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2009 crf150rb rough running

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Help please, I have made the following changes to a stock 2009 crf150rb that ran flawlessly. I put on a FMF powercore4 slip on, quickshot 3, JD jetting kit - 145 main, 42 pilot, red marked needle fifth down from the top, 1.75 turns out, thin o-ring, the fuel I usually ran is a 50/50 mix of 93 octane and cam2, and a new twin air filter and I did this to get a little more umpf. I just ran all the changes at a hare scramble at 1,000ft. elev. and the bike was bogging on hard throttle twist, and when stalled it would not refire, at least 100 kicks and all the tricks for starting a hot bike and at point spectators helped push start me. I know I made the cardinal sin of changing to many things at once but felt the performance changes were not that much. After dropping all the cash on the improvements I would hate to go back to stock. I appreciate any help, thanks.

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Hate to tell you, but some of your improvements were a waste of money.

First, do not run anything more than premium. Higher octanes should only be run when you have a detonation problem. They burn slower (hence detonation control) which equates to less power. When an engine is fully worked with real high compression, a lot of spark advance, the power loss of the higher octane is more than offset by the gains in engine changes.

Slip ons do little but make it nosier. The bike seems faster because it is louder. If you wan to confirm it, do timed tests on a course that you are consistent on.

Quickshot 3 is merely an adjustable leak jet. From what I gathered, you did not have a bog before. Your stock leak jet was fine. Read the directions that came with the quick shot and set it to be the same size as the leak jet you took out. That or put the stock jet back in, take the QS3 off and sell it.

I hope you did not touch the AP timing screw as the setting it is at as well as the leak jet are what manages the bog.

Your bike has an improved AP linkage and does not need the oring mod. Take it off.

Finally, re-read the JD instructions. I hope you opened up the airbox. I believe the 4th clip is way rich for you. You will like the 3rd or even the 2nd better. Also run a stock sized main jet.

Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

There is a lot of advertising hype out there. Unfortunately 90% is BS.

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Thanks for the reply William, just a few more questions please. Do I leave the JD needle in when I go back to the original main jet which I believe is a 138 and make the clip adjustment to that needle? And when you say did I open up the airbox, I didn't think I nneded to make anymore opening in the airbox as it is stock. There were no baffles or snorkles to remove, if thats what you are referring to.

What I'm going to do now is: a) leave slip on on. :thumbsup: take out qs3 and o-ring and go back to stock leak jet condition and no I didn't change any AP settings. c) go back to stock main jet. d) run straight 93.

Thanks again for your help I'll report back on the results.

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The fact you did not open up the airbox is probably part of your problem. I have not seen the instructions from JD for your jet kit but I am sure he talks about opening the box up.

Do everything you say.

Then start off with the main jet HE reccomends for a stock pipe as well as HIS needle reccomendation setting. Then test ride.

If the jetting is a little off, you will not hurt anything on a 4S. If it feels flat/dry at WOT in 4th or 5th gear, go up a size in main. If it sounds wet or heavy, go down a size.

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William, when you say up the airbox, what would you suggest. The airbox is open on the top, covered only by the seat, there are vents in the side plastics, the sides of the airbox could be drilled with holes but that would allow dirt and water in during racing and the bottom has a stock opening, a slit about 2.5" long by .5" wide. I am open for ideas on how, where, to open up some more from stock. Thanks again for your help. Oh, when I ordered my JD jetting kit I indicated to JD all of the components previously mentioned that were to be used (slip on, QS3, air filter) and I did exactly what he said, except he said to try the 150 main too, that I haven't done.

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If JD did not say to cut any additional openings and run it as is with a 150 main, that is what you should do. It is his jet kit. I am a bit surprised there was no mention of increasing the opening however. Normally you simply increase the size of the stock opening. Some bikes even have a outline moulded in to trace or have a few screws to remove that opens it up, straight from the factory. But if JD expects the opening to be unmodified from stock, he has determined that stock is plenty big enough.

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William, the following was JD's suggestion, the instructions that came with the kit were very similar if not the same:

I would suggest using jetting close to the kit instructions in most cases. The jetting with your modifications and Cam2 fuel at 50/50 should be near the following settings-

#42 pilot jet

1 1/2 turns out on the fuel screw, adjusting as needed for a good idle

Red marked needle installed with the clip in the #5 from top position

#145 main jet

Thicker O-ring installed on the accelerator pump linkage as described in the kit instructions.

You might want to compare the top-end performance between the #145 and #150 main jets to be sure which works best.

Adjust the fuel screw when the motor is hot for the best idle as described below-

Setting the fuel screw mixture-

Try adjusting with the motor fully hot, and turning the fuel screw inwards until the idle slows or runs rough, then turn outwards 1 1/4 turns from this position. For example, if the idle slows or runs rough at 1/2 turn, then set the fuel screw to 1 3/4 turns out (1/2 + 1 1/4 = 1 3/4).

See- http://www.pbase.com/jdjetting1/image/82894252 to understand how the fuel screw can affect the idle speed and air/fuel mixture at idle. The target range for the air/fuel mixture is near 12.5 to 13:1 at idle.

Thanks,

James

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JD jet kits have done wonders for some bikes we have owned, but not the 150. William seems to be pointing you in the right direction. We talked several times about putting a slip on, on one of our 150's. There is NO way anything can be louder than the stock silencer on a 150R. I could tell my boy's bike over everything else on the track. We ran a standard 150R and then a 150RB in Hare Scrambles. When my son outgrew the RB, he wanted a 2 stroke. He said he was tired of kicking a hot 4 stroke in the woods. Good luck!

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My 07 crf150rb is running rough and doesn't want to idle I have changed the jet back to standard i have had it out for a ride. The revs stay high for a few seconds after I give it a blip. Thinking my settings must be a bit wrong.

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