Stock 04 CRF150F Jetting

Hey, I'm trying to rejet my 150 back to factory jetting. I put the stock main and pilot jets back in, but I still need to know what the stock needle clip position and air fuel screw position too. Anybody know what these are?

middle position or so on the needle, and 1.5-2turns or so out on the screw

My question is why would you want to go back to 100% stock? I'd at least leave a 42 pilot in it, to make starting easier, maybe richen up the needle if it helps

Well when I put a 42 pilot in, it was way to rich and when I would run it, it wouldn't run right. It ran better stock so I'm switching it back to stock. Also thanks for the info.

If your running an aftermarket pipe and you uncorked it, you'll want to run the bigger jets or you'll run lean...not good for your valaves and you'll run hot. You have to play with the sizes...some bikes like the 115 main, some like the 110 main.

If your not running a aftermarket pipe (or baffle out of your stocker) and not uncorked....leave the 42 main wil run a little richer for first 1/4 of throttle and your bike will start easier and last longer. honda is notorious for making bikes lean out of the factory.

hmmm.. What elevation are you at? Seems weird a 42 pilot would be too rich, but hell you might be right and it might be too much for your bike. Did you try adjusting the fuel screw at all with a 42 pilot, and/or playing with the needle?

Also did your bike start easily with stock jetting, in normal temps (above 40f) with no choke? Or was choke almost always required??

also, this is just a random guess... But have you ever adjusted the valves or changed the plug? If you haven't, or its been more then 1-2 years, then I'd definitely check the valves and get a new plug. But maybe on the off chance you tried uncorking it with the valves out of spec or bad plug it might have made it run worse? Also just out of curiosity what is your current setup and what are you changing on the bike that makes you want to change the jetting?

Also my bike at 800 foot elevation, was always a 5-20 kick to start bike, warm or cold, no matter the temperature... Then I removed air box snorkel, the silencer, 42 pilot, 115 main, and it starts 1-2 kicks almost every time.

Well i bought a 42 pilot and a 115 main jet but nothing else. I already had the baffle out before i even knew what uncorking the 150 was but i bough a new air filter for it cause my was way dirty and removed the snorkel put the jets in tried adjusting the fuel screw and everything but still the 115 main was to big cause it would bog as I hit WOT. I lost the darn stock snorkel so I made one myself out of a piece of plastic to help get the factory effect of the snorkel. Stock jet are in but I have a bog down low so I'm ganna try putting the 42 pilot back in and adjust my fuel screw and see if that clears up my problem.

Not sure how much you want to mess with it, but you might also try a 110 or 105 main jet, and play with the needle. I think they even make a 112 and maybe a 107 jet???

uncorking my 150f made a pretty good difference in power I thought. At least it sure feels like it. And I can only imagine if I'm burning that much more fuel then stock and not running too rich it has to be producing a good deal more power :ride:

Did you leave the spark arrestor in when you took the baffle out?

No I had the spark arrester out. That was the baffle I was talking about. Sorry for the confusion.

No I had the spark arrester out. That was the baffle I was talking about. Sorry for the confusion.

The baffle and spark arrestor are 2 separate pieces. I'm pretty sure you need to leave the spark arrestor in to supply a little back pressure to the engine.

You say you bought a new air filter because the old one was dirty. You can clean them.

If the one you have in it is dirty it will make the bike run rich.

Be sure to clean it well and don't over oil it.

I've had the spark arrestor for over 3 or 4 years and for at least 3 of those years it was riden very hard on mini tracks and I've never had a problem with it causing problems.

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