Using Decomp. Lever on 02' 426 as a "jake brake"?

8 replies to this topic
  • slammmin72

Posted September 23, 2006 - 10:52 PM


is it ok to use the decomp lever on my 426 as a "jake brake" for extra slowing down power when going down long steep hills? my dad claims htey used to have them on their 2 strokes back in the day and thats what they used them for, i just wanna make sure with the new technology that is wont hurt anything. thanks again

  • Satch0922

Posted September 24, 2006 - 03:27 AM


on the four stroke bikes the release actually holds on of the valves open as to release compression for starting purposes. It is NOT wise to use it while the bike is actually running.

  • tacoma426

Posted September 24, 2006 - 07:02 AM


not a good idea

  • TapptOut

Posted September 24, 2006 - 07:10 AM


Not Smart

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  • Vengeancemaster73

Posted September 24, 2006 - 07:16 AM


Nothing is going to happen i believe even if you use it. That would just stall the bike. The piston would kind of be in a "free state" So i think it would just be the same as in pulling in the clutch. But I'm not that familiar with how the 426 engine works.

  • Japster

Posted September 24, 2006 - 07:32 AM


A Jake brake keeps the exhaust valve closed therefore compression braking on every stroke. A de-compression system does the opposite, holds the exhaust valve open so that the motor can freewheel. it should actually spin faster with the decomp lever pulled.

Heres a neat trick. when stalled, laid over & flooded or just being a pain to start, roll down a hill and push the kick starter back a couple inches with your right hand and drop the clutch in 2nd. Works great to clear out a flooded bike. As soon as it sounds like it's trying to start, let go of the KS and away you go. :thumbsup:

  • FFRacing79

Posted September 24, 2006 - 07:51 AM


A Jake brake keeps the exhaust valve closed therefore compression braking on every stroke.

Sorry, but you are absolutely incorrect on this point. You are assuming the diesel engine works like a conventional 4 stroke, which it does not. The jake brake opens the exhaust valve(s) just before maximum compression, thus making the engine act like a large air compressor. Tdub

  • The Spanky

Posted September 24, 2006 - 07:57 AM


Using the decomp lever at high rpms is not smart. The valve stem/tappet is held farther away from the cam lobe by the decompressor, so the lobe beats the crap out of the valve stem and tappet, just like it would if the valve clearance was way too loose. Bad juju.

  • slammmin72

Posted September 24, 2006 - 08:46 AM


thanks everyone...ill be sure not to use it...tahts why i asked.

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