Enclosed is step by step procedure conducting spark plug servicing for the XT-225. The steps include removal, inspection, and installation.

Remove the spark plug boot by hand. A little twisting helps.

I’ll remove plug with my bike bag tools for practice. I carry a 18mm long neck type socket, and tire iron wrench combo, and 3/8 socket adapter for the wrench tire iron tool.

Bike bag tools for spark plug assembled.

Unthreading the plug. Should not be too tight. Just 1/2 turn or so with wrench tool. Rotate counterclockwise to remove, colckwise to install.

Can use hand tool with socket, more efficient!

Plug removed for inspection. Removed plug shown next to new NGK iridium. This plug is from a 2005 XT 225 with 3,200 miles total. The plug was installed at 600 miles. I'm running a 130 main jet, 3 turns of air/fuel screw. The bike is ran at sea level for commuting. XT-225 uses NGK DR8EA as standard resistor type plug or the whizbang NGK DR8EIX Irdium type.

This ideally what the plug would look like. A medium to light tan color is best!

Looksee of plugs views based on temperature range between 932 deg f to 1562 deg f. The "8" in the plug code represents the NGK heat rating of the plug. They vary from 2 to 11.

The NGK spark plug code for our XT225 is as follows: DR8EA where:
"D" = the thread diameter, D=12mm or .472 inch
"R" = construction type, R = Resistor
"8" = heat rating (varies from 2-11) where 2 = hot type and 11 = cold type. note: 7 and 9 are available if desired to change heat range.
"E" = Thread reach, E = 19mm or .75 inch grip
"A" = firing end construction, A = unique end
"I" = special plug type, I = Iridium style

The DR8EIX Iridium next to the DR8EA resistor type

Need to check gap. Yamaha recommends .020 inch to .030 inch. NGK recommends .024 inch. I’ll use .024 inch. Note: NGK does not recommend adjustment of gap beyond .008 of as delivered gap. Electrodes with not align properly.

use this tool to pry the ground electrode toward or away from the center electrode. Should feel slight drag at .024 inch gap when done.

Adjusting gap.

New one right at .024 inch.

Will store new one for bike tool bag.

Keep it protected

[ July 31, 2006: Message edited by: klm4755 ]

Wipe/clean plug hole area

Reinstall in hole. Align normal to hole and engage with FINGERS only! Important not to strip threads.

Use torque wrench to tighten 12.5 ft-lbs. If no torque wrench finger tight then turn 1/4 with wrench. Reattach plug boot. All done!

Another fine presentation by KLM. I will add that I think it's a good idea to put a little anti-sieze compound on the plug threads before screwing it in.

Beware: The torque specifications are intended for clean threads. Antiseize compound will significantly reduce the torque requirements. If you're using a torque wrench and don't reduce the torque setting, you are running a high risk of stripping the threads in the head. I found out the hard way years ago. They're difficult to find but some of the compound manufacturers have recommendations on the percentage reduction.

for what its worth department:: size of spark plugs threads is 14mm pitch of 1.25.

I'm pretty sure it's actually 12mm x 1.25.

oops... I stand corrected... the 14 mm is the older harley plugs. the xt is 12mm, so very sorry for the mis info. the thread pitch is correct at 1.25mm

Great thread... thanks. I rejetted my 2005 XT225 today. I swapped the 125 main for a 130. I previously did the idle jet screw mod... 3 turns out. The plug was a nice tan color before I installed the 130. I ran the bike for about 20 minutes ranging from 1/4 to wide-open throttle. The bike did not break-up at all. I checked the plug and it looked the same. Do I need to install a new plug to get an accurate reading on the new jetting?

I am most concerned with the engine running hot. This past weekend, I rode for three hours in the state forest. I trailered my bike home (1 hour) and set out to wash it. Much to my surprise, the cylinder steamed when I sprayed it with cold water. It had not been run in over an hour and the outside temp was 48F. Does this sound normal?

Thanks,
Bill