Effect of Ethanol in fuel?

[JimPghPA]

I run our Coleman Powermate 5000 Watt / 6250 Watt Peak generator with Tecumseh HM-100 10HP engine every 3 months. I run the carb dry and then drain the main gas tank. I use Sta-Bil and rotate the stock of gas.

Over the last year or so I notice that I have to let the choke on a little bit to get the engine to idle smooth with no load. At first this was only on cold winter days. The last time I ran it ambient was 65 F and it still required a little choke to run smooth with no load. I was thinking that the carb might be getting gummed up. I know the small breather passages can get restricted and of course jets can get build up. I did some searches on the internet about having to use the choke on these gen-sets, and it seams to be a common problem. On one site the owner said he had removed the carb and cleaned it and after putting it back on the engine still requires choke to be on some.

Some say stay away from Sta-Bil in the fuel, and use something else like SeaFoam. I know SeaFoam cleans well but do not know if it preserves gasoline in storage?

One site talked about having problems with 10 micron fuel filters on gravity (not fuel pump) systems. That site said fuel filters for gravity fed systems should be 40 micron or larger filters. I did add an additional filter about a year ago, it is a Purolator F21124 and that is a 10 micron filter, but it is a large filter for a 10 HP engine.

Wall-Mart has 40 micron inline fuel filters, part no. IFF 327 and IFF 328, Briggs & Stratton has a 691035 40 micron, and Auto-Zone has 40 micron part no. 334286 and 334288. I might try one of these soon.

I was beginning to think that the added filter might be causing fuel restriction, but it is at no load that a small amount of choke is required. The engine runs fine with any load on it. Note these engines run at 3600 RPM regardless of load. In a way it is an interesting carburetor design challenge since the engine is going to want to drink the same amount of air at no load as it can drink at full load because it is always at 3600 RPMs. Yea, I know the throttle plate that is regulated by the governor is limiting the air to the engine.

Anyhow, now I am beginning to think that the real problem is the amount of ethanol in the fuel. I see many post about older vehicles getting 10 to 13 percent less MPG because the fuel has ethanol. If the fuel has that much less BTUs then it would make sense that an engine with a carb designed to run on the older no ethanol gasoline might have to have the fuel mixture made rich to get the engine to run normally.

I have very low hours on this engine. Basically it was ran for about 2 hours to break it in, and set RPMs to 3600, it is ran for about 10 minutes every three months, and one black out for a few hours so far. Probably less than 10 hours total on it. Several oil changes, originally broke in with Castrol HD 30, now I have GC in it. What gets me is the amount of choke required has been slowly increasing. At first some choke was only required when running on a very cold winter day. Now some is required when ambient is 65 F.

So what are your thoughts? Is ethanol in the fuel the problem, or should I remove and clean the carb?

I was just about to order the carb rebuild gaskets, and carb mount gasket, when I found the post by someone who removed the carb and cleaned it and the engine still required choke.

I was also considering getting some Amsoil foaming carb cleaner.

Also, it sure would be nice to find some ethanol free gasoline near Pgh PA.

 

[J. A. Rizzo]

You can use a 1 micron fuel filter as long as it has enough surface area to support the flow rate required by the carb. Ethanol in the fuel wouldn't be a problem that got worse over time. It would either be there or it wouldn't. Using 87 octane gas will probably have lower ethanol content than the premium stuff, despite "conventional wisdom" that some believe premium will be "pure gas," which itself is a myth, and less ethanol.

Many small engines have a plastic spacer plate between the intake and the carburetor to keep high heat off the carb. Those insulators take a lot of heat and can easily get warped and cracked from the heat cycling. When that happens, more air gets in on the far side of the carb, after the air filter, and you have to choke it to keep the fuel level high enough. Even seemingly tiny cracks in these insulators can cause problems. Before spending a bunch of money on chemicals, I would take the carb off and carefully inspect the insulator and replace that if it has any imperfections. The gaskets will probably need to be replaced at that point also, especially if they get scraped up or creased trying to remove the carb.

 

[boraticus]

J. A. Rizzo makes a lot of sense concerning the enthanol issue.


To me, it sounds like an adjustment issue. Is there a speed adjustment screw that can be set? Being that the engine is designed to run at 3600 rpm, there likely isn't a low speed circuit nor adjustment. However, there should be some form of adjuster that can control engine speed prior to the governor taking control to deal with load fluctuations. From what you've described, it sounds that once load is applied and the governor is actuated, proper fuel flow is established.

I wouldn't blow money on additives. I used them for years and have weaned my machines off of the snake oils because, I've never seen any tangible proof that any of them worked.

Considering the the machine is virtually new, I doubt that there would be a physical problem with the carb other than it might be out of adjustment or a bit loose. I'd check the mounting bolts/nuts to make sure they're snug. If that doesn't work and there is no adjustment, I'd pull the carb and take a look at it and the insulator.

 

[rclint]

Anytime you have to use your choke to make the engine run after warm up ( or even cranking and very very short warm up time) you have the one and only carb issue. Your carb needs rebuilding, it may be the insulator like posted above, but it has more potential to be in the float, bowl, or one of the internal gaskets... also all the jets, and orifices should also be cleaned..

Fuels create a varnish on small engine carbs, this is what I have seen to cause problems like you have described most of the time.. Take the carb apart soak in one a gallon of the carb soaking chemical you can by at local AA, AZ do not soak any plastic parts, use compressed air to blow out any, and all passages, holes, orifices, jets etc..

 

[Cujet]

My Kawasaki mower hates pump gas. It won't idle and it runs poorly. I use Avgas instead. Runs perfectly. Ethanol is 100% to blame.

I tried adjusting the mower carb, but that does not seem to fix the problem. So, I simply stick with Avgas.

If there is a marina near you, they often sell gas without ethanol, for a nice premium price.

 

[boraticus]

Originally Posted By: Cujet
My Kawasaki mower hates pump gas. It won't idle and it runs poorly. I use Avgas instead. Runs perfectly. Ethanol is 100% to blame.

I tried adjusting the mower carb, but that does not seem to fix the problem. So, I simply stick with Avgas.

If there is a marina near you, they often sell gas without ethanol, for a nice premium price.


That's strange.

What kind of Kawasaki engine? Is it in a riding mower? How old is it?

I have a 430cc 15 h.p. air cooled twin Kawasaki engine in my rider. It's nine years old and it's one of the best starting and running engines I've got. Nothing but regular pump gas.

I've never had an engine that didn't run properly on it and I've got lots of engines in everything from OPE to ATVs to outboard motors to motorcycles. B&S, Honda, Kawasaki, Suzuki, Tecumseh, Toro, Stihl, Husqvarna, Jonsereds, Echo, Johnson, Yamaha, Mercury, Shindaiwa... Not one ever caused me a problem due to type of fuel.

Never met an OPE engine, two or four stroke, that was fussy about fuel or oil.

 

[J. A. Rizzo]

Originally Posted By: Cujet
My Kawasaki mower hates pump gas. It won't idle and it runs poorly. I use Avgas instead. Runs perfectly. Ethanol is 100% to blame.


Very little is 100% certain, so any time somebody claims 100% anything, they're probably full of it. And what evidence do you have to offer for this claim? How come there aren't more people claiming this problem other than you? Maybe it's just your carb. What does "it won't idle" mean? How does it run poorly? Does Avgas have tetraethyl lead in it? What else is different about Avgas that might explain this difference? What does the mower manual say about ethanol in fuel? What does the manual say about octane requirements and lead in the fuel?

 

[candoo]

Jim: I have just been through a similar issue with my honda lawn mower (gcv 135) and honda roto tiller (gxv 50). Over time, the amount of choke required to make the thing run right, needed to be increased.

After disassembling, I cleaned the mower carb with a can of carb cleaner and reassembled. The result: it ran the same (i.e needed some choke to run). Took it to my honda dealer, who screwed it up even more than it already was (but that's another story. ARRRGGHH!).So, I had to fix it myself. I disassembled the carb again, and looked very closely at the main jet. I noticed , with a magnifying glass, that there was some light coloured encrustation type material, inside the nozzle as it exited into the venturi. I removed the deposits with a sewing needle, reassembled, and the mower ran fine again.

I cleaned the smaller rototiller carb in the same way, and it too, ran fine afterwards.

I learned that these small engine carbs need to have their very small passages very clean to allow the engine to run right. Get in there with your magnifier glasses on and inspect those passages -- clean them really well. Remember, some of those deposits may stuck there with greater tenacity than can be removed with solvents alone.

If you're like me there is nothing more to your problem than some tiny bits of dirt in the wrong places, and once removed, you're good to go.

I didn't even bother to get a carb rebuild kit. Just reused the old ones and I did'nt notice any leaks.

Hope this helps.

 

[GT Mike]

The later the model small engine, the leaner they're set. I just worked on a Tecumseh 5.5 HP roto-tiller engine for my dad that had a chronic surge regardless of temperature when there was no load on it. He also complained about it not being real powerful for its size.
I took the bowl off the carb and using a pin drill, enlarged the main jet 0.002" bigger. Fired it up and it runs absolutely flawless now.
Cold, 3 or 4 pumps on the primer bulb and it starts on the first pull, and needs no additional "helper" primes while warming up.

He commented that it's got tons of power and surprisingly it's using considerably less fuel now too! I noticed it's a lot smoother, and that makes sense since it's running more efficiently.

If the carburetor is of the adjustable type, a simple turn of the main and idle metering screws just a tick richer will fix it. If it's of the fixed jet type, a simple modification like I just stated above is going to be golden if you're forced to use E10 fuel.

Edit: Like the poster above me stated, it could just be the jets getting a bit gummy, which of course will restrict the fuel flow. A torch tip cleaner available at any welding supply store works wonderful for cleaning carburetor jets, and with enough time and patience, can also be used to enlarge jets since they're sort of serrated and will file the brass jets. A pin drill is just a lot quicker, but I've used a torch tip cleaner with good results too before I had the drills.

 

[candoo]

Just to support what GT mike said, that Honda service guy I took it to, also said that these newer small engines "run lean". So, I take it that meant smaller jets and fuel passages, therefore more sensitive to being affected by dirt and deposits.

 

[JimPghPA]

Thanks everyone for the responses.