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Old 12-10-2006, 07:37 PM
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Default How do you stop a plug fouling

     

Can anyone help. My RM125 keeps fouling plugs after only 30 mins riding. Are there any carby adjustments like jets of needle pin clip (raise / lower) that I can play with to help plugs last longer than 30 mins. When I remove the plug it is wet with fuel, and makes it impossible to start.
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Old 12-10-2006, 09:10 PM
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Default Re: How do you stop a plug fouling

rejet
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Old 12-11-2006, 12:33 AM
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Default Re: How do you stop a plug fouling

Rejet or change the fuel/oil ratio are heard a lot. There is something you should do before you consider any of that: There is a post in the archives by faded on setting the float. Start there before you consider either of the other two suggestions. Get the carburetor back to the way it needs to be to operate as designed before you go changing brass. To get the ultimate out of your RM125 you would likely need to set your jetting to the way you ride, but trying to do that before you get things like the float setting correct is a waste of time.

You don't mention if it ever worked well, or if this is something that has progressed. Worn crank seals and worn cylinders/rings/piston(s) are another thing that will make it run rich and foul. Reeds are yet another. Cheapest, fastest and easiest thing to do first is the float. The guys you see winning races on TV have it done before each event. If you don't know when yours was done last ("I think the shop did it", isn't a good indication of when) then it probably needs it. While there you can check it for leaking.

You do have a manual don't you?
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Old 12-11-2006, 01:09 AM
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Default Re: How do you stop a plug fouling

faded has some very good writeups if carb adjustments arent doing anything it also could be an electrical problem. weak coil cdi spark plug cap rarely but do go bad. What year? Have you cleaned your airfilter?
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Old 12-16-2006, 06:10 PM
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Default Re: How do you stop a plug fouling

Considering all the things ossagp1 & crdemon mentioned, are you certain your
gas is good? My uncle once put a little diesel in my bike's tank when I wasn't
supposed to ride it. Like an idiot I rode it, it ran for about a mile then I had to
push the darn thing alllll the freakin' way back to the house!!! Lesson learned,
end of story!!!
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Old 12-16-2006, 06:14 PM
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Default Re: How do you stop a plug fouling

If there are no mechanical problems and jetting is close but you are still fouling plugs then try dropping down in heat range to a hotter plug. This would be true for beginners who aren't running the bike hard enough or for trail riders.
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Old 12-16-2006, 07:55 PM
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Default Re: How do you stop a plug fouling

Quote:
Originally Posted by NYMXer View Post
If there are no mechanical problems and jetting is close but you are still fouling plugs then try dropping down in heat range to a hotter plug. This would be true for beginners who aren't running the bike hard enough or for trail riders.
I have done that and it does work, but in reality if the jetting is correct the plug will last months without fouling unless there is some other issue..

Is this an older bike or a new bike. Most Japanese MX bikes are jetted rich from the factory to make sure you don't burn them up when new.. generally changing the pilot jet to one size leaner makes a big difference. Riding slow is what usually fouls the plugs and the pilot jet has more effect at lesser throttle openings. I changed the pilot jet and drop the needle one clip positionon my 99 cr125 and son's 2001 YZ85 when we first got them and they hardly ever fouled a plugs.


But if it was not fouling plugs before and is now, somethine else has changed and you may need to figure out what it was before you rejet.

check out this for jetting basics http://www.mandolyn.com/RSG/jetting.htm
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Old 12-16-2006, 09:09 PM
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Moto Re: How do you stop a plug fouling

Quote:
Originally Posted by ossagp1 View Post
Rejet or change the fuel/oil ratio are heard a lot. There is something you should do before you consider any of that: There is a post in the archives by faded on setting the float. Start there before you consider either of the other two suggestions. Get the carburetor back to the way it needs to be to operate as designed before you go changing brass. To get the ultimate out of your RM125 you would likely need to set your jetting to the way you ride, but trying to do that before you get things like the float setting correct is a waste of time.

You don't mention if it ever worked well, or if this is something that has progressed. Worn crank seals and worn cylinders/rings/piston(s) are another thing that will make it run rich and foul. Reeds are yet another. Cheapest, fastest and easiest thing to do first is the float. The guys you see winning races on TV have it done before each event. If you don't know when yours was done last ("I think the shop did it", isn't a good indication of when) then it probably needs it. While there you can check it for leaking.

You do have a manual don't you?
that about says it all what oil ratio are you runnig ???? what kind of oil are you running ??? what plug are you running ??? when was the last time you cleaned the air filter ?? when you look down the intake boot do you see dirt ??? any water in flywheel cover ??? has any one messed with your timming ??? when was the last time you cleaned your power valve. answer these questions then i can help

P.s. is it bad when your 7 year old is correcting your spelling lol
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Old 12-17-2006, 03:14 AM
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Default Re: How do you stop a plug fouling

Sorry guys, heres some more info on the problem. I have only just got the bike and it has fouled plugs from the start (I've only riden a few times) so it wasn't something I noticed progressivly coming on. I do have fresh gas in the tank and I'm running "Valvoline 2-stroke pre-mix" at 32:1. My plug is what Suzuki recomends in the manual B9egv. No-one has messed with the timing whilst I have owned it. I've inspected the reeds and they look okay - just stock ones but they look as though they are sitting flush and not damaged. As far as the air filter goes, I just pulled it out and cleaning now. My float level is correct aswel (14mm).
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Old 12-17-2006, 09:02 AM
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Default Re: How do you stop a plug fouling

dont forget to set the plug to its proper gap before putting it in too...
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