hi there

since i converted my 2011  125 TXT pro to a 225 i have been suffering from spark plugs getting fouled after 2-3 hours of riding (sometimes less - but i am able to rev the bike and clean the plug temporary)

when i start the bike it usually feels clogged for a few minutes and only after it worms (2-3 minutes ) i rev it up and than i get good power.

i started with #38 pilot and 116 main. now i have 34 pilot and 112 main, but i still get this problem (a little less, but still won't last more than 2 rides and i need to rev it every hour or so)

i stripped all the electrical junk as i suspected electrical issue - it might have helped a little (the engine was cutting in high RPM - now its not) 

i ride at see level, warm temp, BPRE5 plugs, 1-1.2% oil

engine start with no issues

 

any advice will be a real help

thanks 

What plug gap are you running and what 2t oil do you use?

 

i use silkoline (before that motul) 100% synthetic, gap is set to 6 mm, i also tried the iridium plug and it got fouled as well

i have some suspicion that on high RPM i don't get a good spark, usually the engine dies after some time in low RPM - when i want to rev it to clime a hill or a step it bugs and stall. if i am able to start it it back fires and will hardly go up the RPM, sometimes i manage to rev i and clean the plug, sometimes it just stalls and i need to replace the plug '

attaching some pics of the plug

The bike in the thread referenced is mine.  Bought new in 2014 and converted to 225 Spring 2015, Dellorto carb.  Started with 36 pilot @ 3 turns out on the fuel screw, 110 main, Needle clip 3rd down.  Ran fine but very dirty (rich) and poppy.  After much testing, 30 pilot  fuel screw 2.5 turns out, 106 main, needle clip 3rd down.  Much cleaner, no overheating, pulls smoothly off the bottom, revs out well, never a "lean ping."  Overalled my class last weekend's 2 day @ 3600' elevation (1200' @ home). Will be testing a 32 or 33 pilot in the future to see if it improves bottom end power.  I would have thought 36 to 30 was too much change but it works surprisingly well.  My guess is that the wide, nearly 2 mm, squish from the 225 kit results in very low compression allowing very lean pilot to work well.  I use Belray H1-R full syn @ 80:1 and BPR-5-IR iridum plug.

hi

thanks for the reply. i switched to main 105 and idle 34 (with the needle in the lowest position), the plug came out clean after a days ride - and that means i am close to the spot. all other items were checked (exhaust, air filter, reeds etc) - and the bike feels strong and responsive

so i hope this saga is over for me

thanks 

Caps lock!!

GLAD TO HEAR YOU SORTED YOUR BIKE.OUT OF INTEREST WHAT HEAD ARE YOU USING, A STANDARD COMPRESSION 250 OR AN S3 STARS HEAD[iF ITS AN S3 WHAT INSERT ARE YOU USING] REGARDS. 

 i am using the S3 head with normal compression, and i use the thin base gasket (after squish testing)

Maybe time for a new keyboard without the capslock stuck?