1992 Columbia Par Car Misfiring

[Littleg15uk]

1992 Columbia Par Car misfiring
So I have posted several issues before.
The starter would keep turning when I took my foot off gas pedal, New solenoid fixed that.
Muffler was blocked, I left full of Awesome cleaner all week, then through a combination of washing out and banging on a workbench I got a tremendous amount of carbon out. Now I can blow through it from my mouth with little resistance.
Previously it would not fire unless I kept the choke on full, I replaced the junk Chinese carb with a Genuine Walbro. Now it runs without keeping the choke on.

It has a new spark plug, new gas and although it runs it misfires really badly and periodically spits oil and air under pressure from between the bottom of the cylinder and the main crankcase. I thought maybe there was still too much back pressure from the muffler. I took the muffler off and tried it again and it still misfires. ( not sure if it was still leaking air/oil from cylinder/crankcase joint.)

It reads 120PSI on compression test

It has a new air pressure gas pump which provides a steady flow of gas back into the tank if you take the gas pipe off the carb. I can try an electric pump tomorrow. It uses pre mixed gas 85:1 mix.

OK guys what am I missing? what do I try next?

Thanks

[Lochlin]

It sounds like you have a timing issue or your ignition module is going bad.

There is a sticky at the top of the forum that talks about those OEM modules. They are known to be a bear. Unfortunately, they aren't simple to test but there is a testing procedure listed there.

The module itself is located under the screen on the motor.

[Littleg15uk]

Would that cause the motor to spit oil/compressed gasses out from somewhere at the base of the cylinder? I was hoping to take the plastic cylinder cover off and see if I could figure exactly where it’s coming from. Maybe even from the exhaust manifold if the gasket is going?

[Lochlin]

Shoot. I completely missed that. Almost certainly you have a blown base gasket. Indeed, that would cause a lot of the issues that you are seeing. The base gasket is the paper one between the cylinder and crankcase.

You may know this but those are very easy to replace on these carts. Less than 30 mins if you have done it before. No more than an hour if you haven't. It's as easy as removing the 4 head bolts, pulling the cylinder off, putting the new base gasket on, and replacing the cylinder. The toughest part is getting the piston rings to squish back into the cylinder but with a little patience you'll get it.

When you order a new gasket get a couple of them. They tear kinda easy and it's nice to have a couple or three on hand. I would order a couple of rings too for the same reason.

Note that when you reinstall the cylinder things need to be torqued just right so a torque wrench is critical. Also, there is a specific sequence that the bolts should be torqued down with.

Service manuals are here and will describe the process and torque specs:

http://www.buggiesgonewild.com/columbia-parcars/

[raydhd]

BE VERY careful when reinstalling the cylinder over the piston and rings. They are pinned and need to be in place and break easily after being reused.

[Littleg15uk]

I had thought if the gasket was gone to only partially pull the cylinder off and use some ultra copper RTV high temp gasket so I don’t expose the rings, thoughts?

[raydhd]

There is the right way to do the job and other ways. Usually the right way gets results in fixing the problem. In this case it is a fairly quick job just be aware about handling the rings when you reinstall the cylinder.

[Littleg15uk]

Replaced gasket at bottom of cylinder with new one. Still got 120 psi compression, it’s running a bit better but still misfiring and spitting from somewhere, would non combusted fuel due to poor spark cause that. I can’t see exactly where the spitting is. I was going to post a video from my phone but it says invalid file.

[Littleg15uk]

Ok follow up to yesterday it has points, not the ignition module, contacts badly pitted. I cleaned them up as best I could and tried it again, it's getting better, but still not right. The points were arching really badly, The ignition coil measures 1.6ohms on the primary, 11k on the secondary and I don't see a ballast resistor anywhere.
I ordered a Wells DR100 ignition module. 2n2222 transistors. And a 1.6 ohm ballast resistor. Already got 4.7k resistors. To do the HCI conversion re the sticky, Lochlin is that still the most up to date schematic?
Thanks

[Lochlin]

Yeah, that's up to date info.

A previous owner converted your cart from the electronic ignition to points so I bet you have a timing issue. That would explain virtually all of the symptoms that you are seeing. As your timing is off-kilter you are getting a revolution here and there that isn't igniting hence the seeping. I bet the HEI does the trick.

If you want to monkey with the timing I have found that the manual method of lining up the lines on the fan /housing isn't very good. The only luck I have had is driving around with the points showing like yours is and stopping every few feet to make tiny adjustments until I have it. To be honest, though, those carts are miserable to time. I have an 85 that I swear can't be timed right (even though that's not logical). Don't get me wrong, perfectly timed carts will run awesome. It's just getting there that's the problem.