mnstang Posted January 8, 2023 Share Posted January 8, 2023 Is reading the color of spark plugs a reliable way to check mixture combustion? Here is the back story to why I ask. I have my little mod project and I have one cylinder that I'm not seeing really anything for wash on the piston. The other cylinder I have good piston wash and I will see a change in the wash when I change my jetting. But one cylinder I'm just not seeing any wash and I am now two sizes up on that side and I feel like performance is being affected the more I go up in jetting. Both spark plugs look the same and are basically black. Not much of any tan color on either. I am running br9eya spark plugs. In one of my performance manuals it says it is impossible to read spark plugs with ES plugs, and to read spark plugs you should install EX plugs. This manual was before eya plugs existed but I feel like they're close to the ES plug and the EX plug is no longer available. This is fan cooled. I have cylinder head temp gauges and they are looking ok for temps. The one with no wash is about 20 degrees higher but it's also the pto side on a fan cooled. They're usually around 200-210 degrees which is pretty good. I saw 240 today but that was doing half mile pulls on a lake in deep snow so I was holding it open for pretty long. Way longer than it'll see on the trail. I know I should probably get some egt's to really know but I haven't yet because they're expensive. I might end up doing that but seeing if anyone here has anything to say about it. The plugs look fine and head temp looks fine. I'm just not seeing any wash and that is concerning to me. Not sure if there's any reason I wouldn't see wash on the piston besides being lean but the other indicators aren't pointing to lean. The driveability of the sled is great, it runs fine with no issues. Quote Link to comment Share on other sites More sharing options...
Frostynuts Posted January 8, 2023 Share Posted January 8, 2023 Go big on jet sizing on that cylinder until you see lots of wash, and then back down jet sizes to get the wash you want. WTF are you doing playing with a fan cooled machine ? What is it about 50 Hp ? Quote Link to comment Share on other sites More sharing options...
mnstang Posted January 9, 2023 Author Share Posted January 9, 2023 I haven't had on a dyno, don't know the HP, should be over 50. Quote Link to comment Share on other sites More sharing options...
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