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CRF150F Valve Adjustment Procedure

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CRF150F Valve Adjustment Procedure

Postby 4Strokes » Sat May 14, 2016 3:44 pm

Topic: 2003 CRF150F valve adjustment procedure
Author: Uncleford
Posted: 02/19/2007 4:24:10 PM

I tried the search button but came up empty. What is the procedure for adjusting the valves on an 03' CRF150F? The manual calls for .004 intake and exhaust. Thanks for the help!

Reply by hummercat1 on 02/25/2007 5:16:41 PM
I'm not a 100% sure but I think that is right. Just put the motor on Top Dead Center and adjust the valves.

Reply by Uncleford on 02/25/2007 9:26:49 PM
well,I meant to post it up that I figured it out already but for someone else that needs to do it here goes.

  1. Pull the spark plug out
  2. Get on the compression stroke
  3. Spin crank over until you see the hash marks. About an inch later "F"(Fire) comes up then very quickly "T"(guessing TDC)
  4. Stop on "F" at this point if you go past the mark you need to spin it over again to get it right. Don't back up. It's easier if you have a way to hold in place or another person.
  5. Pull the head caps off (if you haven't already)
  6. Get a .004 feeler gauge and check the intake and exhaust valves.
    there should be a slight drag on the thin gauge. If not...
  7. Take a 10mm wrench and loosen the nut on top of the valve. Adjust the small square (for lack of a better word) up or down to get the proper adjustment)Once there then tighten the 10mm nut.
  8. After both are done spin it over re-check your work
  9. Put it back together.
Hope this helps someone. Before I did this to my daughters bike (03 CRF 150F)it was very cold natured. Now after adjusting the valves it will start 1st or 2nd kick in 20 degree weather.

Reply by b_king on 02/26/2007 6:22:22 PM
You shouldn't adjust the valves on the "F" mark. The "F" signifies when the spark plug fires. You should adjust the valves on the "T" mark, for TDC, you are correct Uncleford.

The piston will actually be slightly down from TDC when the spark plug fires. This is because the most compression is available as the piston travels upwards on the compression stroke. So if you adjust the valves on the fire mark, they might be slightly off throughout the entire cycle of the engine.

Good luck!

Reply by Uncleford on 02/26/2007 7:17:10 PM
AArrrg, my bad. Good catch. I read over it before I posted and still didn't catch that. yes, adjust your valves on the "T" not the "F"

(Just as a side note...if you adjust your valves on the F mark your exhaust will be about .002 tight)

Reply by b_king on 02/26/2007 9:02:05 PM
Don't worry Uncleford, it happens to the best of us. Keep up the detailed posts though. Like Admin said, it's nice to see people taking the time to thoroughly explain things for beginners, it helps quite a bit.

On a side note as well, I was just curious if .004" is what the manual calls for both the intake and exhaust. Typically in any engine the exhaust is slightly looser, by about .002-.003" because of the added heat of the exhaust gases and heat expansion.

Reply by Uncleford on 02/26/2007 9:58:37 PM
Yep, that's what the manual called for. I was a little surprised myself.

Reply by sgtshultz on 01/03/2008 7:37:18 PM
OK, what is the compression stroke and how do you know you are on it please?

Reply by Uncleford on 01/03/2008 9:20:18 PM
You would take the spark plug out, stick your finger in the spark plug hole, turn the engine over by hand (I used a socket and ratchet) and you will begin to feel the compression push your finger out. As it does watch where the timing points are and try to creep up on it slowly. If you go past the compression stroke your finger will be pulled inward toward the spark plug hole. if so, continue to rotate the engine over until you get it right. Hope this helps and good luck.

Reply by skikman on 02/23/2011 4:56:09 PM
quote: Originally posted by b_king

Don't worry Uncleford, it happens to the best of us. Keep up the detailed posts though. Like Admin said, it's nice to see people taking the time to thoroughly explain things for beginners, it helps quite a bit.

On a side note as well, I was just curious if .004" is what the manual calls for both the intake and exhaust. Typically in any engine the exhaust is slightly looser, by about .002-.003" because of the added heat of the exhaust gases and heat expansion.

strange my crf 150r gives intake 0.16mm or .006in and exhaust 0.26mm or .010in

Reply by Jeff_in_rc on 02/24/2011 07:42:13 AM
Another way to make sure you are at the correct TDC is to try to wiggle the rockers on the valves and to look at them and make sure they are not pushing down the valves. On a 4 stroke you have 2 points of TDC and you have to make sure the valves are closed to be at the correct TDC for setting the clearence.

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