pulsa jet 5 HP L head runing rich.

[willys55]

Hello folks

I have a 1979 5Hp Briggs flat head on a chipper/shredder that runs well albeit rich. It turns the spark plug black. It does not blow black smoke. I have cleaned the carb as best I could without removing the welch plugs. I removed and inspected the fuel pump membrane and it looks really good for its age, no visible tears or holes.

I was given this chipper as it was sitting inside for 15 years. I did the obvious things - new foam air cleaner, new muffler, cleaned carb, cleaned fuel tank, changed the oil, all looks pretty good. I did notice that the exhaust valve lash is a bit over spec at .013, intake is fine.

Other then the pump membrane, is there anything else one can do/check to help solve this running rich issue. If the jets were accessible, I would try that. I have run about two tank fill's of new gas with a little marvel mystery oil in it. The oil get dark pretty quickly too, maybe from running rich. I don't believe that this motor has that much time on it for its age.


Thoughts?

you didnt change the plug, could be bad plug or weak magneto.

that's the most of my internet superpowers I can share with you.

FYI : Don't be so thin skinned, this is the internet and that limits just how helpful people can be, we can't touch or see what you see, so the more info given from the very beginning the better.

 

[bertsmobile1]

You need to adjust that exhaust .
With that much freedom the exhaust valve will open late & close early which can cause the plug to load up.
Also a cracked flywheel key will cause the timing to be a bit late and that can cause the plug to load up as well.
Heat range has already been mentoined.
Running too high grade fuel can cause the plug to soot up as will a drop in compression.

Modern fuels also tend to load up the plug I try to get all my customers to turn the fuel off and allow the engine to starve rather then turning off the ignition.

 

[Zippster]

Thanks all, I'll respond collectively if that's ok.

I tried a new plug, it did the same rich condition and I ended up putting the old one back in, a CJ8. I think CJ8 is the correct one, but a hotter plug is an idea.

130212-0735-02 78031407 are the numbers of the engine.

I wondered if the wider valve lash could cause this but I was not sure. I installed a new key, so I don't think that is it, good suggestion though, I forgot a few things that I did to it.. I adjusted the idle mix mid way between the engine cutting out on the too far open and too far closed, I was thinking of leaning that out a little...but that exhaust valve, could carbon build up under the seat cause that larger gap?

gas is 87 regular. Same gas I use in all of my other small engines that have a nice light tan color on their plugs, including my 2 stroke lawn boy. I have not checked the magneto or points/condenser. I did do a spark check and using the Mark-1 eyeball and it looks pretty good, but I don't know if its a weak spark.

It runs fine, but the oil gets dark fairly quickly, like in a few hours, I'm thinking from the rich condition. I noticed the black soot on the plug even right after changing the oil, I can't see how the oil would cause this.

I know, maybe I am too thin skinned, but I don't have a lot of patients with internet trolls who don't offer suggestions, but rather provide collected data they have acquired and then sit back on their haunches and act like they solved my problem. It didn't.

Thanks again for the suggestions.

 

[EngineMan]

If the oil gets dark fairly quickly it could be the rings....!

You may already have this...........

 

[Zippster]

Yeah, blow by, but it doesn't smoke when it runs though.

So could they be worn enough to dirty the oil, but not enough to smoke.

As one suggested, maybe I should just run it as is, since it runs well. I'm thinking I might use a straight pipe in place of the muffler to see if it leans out a bit enough to change the plug reading. That might tell me something one way or another.

So I have some good suggestions from the group, and I know that exhaust valve is not within tolerance, might try some easier stuff before I decide to go into that.

Thanks

 

[cpurvis]

Carburetor kits for those old Briggs carburetors are still available and not expensive at all.

I found one for a 1965 B&S 3-hp vertical shaft at a local shop.

Although that diaphragm may look good, it might not be.

 

[Zippster]

You know, I think I read that somewhere on-line, and it is worth a shot, easy peasy to replace too. I looked the one in there now over very carefully and it looks good, but it may not be as pliable as it needs to be.

You're right the parts are not that expensive, I bought an air filter and muffler, I should have added the diaphragm. At the time, after I got it started, I was just interested in getting it running good, (initially it choked on a small amount of yard waste material) to see if it was worth the effort and expense, I found out it is.

Thanks

 

[bertsmobile1]

A faulty diaphragm makes the engine run lean.

A blocked exhaust will make the plug soot up.

You need to run the engine early in the morning.
Hold some white board between the exhaust & the engine so it backgrounds the exhaust.
Get some one to work the governor so the engine accelerates and runs WFO for a few seconds.

The white board will allow you to properly see the colour of the gas.

 

[Boudreaux In Eunice La.]

If your oil is getting dark early it could men you have a sludge build up in the base of the engine.......... The only way to deal with that is to take the sump cover off and clean the whole thing out......

Not a very big job to do and cheap to do..... A whole gasket kit is less than 15 bux..... A sump gasket is about 6 bux.

So a whole set is the better option... I keep the sets in stock and if I need one later I go to the pack marked with one in it.....

Yes a pump diaphram is only a few bux and would be advised to change.......... That gasket on the jet bolt usually comes off in one piece... If not they are very cheap also....

Hope this helps you out Mon Ami Joyeau Noel et Bon Anee from Cajun Country ~!~!

 

[Zippster]

If your oil is getting dark early it could men you have a sludge build up in the base of the engine.......... The only way to deal with that is to take the sump cover off and clean the whole thing out......

Not a very big job to do and cheap to do..... A whole gasket kit is less than 15 bux..... A sump gasket is about 6 bux.

So a whole set is the better option... I keep the sets in stock and if I need one later I go to the pack marked with one in it.....

Yes a pump diaphram is only a few bux and would be advised to change.......... That gasket on the jet bolt usually comes off in one piece... If not they are very cheap also....

Hope this helps you out Mon Ami Joyeau Noel et Bon Anee from Cajun Country ~!~!

That's certainly possible as it sat a long time and the oil was not changed very often, maybe never, I don't know for sure. Before I tear it down, the next oil change I could swish some gas in the sump, drain it, and see how nasty or clean it is before I take it apart.

Ill change the diaphragm for sure, its too cheap not to and it can't hurt. And as Bert said, the exhaust lash is an issue so I can go from there if the diaphragm does not change anything, no harm in trying.

Have a great holiday and new year.