Not sure I understand carbs well enough!!

[lkaskel]

Hi Everyone,
I have a Husky 18 ton log splitter that has a Briggs 110412-0158-E1 engine on it. It may not be the original engine because it has a Yard Machine label on the rewind pull starter. I bought it used a few years ago and it has never run great but it does start every time and it runs well enough to split wood. The main issue is that it surges very dramatically. I decided to really look at it today. I checked the valve lash and it was close but I did adjust it with no change to the performance. I then took the air cleaner/housing off and ran it with a wide open carb. It ran great!!! Ok, so why? I started with installing the filter housing (no filter) and it did not run as well. Not awful but there was a difference. Now, what am I missing? I noticed that on the face of the carb there are 2 bolt holes for mounting the filter housing to the face (with a gasket) and 1 “passage” hole into the guts of the carb. With the housing installed it blocks that hole about ½ way. There is no passage into the housing. This hole is unfiltered to the atmosphere. Does that make sense? Is it possible that this setup is incorrect? Did the previous owner combine parts and he created this issue? Are there other reasons that the engine would run so great with no filter/housing but not so great when installed? The filter housing type and carb face example are shown below.

 

[Auto Doc's]

Hello L.,

That hole is supposed to get filtered air if it has the correct air filter. Your parts picture is the wrong one according to parts tree:

PartsTree - Home of OEM Parts for Outdoor Power Equipment

We are committed to providing you with the largest selection of OEM parts from the best brands, the best diagrams and part search tools anywhere.

www.partstree.com

The air cleaner housing should have a matching hole to the carburetor. The carburetor has to have an atmospheric balance vent to compensate for the difference of an external and internal atmospheric.

I have also seen housing gaskets that were wrong block this hole before, and the same thing would happen.

A couple of pictures of you actually assembly would greatly help figure out this situation.

 

[Scrubcadet10]

This is the O.E. base and gasket set up. how does it compare to yours?

 

[ILENGINE]

View attachment 72272 This is the O.E. base and gasket set up. how does it compare to yours?

The diagram also shows the one in the OP picture on another page of the IPL. I suspect that the carb has been replaced at one time. From a low vent style to the high vent style, and I suspect the OP has the low vent air cleaner base with the high vent carb, which don't work well together.

 

[Auto Doc's]

The diagram also shows the one in the OP picture on another page of the IPL. I suspect that the carb has been replaced at one time. From a low vent style to the high vent style, and I suspect the OP has the low vent air cleaner base with the high vent carb, which don't work well together.

One thing is for certain; they are choking off the air flow to the bowl vent from the sound of the situation.

I have run into this a couple of times with engine swap situations where parts were mixed up in the process.