[ethanownes]

Hi, I have a 2007 crf250r that I just bought and when I start it I use the choke and it warms up then I turn choke off it idles fine, but I just recently took it on a ride and after a while of riding it wouldn't idle when I pulled the clutch or anything. I would pull in the clutch to stop and it would cut out immediately. I couldn't even coast down a hill with the clutch pulled in. And I'm pretty sure if I wasn't revving it during the process of changing gears it would cut out in the middle of that too. Please help? And also when I'm riding and I give it gas as I'm riding and then release, it pops really loud and I think I backfires and stuff like that when I come down from the throttle. Please help with that too!

[JimDirt]

Welcome to the site !!

Most likely your Pilot Jet is dirty , you can clean it , but its best just to replace it , they are inexpensive

It would also be a good idea to check the valves lash , and make sure they are in spec , when the Intakes tighten up , they can give the same symptoms

[ethanownes]

Thanks for the welcome, I don't really have the tools to check the valves at the moment but that should be the problem to the backfiring?

[JimDirt]

Backfiring can indicate a few things , from a Exhaust leak , to a lean condition to Intake Valves tightening up , the simplest thing to check would be Pilot Jet and/or Fuel Screw O-Ring (Fuel Related Lean condition), then Exhaust leak at either the Header where it goes into the head , or at the mid-pipe connection (Air Related Lean condition) , next would be to check the valves (Intakes tightening up will cause backfiring and idle issues and eventually lead to the engine not running at all

With the pilot jet you could still blow thru it , and even see light thru it, and it be clogged enough to cause issues , this is why it is usually recommended to just replace the jet as they are about $6.00 give or take

[ethanownes]

ok, ill see whatsup with the pilot jet. im kinda new to this whole thing so how do i tell which is the pilot jet on the carb. Youtube has been no help for me on the pilot jet!

[JimDirt]

If you loosen the clamps at the front and rear of the carb , you can twist the carb so the bowl bottom is facing you( left side of bike) ( make sure the gas is off) put a rag under the carb , and loosen the large nut on the bottom of the bowl (17mm wrench)let the gas drain before removing it completely , after removing it , look inside towards the front of the bike/carb you will see 2 brass jets , the large HEX shaped one is the Main Jet , the smaller long one with the flat screwdriver slot is the Pilot Jet , it will be closest to the front of the carb , remove it

You can also just remove the entire bowl , so you can see inside the carb better , it is held on with 4 Phillips screws , if its stuck , just lightly tap on it with the screwdriver handle and it should come right off

On the side of the jet near the slot end , will be some numbers , like 42 or 45 , this will be the size of the jet and what you will ask for when replacing it , most bike shops should have it , or you can buy one here
http://www.crfsonly.com/catalog/product ... ts_id/4975

[ethanownes]

Great, thanks for telling me that I understood it all, it was very informative, I'll do that and see what happens!

[JimDirt]

One other thing to add , since this just happened to me last weekend at the track , it might be helpful....If you are using one of those cool metal gas cap vents (the Anodized ones that have the short tube) ,it is possible for the custom ones to go bad , if they clog up (some people just use the stock hose that goes down thru the headstock) , ,if it does clog , the tank can't vent and the bike will not idle and/or lean out only on the bottom end , the bike will still run when revved

So its something to consider if you have one of those , the only way to test if it is bad , is to take it off and ride the bike without it , if it idles and runs fine on low end , then that is the issue

[ethanownes]

ok, yeah i do have one of those so i will check it out, thanks!

[ethanownes]

Alright so the pilot jet did not work. I put it in and fired it up, and then all it did was backfire and pop when I revved it and then turned off when I let off the throttle. I don't know to do anymore and I am getting pretty frustrated that the pilot jet didnt work. The bike recently had a rebuild too so I don't think it's the valves, but it might be I don't know

[mossman77]

Make sure the hot start plunger is seating fully and check the free-play on the lever. Could be stuck open and thereby leaning out your mixture. The idle speed and/or fuel screw could have been maladjusted by the previous owner to compensate, which is why the bike won't idle. Just a guess, but a possibility.

Check the clutch lever free play as well. If okay, then maybe the clutch is sticking.

[ethanownes]

Alright, I know its been a while, but we got it fixed. My uncles checked the valves and they were good. We ended up completely removing the carb, (which is not very hard if you know the steps)and completely cleaned the whole thing with some type of chemical cleaner like brake cleaner or something. That seemed to do the trick and now the bike runs great. We think it was due to the fact that the previous owner left it sitting in his garage for so long that the fuel that was left in the carb made it dirty and was plugging up one of the fuel jets or something causing my bike to run lean. Thanks for your help! Problem SOLVED!

[JimDirt]

Glad its running good now , just be warned that Carb Cleaner or any other caustic solvent , can ruin any O-Rings or rubber parts in the carb , so if it starts acting up any , you might need to replace the Floating Valve Seal , which is the seal on the plate that is riding on the slide , if its damaged the bike will have idling and running issues

Also , if it does the cutting out at low RPM again , and you confirm its not valves , then replace the Pilot Jet with a NEW one , this will most likely cure the issue , unless you have a actual Jet Cleaning Tool , you will not get the jet perfectly clean , even with Carb Cleaner , also the Fuel Screw O-Ring , if you undo the Fuel Screw , it will be from top to bottom ,
Spring
Washer
O-Ring

Make sure they remain in that order and that the O-Ring is not damaged in any way as it will cause a Lean Condition if it gets damaged (carb cleaner can make the o-ring soft and it can/will tear or deform) , hopefully nothing is damaged (rubber wise) and you will be able to enjoy riding the bike for the rest of the season

If your going to park the bike for more than 2 months , then DRAIN the gas from the carb (and the tank) and use it in your Lawn Mower , or car where it will work fine , these bikes do not like old or low octane fuel , especially if the gas has Ethanol , this is the main reason for a clogged carb , which is why a lot of us go to the airport and mix Av Gas with Premium , so the fuel lasts longer , the Ethanol part of the gas can still go bad , but it takes a while longer , Av Gas does not contain Ethanol so it will last a long time on its own

Good luck !!

And thanks for the update !!

[mossman77]

also the Fuel Screw O-Ring , if you undo the Fuel Screw , it will be from top to bottom ,
Spring
Washer
O-Ring

Just to clarify, "top" meaning nearest the head of the fuel screw and "bottom" meaning the tip that gets inserted into the carb. The o-ring should go in the carb first, followed by the metal washer, and lastly the spring (all seated on the fuel screw initially and then screwed in together of course).