Loss of engine brake 2014 yz250f

bryannn
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bryannn
Edited Date/Time 10/20/2015 6:16am
Really noticed it today at the track while going down a hill full of breaking bumps. I usually roll down in 4th shifting into third halfway through and using the engine brake to slow down. Upon downshifting and trying to slow down nothing happened as a I continued almost full speed into the corner before applying traditional brakes. What could cause this? clutch slipping? No rear tire traction? Looking for any ideas possible bike has about 30 hours on it.
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Charper732
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Charper732 10/18/2015 6:23pm
10/18/2015 6:23pm
you'd notice clutch if it were slipping under power. loss of compression = less engine braking. you should be able to tell if the rear tire is getting traction or not.
bryannn
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bryannn 10/18/2015 6:25pm
10/18/2015 6:25pm
Charper732 wrote:
you'd notice clutch if it were slipping under power. loss of compression = less engine braking. you should be able to tell if the rear tire...
you'd notice clutch if it were slipping under power. loss of compression = less engine braking. you should be able to tell if the rear tire is getting traction or not.
sounds about right then. So new top end time?
Charper732
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Charper732 10/18/2015 6:29pm
10/18/2015 6:29pm
Charper732 wrote:
you'd notice clutch if it were slipping under power. loss of compression = less engine braking. you should be able to tell if the rear tire...
you'd notice clutch if it were slipping under power. loss of compression = less engine braking. you should be able to tell if the rear tire is getting traction or not.
bryannn wrote:
sounds about right then. So new top end time?
Don't just throw parts at a problem. Diagnose it. A compression or leakdown tester is cheap and it makes keeping an eye on engine vitals easy.
bryannn
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bryannn 10/18/2015 6:38pm
10/18/2015 6:38pm
Charper732 wrote:
you'd notice clutch if it were slipping under power. loss of compression = less engine braking. you should be able to tell if the rear tire...
you'd notice clutch if it were slipping under power. loss of compression = less engine braking. you should be able to tell if the rear tire is getting traction or not.
bryannn wrote:
sounds about right then. So new top end time?
Charper732 wrote:
Don't just throw parts at a problem. Diagnose it. A compression or leakdown tester is cheap and it makes keeping an eye on engine vitals easy.
already on the to do list for this week.

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Markee
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Markee 10/19/2015 11:57am
10/19/2015 11:57am
"Traditional" braking.
CarlinoJoeVideo
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CarlinoJoeVideo 10/19/2015 2:02pm
10/19/2015 2:02pm
Any chance your idle was higher than normal? This could keep the motor higher in the RPMs and reduce the engine breaking, right?
bryannn
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bryannn 10/19/2015 6:55pm
10/19/2015 6:55pm
CarlinoJoeVideo wrote:
Any chance your idle was higher than normal? This could keep the motor higher in the RPMs and reduce the engine breaking, right?
nope it was where it is normally at.

Also does anyone know if doing a compression testing on a modern dirtbike is any different? I was reading somewhere about the autodecompression skewing results. Any truth to this?
jsmx97
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jsmx97 10/20/2015 6:16am
10/20/2015 6:16am
Check the cheap things first. Valve clearance too tight? Clutch springs worn? Low compression?

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