EZGO WORKHORSE ROBIN 350 fouls plugs with air box connected

[U2SLO4ME]

Hello All,

I could really use some help with this one! I'm working on a 2001 ezgo workhorse 1200 with a robin 350cc engine (pre MCI) belonging to a friend. The spark plugs carbon foul due to a rich fuel condition after approximately 20 min of operation with the air box (with or without the filter installed). without the air box connected it runs perfectly and the plugs are a nice brown color. This cart/engine has all original parts except for what I have replaced and the cart has run fine for years. Here is what I have...

1.I have set the valves .006" (the manual says .004" I read .006" is ideal)
2.tried to clean the carb but broke one of the ears for the float pivot and had
to replace the carb with a non oem but decent new unit. Before installing it
I disassembled, cleaned and verified the jet sizes were the same (90)
main jet.
3.Installed new BPR4ES plugs
4.New Drivebelt
5.When removing the clutch to verify the valve timing I broke the timing
belt. replaced it with a new OEM belt and reset and verified the valve
timing.
6.Engine warm compression is 130 psi on both cylinders dry. and 160 on
both wet. approximately 5% on my leak down tester (not sure exactly
where because of how little is leaking).
7. engine uses NO OIL. and shows no signs of leaking anywhere.
8. no obstructions in the air filtration system and will still foul plugs with the
air filter removed from the airbox.
9. Spark appears to be good and consistent.
10. both carb floats/needle and seat all set to spec and working correctly.
11. clutches are working perfectly.

The Cart has the same symptoms as it did when It arrived at my shop. Plugs foul with airbox attached and runs great with it unhooked. somewhat better after the valve lash adjustment but still a problem.

Only thing I can think of is the 130 psi of compression just isn't quite enough to handle the stock (90) main jet? I have a few smaller jets on order but I'm hesitant to start leaning it out since it ran fine for years with the stock (90) in it.

I know this is a lot of info and I'm sure I forgot to mention a few other things just want to be as accurate as possible. Thanks in advance for any help/suggestions!

Chuck

[trig123]

Originally Posted by U2SLO4ME

Hello All,

I could really use some help with this one! I'm working on a 2001 ezgo workhorse 1200 with a robin 350cc engine (pre MCI) belonging to a friend. The spark plugs carbon foul due to a rich fuel condition after approximately 20 min of operation with the air box (with or without the filter installed). without the air box connected it runs perfectly and the plugs are a nice brown color. This cart/engine has all original parts except for what I have replaced and the cart has run fine for years. Here is what I have...

1.I have set the valves .006" (the manual says .004" I read .006" is ideal)
2.tried to clean the carb but broke one of the ears for the float pivot and had
to replace the carb with a non oem but decent new unit. Before installing it
I disassembled, cleaned and verified the jet sizes were the same (90)
main jet.
3.Installed new BPR4ES plugs
4.New Drivebelt
5.When removing the clutch to verify the valve timing I broke the timing
belt. replaced it with a new OEM belt and reset and verified the valve
timing.
6.Engine warm compression is 130 psi on both cylinders dry. and 160 on
both wet. approximately 5% on my leak down tester (not sure exactly
where because of how little is leaking).
7. engine uses NO OIL. and shows no signs of leaking anywhere.
8. no obstructions in the air filtration system and will still foul plugs with the
air filter removed from the airbox.
9. Spark appears to be good and consistent.
10. both carb floats/needle and seat all set to spec and working correctly.
11. clutches are working perfectly.

The Cart has the same symptoms as it did when It arrived at my shop. Plugs foul with airbox attached and runs great with it unhooked. somewhat better after the valve lash adjustment but still a problem.

Only thing I can think of is the 130 psi of compression just isn't quite enough to handle the stock (90) main jet? I have a few smaller jets on order but I'm hesitant to start leaning it out since it ran fine for years with the stock (90) in it.

I know this is a lot of info and I'm sure I forgot to mention a few other things just want to be as accurate as possible. Thanks in advance for any help/suggestions!

Chuck

Compression is supposed to be checked cold leaving one spark plug in head. Make sure you hold throttle wide open when testing.
170 pounds of compression is what you want to see.
It does look like your engine needs rebuilding though.
Did you look close at the intakes to see if more threads were showing where you adjust them ?
Country cat has your carburetor in stock. I just bought one two weeks ago with 90 jet for $129.99. 72558G01

[U2SLO4ME]

Trig123, thank you for the reply! I have checked compression cold and it was close to the same warm but I will do another test as soon as it cools. The valve lash was the the first thing I did as I know this is a common issue and some of the valves where tight! Don't remember when. I will inspect the threads and report back. I will order the country cat carb if its a oem replacement? My manual shows 160 on fresh rebuild and 125 on the min. is that incorrect? if so, that makes this cart very close to the mins? Thank you again for the Help! It is much appreciated!

[trig123]

Originally Posted by U2SLO4ME

Trig123, thank you for the reply! I have checked compression cold and it was close to the same warm but I will do another test as soon as it cools. The valve lash was the the first thing I did as I know this is a common issue and some of the valves where tight! Don't remember when. I will inspect the threads and report back. I will order the country cat carb if its a oem replacement? My manual shows 160 on fresh rebuild and 125 on the min. is that incorrect? if so, that makes this cart very close to the mins? Thank you again for the Help! It is much appreciated!

Take a picture of those threads and post it here. I am betting the intakes are worn. I have five of these engines and all of mine show 170 pounds of compression. Yours is low and by it going higher wet tells me it about time for a rebuild.
The carburetor is OEM and fits the 350 pre mci engine.

[Cartmaster]

If it runs fine without the airbox, it tells me a couple of things to check, but first, as Trig says. How many threads are showing above the lock nuts on the inner two valves compared to the outer. A picture would be great!. A difference of 30 psi between dry and wet compression tests tell us the rings are worn. Running fine without air box fitted tells me that the PCV valve is probably passing oil vapour. Is there any sign of oil in the airbox. Any at all. It should be bone dry! Remove the hose from the PCV valve that goes to the air box, replace it with a longer hose and direct it from the valve into a drinking water bottle rather than the air box. If the cart now runs fine with the air box and filter fitted and you maybe see a little oil in the bottle, this confirms likely worn rings and the cause of your plugs fouling.

[U2SLO4ME]

Hello again,

Finally had some time to work on the ezgo again. Here is some updated info. Compression cold with one plug in and air cleaner removed is 135 psi and 136.
Valve adjuster Thread height measured to from the top of the nut to the very tip of the adjuster (screwdriver slot) as follows.

Flywheel side exh. .151" Int. .183"

Clutch side Int. .183" exh .171"

It doesn't appear to be burning any noticeable oil. PCV system is dry.

it does have the screwy intake system that picks up air behind the drivers left foot and since its a workhorse and not a golf cart i'm sure its ingested a fair amount of dirt etc over the years eve thought it looks clean.

I don't understand the low percentages i am reading with my leak down tester. Its OTC brand and I have used it many times before so i'm confident its accurate.

Thank you again Fellas for the help!

[trig123]

Originally Posted by U2SLO4ME

Hello again,

Finally had some time to work on the ezgo again. Here is some updated info. Compression cold with one plug in and air cleaner removed is 135 psi and 136.
Valve adjuster Thread height measured to from the top of the nut to the very tip of the adjuster (screwdriver slot) as follows.

Flywheel side exh. .151" Int. .183"

Clutch side Int. .183" exh .171"

It doesn't appear to be burning any noticeable oil. PCV system is dry.

it does have the screwy intake system that picks up air behind the drivers left foot and since its a workhorse and not a golf cart i'm sure its ingested a fair amount of dirt etc over the years eve thought it looks clean.

I don't understand the low percentages i am reading with my leak down tester. Its OTC brand and I have used it many times before so i'm confident its accurate.

Thank you again Fellas for the help!

Your compression is too low. Those intake valves are sinking in the head. Rebuild time is what I think.

[U2SLO4ME]

Thanks Trig.

Agreed!!!! Can you see any adverse affects with trying to lean it out with a smaller main jet as they do not use the cart very often and I really do not not have time to rebuild it until this fall. That being said, any advise on where to find a quality rebuild kit and or suggestions on how to proceed with a rebuild? top end only ect?

Thanks Again Trig and Cartmaster for you help!

[trig123]

Originally Posted by U2SLO4ME

Thanks Trig.

Agreed!!!! Can you see any adverse affects with trying to lean it out with a smaller main jet as they do not use the cart very often and I really do not not have time to rebuild it until this fall. That being said, any advise on where to find a quality rebuild kit and or suggestions on how to proceed with a rebuild? top end only ect?

Thanks Again Trig and Cartmaster for you help!

I actually think it would be a waste of your time. Wish I could say it would help but I don't think it will .

Also just doing the valves is not going to help with compression that low, at least I don't think so.

Most of the time you can get buy with rings, gaskets, seals, valves, timing belt but you need to know if anything else is needed before you start buying parts.

Once in a while the cylinders are worn where standard rings won't work. The rockers also wear. If you know someone who works at a machine shop they can be cleaned up. They can also measure other things for you so you will know what to buy unless you got the tools to do that with.

You just got to know and the only way is tear into it.
I think others here who work on these engines will agree with what I have mentioned.

I wish I could give you better news. Good luck.

[Cartmaster]

I was just writing my reply but saw Trigs latest post. I fully agree, it's time to tear it down. The low compression rising when wet tested is the deciding factor on a full inspection ,otherwise we would have advised just inlet valves and associated gaskets etc.