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1992 Honda 300 spark plug reading

928 Views 9 Replies 6 Participants Last post by  SlammedRanger
Sorry if my grammar is bad, but I have a 1992 Honda 300 that I installed a thrush glass pack on yes bring the hate it was cheap.

Anyways I figured I would have to jet my carb but thought I'd check the plug first I ain't no mechanic checking the plug isn't my thing. Thought I'd ask for you opinions first, I have ran the engine for about 15 to 20 hours after putting the pipe on many heat cycles.

Quad runs good but backfires quite a bit around mid range rpms while engine braking. Although after riding for about 45 minutes and the engine is hot the back firing seems to stop so I don't know. Doesn't ever bog I mostly ride at WOT for best engine braking since it has very not existing brakes lol

I live on a farm so I do use this quad for chores and moving cattle as well so it does do alot of idling and low throttle riding. But anyways enough rambling if you could please look at my pictures and tell me your input that would be really helpful. Thanks

P.s it sounds damn good and I'd say has alittle more top end power still pops a wheelie as well

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Hard to tell from the pictures. But looks lean to me. I would like to see alittle more of a cardboard brown color on the porcelin. That being said the only way to be sure its lean is to do a plug chop. That requires a couple spare plugs and a wide open place to get to 4th gear just before the rev limiter. Shutting it down and pulling the plug to cut the threads off and look for a ring of color about 1/4 off the base of the porcelin.
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You may need to talk to some of the utility quad guys on here on how to properly do the test. I do it on sport quads with a clutch. And when i hit 4th gear and wind it out to just before rev limit i pull the clutch while flipping the kill switch and roll to a stop. Thats the proper way to do the test. I havent the slightest clue how to do that on a quad with no clutch lol. But you will want to warm the quad up on your current plug. Then slap in a new one and go real hard on the throttle through the whole test.
pics are deceiving , I think I would fatten it up 1/4 to 1/2 a turn and see what it looks like then

Slammed , I know you are a sports quad guy and not a utility quad guy , but know you are very knowledgeable with engines , so maybe you can answer this one for me , I also have a 92 300 , which is the 1st gen which I didn't think has a rev limiter , or maybe it does and is just set at a higher RPM than the second gen 300's , I know with a tack on the 92 it will turn up over 7K and doesn't sound like it is kicking out , the 2nd gens I have would only turn up 6K , when I put a no limit CDI on my 96 it will exceed 7K and never sound like it is kicking out
Does the 1st gen 300 have a cdi? The cdi is what sets your rev limit. Honestly on a utility quad i wouldnt put it passed them to not put a limiter on it. Since they werent really designed or meant to be reved out that far anyway.
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