Spark color to me is more for fine tuning. Checking color after a gurgle really shouldn't be apart of the trouble shooting process. Change to a fresh plug once you have your tune semi dialed then check color for adjustments.

It does not look like the truck is running a fuel clunk, I don’t see one in the tank, I don’t really know how the truck was ran with the last guy, the truck had 9 hours, he never cleaned the filter, he just kept leaning his settings

https://drive.google.com/file/d/1pBn...w?usp=drivesdk

https://drive.google.com/file/d/1XY3...w?usp=drivesdk

Looks like i now have enough posts to put links

Please don't worry yourself with that plug lol. Been there when I first started and it will lead you to frustration. I'm gonna say dive in and order up a set of gaskets for the motor, new ring, and carb rebuild kit or just plain buy a WT990. Open her up and you will learn a lot. Look for scoring in the cylinder, mangled gaskets and dirt. I'm almost 100% the carb is dirty if there was no clunk. Get one of those too!

Looks like I’ll be doing some wrenching then, I’m pretty sure it’s just the carb gasket that blew out, would a compression tester help?

Naa, don't bother with that. Your hand is your compression gauge. You should have to stand on one wheel and yank when compression is good. If you can pull with the flick of your wrist that means you need a new ring or top end, usually just a ring.


Yeah start with the fuel clunk and carb or carb gaskets first. And for your piece of mind a new plug lol.

Just know if you re-ring your gonna have to break in the motor. Let it drink a quarter to half tank at idle.

Lol, the pull starter does lift the truck, I have to hold it down to start it

Then there you go. Now just remember when it get's easier to pull that means your ring is wearing. They are only $6

How do I know if it needs a new top end or just a ring? How often do you re ring?

I re-ring, change gaskets and clean/rebuild carb every season. Cheap insurance in my mind. When you feel a loss of compression you will obviously open her up. If you see major scoring/scratches in the cylinder then you'll need a new head kit, if there isn't anything majorly scratched you can re-ring.... I'm waiting on a couple of rings right now for my 27.2cc, the cylinder shows some scoring but should be fine. I'll post up a pic of the head I'm working on so you have better idea.

Is there a method to checking air leak like we used to on the nitro engines, shooting nitro cleaner at where the suspected leak is and seeing if there was a change in rpm, I’m kinda suspicious that the insulator block is cracked

Not that I know of. These motors are nowhere near as finicky as the nitro's. They should hold a tune until you change gas or oil mixture. Of course if you tune in summer it's gonna want different settings in the fall/winter. Typically if I experience your issues it's a gasket somewhere or dirty carb.

Here is a photo of my 27.2cc that I'll be re-ringing soon. This will be the last refresh for this top end I think. Notice the scoring lines. They aren't too bad but that is the beginning of the end for a cylinder. If you can get a finger nail into one of those grooves than it's prob time for a new head.