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| | | Junior Member
 
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Last Login: 2 days ago @ 8:09:27 PM
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| | Ok I thought my starting issues were just cold weather related but last night I couldn't start my CRF250... for the third straight time riding I've had to jump it by pushing it. This time two guys helped push me down a flat road. Once it's started and warmed up it rips though. Any ideas? |
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| | | Junior Member
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Last Login: 11/6/2008 5:19:09 PM
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| | Hard starting can be an indication of valve clearances that are too tight. If that hasn't been checked since break-in I would start there. Otherwise, may be a clogged pilot jet, etc. When buying a used bike I usually take the carb apart, clean it, and verify that it's set to factory spec (correct jets, needle clip in the right position, fuel screw adjusted, etc). As for checking the valves, I have the procedure for my 450 and the 250 should be the same, but I doubt the clearance specs are the same. You'll need feeler gauges and the specs for your bike. If necessary it's a little wierd to adjust them with the Unicam setup, but no big deal. I can walk you through checking them... |
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Last Login: 9/8/2008 11:23:17 AM
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| This is a sign from the God of Motocross.... YOU NEED TO BUY A YAMAHA= BULLET PROOF lol but yea chad's right with the valves.
Jack Forbush 645
125y, 125yc
2007 YZ250F
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| | | Junior Member
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Last Login: 2 days ago @ 8:09:27 PM
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| | Ok I'm getting the valves checked tomorrow, thanks. |
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Last Login: 10/18/2008 9:31:34 PM
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| | hey pat, it is your valves. your intake valves are tight and you cant get enough compression to open them when you kick start it. so you jump it and no problems because it warms up and you get your clearances. Its happened to a couple of guys I ride with, It wont anymore becouse they finally bought a yamaha. GOOD LUCK! |
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Last Login: 11/6/2008 5:19:09 PM
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| Guess I should have explained.
A motor needs 4 things to run. Fuel, compression, spark, timing. When there is no clearance between the cam and valve, that valve remains partially open and breaks the seal inside the combustion chamber, reducing the compression ratio. It will start extremely hard, if at all. If it does run, once it warms up the components expand with heat and that may be enough to regain loss compression which is why it seems like it's fine after it's running.
FYI - to all the brand bashers, ALL of them have the potential to experience this issue. Once the bike is broken in valves and seats can wear in slightly and reduce clearances. It's not anything to worry about, but it does need to be put back in spec.  |
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| | | Junior Member
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Last Login: 2 days ago @ 8:09:27 PM
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| | It's fixed! Yup it was the valves and I just needed 3 shims. That was a very good explanation thanks. It was concerning because eventually it wouldn't start and everybody that tried to kick it over said it had VERY LITTLE compression. I didn't know the valve issue would affect the compression. Now I can't wait to try it out tomorrow. |
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Last Login: 11/6/2008 5:19:09 PM
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| | If it was bad enough not to start you will notice a slight power increase and overall smoother operation. Glad you found the problem! |
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Last Login: 2 days ago @ 8:09:27 PM
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| | Sweet, I can't wait to find out! Another hour and I will be riding... thanks for the advice. Also I found it interesting my mechanic said it was all right to twist the throttle once before starting when cold. I thought that was a no-no? He said it's fine if their cold. |
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