Crf450r 2007 stutter mid rpm

Bailey_Beista
I have recently rejetted my Carb because I was having a hanging idle and the bike was getting very hot. But now that the bike revs and idles back down normally. now I have this weird stutter/ power loss in the mid rpms. It revs fine before and after the mid, with most of the power in the top end. Any ideas or suggestions. When I run the bike leaner the stutter goes away but then I have a hung idle again.
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Paw Paw 271
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Paw Paw 271 3/17/2020 2:54am
3/17/2020 2:54am
Sounds like you have an air leak and a fuel screw that needs to be adjusted.
What jetting are you running?

Paw Paw
Bailey_Beista 3/17/2020 3:34am
3/17/2020 3:34am
So the only jetting I have changed is the pilot which I had to go from a 42 (stock) to a 50 before the bike would return idle after a blip of the throttle. I have the fuel screw 2 turns out at the moment
navyslideby
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navyslideby 3/17/2020 6:51am
3/17/2020 6:51am
That's quite a large increase in pilot jet size..... I would do a leak down test and check for any air leaks anywhere!!! Could be a split boot, a bad seal somewhere, all kinds of things...
Bailey_Beista 3/17/2020 7:00am
3/17/2020 7:00am
navyslideby wrote:
That's quite a large increase in pilot jet size..... I would do a leak down test and check for any air leaks anywhere!!! Could be a...
That's quite a large increase in pilot jet size..... I would do a leak down test and check for any air leaks anywhere!!! Could be a split boot, a bad seal somewhere, all kinds of things...
i was wondering if crack in the exhaust would cause an air leak, but i assumed that if the valves are okay it wouldnt matter to much ?

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Paw Paw 271
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Paw Paw 271 3/17/2020 9:15am
3/17/2020 9:15am
You should be at about 45 on the pilot as it was jetted a bit lean from the factory.
Fuel screw should be from about 2- 2.5 turns out.
The 50 pilot jet tells me you do have a leak.

Paw Paw
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Bailey_Beista 3/17/2020 12:46pm
3/17/2020 12:46pm
Paw Paw 271 wrote:
You should be at about 45 on the pilot as it was jetted a bit lean from the factory. Fuel screw should be from about 2-...
You should be at about 45 on the pilot as it was jetted a bit lean from the factory.
Fuel screw should be from about 2- 2.5 turns out.
The 50 pilot jet tells me you do have a leak.

Paw Paw
I have just done the valves today the exhausts were very tight so changed them and set the ex to 0.011 on both and the intake to 0.005 on both so they are in spec. The bike has loads more compression now. I put a 45 jet in the Carb and will get it running tomorrow and see if anything Has changed
Paw Paw 271
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Paw Paw 271 3/17/2020 3:43pm
3/17/2020 3:43pm
You did reset the auto decompression arm as well, right? If so what did you set it at?
Normally the intake valves get tighter.
Be sure to reset the fuel screw.

Paw Paw
Bailey_Beista 3/18/2020 1:49am
3/18/2020 1:49am
Paw Paw 271 wrote:
You did reset the auto decompression arm as well, right? If so what did you set it at? Normally the intake valves get tighter. Be sure...
You did reset the auto decompression arm as well, right? If so what did you set it at?
Normally the intake valves get tighter.
Be sure to reset the fuel screw.

Paw Paw
Not sure what you mean by resetting the decomp. On my bike the decomp is on the cam gear and has a weight that spins out to decompress. It only goes in one way and doesn't seem adjustable. Just I have put the fuel screw 2 turns out from fully closed
Paw Paw 271
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Paw Paw 271 3/18/2020 3:32am
3/18/2020 3:32am
Sorry, I thought the 2007 still had the decompression arm that needed to be adjusted. I guess I got confused as I thought the change was not until 2008.
Remember that the fuel screw is something that is not a fixed setting, but rather a daily adjustment. It effects the complete fuel delivery, unlike the old air screw which mainly effected the lower rpms.

Paw Paw
Bailey_Beista 3/21/2020 4:36am
3/21/2020 4:36am
Okay so the bike is running much better now looked like it was just a leak from the being shimmed too tight. Jet is back to a 45. Just one question is my shifter. I don't have many problems with the gears but the shift shaft does have some play in and out, just wondered if this should be a concern or if it's okay for play

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