Auto Decomp or not on a XRR?

11 replies to this topic
  • Beelzeboss

Posted January 07, 2007 - 10:02 AM


I have read may threads where people mension the Autodecomp on the BRP. As far as i know theres only the Manual Decomp on the handlebar and not any Autodecomp like the one on,for example, the XR 400.
Ive also read in some early magazines which did a test on the BRP mension the Autodecomp?

Can someone please sort this out for me?:lol:

  • rdahl

Posted January 07, 2007 - 01:46 PM


Check #7

Posted Image

  • Beelzeboss

Posted January 09, 2007 - 01:41 PM


I`ve looked at #7 but it doesnt help me very much:ride:
Could someone please elaborate ?:lol:

  • HawkGT

Posted January 09, 2007 - 02:58 PM


The stock XR650R cam does have an auto decomp and reverse decomp mechanism. This is in addition to the manual decomp mechanism. The auto decomp works off RPM. It relys on centrifugal force to deactivate itself once rpms reach 600 or thereabouts. It's design is identical to the XR400.

They can be removed from the stock cam by pulling off the cam sprocket flange. I imagine most aftermarket cams will accept the installation of the auto-decomp mech.

  • pcjepsen

Posted January 09, 2007 - 08:54 PM


wow does that mean my 01 xr400 has an auto decomp?
I always wondered why it was so easy to kick over.

I disconected the autodecomp cable from my wifes xr250
it's easy enough to kick and I don't need it sticking open in the middle of a long ride.

  • Thumpmeister

Posted January 09, 2007 - 09:20 PM


Actually, the stg. 1 hotcam for the 650R does not allow the use of the auto decomp. I feel this is for the better...

There have been issues w/ the auto decomp on the 650R's, and mine went south. So, I got rid of it all together. My brp never ran so good...

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  • cleonard

Posted January 09, 2007 - 10:00 PM


Taking out the decomp is no big deal. It just means that you have to kick it like you mean it. Removing that anti-kickback is another matter. While proper technique will lessen the chances, you will eventually get a good kickback. Strong kickbacks can hurt you.

  • Beelzeboss

Posted January 10, 2007 - 01:09 AM


So it all depends on how fast you move the kickstarter? If you kick it slow it will not decomp and if you kick it fast the decomp will activate?
Funky system..:lol:

  • Thumpmeister

Posted January 10, 2007 - 11:38 AM


No, how fast you move the kickstart will not have any effect on the auto decomp, since its rpm controlled....

Unless you can kick the starter fast enough make the motor instantly spin about 600 rpm, then the auto decomp will remain on, and turn off after about 600 rpm.

  • DougWood

Posted January 10, 2007 - 11:58 AM


Very imformative. Always wondered how the decomp worked.

  • bork

Posted January 11, 2007 - 06:17 AM


I took it out & only use the manual lever to set piston just past the compression stroke. Works great & would do it again in a heart beat! I cant stand not having the patients to feel the compression stroke out in the middle of no where when your in a hurry after an engine stop. All you gotta do is apply pressure to kick starter & it will get to the point of real hard/almost no movement, then back off your foot pressure a little while you pull in manual lever to let the kickstart move approx 1-4".(just past the top dead center of stroke) Then release lever & follow thru with quick foot pressure.Bbrrrroom! Mine never,never kicks back, unless you open throttle while kicking to start.(BEWARE)

  • bork

Posted January 11, 2007 - 06:21 AM


Also if you do decide to remove. It is easier to buy after market cam without the oil holes, to weld up, for auto-decomp. Wish I would have had a new cam in hand to swap out, when top was apart.(if I had to do again)

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