Robin eh35c help needed!

[SteveL1970]

I do small engine repair as a side income. I have been doing it for years but this has me lost so I came here. A lady brought me this cart that wouldn’t start. I checked the usual, getting fuel and spark. I cleaned the carb, it looked brand new. Valve adjustment is good. I sprayed ether in the carb and it still wouldn’t start. Last night it started. Now it will idle but it won’t speed up. It acts like it is starved for fuel but it smells flooded at the same time. The coil had a little oil on the top so I plan on changing it.
any ideas of what to check next? I have a video of it running I will post in a few minutes.

[cybercart]

What’s compression like on each cylinder? Ideally should be 150 plus.

spraying ether and still no fire, next place to check is for strong consistent spark and double check valve lash.

Toss the feeler gage, and on a cool engine, loosen up the lock nut, and lightly base the valve on the cam, then back off a quarter turn with the screwdriver, and lock it in place. Do this for each valve. That will give you the exact setting needed.

[SteveL1970]

Just checked compression. One cylinder of 135 the other is 60. That might be a problem.
I see I can’t post a video here, I will try to upload to YouTube and post a link.
This evening I will re-check the valves and check the timing marks. Watching the valves and the piston travel it is very close so I don’t think it is timing.

[SteveL1970]

https://youtube.com/shorts/gQcAtnjbg9s?si=Pltf5aEIxq65nY4v

Should be a link to video of it running.

[cybercart]

Almost sounds like it’s using up all the fuel in the bowl and stalling, aftermarket carbs are junk for these engines.

• Check float and needle in carb
• Check fuel lines for obstructions and test for consistent fuel flow to the carb
• drain tank put fresh fuel
• Could be running on one cyl, double check compression, needs at least 100psi at minimum
• does choking help when it stalls?

[SteveL1970]

No choking does not help. Ether while it is running makes no change. Did the carb cleaner test around the intake gaskets to look for a leak, none found.
I did find the spark plug on the drivers side cylinder looks like it has a smaller spark kernel, not as hot of a spark. Cleaned the plugs and traded them, still the drivers side cylinder looks like a weaker spark. Possibly a coil?
tonight I will pull the carb again and check everything. Since I had Covid a few years back I can’t tell if gas smells bad or not. I know she was driving it around town this spring so the gas should be from this year. To me the gas smells like carrots! When I run it the carrot smell gets stronger, my neighbor came over and said it smelled like un-burned gas.

[SteveL1970]

I forgot, I re-adjusted the valves. Compression now is just under 100 on both cylinders. My compression gauge is old and has been beat around the race track a lot so it may not be exactly accurate.

[cybercart]

I forgot, I re-adjusted the valves. Compression now is just under 100 on both cylinders. My compression gauge is old and has been beat around the race track a lot so it may not be exactly accurate.

I’d pump and dump the gas just to easily eliminate it,

since there are so many things to check, just going to randomly list them,

pull the fuel line on the carb and press the gas to see if you get pulsating fuel dribble

shine up with sandpaper one of the ground posts on the coil mounting bracket, and run a jumper ground wire from the coil metal bracket to the battery negative to rule out common grounding issues affecting spark, check if spark improves afterwards, should be sharp and blue

If carb is coming apart for inspection, pull main jet and clean any pin holes with a wire brush bristle

[SteveL1970]

Thanks everyone for the advice.
I will go ahead and clean the tank and add fresh gas just in case. The cool ground is a good idea! I will try that. Do these coils have oil in them? The spot of brown oil on top of the coil this morning made me curious, it wasn’t from the engine and is thick oil.
also will double check the carb. Usually I pull the jets, emulsifier tube and everything out then run a small guitar string through all of the small ports.
the fuel pump is pumping a good steady pulse stream to the carb. I ran a 10 to 15 second test into a catch bottle. It stayed steady.

[SteveL1970]

Is there a way to use an ohm meter and test primary and secondary side of these coils?

[golfcartg]

Is there a way to use an ohm meter and test primary and secondary side of these coils?

You can measure the resistance between both primary wire terminals and between the secondary wires, here is the guide for that

[SteveL1970]

Thank you

[SteveL1970]

The new coil came in today. I changed it, now have no power. Push the go pedal and nothing happens. I can arc across the solenoid and the engine turns but won’t start, not getting spark at the plugs doing it with this method.
going to look at the wiring diagrams sent to me earlier on here to see if I can figure it out.
battery is at 12.5 to 13 volts. Have a good engine ground, have good voltage measured from pos battery post to engine block.

[golfcartg]

The new coil came in today. I changed it, now have no power. Push the go pedal and nothing happens. I can arc across the solenoid and the engine turns but won’t start, not getting spark at the plugs doing it with this method.
going to look at the wiring diagrams sent to me earlier on here to see if I can figure it out.
battery is at 12.5 to 13 volts. Have a good engine ground, have good voltage measured from pos battery post to engine block.

With the key ON and pedal depressed, you should have power to one of the small posts on the solenoid. If not, check the fuse, if the fuse is good, trace back the wire from the small post on the solenoid all the way back to the battery positive for loose, broken or missing connections.

Power runs from battery positive, to fuse, to key switch, to pedal switch, to small post solenoid positive, highlighted in red in attached pic.

[golfcartg]

[SteveL1970]

Thank you for the diagram, it will help! I suspect a loose wire connector somewhere. The reverse warning was working every time, now it only works once in a while. The gas gauge is also not working. Later tonight I will start tracking the power wires to see if and where I am losing the circuit.
there are a couple of fuses. One in a fuse holder mounted under the seat beside the choke knob. I think this is something aftermarket. There is one under the cover beside the solenoid. So far that’s all I found for fuses.

[SteveL1970]

I think I am dealing with multiple issues. I was not getting power to the exciter wire on the solenoid. Cleaned the contacts on the fuse and now the reverse alarm works and the test light shows I am getting power when the gas pedal is pushed. Engine still won’t turn over. I pushed the go pedal repeatedly and the engine started turning over, no spark from the coil using my in line spark tester. Gas pedal won’t turn the engine over consistently. Maybe every 20 times I push it will the engine turn but I am getting power to the small connector on the solenoid every time I push the pedal.
on a typical engine I would say bad solenoid but not sure about the lack of spark.

[golfcartg]

It's not uncommon for a brand new coil to be faulty right out of the box, especially if it's an Amazon special. These coils are made with lower quality materials particularly in the internal windings and insulation, which leads to poor performance or immediate failure. OEM coils are built to higher standards. When OEM parts aren't available, Red Hawk is the next best option, as they seem to offer better performance compared to the generic aftermarkets flooding the market. Test the new coil or temporarily revert back to the old one to see if the problem persists

Good sign you're consistently getting power to the solenoid's small positive terminal. This indicates that the solenoid activation circuit is working correctly. It's also not unusual for solenoids to fail over time particularly if they’ve been under heavy use. Before replacing the solenoid though, it's a good idea to rule out issues with the battery, starter and connections first to make sure they aren't contributing to the problem

[SteveL1970]

So, how does this make sense. The new coil was testing 2.8 across the primary and 15.2k across the plug wires. I took it off and put the old one back on. Now I am exactly back where we started, it will turn over with the gas pedal and won’t start. Not sure why it wouldn’t turn over with the new coil, the ground is the same

[golfcartg]

That's good that it turns over again, that rules out the starter/generator and the solenoid along with the solenoid activation circuit

[SteveL1970]

This is what it is back to doing when I try to start it.

[golfcartg]

It does not sound like you are getting consistent spark which suggests a bad ignitor, but more testing is needed before throwing parts at it, what does the spark look like with the plugs pulled out and grounded to the head?

[SteveL1970]

I will post a video of each plug firing. I would like to see a hotter spark and it doesn’t look as consistent as I think they should.

[SteveL1970]

Right side in the first link.

[SteveL1970]

[golfcartg]

Spark looks consistent and good enough, I think I like the second video spark better. These engines need the back pressure from the air filter installed to run. Make sure the air cleaner is in place and sealed tight when trying to run it. It helps pull the fuel/air mixture into the combustion chamber.

We are going to do a quick test.

1. Hook up battery booster pack or jumper cables to the cart in addition to the battery, goal here is we want more than enough cranking amps to play with
2. Funnel a little gas into each cylinder through spark plug holes
3. Replace spark plugs, and seal up air intake and air filter proper
4. Try to start engine with or without choke

If no fire, we need to look closer at the compression and get our hands on a good compression reader for some detailed tests.

[SteveL1970]

I will do that tomorrow. Have to head out to work tonight.
I had the air filter on, I pulled it off and tried some starting fluid in the carb while cranking.
I have another compression gauge somewhere, I will locate it and give it a test and report back.

[SteveL1970]

I started the day dumping about a teaspoon of gas in each cylinder then trying to start the engine. It cranked a little bit then started. It will run on low idle but falls flat when accelerating. After it warmed up a little I could slowly bring the engine speed up. I shut it off a few seconds and started it again, it did start but ran the same. Pull the choke and it dies out.
found my good compression gauge, both cylinders are at 120 psi.
I will attach videos of it running. Possibly the high idle circuit in the carburetor is blocked.

[SteveL1970]

This is what it does when I accelerate.

[SteveL1970]

This was after it sat for a few minutes after the first run.

[SteveL1970]

Thank you to everyone for posting advice on this cart. It has me frustrated!
I went to tech school back in the late ‘80s for automotive. Life had other plans for me so I never worked in a shop professionally. Since then I have worked out of my garage in my off time doing light mechanic work. I quit for a few years but have started doing it again for about the past 10 years. I do work for people that can’t afford shop rates, a lot for the elderly in our town. I end up working on lawn mowers, cars and trucks, motorcycles, anything people need help with. The money I made in the shop paid for my son and daughters racing, they raced go karts and later 600 sprint cars. I built their engines and kept them in the top 3 at all tracks we raced at. Track champions and points leaders at the local track. I don’t advertise as a business but people keep coming with stuff they need fixed. When I get this one done I have 2 boats and a motor home to work on.
This golf cart has me questioning everything I know!

[golfcartg]

Very good. The engine sounds great, but there are a few more important tests we need to perform. Although the compression reading is on the lower side, we will ignore that for now since the engine is running, and we can revisit it later if necessary.

You mentioned that you cleaned the carburetor, did you also remove the main jet and nozzle to check for pinholes and clean them? (refer to #5 in the attached diagram). Be cautious, as the main jet is often seized in place if it hasn’t been removed yet. Also, as far as you know has the carburetor been replaced, and if so, is it a stock or aftermarket part? Aftermarket carburetors can sometimes exacerbate fuel delivery issues.

[SteveL1970]

Yes I did. I use a guitar string to clean out all of the holes in the jet and the emulsion tube.
as far as I know it is the original factory carb.

[golfcartg]

That finishes up the fuel delivery part of this test.

If you’ve got some extra cash, you might want to try swapping the carburetor for an OEM or Red Hawk replacement, just avoid the aftermarket ones. But before throwing money at it, let's take a closer look at the compression. Could you rerun the compression test and jot down the numbers? Then, add a tablespoon or two of 10w30 oil to each cylinder, rerun the test, and note those numbers too. I’d like to see if there’s any difference between the readings.

By the way, I’ve got to say, with all the experience you’ve got with go kart engines to sprint cars you clearly know your stuff. It’s absolutely frustrating when something like this golf cart makes you second guess things, but given everything you handled I’m confident we'll get it sorted out.

[SteveL1970]

I am getting ready to go to work but I had a thought. I pulled both spark plugs and ran a compression test in the left cylinder first. The reading was lower, I think under 90 pounds. I put the spark plug back in the right cylinder and checked compression in the left and it came up to 120. That makes me curious about a possible bad head gasket or cracked head allowing compression to cross between the cylinders.
I thought about the oil in the cylinder and recheck compression, that’s an old trick we used to do back in the day. I will do the oil trick to see if it increases compression.

[golfcartg]

That’s a solid observation and it’s definitely something to take into account with the oil compression check. Exactly right, what we’re doing here is essentially checking to see if adding the oil boosts the compression, which could help confirm whether the issue is with the rings or something else. Be sure to try it both with and without the second spark plug removed, and jot all the numbers down for reference. If the compression doesn’t increase with the oil added, the next place to investigate is the valve lash.

I’ve always had great results using the valve adjustment method cybercart mentioned in post #2, it’s pretty much the "go-to" technique around here for getting that perfect gap. Just make sure the lobe is pointing away as shown in the attached pic to get it spot on.

[golfcartg]

Basically once the compression readings are carefully documented in all scenarios, we'll get the complete picture including after adding oil to the cylinders. As a final step, readjust or double check the valve lash, and then run the engine and recheck the compression.

If the compression remains low, our final step would be to verify that the timing belt hasn’t skipped a tooth, though this is less likely since the engine is running. If everything still indicates lower compression, it may be time to consider an engine rebuild as the next viable option.

At that point, I would inform the customer of the diagnosis that the cart needs an engine rebuild and possibly a new OEM carburetor. Removing the engine is fairly simple, and the rebuild process isn’t too tough, here is the rebuild guide for you.

The head gasket is needed, piston rings, valve seals, crank seals, timing belt, check the timing. After the rebuild, the engine should be in good shape for many years.

[SteveL1970]

Well, I added oil to the cylinders and ran a compression test. With oil in the cylinders compression hit 140. Both with the opposite spark plug removed and the opposite spark plug in the compression was 140.

[golfcartg]

Very good. This increase in compression after adding oil indicates that the piston rings may be worn out. The oil temporarily seals the gaps caused by the worn rings, leading to the higher compression reading. This wear also hints at the possibility of worn cylinder walls, where the smooth surface that allows the piston to move efficiently has deteriorated over time. This could happen due to wide gaps between oil changes or a dirty oil filter. Valve seals might also be failing, allowing air to seep through and causing further loss of compression.

Given these signs, you could try replacing the carburetor as this might address any fueling issues and improve performance slightly. However, if the compression remains low without the oil in the combustion chamber, it's likely time for a rebuild. If they decide to rebuild, make sure to inspect the timing belt setting before the process. A timing belt that has skipped a tooth can cause all sorts of performance issues, but usually it will not run at all in this situation. But it is worth having a look at that time.

[SteveL1970]

I am considering a pressure test to see where compression is going. I can position the piston just before BDC while both valves are still closed and put a little air pressure to the cylinders. That might tell us where the compression is going. Also I will use my inspection camera to see if I can see the cylinder walls.
I will talk to the owner and see what she wants to do next with your suggestions. I won’t have time to work on it again until Sunday night. Today an elderly man stopped by to have his boat tuned up. He wants to take his granddaughter fishing tomorrow and his motor was hard to start. I will look at the cart more Sunday night but I have to agree, the oil sealed up the rings increasing compression. It is still potentially a carb issue too.
thanks for all of the information. I will post back as I go along on this project.

[golfcartg]

Glad I was able to provide all of the information needed, take care Steve