Needle, seat, and spring

This is a 20HP with a Tillotson MD carb. The needle does not have a rubber tip but it does have a spring. The spring has a little tail on it. I want to know for sure how the float tang relates to the needle. I made a little drawing. Is the top or bottom one correct? Mine's like the top one right now.



I'm thinking about removing the bowl tomorrow and pumping some fuel into it while holding it level to see what it's doing. Is this a good trouble shooting technique?

Re: Needle, seat, and spring

top pic is right

Re: Needle, seat, and spring

This is from the manual


The rubber tip was an update. I would think all the new carb kits have them now. Yours must be an original.

Re: Needle, seat, and spring

eurolarva said:

Yours must be an original.

Click to expand...

I believe it is. It's not like your pic. There's no spring there. The spring is tiny and it's attached to the arse end of the needle.

My engine is a model 202HD. Sierra doesn't have a complete kit for mine. They don't even sell a needle and seat for it. Hell, I don't think they sell anything for it.

I purchased a NOS (new old stock) carb kit from Franz. It did not contain a new needle and seat. He said he had 2 more kits in stock and neither of those had a needle and seat either.

I'm just trying to track down this flooding issue.

Re: Needle, seat, and spring

can you take a digital pic of the needle valve next to a ruler? What you are describing as a spring is it possible that is the retainer clip for the needle valve. When you contacted franz did you ask if a 18-7037 sierra kit would work on it? See photo. Iems 2 and 3 are the same unfortunatly I think they came from the 18-7037 kit. I have rebuilt a few carbs and these were in my junk box.

Re: Needle, seat, and spring

Next time I have it apart I will take some pictures. It's a square needle for sure. I've looked through the Sierra parts catalogs online. They have needle and seats for 20HP, but they don't mention my model number.

When looking for parts, you will almost never see anything that says it fits a 202HD.

Re: Needle, seat, and spring

Here's mine. It's about 1/2 inch long give or take.

I preformed my "bench test" and am satisfied with the results. I removed the bowl from the carb and held it level while I squeezed the bulb. The bowl filled with fuel close to the rim and then stopped when the float closed the needle valve. I was not able to pump any more fuel into the bowl by squeezing the bulb once the needle valve was closed. I believe this proves that all the parts in the bowl are functioning properly.

I don't know why it's flooding, but this ain't it.


I was also pleased to find that for the first time ever there wasn't trash in my float bowl.


For now, it's still a mystery why it's running like crap (sometimes) and hard to start (sometimes).