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cr125 eating plugs

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my 2002 cr125 is eating spark plugs like crazy. im running 50:1 oil to gas ratio. its fine when its on the track but when i turn the bike off it wont turn on again. its like once the motor is off the plug instantly fouls out and wont spark anymore. any ideas? the top end has about 10 hours on it. and whenever i pull the plug after it fould it has oil on it.

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You should be able to run your 2002 CR125R at 32:1 or 40:1 without having any plug fouling issues after you install the JD jet kit--providing that your float height is set properly. The bike should start easier and run cleaner as well. James Dean of JD Jetting is very helpful with regards to customer assistance.

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Ron is right, I would run at 32 to 1 after you install the kit. one other thing, the kit comes with a 32.5 pilot jet. That was to lean for the area I ride. There was a pause or a bogg in the lower gears. so I installed a #50 pilot that I got from the honda dealer and my bike rips now. nomore plug fouling.

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Definitely just your jetting. I would not go as lean as 50:1 on the mix for a 125, but maybe that is just me. I would stay at 40:1 at the very least personally.

Also, if your looking to buy that kit, try getting it from the TT store, you should be able to get it for cheaper than the actual JD site, and support the site at the same time. :p

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Any chance that the crank seal is leaking? If not, what everyone else is saying is quite true!!

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You should almost never run 50:1 in a 125 , unless its jetted for it you should run 32:1 / That JD kit is good you will like it

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Just a couple of things:

1. You need to lower the float height in the carburetor. The JD kit will fix most of this, but the floats are notoriously high on CR125's.

2. Not sure if you are aware of this, it's kind of counter-intuitive, but 50:1 actually runs RICHER than say 32:1. There is simply a lot more gas per oil that has to be burned.

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50:1 ratio is insane man, run her 32:1 and if she still fouls plugs then do some carb tuning, wouldnt hurt to clean it

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I agree with everything that's been said here, just wanted to add that some like to go to a one step hotter plug if there still fouling. YMMV. :moon:

As well, there was a study done in the mid 90's that tested fuel to oil ratio's and how they effected performance and horsepower. It was done for off shore boat racing. It showed that the more oil, the closer to 1:1 you were, the more horsepower you could get out of the engine. Some of these guys were running 6:1!:moon:

The way I understand it was that the leaner gas mixture allowed them to get more HP and the oil kept them from getting detonation. BUT by no means do I suggest you use anything less than a 32:1 ratio. That's what these bikes were designed for. :p

When I got my '06 CR125 I was told that not only was it impossible to jet, but that the only way to get it right was to go to J.D. jetting.

I've proven them wrong :lol: I use only honda parts and my bike runs great.

Good Luck and tell us how it goes :ride:

- iRock

P.S. - I have no idea where I found this study, it was just in passing, and in no way can I provide a link for it. I may also be wrong about the leaner = more horsepower thing. Oh well!

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ive seen similar data to what you did iRock.

true on all the above posts, 50:1 just isnt enough oil, i run 32:1 in my cr125 and shes clean burning, and only slightly lean when the temps get below 50.

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As well, there was a study done in the mid 90's that tested fuel to oil ratio's and how they effected performance and horsepower. It was done for off shore boat racing. It showed that the more oil, the closer to 1:1 you were, the more horsepower you could get out of the engine. Some of these guys were running 6:1!:p

When I got my '06 CR125 I was told that not only was it impossible to jet, but that the only way to get it right was to go to J.D. jetting.

I've proven them wrong :ride: I use only honda parts and my bike runs great.

The whole "more oil = leaner running" and vice-versa is a myth. Higher mix ratios give more power primarily because oil has more energy per unit volume than gasoline (140kBTU vs 125kBTU per gallon). It all burns, and if you can get the energy out, you're ahead of the game with more oil. I run ~32:1 in everything.

+1 on the not using the JD kit. 90% of the people spend $70 and end up STILL having jetting problems. At least half of the jetting help posts I see on here have the JD kit installed. That, and the 32.5 pilot is a blatent band-aid for a non-ideal needle, and an ideal needle is what you're supposed to be getting.

I adjusted my float, bought a honda -70 series needle for $10 (fatter L1 section w/ stock taper; -68 is stock) in position 3, left in the stock jets but turned out my air screw 3 turns. Bike runs fine as is, although it really does need a leaner pilot - I'll probably go to a 45 or 47.5 once I get around to it. It idles fine, but will load up after several minutes at idle - no where close to fouling, however. Also, the stock 430 main is slightly lean, but close enough for woods work.

JayC

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The whole "more oil = leaner running" and vice-versa is a myth. Higher mix ratios give more power primarily because oil has more energy per unit volume than gasoline (140kBTU vs 125kBTU per gallon). It all burns, and if you can get the energy out, you're ahead of the game with more oil. I run ~32:1 in everything.

JayC

Hence my disclaimer! :p

But seriously, my second thought was about the energy content. Its the same reason that diesel produces more energy than gasoline. C16H34 has a lot more potential energy than C8H18. And I say potential energy because at some point the carbon chains become so long that efficient combustion is relatively impossible (in an engine setting anyway).

But at the same time, I do believe there is a correlation between leaner fuel ratios and more power. Not necessarily in the since of sheer numbers, but there is some documented evidence out there that shows that a leaner fuel ratio will be a bit more efficient than a standard one. Obtaining this poses a significant problem though. Leaner = Hotter. This is why the leaner you go, the higher the octane rating you need, so as to avoid detonation and in extreme cases, meltdown.

What's this I hear about the float height? This is probably the one setting in my carb I haven't messed with yet. So what's the hu-bub?

- iRock

JayC: How have things been, eh? Did you ever get those rad guards? :ride:

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thanks for all the help guys. when i got the bike there was a dynojet sticker on it so thats making me thing he did something with the jets so im gonna pull the carb off in the morning and see whats up. and how do i adjust the float height?

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thanks for all the help guys. when i got the bike there was a dynojet sticker on it so thats making me thing he did something with the jets so im gonna pull the carb off in the morning and see whats up. and how do i adjust the float height?

Check this: Is your two-stroke running rich? Read here.

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I had a bike that randomly started to foul plugs with no jetting or oil ratio changes. The crank seals were good. The ignition coil had failed. Also, blown head gaskets and water in the gas can certainly feel like a fouled plug. A fouled plug, once it's fouled, will never fire again unless you clean it. Pull the plug and ground it against the head. Have someone kick the bike over. If it arcs from the center electrode or insulator to the side, it's certainly fouled. If it crosses the gap, you've got other issues.

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Just a couple of things:

1. You need to lower the float height in the carburetor. The JD kit will fix most of this, but the floats are notoriously high on CR125's.

2. Not sure if you are aware of this, it's kind of counter-intuitive, but 50:1 actually runs RICHER than say 32:1. There is simply a lot more gas per oil that has to be burned.

I think most people refer oil rich (20=1 or oil lean (50=1) but you are right about the terminology with rich in gas is lean on oil , we should all just start refering to oil rich or oil lean but 50=1 gas rich is just piston dry stupid. same with all the run br8es plugs to cure fouling, in the late 80's I remember team honda running number 8 plugs but they researched and made it work with fuel and timing then tossed the whole topend after every race. Just take the time to read an owners manual , it tells you how to jet in less then 20 minutes of reading.

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The whole "more oil = leaner running" and vice-versa is a myth. Higher mix ratios give more power primarily because oil has more energy per unit volume than gasoline (140kBTU vs 125kBTU per gallon). It all burns, and if you can get the energy out, you're ahead of the game with more oil. I run ~32:1 in everything.

+1 on the not using the JD kit. 90% of the people spend $70 and end up STILL having jetting problems. At least half of the jetting help posts I see on here have the JD kit installed. That, and the 32.5 pilot is a blatent band-aid for a non-ideal needle, and an ideal needle is what you're supposed to be getting.

I adjusted my float, bought a honda -70 series needle for $10 (fatter L1 section w/ stock taper; -68 is stock) in position 3, left in the stock jets but turned out my air screw 3 turns. Bike runs fine as is, although it really does need a leaner pilot - I'll probably go to a 45 or 47.5 once I get around to it. It idles fine, but will load up after several minutes at idle - no where close to fouling, however. Also, the stock 430 main is slightly lean, but close enough for woods work.

JayC

Could you please e-mail me the number on the 70 series needle you are using to poe400@aol.com? Is it a 6dgy69-70? I need to know for sure. Many, many thanks.

Scott

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