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 Post subject: Rebel 250 - How to adjust valve clearance
PostPosted: Wed Apr 06, 2005 6:56 pm 
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Country: USA
State/Province: MN
City: Fergus Falls
This page is designed to help the beginner set the valve adjustment on his or her Rebel 250. Setting the valves is critical to the bike making power. Valves that are too tight can burn, and valves that are too loose can rob power.

Please read these instructions carefully before attempting to do any of the work. If you feel that any of these steps are beyond your ability seek help or ask a mechanic friend for help.

To begin with, you will need to have the following tools on hand:
    8mm wrench
    9mm wrench
    10mm wrench
    12mm wrench
    5/8" Spark plug socket
    Large flat-head screwdriver
    Needle-nose pliers
    15mm socket and ratchet
    Metric feeler gauges that go to 0.05mm
For reference, cylinder #1 is on the left side (as sitting on the bike), and cylinder #2 is on the right.

Perform these steps on a COLD engine
    1. Disconnect the negative terminal on the battery.
    2. Remove the rear seat.
    3. Remove the driver seat.
    4. Turn the fuel valve off and remove the fuel hose.
    5. Remove the bolts holding the gas tank and remove the tank (remember to disconnect the vent tube if applicable).
    6. Remove the spark plug boots, and remove the spark plugs.
    7. Move the spark plug wires out of the way of the top of the engine.
    8. Remove the two bolts that hold the valve cover on, and remove the valve cover.
    9. Remove both the crankshaft cap and the timing cover cap (flat head 'screws' on the left side engine cover).
    10. Using the 15mm socket and wrench, turn the crankshaft COUNTERCLOCKWISE until you can see the "T" mark through the timing hole (Image 1)
    --Note--
    If you are having difficulty finding the "T" mark on the timing hole, look at the left end of the camshaft. There is a notch about the size of a pencil eraser. When this notch is pointing towards the rear of the bike, cylinder #1 is ready for adjustment (#1 is the left side when sitting on the bike). If the notch is pointing towards the front of the bike, cylinder #2 is ready (right side of the bike). (Image 2)
Image 1
Image

Image 2
Image

Image 3
Image
    Valve Adjustment
    11. The rocker is the dark piece of metal with a nut and a screw going through it (Image 3). Grab one of the rockers on cylinder #1 and give it a slight tug up and down. If it moves slightly or you hear a ticking, then cylinder #1 is at top dead center. If it is very tight, turn the engine one full turn until you see the "T" mark again and check for movement on the rockers again. If neither side ticks, check the notch on the end of the camshaft. If it is pointing towards the rear of the bike you are ready to adjust cylinder #1.
    12. Loosen the nut on top of the rocker arm, and back the screw out a turn or two (the feeler gauge is so thin you cannot push it between the valve and the lifter).
    13. Take your 0.05mm feeler gauge and insert it between the screw on the rocker arm and the top of the valve. (Image 4)
Image 4
Image
    14. Turn the screw clockwise to tighten down against the feeler gauge. Slightly pull on the feeler gauge, but don't pull it completely out. The clearance is about right when it takes a marginal amount of effort to move the feeler gauge (it shouldn't be difficult but it shouldn't move on it's own without a pull). Be sure to keep the gauge between the valve and the lifter. If you get towards the end of the gauge, loosen the lifter slightly and push the gauge back in.
    15. When you have the clearance correct, take the needle-nose pliers and hold onto the top of the screw (or use the screwdriver), and tighten down the nut with the wrench. Be certain that the screw does not move when you tighten the nut.
    16. Now pull the feeler gauge out. You should feel about the same resistance as you did before. If there is significantly more or less resistance, loosen the nut and readjust the screw.
    17. Repeat this procedure (Starting from step 11, above) for the other valve on cylinder #1.
    18. Turn the engine one rotation until you see the "T" mark through the timing hole, or the notch in the camshaft is pointing towards the front of the bike. You may now repeat the above procedure (Starting from step 11, above) for cylinder #2.
Congratulations! You have successfully adjusted your valve clearances on your Rebel 250! To button up the engine:
    1. Reinstall the valve cover and gently tighten down the two bolts that hold it to the engine.
    2. Replace both plugs over the crankshaft and timing hole (on the left engine case).
    3. Re-install the spark plugs and attach the spark plug wires.
    4. Re-attach the gas tank breather (if applicable) and the fuel line, and then reinstall the gas tank.
    5. Install the Drivers and rear seats
    6. Reconnect the battery, turn on the gas and go have some fun!

--Items of interest--
    * When adjusting the screw, don't push down on the screwdriver. If you have pressure on the screw the 'feel' of the guage will not be accurate and your valves will be loose.

    * Don't rush yourself. This process will easily take 45 minutes to an hour, depending on your skill. It is better to take your time and get it right rather than try to race the clock.

    * While you have the valve cover off, now would be a good time to check the torque of the head nuts and bolts
    Cylinder Head nuts - 17 lb/ft
    Cylinder Head bolts - 8 lb/ft
Tom O.


Last edited by tjobowa on Sun Apr 27, 2008 8:52 pm, edited 4 times in total.

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 Post subject: Re: Rebel 250 - How to adjust valve clearance
PostPosted: Thu Apr 07, 2005 3:02 pm 
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very good - nicely done

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 Post subject:
PostPosted: Mon May 01, 2006 6:23 pm 
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Joined: Oct 16, 2005
Motorcycle: 1989NX250
Rebel: 250
Country: USA
State/Province: AZ
City: Green Valley
#11 didn't work for me (notch pointing to sides of engine), so I put a thumb over the spark plug hole to determine the compression stroke and do the valve adjustment at TDC of the compression stroke.

Somehow that seems like a simple solution to determining the top of the compression stroke versus the top of the exhaust stroke.

John

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 Post subject:
PostPosted: Tue May 02, 2006 7:26 am 
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City: Fergus Falls
John,
Were you looking at the notch on the crankshaft, or on the camshaft?

I'm just wondering if a couple more pictures here would help...

Tom O.


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 Post subject:
PostPosted: Tue May 02, 2006 11:03 am 
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Joined: Oct 16, 2005
Motorcycle: 1989NX250
Rebel: 250
Country: USA
State/Province: AZ
City: Green Valley
Tom:

Camshaft.

On the #2 cylinder (right side as riding) there were four faint score marks on the washer-like end of the cam. On the #1 cylinder side, there was a groove that did not point down to the crankshaft when either cylinder had the piston at the top of its stroke.

I never got "ticking" from the valves, so went with the logic of valves closed at the top of the compression stroke, and I can feel the pressure of the compression stroke by putting a thumb or finger over the sparkplug hole.

To be truthful, I'm more comfortable with feeling the pressure in the cylinder build up as I'm rotating the crankshaft as the indicator that the valves are closed and ready to adjust when the timing mark is in the proper place.

John

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 Post subject:
PostPosted: Wed Aug 16, 2006 11:05 am 
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Country: USA
State/Province: CA
City: Bay Area
I have a problem, my 1999 cmx 250 started making a REALLY bad clicking noise. I completed this valve procedure, everything went well, and the bike started, but it still clicks...

I got a little confused by which cylinder was at TDC when.

The timing mark looked a little different, (I'll see if I can get a photo up here).

and I have no idea where the breather tube from the gas tank goes.

Mine has the emissions cannister on it, it is from california.

Any help would be appreciated!


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PostPosted: Wed Aug 16, 2006 12:56 pm 
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State/Province: CA
City: San Dimas (la County)
tom's explanation has been very helpful to me and a lot of others but i think that notch he is talking about on the camshaft is supposed to be pointing to the rear (on the right hand side of the engine) for the number 1 cylinder (left side as you sit on it) to be at tdc.

the vent line from up and under the gas tank fits onto the charcoal cannister on california bikes -- black box just behind the air box (remove outer side cover of the air box first -- feel back there -- the little black nipple sticks out horizontally toward the front about a third of the way down).


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 Post subject:
PostPosted: Wed Aug 16, 2006 5:03 pm 
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State/Province: CA
City: Bay Area
First and foremost (I may have forgoten to say this)

THANKS TOM!!! I feel very good about adjusting the valves on my bike, now.

Regarding the camshaft: The notch I found was on the left hand side of cam. Either pointing towards the front of the bike or the rear when the crank was at top dead center, depending on which cylinder is being adjusted, not so much "the center"


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 Post subject:
PostPosted: Sat Oct 14, 2006 3:26 pm 
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Joined: Aug 16, 2005
Motorcycle: 08 Versys, 97 C-10, 79 KZ650
Rebel: 250
Country: USA
State/Province: NC
City: Newport
OK guys, just started valve adjust on the bike everything is going peachy. Being a little mechanical inclined I have done this on other vehicles. 0.05mm seemed a little tight to me, I went to the owners manual (haven't bought Clymers or Honda manual) it gives 0.08mm clearance for valves cold. Has Honda updated this or have you learned something you didn't share?
This thread has been a great help, please don't take this in a bad way, I am just a curious sort.

Dan

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 Post subject:
PostPosted: Sat Oct 14, 2006 3:32 pm 
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Joined: Oct 16, 2005
Motorcycle: 1989NX250
Rebel: 250
Country: USA
State/Province: AZ
City: Green Valley
Rebel Service Manual (1996-2006) lists 0.06-0.10 mm or 0.002-0.004 inch.

Myself, I use a 0.003 inch feeler gage.

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John, 2014 CB500XA (Daily Rider), 2009 CRF230L (L'il Red Piglet), 1989 NX250 - sold, 2001 Rebel - sold
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 Post subject:
PostPosted: Sat Oct 14, 2006 3:33 pm 
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Best Loser!

Joined: Aug 16, 2005
Motorcycle: 08 Versys, 97 C-10, 79 KZ650
Rebel: 250
Country: USA
State/Province: NC
City: Newport
Thanks John,

Now back to the garage.

Dan

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 Post subject:
PostPosted: Tue Oct 17, 2006 11:21 am 
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After finishing adjusting my valves last night, and tightening the (2) bolts on the valve cover, I broke off the right one, and obviously did some damage to the threads on the left.

Any torque recommendationss for those? I was using a 6 " 1/4 drive socket; I really didn't think I'd be able to break them.

Advise for getting the broken bolt out? I guess I need to take the valve holder assembly out and start the screw removal process.

I'm worried also about the metal bits that easily could fall down into the valve area.

Does this happen a lot?

Thanks,


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PostPosted: Tue Oct 17, 2006 11:40 am 
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Joined: Oct 16, 2005
Motorcycle: 1989NX250
Rebel: 250
Country: USA
State/Province: AZ
City: Green Valley
Unfortunately, yes it does happen a lot.

The torque spec for the cover bolt is 7 ft-lbs. Many torque wrenches start at 10 ft-lbs (i.e. when it clicks it is too tight).

I use open/closed end wrenches and try to "snug" the valve cover bolts.

There is/are a thread or six on removing these broken off bolts. Try searching for them.

John

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PostPosted: Tue Oct 17, 2006 12:48 pm 
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State/Province: CA
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those things are pretty much just hand tight. you don't need more than snug to keep oil from coming out around a good fresh rubber valve cover gasket.

bad news / good news.

the bad news is if that is stripped on one side, the threads are in the "tower" of the rocker assemby.

the good news is it is pretty easy to just buy replacement rockers (with the springs, everything already assembled) from jack -- he doesn't have a huge demand for those things (ask me how i know -- actually mine was stripped on one side when i got the bike) and pretty much should always have some around.

it is an easy change out -- do both sides -- they are marked a and b or left and right or something -- so they will be balanced. i actually improved performance when i did that -- the used ones i got were in better shape than the ones i had (at the valves).


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PostPosted: Tue Mar 13, 2007 10:00 am 
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Bookmark for future reference.

Thanks


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PostPosted: Fri Jul 20, 2007 10:34 am 
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Tjobowa,thanks!!! for posting the pics and info,i adjusted my valves last night on my 2005 rebel,800miles,,I set them at .003in, your step by step instructions were great,,I applied a little pressure with my fingers holding the rocker arm up while sliding the feeler guage in and adjusting, i did see the square notch on the left side of the cam which helped a lot,,,the bike sounds great, the ticking seems to have gone away,very slight now but thats normal , the valve ajustment screws were off by half a turn or so


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PostPosted: Fri Apr 25, 2008 8:57 pm 
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Joined: Apr 16, 2008
Country: USA
State/Province: TX
City: West
Ok i did this adjustment on one bike and it went well. Yet i did this to another tonight and no the bike has slowed down. 55 about top speed. Before hand it was around 75 to 80. What have i done wrong? I thought maybe i did them to tight so i went back in and re adjusted them, maybe 60 now. Any clues on what ive done wrong?

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PostPosted: Fri Apr 25, 2008 9:22 pm 
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State/Province: TX
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Ok i have been reading post out the whazoo, and i think i might have found my own problem. I adjusted the valves were hot right after running the motor. Could that cause the issue that i am having now? The other valve job i did was done after the bike had sit all day long.

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First Bike 1972 Honda CB 350 this bike was great!! Had great UMPH! if you gassed it at 70 75. and still got 60 to 65 mpg


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PostPosted: Fri Apr 25, 2008 9:23 pm 
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supposed to be done totally cold ... yes

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PostPosted: Fri Apr 25, 2008 10:28 pm 
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State/Province: TX
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Ok then i guess i should describe this. First i did as i said as far as adj the valves while hot. I ran the bike down the road about 1/2 mile. Took it back, loosened the valves (while still hot), then ran it again. bout a half mile. This time it felt better but top end was still not there. Thats when i came in and made the post. I intend to let the bike sit over night then redo the adjustment. Question is have i already screwed this thing up. Am i gonna be after a head for this thing? Thanks MR for the quick response.

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First Bike 1972 Honda CB 350 this bike was great!! Had great UMPH! if you gassed it at 70 75. and still got 60 to 65 mpg


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