Plugs or piston wash?

[eavega]

Just recently got a new gadget, a borescope camera you can attach to your phone. I decided to take a peek at pistons in my 1995 SPX, just out of curiosity. Attached are the pictures of what I saw. I never really knew a thing about piston wash, but I did know how to read plugs. Earlier this year I did a plug chop, and the results were as expected, a nice tan color on the plugs. Now, I only know about piston wash from what I read on the internet, and most of that is from snowmobile forums. I am seeing clean portions of the piston right around the ports, but perhaps they should have bigger spots. I may be running a tad lean on my ski. Can you folks tell me if the piston wash indicates lean? Should I trust the plugs or the pistons more? Thanks in advance for your comments.

 

[mikidymac]

I would have to say a little lean too. I am no piston wash expert but the more fuel you dump in the cleaner the top of the piston will be. So one itat is too rich will be wet and very clean whereas one that is lean and ready to blow will be black with no wash.

There are a few guys here that can read piston wash like a book so hopefully they will chime in.

 

[eavega]

So what is the solution to enrich my mixture? My initial setting on the carbs was 1 1/8 out for low-speed, 0 for high speed. Assume if I open the high-speed its just going to let more air into the mix and further lean out the mixture. Should I start by adjusting low-speed? What else should I look for that would cause me to be running lean?

Rgds

Eric

 

[mikidymac]

No, these carbs are not like a dirt bike. The screw lets more fuel in not air. So the further the screw is out the richer it becomes.

 

[eavega]

No, these carbs are not like a dirt bike. The screw lets more fuel in not air. So the further the screw is out the richer it becomes.

Excellent, then time to start adjusting the screws. Is there any way to determine if its running lean at all throttle settings? I'll assume mid throttle is okay, as that is controlled by pop-off, and my pop-off values were spot on when I rebuilt carbs last year. Since the ski is mostly run with the throttle pegged, should I start with the high speed screw?

-E

 

[mikidymac]

If it is an all stock ski it should run perfect with the factory settings. If it doesn't then something else is off.

 

[1983]

If its stock, as stated above set it to stock settings or it will run like crap

 

[eavega]

So if I am all stock, running very well, plugs tell me I am running well, but piston wash above is telling me I'm running a tad lean, how do I correct? Where should I start looking? Am I overthinking this? Quite honestly if I had not gotten the borescope camera, I would not even be asking this question. Reading the plugs I would've assumed I was running correctly.

-E

 

[mikidymac]

I would say just run it and don't over think it.
If you want you could try opening the high screw 1/8 turn and even the low and see if it runs worse. You can't hurt it richening it up but it might not run great.