EZGO - No Power - Not the Valves - Air Assembly the Cause - Why??

Danny.prouty

New Member
Loss of power in ezgo workhorse st350 when motor is warm/hot. Motor needs to fully cool before I have power again.

I have adjusted valves to .004, .006, .008, .009, as well as the bottom out and then back 1/4 turn trick. No significant differences in performance at any of these lash settings. Cart still loses power after a couple mins running.

Today I removed 2 new spark plugs I installed last year and found dry, black carbon buildup so decided to look for air flow problems (again).

I removed carb hose from the air filter assembly and sure enough the motor roared and cart chugs up hills no problem even when it's hot. If I re-connect the carb hose to the filter assembly, even without the filter installed, it has no power. If I remove the air intake hose from the air filter assembly she still has no power even with filter removed. Remove the air assembly from the mix and she's happy. Wtf!?

So, I removed the air filter assembly for a close inspection and don't see any issues. W.t.f...is going on?? Runs like new with no air restriction. I'm suspecting I did something wrong when I installed carb. Would incorrect float adjustment do this?

The carb, fuel pump, fuel filter and fuel hoses, plus both spark plugs were all replaced last year. My OG problem was bad fuel and gummed up carb...
 

Danny.prouty

New Member
I dont see how it could be, that rubber is fairly thick. Hadn't considered that though -- will take the seat off and give it a run and see what it looks like. Idk why it would collapse when it's attached to the air assembly. There is a very small valve in the 45° elbow where the carb air intake and the air filter assembly interface. I'm not positive what it does, but it's about a 2-3mm diameter pathway from so can't be robbing much if it is blowing air.

I'm leaning towards adjusting the float. Running out of ideas.

I saw another thread where a guy had same thing...good performace without the intake hose connected. He replaced his head finally and that worked, but he could not find a problem with his old head and they are like $300 so not sure I wanna go that route on an old cart.

I figured it was just the smaller diameter air inlet on the air assembly, plus the air inlet hole for the filter circuit when the cap is off. You wouldn't think it would make that big a difference.
 

cartmaster

Cartaholic
What year is the cart, Which engine do you have and which air filter assembly is fitted. There are several options. On some air assemblies there is a baffle plate that if fitted incorrectly can cause this exact problem. Maybe a few pictures would help. Air assembly open so we can see inside, where you think the restriction seems to be and front and rear of engine. All this may lead us to an answer.
Something is altering the air fuel mixture! Does it feel like it is trying to run with full choke?
 

Danny.prouty

New Member
Hello Cartmaster -- so it dies with choke if engine is warm. I have the '01 Workhorse - st350. Mnf code: F101. I think its the standard 4 stroke 350 motor.

It's the cylinder type air filter assembly from Nelson Industries. Link below to the us patent which has just about every detail you could hope for including diagrams. It's alot to digest, but super useful. You can analyze every part of it in perfectly described detail, but it's alot.


Full disclosure, and here we go...the air assembly does have some damage to the exterior wall directly opposite the air intake for the exterior of the air filter housing -- it's a 2cm wide hole that goes through to the outer filter chamber. It's been like that ever since I owned it and not caused this issue. I cover it with ductape to keep the dust out and minimize air coming through. It shouldn't really matter since the hole penetrates into the same exterior chamber of the filter as the air intake for the filter assembly which is also for the dirty air and even though it could rob some flow from the actual intake in the same air chamber, it is still getting the air. Been like that since I bought it.

This all started with an electrical issue which in turn turned into bad fuel in the carb. I ended up replacing the spark plugs, all the fuel lines including the intake in the fuel tank, fuel filter, fuel pump and a new carb. It finally cranked up after all of that, but with this power issue.

I know that crack is sus, but I don't think it's the problem. You are for sure right about the air/fuel mix...the air filter system restricts the air flow just enough with the smaller diameter intake vs the full bore of the intake hose. Gotta be the carb letting too much gas in for the amount of air which is giving me sooty plugs. Whatya think? Am I crazy?
 

Attachments

  • 20220911_072543.jpg
    20220911_072543.jpg
    185.8 KB · Views: 11
  • 20220911_075747.jpg
    20220911_075747.jpg
    125.2 KB · Views: 11
  • 20220911_073237.jpg
    20220911_073237.jpg
    127.4 KB · Views: 12
  • 20220911_073229.jpg
    20220911_073229.jpg
    149.6 KB · Views: 11
  • 20220911_073149.jpg
    20220911_073149.jpg
    115.2 KB · Views: 11
  • 20220911_072602.jpg
    20220911_072602.jpg
    172.2 KB · Views: 11

cartmaster

Cartaholic
If I recall correctly, the adapter that bolts to the carb for the air filer hose may have a metal baffle plate in it that occasionally gets installed in the wrong position and restricts air flow. I mention this as you say you had the carb off previously. Worth a look in my opinion.
 

Danny.prouty

New Member
Hmmmm...yes, it does. And yes, I believe you're correct about there being more than one way to position the plate. Now that I think about the horror show of getting all of that back fogether. I somehow lost one of the nuts that attaches said baffle and went bonkers looking for it. Never did find it. I'll fiddle with the plate and report back. Thanks...
 

cartmaster

Cartaholic
I can't see the air filter assembly causing the issue to be honest. I service a whole range of machinery that use the exact same assembly without issue. The white plug is just to blank a threaded hole that has a vacuum gauge fitted to monitor air flow on some machines and the elbow itself can have various size bores depending on the air requirements for a particular engine. The same filter is used on medium sized four cylinder diesel engines so it should not restrict enough to affect your engine. The issue has in my mind got to be at or in the carb or intake. Your tank tape repair is fine lol. Done it myself a few times. The rubber wedge cone thing should point downward to collect dust and you squeeze it to empty it out occasionally. Only thing to go wrong is fitting the filter element the wrong way round and completely blocking the inlet. And trust me I have seen it done when called out on a no start machine lol. Actually it looks like maybe the dust collector may be missing on yours. No biggie!
 

Danny.prouty

New Member
So the carb baffle plate was reversed, but the problem persists after flopping it. I was hopeful, but our hill dashed that quick. At least now I can yank off the carb hose and chug back up our hill instead of waiting for her to cool down 1st. Thanks for the info on the vaccum gauge, I was def curious what it did. Seems like a pretty well engineered filter. Lol I wouldn't put it past myself to put the lement in backwards. Unfortunately though not this time.

I guess I need to pull out the carb again and inspect the float.

Lol yup, dust collector is MIA. I think I pulled it off last year and it sprouted legs after I forgot what it was for. New one is on the way. Ahhh the joys of small combustion engines. My guess is if I was a rich man I wouldn't mess with old equipment like this, so I guess that's a perk of being broke. This is definitely more inteteresting than dropping 15k on a brand new UTV. But then again I would have had an operating utv for the last year. And I know something else is bout to go wrong. The rubber on the bushings for my shocks looks like it was made last century and probably was actually.
 

cartmaster

Cartaholic
Ok. A couple of things to check before pulling the carb. Make sure the choke is definitely opening fully when you push the cable in. Second, you say the valves are gapped ok, but. Maybe they are worn out. Do me favor and remove the valve cover, look at the amount of thread showing above the locknuts on the adjusters and compare the inner two against the outer two. If you have more threads showing on the inner two, I would suspect the inlet valves are sinking into the valve seats. This can disrupt the air flowing in and seem like the engine is choking. In fact, a picture would be good so I can see. Poor running on these engines is often attruted to sunken valves on these pre MCI's. It is possible this may be your problem. Without me being there it is difficult to pinpoint the issue.
 

cartmaster

Cartaholic
I just got work and took a close look at your pictures on a big screen PC. Has this just started to happen on a previously working cart or have you acquired the cart as a non runner and trying to get it working? I only ask as it looks like you have an aftermarket carb fitted. This may well be the cause of your problem. These are know to give such issues as running rich or lean. It sounds very much like it is running way too rich and removing any air flow restrictions allow it to run half decent. The clues here are poor running under load, black carbon on the plugs etc. Regarding the metal baffle, I cannot recall the fitment on these later filter systems but on the earlier square filter boxes, it was fitted on stand offs to allow air to flow around it. Maybe it has not been fitted as it should be? You could try removing it and see if it makes a difference. I have a feeling it is only there to prevent a fire under California laws or something. I have run these carts without the plate before and they ran fine. I may have a parts book for these so I will take a look to see if there is anything obvious to check.
 

Danny.prouty

New Member
Hey Cartmaster -- thanks very much for your input here! I have been starting to wonder about worn valves, but the cart ran well until Spring last year.

Here's how it went south...I had some old fuel in her through winter, but she still ran okay in Spring. Overnight there was an electrical issue, nothing at all when I applied throttle and no headlights. Long story short I replaced battery, fuses, and plugs and made sure the coils were good. Nothing worked...until suddenly it did. I'm assuming a short somewhere, but never found it. The headlights don't always work so think it's related, but she hasn't lost juice again since.

By this time though it was Summer and with that bad gas she would only turn over with that pitiful little chug. I tried cleaning the carb and jets, no go. Adjusted valves, no go. I replaced the fuel pump and fuel lines but still that same pitiful chug. I picked up the after market carb and she cranked right up, but with the power issue. So you're prob on to it suspecting the carb. I didn't realize the aftermarket carbs were sus. I still have the orignal carb and can't find anything wrong with it. Can you still get the OG carbs anywhere?

Yeah I think that baffle plate is just a spark arrestor. Correct, it's mounted on 2 studs with stand offs. 2 of the 4 carb studs go right into the motor manifold and 2 are the posts with the stand offs that thread in and you attach the baffle onto the end. Pretty confident it's right. It's as far out as it could go and looks right compared to the ezgo diagrams.

I think the valve threads are all about the same height. I'll take some pics of the for you.
 

Danny.prouty

New Member
Cartmaster -- you're more than worthy of your name. I slapped the old carb on and after some choke she started sputtering and coughing and then she came to life...she is humming along again nicely, chugging up our hills with the air filter assembly fully connected! Thanks for you solid advice!

It was a rough project, but it's satisfying having only spent a pair of clean hands (not counting the $100 in parts). And I can now swap the carb and adjust valves in about 1hr flat , lol.
 

Attachments

  • 20220912_150400.jpg
    20220912_150400.jpg
    119.2 KB · Views: 8
  • 20220912_150158.jpg
    20220912_150158.jpg
    172.6 KB · Views: 8

cartmaster

Cartaholic
As Isaac asimovs Bicentennial man said. "Glad to be of service"
Now go and enjoy the fruits of your endeavours.
Shame I won't make it to 200 years. Lol.
 

cartmaster

Cartaholic
Seeing a kid smiling like that with his dad just makes it the icing on the cake. I might just have to add that picture to my success story board.
 
Top