what causes deceleration pop

[Tony477g]

since i bought the bike used its had a bad deceleration pop. Runs fine besides trying to go from no throttle to full then it'll bog. Could it be jetting? Maybe the pipe needs to be repacked. I live in nevada and right now the weather is around 100 degrees and the altitude is 2014 feet. Right now what i have in the carb is the stock jets. Is it easy getting in the carb and changing the jets? looked at manual and seemed kind of tricky compared to the 2 stroke. also if it does need to be repacked how do i do it? 09 crf250r everything stock

[CRF DOC]

Decel pop is most commonly caused by a lean condition in the pilot circuit.

An incorrectly adjusted fuel screw, a missing o-ring or washer on the fuel screw, a partially clogged pilot jet, a clogged passageway above the pilot jet, or a poor sealing crush gasket at the header can all be causes of decel pop.

[Tony477g]

but not the silencer cans? Is it hard to get into the crf's carb? Looked at the manual and the carb doesnt look like the carb on the 2 stroke, its this long thing. also could my bike blow up if i keep riding it like this.

[Charlie C]

An exhaust leak will also cause a decel pop. Doubtful that it's going to blow, but a lean condition can cause a major malfunction and possibly destroy some vital parts.

[CRF DOC]

but not the silencer cans? Is it hard to get into the crf's carb? Looked at the manual and the carb doesnt look like the carb on the 2 stroke, its this long thing. also could my bike blow up if i keep riding it like this.

You can access the jets through the bottom of the carb. It is not easy.

The best way is to pull the subframe, pull the shock and remove the carb from the bike. That way you can completely disassemble the carb and thoroughly clean and inspect all the components and passageways.

[Tony477g]

I actually have noticed that the bike has a little air coming from both cans. http://image.dirtrider.com/f/16626139/141_0901_02_z+dirt_rider_first_test+2009_honda_cRF250R_exhaust.jpg

On the actual cans where the pieces join, not where it joins the mid pipe but on the actual can where it has the screws close to the tip and close to the end where it has the other screws at the lower part seems like it has more air coming out and burn marks

[MX-WFO]

Its a lean pilot circuit, and/ or i bet you a gentlemans bet that you also need a new pipe manifold crush washer (they are copper) and it fits into the cylinder where the pipe comes out of the exhaust pipe. You can only use them ONCE!!

[92db]

Blown out packing also contributes to popping.

[36MotoMarc]

Don't rule out tight exhaust valves or poor valveseats, unless they have been checked/serviced recently. But it usually is a lean condition or grossly rich condition.

[Tony477g]

both have been checked look good. what would you guys recommend for jetting then

[Tony477g]

Now ive found a problem, i dont know from where but dirt has been gettin through the air box. I opened it up because i was going to change it before i rode, took the airfilter off and saw inside some dirt

[Tony477g]

Dont know if any went down or not but still it was there. What should i do and whats the worst that can happen

[Keith72]

Stock jets at that altitude and that temp is a little rich I would think. Thats probably why you have the bog when you open the throttle quick. There a a few threads here with jetting that will get you close. I will advise that you dont change the leak jet until you change the pilot and main jet. Then if you still have a small bog a different leak jet may be needed.

[Keith72]

Now ive found a problem, i dont know from where but dirt has been gettin through the air box. I opened it up because i was going to change it before i rode, took the airfilter off and saw inside some dirt

The seal between the air box and the air boot is known to be bad. Take it apart and reseal it. A lot of people have had the same thing happen. Its the first thing I did when I got my 09.

[Tony477g]

anything going to happen though? because im sure its been sucking dirt for a while

[CRF DOC]

anything going to happen though? because im sure its been sucking dirt for a while

Sucking dirt does the intake valves no favors. If they are stock, and you've been sucking dirt, get ready for valve issues. The dirt specks get embedded in the seats and destroy the coating on the OEM valves. This will lead to premature failure.

[Tony477g]

I dont think its sucked a lot of dirt though. So maybe nothing will happen.... i hope. so back to the original question, I dont think its jetting, I would think its the exhaust because it even has burn marks from where its leaking. could i weld it so that it'll stop or do i need to buy a new exhaust. Really dont have the money to buy a new exhaust though since the ones ive seen on ebay stock are like 224

[CRF DOC]

If the leak is out at the can, it's not the culprit. The decel pop would only be from air entering the system at the head/ header seal.

When you rap the throttle, does the engine return to a smooth idle rapidly or does it take some time to settle down?

[Tony477g]

its a smooth idle rapidly

[CRF DOC]

Try opening the fuel screw 1/4 turn. See if that corrects the issue.