My generator stopped working and I had it to three shops. One got it working and after ten hours, it died (he said he decarbonized). The second two guys couldn't get it running. So I thought it must be something deep inside wrong.So I pulled the whole thing apart. Labeled things and put them in baggies. Took pics as I disassembled.I am now examining the parts. I found an old GX-100 shop manual online. This has the specs on things like valves, piston wear dimensions, etc.I have zero experience, but, having said that, it doesn't look to bad inside. Like I can still see the machining lines on the piston. You know where the cutter went over it?The valves look somewhat suspect. I did wiggle the valves in the guides and the Intake is tight. The exhaust wiggles a bit more. There is some carbon around the edges of the valve seats. The valve doesn't look like a nice 45 degree flat either. It's kind of cupped where it touches the seat. But I have not cleaned the valves yet, so that might be an illusion with the crud.I am trying to find this big defect that prevented the motor from running, but it is not sticking out at me.Could the valve carbon have caused decompression?I do remember at the end, when it did run, it had lost power.Any comments or big belly laughs weclome. lol.

So, say if I order a new cylinder and two valves. Will they mate perfectly out of the box?Also, will the valve guides be already pressed into the new cylinder?

Three things are important - compression, spark and fuel. Even if they don't arrive when they should, it should at least backfire if they're all present. You should have checked the compression before you took it apart. Did it have a good hot spark? Was the plug wet with gasoline?

advice from an old guy....buy another generator.

It could have been as simple as the carburetor fuel shut off being stuck or sluggish. I wish you would have asked before disassembling the thing.

edbehnke wrote:advice from an old guy....buy another generator.Unless you just enjoy projects...this is my answer if the pros can't get it going.

Rebuilding my eu2000i... (never did this before)

BobsYourUncle
Nomad
Apr 07, 2020
mich800 wrote:

Could be something as simple as a faulty low oil sensor or stuck gas cap vent. Options now seem to be complete rebuild or reassemble and start the troubleshoot process over.

"I do remember at the end, when it did run, it had lost power."

what does this mean other than running poorly.

Your comment about the gas cap vent struck my memory banks...

A few years back I could not for the life of me get my Honda 2000 to fire. I pulled and pulled and pulled until I thought my arm was going to fall off. It had initially started and died shortly after.
On with the choke, off with the choke, everything I could think of. No blinking way it was going to run.

I sat there staring at it, looking at various parts and then I set my gaze on the gas cap. Off On. Hmmm. The little lever thing was pointing at Off.
Hmmph.... Switched it to on, hit the choke, couple pulls and away it went. Slap to forehead....:S

Some stupid yardape (looking at the guy in the mirror...) turned it off after last use. Yeah, me, I turned it off.
Ran like a charm after I turned the gas cap lever.

Just a thought, maybe that's what happened. Very easy to overlook. Also easy to accidentally turn it when removing or replacing the gas cap.
mich800
Explorer
Apr 06, 2020
theoldwizard1 wrote:
groundhogy wrote:
One thing I am wondering. It has spark. But is it possible to have a weak spark?

All small engine have had electronic ignition for the past 30-40 years. It either has adequate spark or it will have no spark.

Agree. And with no pre-disassembly data like compression and base motor health it will be difficult to troubleshoot at this point. Could be something as simple as a faulty low oil sensor or stuck gas cap vent. Options now seem to be complete rebuild or reassemble and start the troubleshoot process over.

"I do remember at the end, when it did run, it had lost power."

what does this mean other than running poorly.
Lwiddis
Explorer II
Apr 06, 2020
Do you want to go camping (when we can) or rebuild small engines?
theoldwizard1
Explorer II
Apr 06, 2020
Roger10378 wrote:
Another problem with small engines is that the valve seats wear enough that the valves don't seat anymore. Did you check the gap before you disassembled?

While excess clearance on valve adjuster may indicate worn valve seats, it does not mean that the valve is not sealing.

Compression test and leak down test are the gold standard for checking engine combustion chamber seal.

Excessive valve stem to valve guide clearance will result in high oil consumption but if the valves are sealing, the engine will run.
theoldwizard1
Explorer II
Apr 06, 2020
groundhogy wrote:
One thing I am wondering. It has spark. But is it possible to have a weak spark?

All small engine have had electronic ignition for the past 30-40 years. It either has adequate spark or it will have no spark.
theoldwizard1
Explorer II
Apr 06, 2020
BobsYourUncle wrote:
If your valves seating properly is an issue, or you think it's an issue, you could try "lapping" them.

If it is a part, you might a well "lap" the valves. Several videos on YouTube on how to do it (this procedure is NOT engine specific, just don't go crazy; it only takes a little).

I don't know if that engine has a compression release (typically a mechanism that will hold the exhaust valve open slightly longer). You need to disable it and do a compression test. You should be get around 100 psi.

As you are re-assembling, check to make sure you are getting spark.

The old saying is "you need fuel, air and spark", but you also need compression and they all have to happen AT THE RIGHT TIME !

Good luck, keep us posted.
badsix
Explorer
Apr 06, 2020
Roger10378 wrote:
Another problem with small engines is that the valve seats wear enough that the valves don't seat anymore. Did you check the gap before you disassembled? If not you need to reassemble enough to check. If there is not enough gap between the valve and lifter you will have to grind enough off the valve stem to get the right gap. I don't know the spec for your engine but it is usually in the .005-.010 inch area.

YES, this is the main culprit when you have low compression on these small engines.
Jay D.
badsix
Explorer
Apr 06, 2020
yep, you should have checked the compression first. one of the shops you took it to must have? if you have good compression no need to disassemble the engine i'm thinking electrical problem and they can be hard to track down could be CDI box or stator.
Jay D.
groundhogy
Explorer
Apr 06, 2020
Petes Cycle guy reported that he decarbonized.
groundhogy
Explorer
Apr 06, 2020
Since i have it apart, should i just buy a cylinder and new valves?

When you buy them new, are the mating surfaces all perfect?
Do the valve guides come with cylinder?

If so, i can make the unit like new, without needing to visit the machine shop which is 3 hours drive from my current location.

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