Compression issue?

[Blipsnchips]

We got our daughters a little 125cc go kart a few years back for Christmas and it’s generally run fine. The girls and I have done oil changes and cleaned the air filter/carb pretty regularly, fixed broken suspension from crashing, ect… Last time they used it the throttle got stuck and she had a hard time stopping it. I fiddle around with it a bit and found the sleeve inside the carb was sticking. I cleaned the whole carb out and it still was sticking. Tried buffing it with a dremel with no luck so I got a new carb. Just the generic carb a parts place had, essentially the same thing as what was there. I put it on and when I tried to start it, it wouldn’t start. I messed with the choke and still nothing. It actually got worse and didn’t even want to turn over. I pulled the plug and it’s super wet. So I put it in gear and push it a few feet, rolls just fine. Put the plug back in, not so much. Fights moving more than a rocking amount. There is clearly too much compression it appears to be hydro locked with fuel? Is that a thing? I’m not really schooled on much more than maintenance, part swapping and rigging “mechanical” things so I’m kind of stuck where to go from here. I’d like to avoid taking it to the place we got it from to have fixed but if need be I will. I’d love to just dive into it with my girls though and fix it ourselves. I left the plug out and let it attempt to dry some of the fuel out for a few days. I can now plug the plug hole and push it a bit easier but still feel really high compression wise. Seems like the new carburetor dumped fuel in and started this issue? Any recommendations of where to start would be awesome.

 

[Denny]

Pretty pups you got there!
First off do you have a nice and blue spark? To check put plug back on the wire and ground the electrode end to the head and crank it over.

 

[Blipsnchips]

Pretty pups you got there!
First off do you have a nice and blue spark? To check put plug back on the wire and ground the electrode end to the head and crank it over.

Thanks! They are always “helping” me…

Yeah I have good spark. Plug was a bit dirty but I hit it with a brush.

 

[Denny]

Does it pop or even try to fire in any way?
If not try replacing the plug for ships and giggles. A compression test would not be a bad idea either. I’m not real well versed on these buggy type kart engines. It is a 4 stroke engine correct?

 

[Blipsnchips]

Correct it’s a 4 stroke. After checking the spark again I questioned it. I’m currently solo and it was really tough to press the brake to engage the safety interlock for starting. I went to autozone and got a spark tester and it’s definitely not bright blue like the plug looked, It’s orange. The angle of my dangle must have been too bad to see it clearly. Btw anyone looking for a tester or other random tools they have a ton of OEM stuff of clearance at the zone. So I guess ignition would be the next step? Yesterday it wouldn’t even turn over, it was solid with the plug in. Like drag the wheels to move it solid. I don’t think I should even try to start it again before I get a new ignition right? Just end up with that same flooded hydro lock state. Looking back it has always kinda been a real turd with start up.

 

[Denny]

Does the oil smell like gasoline? Is it kind of watery? Does it pop or anything when you crank it?

 

[Denny]

Does the oil smell like gasoline? Is it kind of watery? Does it pop or anything when you crank it? Might want to make sure the battery is fully charged up too. That will affect spark.

 

[Blipsnchips]

Unfortunately we just changed the oil so it hasnt had any time on it at all. When we changed it it just kind of smelled like old small engine oil. Wasn’t super watery but definitely broken down a bit. Battery is fully charged, but I do have a bran new battery that I can toss on the charger and throw in. As far as popping or anything…. Here’s s quick rundown of what happened. Ran decent but the sleeve in the carb was sticking so it would get stuck throttle open. Changed the carb and cranked it over maybe 12-24 time total. Each crank got weaker and weaker didn’t even attempt to start. In the past when I’ve swapped carburetors out on stuff you can usually get a since that it’s trying to do something. This one didn’t, other than dump gas. I should have probably looked up where to set the air/fuel screw and idle but have been ok just winging it in the past. It did the crab k no start until it just wouldn’t crank at all. The battery was low at that point. But I charged it and it would only crank with the plug out. I figured I’d do what’d you do with a hydro locked car and crank it no plug. Which it did just fine, but nothing came out like with a hydro locked car. I’ve let it sit overnight plug out to hope evap the fuel if that’s what it is even. But I haven’t tried cranking it again to see what’ll happen.

 

[Denny]

What does the barrel and bore look like in the old carb? Still got it? Can we see some pictures?

 

[Hellion]

Last time they used it the throttle got stuck and she had a hard time stopping it.

Make sure your vehicles have a kill switch that is functional and accessible. Throttle cables and throttle plates have a notorious stuck/failure rate in this hobby, mostly out of neglect. Lube the throttle (and brake) cables until the lube comes out both ends.

 

[Blipsnchips]

What does the barrel and bore look like in the old carb? Still got it? Can we see some pictures?

 

[ezcome-ezgo]

Maybe something snapped in the valvetrain keeping the valves shut?

 

[Blipsnchips]

Make sure your vehicles have a kill switch that is functional and accessible. Throttle cables and throttle plates have a notorious stuck/failure rate in this hobby, mostly out of neglect. Lube the throttle (and brake) cables until the lube comes out both ends.

I was very surprised it didn’t have one built in. I guess they figure the key and ignition are good enough. Switch in it to just kill the power completely.

 

[Blipsnchips]

Maybe something snapped in the valvetrain keeping the valves shut?

Wouldn’t that just seize it up or not allow the position to go up and down?

 

[Denny]

I’m not seeing a good reason for the barrel to be sticking in the carb. You do have the big spring that goes between the barrel and the cap right? Run a compression check also to see what kind of numbers you get?

 

[ezcome-ezgo]

Wouldn’t that just seize it up or not allow the position to go up and down?

Well you said it will only crank with the plug out, sounds like the valves are perpetually closed. A valve could be closed and have no impact on the piston position.

 

[bob58o]

Hydro locked with fuel is a thing. AFAIK.

If float / float-needle isn’t operating correctly and there isn’t a fuel shut off valve, if gas floods the carb, does it find its way into the intake port, then into the combustion chamber?

im just thinking out loud. I didn’t read most of the above because reading is for L7 weenies.

Added..

Imagine a small pushrod engine without pushrods…
The Crankshaft turns, the cam shaft turns, but the valves stay shut because nothing is opposing the valve spring pressure because the pushrods aren’t pushing the rocker arms.
The piston moves with the crankshaft, but the valves aren’t opening.

If you haven’t looked under the valve cover. It is always a good place to have a look. EZ^2 has been known to hide gremlins inside valve covers from time to time.

 

[Blipsnchips]

I’m not seeing a good reason for the barrel to be sticking in the carb. You do have the big spring that goes between the barrel and the cap right? Run a compression check also to see what kind of numbers you get?

Yep I can’t see any reason for it to stick either. But it sure is sticking. Lol. I had to use a pick to even pry it out of the barrel. It wasn’t bad beigr but after buffing it both the barrel and the sleeve are smooth as butter. Something must be deformed in there somehow. I had emailed the kart supplier and they said these cheap Chinese carbs seem to do it often.

Hydro locked with fuel is a thing. AFAIK.

If float / float-needle isn’t operating correctly and there isn’t a fuel shut off valve, if gas floods the carb, does it find its way into the intake port, then into the combustion chamber?

im just thinking out loud. I didn’t read most of the above because reading is for L7 weenies.

Added..

Imagine a small pushrod engine without pushrods…
The Crankshaft turns, the cam shaft turns, but the valves stay shut because nothing is opposing the valve spring pressure because the pushrods aren’t pushing the rocker arms.
The piston moves with the crankshaft, but the valves aren’t opening.

If you haven’t looked under the valve cover. It is always a good place to have a look. EZ^2 has been known to hide gremlins inside valve covers from time to time.

I have not pulled the valve cover off yet but I will do that tomorrow when I have some time again. I did stop at the parts store and pick up a compression tester so I’ll test that as well. Kids have the day off so it’ll actually be easier to do with one of them helping me. The dang safety feature of having to have the brake pressed makes it a real hassle to see Andy thing going on at the back end.

“im just thinking out loud. I didn’t read most of the above because reading is for L7 weenies.”

 

[Blipsnchips]

I’m half tempted to just jam a Predator engine into it. I have one on my Allis Chalmers garden tractor and it’s a beast of an engine that’s pretty dang reliable.

 

[Denny]

I’m half tempted to just jam a Predator engine into it. I have one on my Allis Chalmers garden tractor and it’s a beast of an engine that’s pretty dang reliable.

Sure would make it more reliable!
And don’t worry about talking to yourself because most of us old guys on here do it all the time. No one else will listen to us.