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So my bike has been running good since I got it, and started riding it beginning of last July. Last week it started missing just after fueling up, I thought I had got bad gas, so ran it out and and fueled up many times and it just got worse over the last 7 days to where yesterday it was almost dying at stop lights and running so rough I would sear a cylinder was dropping out... missing bad on acceleration, and anything at low idle. When I got out of work I took it to my local shop (Motorcycle goodies in Everett WA) and told the owner what was going on, he had me pull it around back and said "we'll start with a set of plugs and see how that goes" about 20 mins later it was cooled down enough, his mechanic came out and started working on it... after a m in I hear "Holy ****!" ... I look over and said sounds like you found the problem?? He laughed and said " This might be the problem...lol" then asked me what I added to my fuel. I responded nothing, and I always put good 92 octane premium in it. and he said well come look at this...
The bottom plug was my front cyclinder... He said "no wonder it felt like a cylinder was cutting out....because it was"
Isn't it awesome when there's an easy, cheap fix....
FWIW..... Those plugs look really old....
Twin Cam plugs are very easy to change, and inexpensive to buy (even at a dealer)... I rarely go two years or over 10K miles (2 services) on a set of plugs.. I've yet to replace a set of plugs that weren't still in very good, serviceable condition. It's just cheap, good insurance to me...
I'm gonna guess that front plug being bad is the short term cause of the engine "running so rough I would sear a cylinder was dropping out" ...
If the plugs are half as old as they look, it would be hard to guess what else maybe going on just from the plugs... but....
Both plugs look to have been out in the elements for quite awhile, that can negatively affect many different systems on the bike.
The bad plug also has oil in the threads and appears to have been burning more than just gas & air....
I suspect the bike will need more than just plugs for long term health, but we'll never be able to guess based on the small amount of info shared to this point...
Last edited by hattitude; May 2, 2025 at 05:38 PM.
I'm gonna guess that front plug being bad is the short term cause of the engine "running so rough I would sear a cylinder was dropping out" ...
If the plugs are half as old as they look, it would be hard to guess what else maybe going on just from the plugs... but....
Both plugs look to have been out in the elements for quite awhile, that can negatively affect many different systems on the bike.
The bad plug also has oil in the threads and appears to have been burning more than just gas & air....
I suspect the bike will need more than just plugs for long term health, but we'll never be able to guess based on the small amount of info shared to this point...
Not sure when she spent time outside in the elements, the guys I got her from swore it had been garaged... but I found many ...untruths to things he told me.... When I put her on the road last July I changed all fluids, put new brake pads too, adjusted clutch...but It did not occur to me to change the plugs, as the bike was running good it seemed to me. I cover her when she has to be left out, and other than that I park in garage almost nightly. The bike ran good right up until it did not other than backfiring on deceleration. It had a Power commander 5, and from all I can tell the PO downed the bike and trashed the 2 into 1 pipes that were on the bike with the original tune. Looks like he switched to the 2 into 2 slip ons that are on now. I figured pulling the power commander would make it run better, and it did indeed. No telling how long those plugs were in there, and I put about about 15k miles on it before it started running rough. I know now that I should change plugs about every 10k, and will do so. Not sure if PO was using additives for the fuel, but that is a possibility. I will keep an eye on the plugs to see if it starts building up crud again and go from there.
Last edited by Willburrrr2003; May 6, 2025 at 07:35 AM.
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