a local short-track engine builder that could probably help me out.

The next day was Labor Day but I thought I’d drive by his shop just to see if he was working. A car in the lot let me know he was. As I walked through the door a bell announced my entrance but nobody came to the counter. After a few minutes, I walked around back and there he was grinding on something. I got his attention and told him a friend of mine said he could help me out. He stopped what he was doing, came to the counter, and looked at the diaphragm and carburetor. “That’s off a Ford 390, ain’t it?” Bingo. This guy obviously knew his stuff. He told me he thought he had what I needed and disappeared into the back for a few minutes. When he came back he handed me the correct part. I asked him what I owed him and he said, “Aw, just give me a dollar. But your leak is coming from that broken screw hole.” He confirmed my suspicion that the screw didn’t have enough grip to hold the diaphragm tight thus allowing the gas to leak. [See the lower right of the orange circle in picture 1. This also shows the condition of the carb as I purchased it in all its varnished glory.]

Once home, I put a little blue Loctite on the screws (can’t help it, you Loctite everything on a Harley) and a dab of gasket sealant around the bottom right where the hole was broken and tightened the diaphragm up. I’m a month into this project now, and so far my fix is holding with no leaking. Also, since I had no idea how old it was, I went ahead and replaced the carburetor base plate gasket at this time.

I had already decided that whatever we had to work on we would go ahead and clean it before putting it back into service. Now was the carb’s turn. As you can see from picture 2, the carb and air cleaner were pretty dirty. There was a ton of “varnish” on the carb from the gas leak, engine heat, and no telling how many years of use. Also, the PO had at some time painted the air cleaner cover and base black and it was beginning to peel. That needed cleaning up, too.

I learned a trick a few years ago while racing remote control cars that would take care of the varnish on the carb. Easy Off oven cleaner, as you can imagine, will eat right through this baked-on gunk. But you have to be careful because one of the side effects is that it will also take paint off whatever it touches. In the case of the air cleaner, that was just what I needed. I put the foam on the carb being careful not to get it near the newly installed diaphragm because I didn’t know what effect it would have on the soft material. I also coated the air cleaner cover and base with a generous amount and set them aside to soak for a day. At the same time, I tried a forum hint and soaked the wing nut in vinegar to see if it would really get rid of the rust and it actually did a pretty good job. One other caution about Easy Off – it will cause blisters if it comes into direct contact with your skin. Don’t ask me how I know.

The next day the Easy Off had done its job on the air cleaner and I wiped the paint off with a shop rag. Some aluminum polish gave it a nice little shine after being covered with paint for who knows how long. With some more effort the carb varnish also came off. I then used some Simple Green and a little more elbow grease to clean the rest of the carb. While I was at it, I decided to go ahead and give JP a new air filter so he could breathe. I sat it on its base, tightened everything up and felt a sense of accomplishment at what I had learned. I still need to either clean or replace the spring on the side and maybe replace the throttle linkage to finish the clean-up. Picture 3 shows the finished (for now) product.

I’m pretty pleased with the results of my first small project

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Posted September 30, 2010 by jglee920 in Engine

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