fast & slow mixture screws

[brmosh]

I have a 1958 18 hp Johnson. Ran good. When I used it the slow and fast idle adjustments would vibrate around and out of place. I took them out and cleaned them But didn't get them back on the right adjustment. Now the motor starts hard and when started will not throttle up. Does anyone know how to adjust the idle screws and is there anything that will keep them from vibrating out of adjustment?

 

[dostoy320]

Re: fast & slow mixture screws

Hey brmosh,<br /><br />A while back, someone on the forum pointed me in the direction of this post, which seemed to lay out the specifics of setting those low/high speed adjustments pretty nicely.

 

[Paul Moir]

Re: fast & slow mixture screws

To keep them from vibrating out, tighten the packing nut. It's the brass nut hex shaped part directly behind the mixture knob, surrounding the mixture control. If it can't be tightened any more, it's time to order up a new carb kit and rebuild it. In a pinch, you can remove the packing nut and jam some teflon packing from the plumbing supply section into it, and then tighten down the packing nut onto it.<br /> <br />Good luck!

 

[petrolhead]

Re: fast & slow mixture screws

I have that same engine and did a carb service last week, the old packing was rock hard and brittle, replace it with new packing and they won't vibrate any more.

 

[brmosh]

Re: fast & slow mixture screws

Thanks for the info. I think it will make the old motor work great.

 

[mikeythe2]

Re: fast & slow mixture screws

have a 57 fast twin that did the same thing so i took a rubber band a wrapped it from the high idle screw to low idle screw.