Briggs and Stratton Warped PLASTIC Intake Manifolfd

mxsmith4 · Oct 7, 2013

My Scotts 2048 (I hear that hissing sound) was not idling and lost power at full throttle puffing black exhaust. I am rebuilding the carb but noticed that the intake manifold was warped. Parts on order so I don't know if this is going to fix it, but I thought I 'd post it just in case others where going through the forum looking for weird stuff. I have a well maintained and disappointing 20HP Intek PoS (piece of s***) with 370 hours, 406777-0128-E1.

I will say I saw no damage due to 10% ethanol which I use (like I have a choice in NJ), carb was clean as a whistle and more than 10 years old.

dconine · Oct 7, 2013

I have had a lot of these apart and that is normal to see. Whenever you get that new manifold installed and tighten those mounting studs down, you will see it slightly warp again.

It doesn't leak though, if you look at the raised areas around the intake holes that is where the actual seating takes place, not the entire manifold. Rather strange but every one I have worked on has done that.

mxsmith4 · Oct 8, 2013

Thanks for the info, this is my first time rebuilding a carb on this engine. When I disassembled the unit again I noticed the raised areas on the manifold but the gasket only showed about 2/3's of an imprint of the raised area and an imprint was missing from the gasket center. I'll reassemble and give it a shot.

Midniteoyl · Oct 8, 2013

Thats why there should be a proper 'sequence' to the tighten of the bolts...

dconine · Oct 8, 2013

The problem is there is only four studs to tighten the carb against the manifold. Even if you just barely snug them, you can still see it warp some.

This problem could be relieved by using the cast aluminum manifold, which they do use on their professional series of these engines.

Midniteoyl · Oct 8, 2013

I see.. for some reason I thought there was 5 bolts..? Larger washers would work.. even if you need to shape them.

mxsmith4 · Oct 11, 2013

I completed the carburetor rebuild and replaced the intake manifold. Problem solved. I suspect it was the carburetor that was the cause given the comments from dconine on the manifolds warping but not leaking. While I was at it I adjusted the valves too.

Thanks all for your help and suggestions.