Ernie's Repair

06/17/2026

So I am putting the final parts onto the engine of a Polaris Ranger ATV, and discovered I was missing the short 6mm screws needed for the second exhaust pipe shield. Forgetting for a moment that Polaris is a U.S. company, and thinking that all of the engine parts are metric, I assumed (yeah, I know) that the bolt was 6mm. A 6mmx1 bolt would start only half a turn. Wrong thread pitch. My thread gauges do not have a coarser thread pitch than 1mm.

I found what I thought was a 6mm screw used for the ATV cabin, and it went in fine. Very coarse pitch. It also only goes into my 6mm thread gauge about a half turn. Then I tried a 1/4-20 screw. Perfect fit. Hmmm. What is the difference between a 1/4-20 screw and a 6mmx.8 screw I wonder?

Well, 1/4 inch is .25X25.4, or 6.35 MM. and the pitch? 20 threads per inch is 20/25.4, or .787 pitch. In order to get the Metric thread number, we have to divide into 1 to get the millimeters per thread value, which is 1.27. Given the standard tollerances, I am now thinking that a 6mmx1.25 screw is equivalent to a 1/4-20 screw.

Unless...everything that appears to be 6mmx1.25 on this Polaris is actually 1/4-20, and not metric at all. and by most sources, 6mmx1 is the only pitch for a 6mm screw. This should not be a brain twister, but it did get me. I really should not be so surprised, since working on American cars are often mixed Metric and SAE.

06/01/2026

Some consumer air compressors, specifically oil lubricated, air cooled, compressors can be run continuously without damage. However, there are these compact pancake compressors that are strictly air cooled, designed for use with low air volume pneumatic tools, that can overheat when run continuous and will warp the reed valves at the top of the cylinder. Here are some pictures.

The reed valves are suppose to lay flat and check flow in their closed direction and only allow flow when forced open by air. When they are bent like this and not closed, they allow flow in both directions and the pump quits pumping.

05/31/2026

I am inspired to share various insights of technical information by spontaneous events in my shop. I have learned most of what I have learned by making mistakes. This short video on JIS screws is another great example.

04/23/2026

So you just drained the fuel out of the carburetor of a lawn mower engine that would not start. You check the passages, float valve, jets. All clean. And then you look on your bench where the gas was from the carburetor, and you see this. Now you know why the mower wouldn't start.

04/14/2026

He's right.

226 likes, 18 comments. “ ”

04/13/2026

A week ago, or there abouts, I helped a customer with his lawn mower. It needed a carburetor cleaning, but in the process of investigation I discovered a non-reinforced fuel line that intrigued me, because it was slim, thin walled, and able to navigate the path between the fuel tank and the carburetor without getting caught in the governor linkage.

So I took the ASE number from the fuel line, and looked it up and ordered some, and what I got using that number disappointed me, because it was the same SAE 30R7 nitrile line with reinforcement, 1/4" ID and half inch OD. 30R7 is the stuff I tell people about that is the go-to fuel line for Ethanol gas, but does not do well in Ethanol. I keep a show and tell piece to show people that the Nitrile liner does not hold up to ethanol and actually disintegrates and plugs the fuel line.

So now further motivated to find an Ethanol resistant thin wall fuel line suitable for gravity fed, or low pressure fuel lines without reinforcement, I found Tygon A-60-G. This tubing is used for peristaltic pumps, is very flexible and the resistance to Ethanol, according to the data sheet is "Good".

And with a little more research on Tygon, I found F 4040 A. This tubing is yellow, thin wall non-reinforced. It is the same tubing used for fuel lines of chain saws and w**d eaters, and can be bought in 1/4" ID for less than half price per foot of SAE 30R7. I do not have a chemical compatibility chart for F 4040 A, but the data sheet specifically says that F 4040 A is made for small engines.

So from now on, I will be using this tubing on small engine repairs, because of its resistance to ethanol, and is recommended for use with ethanol fuels.

06/02/2025

Sharpening the mower blades on a riding mower.

05/31/2025

I am troubleshooting a Polaris Outlaw 50 that has rough idle with intermittent backfire. Symptoms of wildly varying idle RPM were improved after adjusting valve backlash. The valves were riding on the cam and were not completely closing. Compression went from 100psi to 125 psi, but the backfire problem did not change.

I am thinking that the CDI module or the pickup coil is intemittent, but I am leaning toward the CDI, because of the intermittent backfire. Any thoughts?

12/09/2024

I was discussing with a friend my experience with working on old equipment, and recalled that I had pictures of a 1934 Diesel 40 caterpillar tractor that I had removed the left track and split the transmission and engine so I could replace the first/third gear cluster, overhaul the clutch, and replace the broken main spring. I found the pictures! The pictures were taken in the West Central Mountains of Idaho about 5 miles South of Cascade Idaho. The time was either 1992 or 1993. Here they are:

08/28/2024

This pic illustrates the nitrile liner in SAE 30R7 1/4 inch fuel line hose, which is recommended for ethanol mix gasoline. Notice how the nitrile liner has separated, shrunk, and split.

Nitrile is better than butyl, but not as good as the twice as expensive fluorelastemer used on SAE 30R9.

This piece was cut off of the end of a fuel line that was leaking, because the split was not sealing to the fitting.