More Carburetor Questions

[Dark Horse]

I feel like I'm becoming a PITA asking all these questions lately. But here goes again.

I know that the idle adjusting screw has been a subject of discussion here in the past. Sticking and breakage problems, etc.

I was fortunate that all mine removed without incident. Now that I am putting things back together every thing has gone back fine with the exception of the #1 Carb.

Is it common to have one carburetor in worse condition than the other three?

My number one had the bad diaphragm (see "carburetor diaphragm" thread).

Now I find that the idle adjusting screw on #1 does not want to go back in the same depth that the other three went in. All the others had the pin end of the screw protrude into the bore of the carb about 3/64 of an inch.

When installing this screw it starts to get tight before the pin end reaches the small hole in the carb main bore. As this is my first time tearing down these carbs I don't recall how far it was in before removing it.

Because of past experiences of others I'm reluctant to use much force on this screw.

Any suggestions?

Also my Clymers manual says to install these all the way in and back them out about 1-1/4 turns as a starting adjustment. Any experience with this adjustment from the group will be welcome also.

TIA, again.

Bob Udy

[Ken Talbot]

Remove the pin again and check to see that it didn't get bent while it was out. Use a fine brush to clean the threads, and see if you can clean the threads in the carb body with a q-tip and solvent. Give the pin a light dab of oil then see if it will go back in smoothly.

Once you have all 4 pins going in okay, follow the Clymers' instruction, paying very careful attention to the word "LIGHTLY" seated. A wee dab of oil oil on each tip might also help to ensure that none of them binds when seated. 1 1/4 turns out will work as a starting point, but so will 2 turns. It really doesn't matter because the first thing you're going to do once you have the carbs sync'd and the idle adjusted is to start by adjusting each screw by a significant amount each way, first out then in.

You're going to be listening very closely for a change in engine speed and smoothness. You want to adjust so far out that you hear the idle speed fall off. Then you adjust in to where it smooths out, and keep adjusting till it falls off again. Come back out to the "sweet spot", then move on to another screw. You'll want to start this phase of the tune-up with the idle adjusted down to about 700 rpm. When you find the sweet spot for each screw, the idle will probably come up a bit. When and if it does, adjust it back down to 700 for the next screw.

When you've got all the pilot screws in their sweet spots, re-sync the carbs as they may have drifted a bit. Run through the pilot screw adjustment sequence again, and have a final lok at the sync. You should then be ready to adjust the idle speed back up to 1000 or 1100 prms depending on your personal preference, and you're ready to ride.

[Dark Horse]

Thanks

Thanks again, Ken!

It will be a while until I get to the point of adjustment and sync. I'm buying a diaphragm/slide from Andreas Weiss. He won't be sending it until later this week.

In the mean time I'll try your suggestions on getting the idle screw in #1. I tried cleaning the threads and WD40 for lubrication. But I didn't consider that it might be bent.

The other three went in without a hitch. I really appreciate your all your help.

Bob

[prometheus578]

"Sumptin's Screwy"

You've obviously thought of this already, so I won't tell you to take that screw out and swap it with one of the others. This will tell you you if #1's hole is loopy, or if #1 pilot screw is loopy.

[Winterhawk]

Run a 6mm ~ 0.6mm bottoming tap down the mixture holes and try a good screw.

[skids]

Hey, this is a family site!

Originally posted by Winterhawk
Run a 6mm ~ 0.6mm bottoming tap down the mixture holes and try a good screw.