south Texas, sea level, 410 main, clip at 2nd posit fm top, 40:1 Repsol, airscrew 3 turns out, BR8ES.
I came to this site looking for some information on tuning/modifying my CR and I found a lot of useful stuff... just gonna pay it forward.
Bought a new 2005 CR250R the spring of '06 and rode it all summer (first 2-stroke, first MX bike). Fouled a lot of plugs and silencer was dripping "black stuff" (I assume that's oil) from both ends. Stock plug was an NGK BR9EG-8-N but I ended up running BR8ES plugs on 93 octane at 36:1 with Yamalube 2-R. I live in south Texas (sea level) and I think 90 degrees F is a good guess at the average summer temperature here. The bike's chararcterists were as follows: easy to start but always took about 15-30 seconds of initial riding to get the throttle response crisp. Good power but overrev died quickly.
I recently bought Moose repacking for my silencer, a 410 main jet, a buttload of NGK 8 and 9 plugs, and Repsol synthetic (40:1) to get ready for this next summer.
Silencer - the repack was simple, just remove two bolts from the silencer and the endplate/tube pulls out, took a lot off force though. The stock packing was saturated and it completely/tightly filled the space between the tube and silencer housing. I cleaned off the tube (it was just wet with dirty oil), wrapped the sheet of packing around the tube and shoved it back in. Didn't need to use masking tape or anything like that as the fit was like a bad third date... not as tight as I was expecting.
Carb - pulled the carb and verified the stock settings (which I hadn't touched til this point): #420 main, 40 pilot, clip in 3rd position. Airscrew was out 1 3/4 turns. I was surprised that the floats were not even... one float was at .3 inches and the other was a little less. (The metal bracket that holds the floats was bent on one side.) I adjusted the float level, installed the 410 and raised the clip to the 2nd position from the top of the needle. The TPS was turned almost fully clockwise in its adjustment and I returned it to its previous position but noticed that it didn't like to seat in there smoothly even with everything lined up properly. You do have to make sure you set the rheostat into the proper groove when reinstalling. No need to mark anything as there's only one way to put it back on.
RC valve - popped the cover and disconnected the cables from the valve to make sure it was moving freely. I had previously made the "12 mm adjustment" so didn't mess with that. Also verified movement of the valve when brapping the throttle.
Tuning - funny how neighbors are... Up to now I hadn't done anything to the bike except 1) use a hotter plug, 2) change the ratio of my mixture from stock recommendation (32:1) to 36:1, and 3) adjust the RC valve to 12mm (which it was nearly already set to). I had now changed my premix oil and ratio, main jet, clip position, and went back to the recommended stock plug. Airscrew still at 1 3/4 turns out.
-started bike. I was happy to see it start, but noticed that keeping it running near idle with the throtle caused it to load up very fast. A few long braps on the throttle would clear it, but it again would load up very quickly.
- adjusted the idle - had to turn the screw almost all the way in (flush with the locknut) to get the rpm to come up a little.
- adjusted airscrew - in this process I ended up fouling the 9 plug during one of the acceleration runs. I believe it was because I had been dicking around with it for so long just adjusting the idle/airscrew. I fouled another 9 almost immediately after installing and decided to go with an 8. With the stock pilot (which I believe is rich), found the best idle at 3 - 4 turns out. Ended up leaving it at 3. Doesn't load up. Made some runs in 2nd gear from idle then cracking it wide open. It had good accel and no hesitation.
- main jet - i rode the bike to an area with a long straightaway with a new plug and wrench in pocket, installed new plug, started bike and did a wide open run thru all the gears, chopped motor (clutch, kill, throttle) turned bike around and ran it back same way (might wanna wear some glasses at a minimum, I didn't). Pulled the plug. After comparing it to a new one, I noticed that the top half of the insulator was only slightly discolored (light light tan). I initially thought it was way too lean. But from what I've gathered here on this site, the place to look is deep inside the plug near the base. It had a nice brownish ring from the base to about half way up the insulator which was something I was glad to see. The bike ran very fast and I now had considerably more power in the overrev.
- needle - did the same test as above but this time used 1/4 to 3/4 throttle (mostly at 1/2). That plug had same color to it, but the ring was more pronouced and defined and it only came up about 1/3 of the insulator. Again I was happy.
I threw the sidecovers on and ended up riding for about 2 hours straight as I was having an absolute blast with the new setup. What an improvement.
I came to this site looking for some information on tuning/modifying my CR and I found a lot of useful stuff... just gonna pay it forward.
Bought a new 2005 CR250R the spring of '06 and rode it all summer (first 2-stroke, first MX bike). Fouled a lot of plugs and silencer was dripping "black stuff" (I assume that's oil) from both ends. Stock plug was an NGK BR9EG-8-N but I ended up running BR8ES plugs on 93 octane at 36:1 with Yamalube 2-R. I live in south Texas (sea level) and I think 90 degrees F is a good guess at the average summer temperature here. The bike's chararcterists were as follows: easy to start but always took about 15-30 seconds of initial riding to get the throttle response crisp. Good power but overrev died quickly.
I recently bought Moose repacking for my silencer, a 410 main jet, a buttload of NGK 8 and 9 plugs, and Repsol synthetic (40:1) to get ready for this next summer.
Silencer - the repack was simple, just remove two bolts from the silencer and the endplate/tube pulls out, took a lot off force though. The stock packing was saturated and it completely/tightly filled the space between the tube and silencer housing. I cleaned off the tube (it was just wet with dirty oil), wrapped the sheet of packing around the tube and shoved it back in. Didn't need to use masking tape or anything like that as the fit was like a bad third date... not as tight as I was expecting.
Carb - pulled the carb and verified the stock settings (which I hadn't touched til this point): #420 main, 40 pilot, clip in 3rd position. Airscrew was out 1 3/4 turns. I was surprised that the floats were not even... one float was at .3 inches and the other was a little less. (The metal bracket that holds the floats was bent on one side.) I adjusted the float level, installed the 410 and raised the clip to the 2nd position from the top of the needle. The TPS was turned almost fully clockwise in its adjustment and I returned it to its previous position but noticed that it didn't like to seat in there smoothly even with everything lined up properly. You do have to make sure you set the rheostat into the proper groove when reinstalling. No need to mark anything as there's only one way to put it back on.
RC valve - popped the cover and disconnected the cables from the valve to make sure it was moving freely. I had previously made the "12 mm adjustment" so didn't mess with that. Also verified movement of the valve when brapping the throttle.
Tuning - funny how neighbors are... Up to now I hadn't done anything to the bike except 1) use a hotter plug, 2) change the ratio of my mixture from stock recommendation (32:1) to 36:1, and 3) adjust the RC valve to 12mm (which it was nearly already set to). I had now changed my premix oil and ratio, main jet, clip position, and went back to the recommended stock plug. Airscrew still at 1 3/4 turns out.
-started bike. I was happy to see it start, but noticed that keeping it running near idle with the throtle caused it to load up very fast. A few long braps on the throttle would clear it, but it again would load up very quickly.
- adjusted the idle - had to turn the screw almost all the way in (flush with the locknut) to get the rpm to come up a little.
- adjusted airscrew - in this process I ended up fouling the 9 plug during one of the acceleration runs. I believe it was because I had been dicking around with it for so long just adjusting the idle/airscrew. I fouled another 9 almost immediately after installing and decided to go with an 8. With the stock pilot (which I believe is rich), found the best idle at 3 - 4 turns out. Ended up leaving it at 3. Doesn't load up. Made some runs in 2nd gear from idle then cracking it wide open. It had good accel and no hesitation.
- main jet - i rode the bike to an area with a long straightaway with a new plug and wrench in pocket, installed new plug, started bike and did a wide open run thru all the gears, chopped motor (clutch, kill, throttle) turned bike around and ran it back same way (might wanna wear some glasses at a minimum, I didn't). Pulled the plug. After comparing it to a new one, I noticed that the top half of the insulator was only slightly discolored (light light tan). I initially thought it was way too lean. But from what I've gathered here on this site, the place to look is deep inside the plug near the base. It had a nice brownish ring from the base to about half way up the insulator which was something I was glad to see. The bike ran very fast and I now had considerably more power in the overrev.
- needle - did the same test as above but this time used 1/4 to 3/4 throttle (mostly at 1/2). That plug had same color to it, but the ring was more pronouced and defined and it only came up about 1/3 of the insulator. Again I was happy.
I threw the sidecovers on and ended up riding for about 2 hours straight as I was having an absolute blast with the new setup. What an improvement.
