Getting too much air somewhere in the intake on the H...

Absent Minded Farmer · Jun 5, 2012

Hey guys, I'm hunting down an air leak & am not sure what to check next. There's plenty of fuel going to the carb, the gasket from the carb to the manifold is fresh, the manifold itself looks to be a recent replacement & those gaskets look new, too. I sprayed over every gasket & seal with WD-40 from the carb to the head gasket & did not notice a change in enging speed or performance. At least I think WD-40 is what should be used. Something told me spraying ether all over a running engine might not be the best idea. Could be wrong, though.

All of this makes me wonder if there's a leak somewhere in the head gasket or if there's a crack in the head that's allowing both air & oil where it shouldn't belong? I'm also wondering why there were those cheater cups on plugs 2 & 4 when all 4 new plugs, sans cups, have an equal amount of light oil residue & a few specks of carbon. This is after only about 10 hours of use. Might that not be enough time to foul a plug?

Appreciate the help,
Mike

roy prins · Jun 5, 2012

i have had a head gasket that was out between no. 2 and 3 cyl. it would run but not very good-- it was changing air between the two--but it never leaked any fluids--looks like you need to pull the head-sorry for any bad news but i dont think you have any choice-- good luck -- Roys toys

John G. Hasler · Jun 5, 2012

> I sprayed over every gasket & seal with WD-40
> from the carb to the head gasket & did not
> notice a change in enging speed or performance.
> At least I think WD-40 is what should be used.

Propane.

Absent Minded Farmer · Jun 5, 2012

Don't have any propane at the moment. Will mapp gas burn too hot?

Mike

Absent Minded Farmer · Jun 5, 2012

Darnit!! I knew I forgot a detail, it purrs like a kitten at a little less than half choked. There seems to be a fine line between a hair over or a hair under that position. Don't know if that detail helps or not.

Mike

Huskers86 · Jun 5, 2012

I use carb cleaner and maybe clean and kit your carb. It is faily easy and inexpensive.

Absent Minded Farmer · Jun 5, 2012

I was thinking it might be the head or head gasket, too. I'm going to go over everything with propane, if I can't use mapp, & search for a leak again. Whatever the case, I hope it holds out long enough to cut a couple acres of hay.

Thanks,
Mike

Absent Minded Farmer · Jun 5, 2012

Not a bad idea. Dosen't look like the carb's seen a tune up in a while & I do like a good romp through a carburetor, so I may give that a whirl.

Thanks,
Mike

Janicholson · Jun 5, 2012

If the carb is lean, and the fuel supply is OK, it needs to be cleaned and a wire run through every passage and orifice. Probably a restriction in the main jet. If turning out the load adjustment screw does not do it it is likely the carb. Thw connection between the intake manifold, and the exhaust manifold can crack, allowing exhaust into the intaks, EGR on the loose. It might be a long shot but worth knowing about. Jim

John G. Hasler · Jun 5, 2012

> Will mapp gas burn too hot?

Should work fine. You aren't going to be running the tractor on it.

Absent Minded Farmer · Jun 5, 2012

Thanks, I'll give it a try tomorrow.

Mike

Absent Minded Farmer · Jun 5, 2012

No, there's no amount of adjustment that changes the starvation problem. I agree a cleaning is in order. If the clean up & overhaul dosen't change anything, maybe a different manifold is in order. It's fairly new, but I've been kicking around the idea of changing it anyhow. There's a gap between the edge of the manifold & gasket where it meets up with the head. Maybe, just maybe, the manifold is poorly machined or warped elsewhere or, as you stated, an internal crack. I'll get a pic posted of the gasket gap-osis tomorrow.

Thanks for the heads up!
Mike

Heat Houser · Jun 5, 2012

Another way to look for vacuum leaks is to spray/smear a thin layer of shaving cream on the joint. Run it and then you will need to look closely to see if a "hole" is pulled down through the shaving cream.

mkirsch · Jun 6, 2012

An unlit propane or MAPP torch is perfectly fine for the test. All it has to be is a flammable gas. The engine fan will blow any residual gas away long before it can build up to be a fire risk.

I'd only worry if you were doing this under a hermetically sealed tarp, but then you'd probably die from carbon monoxide poisoning long before the gas built up to flammable levels.

JRSutton · Jun 6, 2012

Might have missed something - but what makes you believe there's an air leak?

Generally speaking, any signs of an air leak can also point to gas blockage in the carb, and that's about 10 times more likely. Too much air is just another way of saying not enough gas.

Have you cleaned the carb thoroughly?

You can use thin wire to poke out all the passages. But if working on small engines/carbs is something you do more than once or twice every few years, I highly recommend an ultrasonic cleaner with a tank large enough to fit your carb.

Open up the carb, drop it in, comes out like new.

Absent Minded Farmer · Jun 6, 2012

ACH! Now I have to put the tarp away. ;v) I was wondering about the breeze from the fan blowing the gas away. Should I block the breeze with a piece of cardboard or will that allow too much gas to build up?

Mike

Absent Minded Farmer · Jun 6, 2012

Haven't cleaned out the carb yet. I have a good carb I can use in the mean time to see if that's the issue. The ultrasonic cleaner has been on the "to get" list for a while. I'll have to move it up in priority.

Thanks,
Mike

Absent Minded Farmer · Jun 6, 2012

The carb must be pretty gunked up. I took the carb off of ol' Faithful H & put it on the new one. It ran rough for a minute & , out of habbit, I choked it a bit & the enging began to run rough. So I let the choke alone & the roughness cleared up. When the engine warmed up, I dialed in the carb & Presto! A smooth running engine. I couldn't be happier & can't thank you guys enough!! Now I can get caught up & finish this tractor so I can get my hay off. I can play carb tech all I want then.

Ice cream for everyone!
Mike

rhtx55 · Jun 6, 2012

Have you tried backing out the main jet adjustment a turn or two on the carb??
Screw it all the way in (gently) until it seats then back it out 3 & 1/2 turns, see if it will start & run without choking, go as many as 5 1/2 turns out, if that doesn't fix it, It's time to check the gas flow to the carb, the float level, and finally clean both jets in the carb, or just rebuild it.

Getting too much air somewhere in the intake on the H...

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