Rough Idle & Delayed throttle response

[smithman123]

I have recently rebuilt the carb on my 71 m38a1 and have noticed that it idles rough and when applying the throttle there is a large delay? Is this due to an incorrect carb setting? As well, what is the screw on the outside of the carb for? I originally thought this was an idle screw but seems like I was mistaken? I has a spring attached on the shaft of it and has a washer with a tab that hooks into the carb. Any help is greatly appreciated!

 

[NDT]

Welcome. That screw is indeed the idle mixture adjustment. When you rebuilt it, did the check ball or balls (forgot quantity) go back in the right places?

 

[smithman123]

I believe I put everything back in as found just with the new parts. With that said i believe I only had a few left overs from the rebuild kit but I accounted for where they went. In regards to that screw, does the more you turn it in the more fuel to the carb or vice versa? I have found starting to be an issue with it as well which is most likely a related issue. If it dosn't start on the first go I have to use starter fluid.

 

[NDT]

In is lean. Could you have fuel contamination that came up from the tank and messed up your fresh rebuild?

 

[smithman123]

Very possible as I did have a bunch of really bad gas go through before I thought to drain the tank (It was a stupid moment for me) Should I pull it off and clean it out or would a gas additive carb cleaner fix this?

 

[Karl kostman]

I would drop the tank and do a good cleaning, I have and M37 and when i drained the tank I also needed to pull the sending unit and got a look inside the tank and it was NASTY beyond words. The tanks are easy t take off and reinstall and you KNOW what you have then and really besides a few hours you have nothing to lose!
Karl