Solution for tower erosion

[cfairweather]

GL1000 carburetors often have tower erosion where the fuel jets are inserted. When excessive erosion occurs, the fuel jet O-rings are not able to seal properly. In the past, I have just selected larger O-Rings to resolve the issue, but I have always thought must be a better way. The past couple of days, I have worked on this problem and I think I have a solution. I only recommend this to people that have a lathe or a good drill press because you need to drill very straight and precise holes.

In a nutshell, I drilled out M4 and M5 rivets and then drilled out the tower jet holes so the modified rivets would fit very tightly into the holes. This post is only a brief explanation of what I did and the details are not included.

The big challenge with this project was drilling out the rivets without damaging them. The walls on the rivets will be very thin after you drill them out. To drill a perfectly straight hole, I used my Grizzly 9729 combo lathe with the rivets inserted in the spindle and a bit in the tail chuck.

To drill the tower holes out, I used the bed of the mill to securely clamp the carburetor and then carefully used the mill/drill press to drill the hole. In some of the pictures below, I used a worthless carburetor to test my idea. If you decide to try this, I recommend playing with a bad carb until you perfect your methods.

In the primary jet hole, there is a small hole that connects the middle hole for the slow jet. You must add a hole to the rivet wall so this important passage is not blocked. Look at the picture of the rivet on the drill bit and you will see the hole I am referring to.

For the primary fuel jet hole (the smaller hole), you will need to drill the M4 rivet out with a #7 bit. The tower hole needs to be drilled out with a #1 bit.

For the secondary fuel jet hole (the larger hole), you will need to drill out the M5 rivet with a #C bit. The tower hole needs to be drilled out with a 6.8mm bit.

Using these sizes, you will be able to use a hammer to “press fit” the rivets into the holes. I then used a file to remove excess material from the rivets. I am very pleased with the results.

[gltriker]

Finally!! An Elegant solution Cedric

[Whiskerfish]

Nice!!

[cfairweather]

I will be ordering some brass tubing with the correct ID and OD, which will make this task much easier. It will eliminate the need to modify rivets. If I can make this easy enough, I will put together a kit. Almost all of these carbs have some degree of erosion in the holes, so it might make sense to do this during a rebuild. Here is a tip: To ensure you get the hole drilled exactly in the correct place, I find a drill bit that will fit in the existing hole and get the drill press perfectly aligned. Then, replace the bit with the correct size to drill the hole. Look closely at how I clamped the carb to the lathe. It it very secure using this method and I even did it that way with a complete rack of carbs.

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[gltriker]

This begs the Big question....
Are you prepared for the onslaught of requests to perform the entire Solution?

[cfairweather]

Cliff- I haven't considered that , but if I can make this easy enough, a person with good skills and a drill press should be able to do it. I am excited to try the tubing that I found, because it should simplify the process. I am interested in hearing from those of you that rebuild a lot of GL1000 carbs. Do you see marginal holes on a regular basis?