MTFCA Forum

I fired up my '19 for the first time since last fall and though started, it ran poorly. In fact, it barely made it around the block. I had to work the choke a lot to keep it running. I decided to pull the carb (bronze L4) for a clean. I've never had it off the car or completely apart. I discovered that it is missing the flapper.

What is the purpose of this part? Typically how does the engine run without it? Where can I get a replacement? My car has always had a bit of a misfire at idle. I'm wondering if the missing flapper might be the reason.

Thanks

The reason you had to work the choke a lot is because of the missing flapper. That flapper is a weighted air valve. When idling the flapper is closed it allows less air to flow and more gasoline to be picked up. As the engine speed increases the airflow causes the flapper to rise up and allow more air to flow through and lean out the mixture. As you describe, without that flapper it will barely run at all because it would be starved for fuel pretty much all the time.

I have a couple of the later, tongue shaped style flapper, I'd be happy to send you one if you can use it, PM or email me via the forum with your shipping address and I'll send you one.

Based on the cross section below, it's possible that your brass L4 may use the earlier, more ball shaped flapper, in which case one of mine won't fit.

If you are missing the flapper chances are you are also missing the bumper that fits in the air valve cap. If so and it is the earlier carb with larger air valve cap, you can make one out of cork. Langs sells the smaller later L4 bumper.

It is missing the cork bumper for the valve. Thankfully the pin for the flapper is still on the screw. If anyone knows of a source for the flapper for this carb, please let me know. I'd also buy a complete carb if necessary.

Matt, I boxed up one of my later flappers and one of the small cork bumpers that the vendors sell for the later carbs, they should ship out tomorrow (Monday) in a single small USPS Priority mail flat rate box. Please send them back if they don't fit your carb.

BTW, here is a drawing of the later Kingston L4 courtesy of Martynn Vowell:

Many thanks, Mark!