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Why is it Eating Plugs (Pics)


Stinger

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My step bro picked up a 250R that ran like shit but had a ton of mods (I'm still trying to figure out what all was modded). It is supposed to run on VP110 because it's got 200 psi compression.

 

Anyway, after I got the main jet set so it would run WOT without bogging, we checked the plug and it was rich but I was ok with that for now.

 

After about 2 hours of riding the spark plugs ground strap broke off and pounded itself around inside the combustion chamber...time for a rebuild.

 

Jetted it one size leaner, out in a stock size dome, went for another ride. Got about 1.5 gallons of VP through it and it ran out of gas. Swapped in some Premium pump gas and went for a spin. Ran good, no odd noises or anything. After about another 2 hours of riding it started sputtering. Pulled the plug to find the gap at about .060" because the electrode had apparently burned away so it's now nearly level with the ceramic part of the plug.

 

I figured it had to be detonating because of the pump gas. Pulled the side cover to see if the timing was advanced...doesn't look like it. Compression is stock, timing is stock (I think), port work is very minor.

 

What the hell is wrong with this thing? It is KILLING every plug I put in it???

 

Pics:

 

250RPlugs1.jpg

250RPlugs2.jpg

250RPlugs3.jpg

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At 200 psi on pump gas you were detonating, had to be no question. That alone will kill your plug and usually your piston. Recheck your compression, run 110 and make sure you have the correct size and heat range plug for that motor. I don't know what is requires but you may check with others that own them.

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i used to have a 250R and i think the plug was br9 or br8 i dont remember but it fouled and ate plugs like crazy..finaly figured out it was the oil i was running was total crap..maxima..it hated that oil in that motor..i started premixing with golden spectra and got good results..but that was a long time ago..there are better oils out there now :shrugani:

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If it is burning/melting plugs , it is either a lean jetting condition, air leak (need to pressure test the engine), or a octane issue ! Those are the 3 that normally cause that!! :(

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If you read what I said above, it had 200psi when I was running VP110 before the first plug failure. After I had to rebuild, I put in a stock sized dome and swapped to pump gas.

 

Why would a 250R with a stock dome and stock timing be detonating on premium pump gas?

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i would go to a stock degree key. i am a mechanic and when you burn tips it is from too advanced timing or poor grounds in the secondary ignition system check all your grounds in the harness and pay close attention to any aftermarket kill switches. also make sure your plugs are getting a good ground at the head. make sure there is no carbon in the thead holes of your head. if not the spark trys to ground at the base of the plug electrode therefore burning it off.

Edited by 2twin350s
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I've considered that it could be a plug grounding issue. I just figured a ProDesign head would create a good ground since so many people use them without issue. I suppose it could be an isolated thing though.

 

Do the 250R's use the same flywheel puller as a Banshee? I need to pull the flywheel to see if it's got an advance key in it...

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as far as i know the hondas use a different puller. in most cases, if you go to the hardware store you can find a bolt to use in the center to force against the crank instead of buying a puller. but be very careful. that is how i remove them on 250x and 300 ex. i think they are the same setup with a 250r.dont quote me on that though. pull the cover and see what setup it has.

Edited by 2twin350s
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