sixds

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Mar 25, 2007
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the plug on my yz125 has a reddish color on the electrode and the insulator. when i got the bike it had an 8 heat range spark plug and was too rich. after the rebuild i put the stock 9 heat range plug in. i havent done anything with the carburator. the bike is really hard to start cold.
is this normal?

suggestions?

thanks.
 

sixds

Member
Mar 25, 2007
779
0
well i dropped the clip one position on the needle today just to see what it would do.. the plug was black accept for just the tip of the electrode was white. i put the clip back up to the stock position and it was still reddish coloring but i noticed the white. i think there might be an air leak or something.

suggestions?
 

84cr125

Member
Apr 8, 2007
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if he was drawing oil in from the crankcase, he would be oil fouling his plugs. They would not be looking redish. redish colour plugs mean that the bike is running too cold.

what type of riding do you do? a 9 heat range is recommended in manuals becase the manual is built around the idea that your yz is under racing conditions and a 9 plug is needed for that. But if your just doing trails and occasionaly hitting the tracks use the 8 heat range, its more adaptable with a few tweeks of the carb.

My advice would be to put the 8 heat range plug in and see how it runs from there and see if you need to re-jet your bike. keeping in mind that you should be using a new spark plug when you diagnose the heat range of your engine.
 

Rich Rohrich

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Jul 27, 1999
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What's in the fuel you are running? Some metallic additives will leave reddish brown deposits behind.

The additive MMT which is used in a lot of OTC octane boosters will look like this.
 

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sixds

Member
Mar 25, 2007
779
0
im running premium 93 octane fuel, i have no clue whats in it. i will take a picture next time i get my hands on a camera.

how do you get the thread part off of the spark plug Rich?
 

Rich Rohrich

Moderator / BioHazard
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sixds said:
how do you get the thread part off of the spark plug Rich?

I cut it off on a lathe.
 

sixds

Member
Mar 25, 2007
779
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how involved is changing the right hand crank seal? i have one from a pack of moose gaskets but i want to know what im in for before i tear into the bike.
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
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Merrillville,Indiana
The right side requires no special tools. Hotrod is selling complete engine kits for like 300 dollars. Then you will need special tools,if you are sure the seal is bad,the seal went bad for a reason. 02 125,how many bottom ends has it seen? Your plug does not look like the picture,yours looks like a coating of tar and wet?
 

sixds

Member
Mar 25, 2007
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im takin a picture of the plug tomorrow, i dont know how long its been for a bottom end because i just got the bike a few months ago
 

j.lawson

Member
Jul 18, 2007
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If the seal was the problem it would,nt make the spark plug red...??? why would it, if the oil from the crankcase is getting into the cylinder, via a bad seal, the bike would smoke very very much and sputter and run very poorly.
My buddy's 98 cr 125 has a bad right side seal and that is the case, his plug looks fine besides heavy black sut, no reddish color at all. atleast, the above is the case with his bike and other bike's i'v seen with this problem, but I'm no expert either.
 

sixds

Member
Mar 25, 2007
779
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when i rebuilt the top end i checked the side to side clearance of the connecting rod and the clearance when you pull up and down on the crank. there was no up and down movement just a little side to side.

its not using any gearbox oil and its running great. the plug was a tan color before the rebuild and now its reddish. i just want to know what changed.

also, i am using the stock 9 heat range plug instead of the 8.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
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Merrillville,Indiana
Do you wring out the excess oil,do you use all their products? Can you try different fuel? Just because something looks red does not necessarily mean it will leave a red residue.
 

sixds

Member
Mar 25, 2007
779
0
i wring out the excess oil.

another thing though. when im starting it cold it starts with the choke in 3 good kicks, but then it revs up really high. then when you put the choke down it just dies, so i just flick the choke on and off to keep it revving until its warm enough to idle.

would that have anything to do with it? it didnt do that before the rebuild.
 
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