UT400 valve lash

[Jon C]

Hello to anyone who reads this. I am Jon and I own J&M Outdoor Power, a very small, small engine repair shop. I was approached by Coleman about 6 months ago to become one of their Warranty Centers.

I recently received 3 different UT400's and a UT500 all with similar issues. These units range from 2 months to 2 years old. Customers state that the unit(s) was/were running fine, then heard a pop and a loss of power, two would no longer start. The two that would run would not achieve normal operating speed (around 20mph I would say) without redlining the RPMs. I quickly found that the Valve lash on each unit had become too large on some(both intake and exhaust) and too tight on one(just intake). 

After setting the gaps to .005(I found multiple different people suggesting bigger and smaller gaps, but no definitive Coleman Spec number yet) every unit starts, runs, and achieves top speed without issue.

I don't know how many others have come across these issues, and I wanted to get something out on the web for others in the same predicament. 

Please let me know if you have had similar issues.

Edit: I realize that this will not be a fix all solution for this issue, as the oil level and condition should be verified before moving to the valves. Many times improper oil conditions will cause valve lash to change. These units all have good oil and proper oil changes.

Edited May 14, 2023 by Jon C
Additional info

[Rainman]

Hey Jon, I purchased my 2021 UT400 a few months ago as a new unit from Tractor Supply, which I found out was actually a used unit. It always started up on the first try after a couple cranks of the engine, but now, I have to try at least three times to get it started before it does and then it runs rough. Even backfired a couple times, stalled, etc.

After it warms up it seems to run and start a lot better. I added some Seafoam to the fuel tank since I didn't know how good the gas was in it at the time of purchase and that's when it started getting worse. I may have a clogged fuel filter or maybe the spark plug may be fouled, so I will check them out next before doing anything else.

Like I said, it's a 2021 and only has about 11 hours and 25 miles on it. You mentioned to condition of the oil before adjusting the valve lash, which will be another thing I will look into. But at what hour/mileage should the first oil change be? I'm sure it never was changed, so I also want to plan that with my initial maintenance.

Thanks in advance ...

[Jon C]

4 hours ago, Rainman said:

Hey Jon, I purchased my 2021 UT400 a few months ago as a new unit from Tractor Supply, which I found out was actually a used unit. It always started up on the first try after a couple cranks of the engine, but now, I have to try at least three times to get it started before it does and then it runs rough. Even backfired a couple times, stalled, etc.

After it warms up it seems to run and start a lot better. I added some Seafoam to the fuel tank since I didn't know how good the gas was in it at the time of purchase and that's when it started getting worse. I may have a clogged fuel filter or maybe the spark plug may be fouled, so I will check them out next before doing anything else.

Like I said, it's a 2021 and only has about 11 hours and 25 miles on it. You mentioned to condition of the oil before adjusting the valve lash, which will be another thing I will look into. But at what hour/mileage should the first oil change be? I'm sure it never was changed, so I also want to plan that with my initial maintenance.

Thanks in advance ...

Rainman, six months, 100 hours, or 1000 miles is a general interval for ATV/UTV oil changes. Searching for hisun/colemans recommended intervals only turn up 800 numbers. The seafood is made of mostly naphtha and isopropyl alcohol. That stuff will destroy any seals, plastic, rubber, rust, etc it comes into contact with. Known to ruin injectors, so user beware. Hopefully you got your situation figured out, and take it slow in the driveway.

[aefron88]

Straight from the FSM (available in the downloads section)

Service intervals:

So 10hrs/50 miles for breaking. 100 hours/500 miles for regular oil changes per the manufacturer.

Valve lash:

 

Seafoam as mentioned is not a cure all. If you have water in the fuel or its stale (which it is if it wasnt stabilized and its more than a month or two old) I would siphon out what you can and put fresh stuff in. Old fuel can be slowly mixed in with your car fuel to dilute it so it burns properly.

Techron is a good injector cleaner additive (or anything with PEA) if you think you need that, but these multec 2.5 injectors are pretty cheap anyway.