HOW TO: RHC's Decompressor Mod - Easier Starting!
  • rvand12
    Posts: 14
    Joined: Wed Apr 25, 2012 10:36 pm

    by rvand12 » Sun May 12, 2013 10:15 pm

    How tight do you wind the spring on reinstall? I just did this mod to my bike. Great instructions thanks! Everything went smooth until I kicked it over after finishing.
    Big rattle from head.
    Yes the bolt is seated and tight, clip holding rod.
    Supposed to wind the spring a couple of turns?
    Thanks again
    Ray
    CRF250R
    CRF150RB
  • RideOrBeRidden
    Posts: 3
    Joined: Wed Sep 08, 2010 4:40 am

    by RideOrBeRidden » Wed Jun 12, 2013 3:58 am

    I just did this mod to my fully rebuilt 04 model that has an 08 head and cam fitted.
    It seems to be a good thing [the mod].

    Rvand12, you only wind it the minimum to get it fitted which is about 3/4 of a turn.
    It sounds like you have gone too many turns and it is holding the decomp open after the bike fires up.
  • sandman1111
    Posts: 2
    Joined: Sun May 26, 2013 10:06 am

    by sandman1111 » Wed Jun 12, 2013 1:48 pm

    My bike wants to idle only when the idle is set higher then normal. I noticed that someone has grinded a bit more off, would that make my bike to idle higher then normal?
  • fmlstewart
    Posts: 13
    Joined: Sat Jul 06, 2013 8:25 pm

    by fmlstewart » Tue Jul 16, 2013 9:30 am

    Just curious, is this hardened metal or have a hardened coating? If I grind away the hardened surface will the rest of the lobe wear faster? I definitely WANT to try this as my bike is pretty difficult to start after it gets hot, but I don't want to end up replacing an $80 part that wore out prematurely after being ground down.
  • KevBrewDog
    Posts: 1
    Joined: Mon Apr 28, 2014 7:54 am

    by KevBrewDog » Mon Apr 28, 2014 6:09 pm

    Saw this thread. I bought a Hotcams Stage 1 cam for my 2006 CRF250X and was meticulous on following the proper install and break in. After the break in, I started the bike up (after cool down) and noticed a "clack, clack, clack" noise at idle. When I raised the RPMs on the throttle, the noise disappeared.

    I began to troubleshoot and was able to determine the clack noise only occurred when the RPMs dropped below 1900 RPMS (I have a Hardline Hour/Tach on my bike). The clack noise is pronounced below 1900 RPMs, and if dipping down to the low 1800 RPMs, becomes so pronounced that the bike wants to stall. As soon as i raise the RPMs, the clack noise goes away.

    I then checked my valve lash and was within spec for the exhaust (.012" and intake R=.00475" L=.006)

    I called Hotcams and explained to them my problem and they said they did not have any other cases in their history of a similar type.

    When I started doing more troubleshooting, I first replaced the cam auto-decompressor spring with a brand new Honda part. I made sure to wind the spring only 3/4 of a turn, just to get it around to stay on the flat portion of the end of the cam. This did not rectify the issue.

    I then did some more "process of elimination" troubleshooting and removed the cam auto-decompressor (since I saw some email threads on this that it may be an issue with the little nub/lobe hitting the rocker arm lobe).

    Next, I removed the auto-decompressor itself from the Hotcams stage1 cam. Surely enough, after removing the auto-decompressor mechanism from the cam, I was able to start the bike, and the noise went away. No clacking noise at any RPM level. I even adjusted the idle down to 1700 RPMs, and no noise.

    I never had this clacking noise with my stock CRF cam (with the auto-decompressor attached).

    Two questions:

    1) I was wondering if I can run the bike with the Hotcams stage 1 cam without the cam auto-decompressor. The bike starts without it. Not sure if there are certain scenarios where the auto-decompressor comes into play in a key way (altitude, temperature, humidity, valve lash?)

    2) Would the modification of grinding the nub/lobe(found in this article) resolve this issue?

    Thanks for the support.
  • MikeOK
    Posts: 40
    Joined: Mon May 18, 2009 10:19 am

    by MikeOK » Sat May 03, 2014 1:23 pm

    Great write-up, thanks. I'm going to try this on my 07 and see if it helps my starting.
  • samueljackson
    Posts: 1
    Joined: Tue May 06, 2014 2:25 am

    by samueljackson » Tue May 13, 2014 10:59 am

    Did This to mine 08 250R Works fine.
  • User avatar
    momuzik
    Posts: 63
    Joined: Sun Oct 06, 2013 11:47 pm

    decomp mod for crf450

    by momuzik » Thu Jul 24, 2014 8:49 pm

    will this also work for a crf450??
  • holdfasthank
    Posts: 1
    Joined: Sat Dec 20, 2014 1:29 pm

    by holdfasthank » Sun Dec 21, 2014 3:35 pm

    save for later
  • shalna
    Posts: 1
    Joined: Mon Aug 07, 2017 1:52 am

    Re: HOW TO: RHC's Decompressor Mod - Easier Starting!

    by shalna » Mon Aug 07, 2017 2:36 am

    Hi guys, greeting from Latvia. :)

    I am new to this forum and I am having the same problem with my crf. Its a 2008 crf 250r. Today I will check valve clearences because maybe there is the problem.

    :arrow: Maybe its just me, or there arent any pictures left in this thread. I was thinking of doing this mod to my bike.

    thanks,
    Andris
  • User avatar
    crfsonly
    Owner
    Posts: 9651
    Joined: Thu Apr 01, 2004 3:45 pm

    Re: HOW TO: RHC's Decompressor Mod - Easier Starting!

    by crfsonly » Mon Aug 07, 2017 8:53 am

    Welcome to CRF's Only. Yeah, it looks like the original poster took them down. Bummer!
    OEM Parts for Honda - Yamaha - Suzuki - Kawasaki: http://yeltrik.com
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