This past weekend I went out to racehorse creek and did some riding on my new bike. Loved it! So much lol anyways I have a few questions. First thing I noticed was most times after stalling it or shutting it off hot it was a real pain to fire it back up even with using the hot start lever. Anyone else have troubles on there Yam like this? I checked the plug and that looked fine, once started it ran like a champ again. Secondly, on the second day of riding i noticed my idle would keep creeping up. I would stop and adjust it back then twenty min later its creeping higher and higher. Thoughts and direction on that? Other than that the bike went everywhere I pointed it! Any help will be greatly appreciated.
09 YZ250f help
- Thread starter mxracer14
- Start date
takethebounce
Active VIP Member
Sounds like a typical 4 thumper MX motor.
Modern carb 4 stroke mx bikes can be a real pleasure to start sometimes when hot. Typically if you don't get it to fire on the first kick you then grab the hot start and try it again and hopefully it goes. If not it likely becomes a real pain.
4 strokes also don't like to be kicked like a 2 stroke. They fire better when a smooth kick at the top of the compression stroke is found.
The best way to try at that point is to clear the carb. Hold the throttle wide open while holding the hot start and kick. Usually it wakes up pretty quick.
I am sure it was nice and hot as well. Hot temps and higher elevation is going to play tricks on the jetting. Make the pilot jet and needle setting is proper for your riding area. Get yourself a fuel screw as well. You can dial in your pilot screw easier.
The idle changes could be related to the fuel screw or pilot being wrong as the idle works off the pilot from idle to 1/8 throttle. Hanging idle can also be a throttle cable being sticky or too much play in the return cable. Make sure both cables are adjusted correctly.
Sent from my HTC-Z710a using Tapatalk 2
Modern carb 4 stroke mx bikes can be a real pleasure to start sometimes when hot. Typically if you don't get it to fire on the first kick you then grab the hot start and try it again and hopefully it goes. If not it likely becomes a real pain.
4 strokes also don't like to be kicked like a 2 stroke. They fire better when a smooth kick at the top of the compression stroke is found.
The best way to try at that point is to clear the carb. Hold the throttle wide open while holding the hot start and kick. Usually it wakes up pretty quick.
I am sure it was nice and hot as well. Hot temps and higher elevation is going to play tricks on the jetting. Make the pilot jet and needle setting is proper for your riding area. Get yourself a fuel screw as well. You can dial in your pilot screw easier.
The idle changes could be related to the fuel screw or pilot being wrong as the idle works off the pilot from idle to 1/8 throttle. Hanging idle can also be a throttle cable being sticky or too much play in the return cable. Make sure both cables are adjusted correctly.
Sent from my HTC-Z710a using Tapatalk 2
- Thread starter
- #3
Ya it was a cooker out there this weekend. Ill read up on which jet and needle setting I should be running. Also, can you expand on the fuel screw? Is that like the idle screw or am I out to lunch lol still learning all differences from my yz250 2 stroke. Didnt think to check throttle cable, when I burped it a time or two the idle would start to drop down again. Thats sounding like the cable is sticking somewhere eh. Thanks for your advice takethebounce.
takethebounce
Active VIP Member
It is somewhat difficult to determine what exactly is happening with your bike without trying it first hand.
Go on thumpertalk and search for hanging idle in the yammy section and you will get some good advice as well. Modern 4 stroke carbs are very similar. Your bike can likely benefit from a pilot jet change and needle clip position change.
Your pilot screw is not your idle. The pilot screw basically adjusts your air/fuel mixture from idle. It's easy to adjust and normally gets adjusted in half turn intervals from 1.5 turns to 2.5. Adjusting it will give you a crisp throttle response. The pilot jet then takes over followed by the needle and then the main jet.
You should be able to download an operators manual online for free. The Yamaha manuals are typically good with more info than other jap bikes.
Sent from my HTC-Z710a using Tapatalk 2
Go on thumpertalk and search for hanging idle in the yammy section and you will get some good advice as well. Modern 4 stroke carbs are very similar. Your bike can likely benefit from a pilot jet change and needle clip position change.
Your pilot screw is not your idle. The pilot screw basically adjusts your air/fuel mixture from idle. It's easy to adjust and normally gets adjusted in half turn intervals from 1.5 turns to 2.5. Adjusting it will give you a crisp throttle response. The pilot jet then takes over followed by the needle and then the main jet.
You should be able to download an operators manual online for free. The Yamaha manuals are typically good with more info than other jap bikes.
Sent from my HTC-Z710a using Tapatalk 2
TheMuffinMan
Active VIP Member
Good little trick I learned for starting 250f's is to hold the throttle open just a hair when kicking it. You don't want to move the throttle at all while kicking as that will activate the accelerator pump flooding the engine, but if you open it just a bit, hold it there, and then kick, you'll find it starts much easier hot or cold. As for the idle issues, bounce is right, the fuel screw is the first place you should look. Other possible culprits are an air leak, valves out of adjustment, or compression loss due to worn piston rings.
GYMBRAT
Active VIP Member
Mine did it because my valves were pooched, WHORE to start once hot. But when it did start it ran like new......food for thought.
I still LOVE my 2stroke cold smokers
I still LOVE my 2stroke cold smokers
- Thread starter
- #7
Thanks guys, gives me some direction to start playing. I have the manual coming, the kid I bought the bike from has been looking for it since I bouight it last month and has finally found it so that willl be a good start. \
I do miss my 05 250 smoker, she was a blast to ride. One day I will have both again haha
I do miss my 05 250 smoker, she was a blast to ride. One day I will have both again haha
dirtbike4life250
Member
i have a 2010 yz250f and i find im having the same problem its a real bitch to start sometimes when im riding it hard... and i shut her down and or drop it.. i find its hard to start.. but if im riding it smoothly it fire's on the first kick.... i found holding the kill switch and kicking it over a few times. then kicking it with a little gas it normaly fire's up.. iv had it back to the dealer multiple times for the hot start lever sticking closed too...
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