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Trying to help a buddy

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A buddy of mine has a 2012 crf expert with around 1 hour on it.

When he got the bike the dealer had turned the air screw out 3 full turns to get it to idle.

We installed a 42 pilot (was 38) and a 138 main (was 140) and the air screw is at 2 full turns out.

The bike idles fine and starts right up hot or cold. it just has a small bog in it on the stand and if you are a gear to high in the corner and pull back on the gas it will bog.

Pulled the plug and its just a tad white / tan. Also the pipe is just a tad purple.

Should we install a 45 pilot in place of the 42 ? or where do I try and help him at.

Also we are in fla about high 80s and humidity in the low 80s too.

Thanks Ron.

Edited by Ron731

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As I understand it, the 2012 has a linked accelerator pump and doesn't need the o-ring mod, but tuning the leak jet would probably help. I installed a QS/3 at the recommendation of weantright, and have never regretted the cost. In combination with the fuel screw, it tunes out any hint of bogs with changes in altitude and temperature.

As for the pilot jet, see this:

http://www.thumpertalk.com/topic/271735-how-to-confirm-your-pilot-circuit-setting/

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As I understand it, the 2012 has a linked accelerator pump and doesn't need the o-ring mod, but tuning the leak jet would probably help. I installed a QS/3 at the recommendation of weantright, and have never regretted the cost. In combination with the fuel screw, it tunes out any hint of bogs with changes in altitude and temperature.

As for the pilot jet, see this:

http://www.thumperta...ircuit-setting/

Thanks for the info we are about 2 out on the air screw.

Maybe we will look into the QS/3 for the bike.

I was just do not want him to lean the bike out to much and blow it up.

As i said befor the plug was just a tad white / tan and it had me concerned

In my kids and wife's 09 crf 150 RB I did a 45 pilot and it helped a ton.

On the pilot a 42 has less fuel then a 45 right ?

Ron.

Edited by Ron731

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As i said befor the plug was just a tad white / tan and it had me concerned

On the pilot a 42 has less fuel then a 45 right ?

Did you do a plug chop to get your reading (that means running WOT in 5th on the flat, or pulling hard uphill in a lower gear, and clutching in and killing the engine at the same time)? That will tell you something about how close your main jet is. When the engine idles, the plug color will change. You don't want it lean on the main, or the the needle (s/b 3rd clip). From what the shop manual suggests, and what others on this forum have reported, your main and pilot should be in the ballpark. Two turns out is just about perfect. I wouldn't worry about the plug color if it was taken after idling.

These are quotes from the '09 Owner's Manual. You could look up the corresponding information from the '12 OM:

"Adjust the pilot screw to obtain the best off-idle performance. If the engine blubbers (rich) exiting a corner, turn the screw clockwise to lean the mixture. If the engine surges (lean) exiting a corner, turn the pilot screw counterclockwise to richen the mixture. The minimum range of pilot screw adjustment is 1 1/2 to 2 1/4 turns out from the lightly seated position. If you exceed 2 1/4 turns out, the next larger slow jet is needed. If you are under 1 1/2 turns out, the next smaller slow jet is needed."

"Leak jet: the smaller the number the smaller the jet bore diameter. This controls the amount of fuel returned to the float chamber under pressure, therefore the flow amount is increased or decreased. With a smaller jet, pressure is raised faster and the elapsed time before the fuel starts flowing is shorter."

Stock leak jet is 60, and with the QS/3 I find I am set at about 58 at 6,500 ft. QS/3 eliminates the need to ever worry about the leak jet size. As I gain altitude, or the temperature changes significantly, a quick tweak, first with the pilot screw, then with the QS/3 and any trace of bog is eliminated.

Edited by Old Plonker
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Did you do a plug chop to get your reading (that means running WOT in 5th on the flat, or pulling hard uphill in a lower gear, and clutching in and killing the engine at the same time)? That will tell you something about how close your main jet is. When the engine idles, the plug color will change. You don't want it lean on the main, or the the needle (s/b 3rd clip). From what the shop manual suggests, and what others on this forum have reported, your main and pilot should be in the ballpark. Two turns out is just about perfect. I wouldn't worry about the plug color if it was taken after idling.

These are quotes from the '09 Owner's Manual. You could look up the corresponding information from the '12 OM:

"Adjust the pilot screw to obtain the best off-idle performance. If the engine blubbers (rich) exiting a corner, turn the screw clockwise to lean the mixture. If the engine surges (lean) exiting a corner, turn the pilot screw counterclockwise to richen the mixture. The minimum range of pilot screw adjustment is 1 1/2 to 2 1/4 turns out from the lightly seated position. If you exceed 2 1/4 turns out, the next larger slow jet is needed. If you are under 1 1/2 turns out, the next smaller slow jet is needed."

"Leak jet: the smaller the number the smaller the jet bore diameter. This controls the amount of fuel returned to the float chamber under pressure, therefore the flow amount is increased or decreased. With a smaller jet, pressure is raised faster and the elapsed time before the fuel starts flowing is shorter."

Stock leak jet is 60, and with the QS/3 I find I am set at about 58 at 6,500 ft. QS/3 eliminates the need to ever worry about the leak jet size. As I gain altitude, or the temperature changes significantly, a quick tweak, first with the pilot screw, then with the QS/3 and any trace of bog is eliminated.

Thanks once again.

I would say on the plug chop was maybe 4th 3/4 on the gas and pulled in the clutch and hit the off button.

LOL not a lot of hills here in Fl. Will have to save that for our next track day.

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Thanks once again.

I would say on the plug chop was maybe 4th 3/4 on the gas and pulled in the clutch and hit the off button.

LOL not a lot of hills here in Fl. Will have to save that for our next track day.

I heard the you have a 300 ft. hill somewhere in FL. It's almost 1,000 ft. downhill to the center of town here!

You might go back to the 140 to be on the safe side, unless it really is too rich. Maybe drop the needle one notch with the 140? The way I learned it, get the main right first, then the needle, then the slide cutaway (not a concern with the FCR, I don't think), then the pilot. The FCR's a/p adds the last twist: the leak jet, which has the biggest effect on bogs, where you whack the throttle on hard.

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Need to verify where the needle is at. If the needle is in the 2nd position (from the top) you will have a bog. For most application mid position is best. Next check where your AP is squirting if at all and adjust. With a 42 pilot I found a 140 main worked better than a 138 for larger temp swings. Lastly I feel you will need a 50-55 leak jet or a QS3.

At 80*F and the humid Florida weather 138 would be fine.

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Need to verify where the needle is at. If the needle is in the 2nd position (from the top) you will have a bog. For most application mid position is best. Next check where your AP is squirting if at all and adjust. With a 42 pilot I found a 140 main worked better than a 138 for larger temp swings. Lastly I feel you will need a 50-55 leak jet or a QS3.

At 80*F and the humid Florida weather 138 would be fine.

Need to verify where the needle is at. If the needle is in the 2nd position (from the top) you will have a bog. For most application mid position is best. Next check where your AP is squirting if at all and adjust. With a 42 pilot I found a 140 main worked better than a 138 for larger temp swings. Lastly I feel you will need a 50-55 leak jet or a QS3.

At 80*F and the humid Florida weather 138 would be fine.

Yea soon to be high 90s soon.

Thanks for the info how do I check the AP to see it squirting and how do you adjust it.

Thanks Ron.

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Look down the carb from the air box side. Squirt should just miss the slide (as it goes up) and be strong and straight. Adjustment is on the right side of the carb behind the black plastic cover. Also the nozzle can be clogged preventing a strong straight squirt. Inside the carb under the bowl is the diaphragm, rod and spring. Dirt and some gas will tear this diaphragm apart sending rubber into the nozzle.

90's stick with a 138 and you could even go smaller one size.

Edited by weantright

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