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Valve replacement - Step by step

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Guys, I replaced the valves and kept notes. I already rode a couple of 50 plus mile days, so I will say it worked. I have pictures I need to scan and put in the link in the next few weeks. If you decide to try it, this pretty well sums it up. Anyone needing the aluminum spring compressor, let me know, I might be able to send you a copy.

REPLACING ENGINE VALVES

DISASSEMBLY – Keep your small part together in plastic bags to simplify reassembly.

ENGINE & FRAME ACCESSORIES TO REMOVE

1) Seat

2) Plastic side panels

3) Plastic radiator scoops

4) Gas tank

5) Clean or cover the upper frame rails

6) Carburator

7) Exhaust system

8) Head stay at the top of the frame

REMOVE OUTER CONNECTIONS TO THE HEAD

1) Set the Flywheel to TDC

2) Left side radiator hose

3) Top oil pipe to the head – left side

4) Auto cam chain tensioner (ACT)

5) Lower spring and bolt tensioner (17mm)

HEAD REMOVAL

1) Eight cam cap cover bolts in reverse

2) Remove cap – watch for two hollow dowel pins

3) Cams

4) Secure the cam chain or stuff the cam chain channel with clean rags, in the barrel. This will secure the chain and protect the lower engine from debris.

5) Head bolts (8mm hex and 6mm bolts in chain channel)

6) Tape the 6mm socket to an extension to prevent it falling in lower case

7) Tap head with plastic mallet to loosen from barrel.

8) Leave the barrel undisturbed to protect the base gasket.

9) Work the head off the engine.

10) The rear plastic chain guide forces you to manipulate the head next to the frame.

VALVE DISASSEMBLY

1) Compress the spring with the clamp.

2) Spray Contact cleaner/ WD-40 on the collet to break oil film

3) Cover the valve stem/springs with a rag and use compressed air to remove the split collet.

4) Recover the split collets with a pen magnet.

5) Bag and label each valve assembly.

6) Use needle nose pliers to gently rock the oil seals off the valve stem.

7) Use needle nose pliers and spray solvent to to remove the spring guides at the base of the valve stem.

8) The head should now be ready to clean.

9) Clean the head combustion chamber, exhaust ports, and valves you plan to replace.

VALVE LAPPING

It leaves a slightly polished ring on the valve. This only tells you there is a seal between the valve seat and valve. If the polished ring does not show, the valve seat needs to be machined.

1) Drill 4 holes in a piece of wood and mark it with an arrow to identify a specific valve for the seat.

2) Apply a bluing dye or a felt marker to cover the valve seat surface and valve face.

3) Apply valve grinding compound to the valve or the valve seat.

4) Insert a weak spring on the valve stem and install the valve into the head.

5) Connect a clear suction cup with a socket and extension to the valve face.

6) Rotate the extension back and forth. You can hear the grinding between the two surfaces.

7) Stop after 4-5 rotations or until you don’t hear the grinding.

8) Let the spring raise the valve and push down on the valve again repeating the 4-5 rotation drill.

9) Repeat the drill 5 times.

10) Apply some grinding compound and repeat the drill again.

11) Remove grinding compound, check the seats for ink, and replace the valve in the pegboard.

12) If there is no ink the sealing surfaces should be okay.

13) Repeat process for the other valves.

VALVE REASSEMBY

1) Clean the head with soap and hot water.

2) Install all four oil seals on the end of the valve guides with needle nose pliers. Push down and rotate gently until you feel it click on the valve guide. Some assembly oil can help.

3) Apply some grease to the spring base plate and and place it at the base of the valve guide.

4) Put the head on it’s side and install the springs and top ‘keeper clip’.

5) You are now ready to compress the spring and replace both of the ‘half acorn’ keepers.

SPECIAL TOOLS

1) I took a 6” C-Clamp and put a nylon type chair glide on the base with double stick tape.

2) I cut a hollow aluminum tube 1-1/4” long and cross drilled it ¾” to install the keepers.

3) I installed the tube to the screw anvil using double side foam tape.

SPRING COMPRESSION AND KEEPER INSTALLATION

1) Using the C-clamp, place the base on the valve head and the tube on the keeper clip.

2) Compress the spring slowly until you can see the top 3/8” or so of the valve stem. You need enough valve stem showing to install the keeper.

3) Place a small amount of grease in the keeper and grasp the large diameter with needle nose pliers . It is slippery, but nn pliers will get it on the shaft.

4) From there, you can move it into the ring slot on the valve stem with small wire picks or a screwdriver.

5) Slide the first keeper half to the opposite side of the valve stem and repeat with the second keeper.

6) Release spring tension and check the top of the keepers.

KEEPER TIPS

1) Use of grease should overcome the magnetism in small screwdrivers and wire picks.

2) Good close in vision is a must.

3) For the left side of the head, (sitting on the bike) the working hole of the tube will be accessible from the left side of the head.

4) For the right side, (chain channel) of the head, the working hole of the tube will face front to rear of the head,

5) Put the C-clamp in a vise for the chain channel side to let gravity (and grease) help you install the keepers.

6) Do not release spring tension on keepers if they are sitting on the valve stem below the ring slot. The pressure on the keeper plate will not slide them into place. They will bind on the valve stem.

7) Check the keepers by looking at the top of the valve stem. They should have the same end gap or it should be split if they are installed exactly opposite.

LEAK DOWN TEST

At the suggestion of a TT’r., I did a liquid leak test prior to replacing the head. I stuffed four gun cleaning patch into the ports to detect any leaking from the combustion chamber to the head ports. I put the head on the bench with the combustion chamber up and filled it with contact cleaner. I let it sit for a minute and wiped out the combustion chamber. I pulled each gun patch and checked them for contact cleaner. None of them were wet so I installed the head.

HEAD INSTALLATION

1) Place the new gasket on the clean barrel / piston surface over the dowels.

2) Place the head on the barrel.

3) Use needle nose pliers to pull the cam chain through the cam channel in the head. Secure/hold the chain while you pull the stuffed rags in the barrel up into the head chain channel.

4) Torque the 4 head bolts (8mm allen) and chain channel bolts (6mm). You will have to work around the rags in the channel.

5) Install the shims and buckets as they were initially removed.

6) Check the TDC on the flywheel again.

7) Install the lower chain tension spring and bolt tensioner (17mm)

8) Remove the rags and secure the cam chain.

9) Install the chain on the exhaust cam.

10) Roll the exhaust cam in position until the ‘ex’ lines up with the case line.

11) Put the chain over the intake cam.

12) Roll the intake cam in position until the ‘in’ lines up with the case line.

13) Count the 32 pins from side to side (16 links) to verify the chain distance over the case line.

14) Install the cam cap and torque halfway to specs to measure the bucket to camshaft gap.

15) After final shims are determined and placed, torque the head per specs and install the head cover.

16) Install the auto cam tensioner in the side of the barrel.

ENGINE ACCESSORIES TO REPLACE

1) Left side radiator hose

2) Top oil pipe to the head – left side

3) Antifreeze

4) Spark Plug

FRAME ACCESSORIES TO REPLACE

1) Seat

2) Plastic side panels

3) Plastic radiator scoops

4) Gas tank

5) Clean or cover the upper frame rails

6) Carburator

7) Exhaust system

8) Head stay at the top of the frame

NOTES

1) Start the engine and check the oil for emulsified (milky) appearance. This will indicate a leak from cooling to the oil system.

2) I recommend running 1 oz. of Seafoam per gallon of gasoline to help clean the piston and combustion chamber. The carbon almost wipes off.

3) Set your valves as far open as recommended by the manufacturer.

4) Both exhaust valves set at .25mm with a .290mm shim.

5) Left intake set at .203mm with a .282mm shim.

6) Right intake is set at .203mm with a .276mm shim. (seat with the most wear)

7) Carpet cleaner and plastic brush will remove the baked on dirt on the aluminum parts.

8) Readjust the air screw on the CVK carb. I had been compensating with poor valve performance to get good low speed performance.

9) There is generally less back popping on deacceleration after the valves have been replaced.

10) I retorqued the head after the first ride, but found no change in settings.

11) Groit’s Garage.com has metric feeler gauges in .1mm increments. Most Metric gauges I found, skip sizes.

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Burnrider - thanks for the writeup. I'll look forward to the pics. Did you replace the valve springs? If not, did you measure their tension? From what I'm reading, they may be the source of my problems, but since you've gotten so many miles out of your engine, maybe yours are OK.

Did you custom size (sandpaper down) the shims to get them so exact? Or were they just that much off spec. Again, thanks for the writeup.

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Burnrider;

From all that I've read, you shouldn't lap the valves, that is if they are stock. The lapping removes the coating on the valve face. Seems like you could do the same check without the lapping compound.

Thanks for taking the time to write up the procedure.

Ride on

Brewster

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I did not replace the valve springs. If I did it again, I would have replaced the intake valve springs. I got this info from the 250CFR forum. It seems Honda has weak valve springs from the beginning, don't know about Kawasaki. Maybe Brett or Brandon can tell us what they did.

Shums- My local dealer said his shims were labeled in fives.

(ie. 285, 290, 295) when I went to his shop, I measured some intermediate sizes as well from his stock (ie 284, 287)

My own idea is to shim it as close to maximum allowable as possible, within that "five" range. I did not sand the shims. If your local dealer has a lot of used shims, I'll bet with a few minutes, you can check through the plastic parts box and find slightly different sizes in one labeled slot, just from wear.

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Burnrider;

From all that I've read, you shouldn't lap the valves, that is if they are stock. The lapping removes the coating on the valve face. Seems like you could do the same check without the lapping compound.

Thanks for taking the time to write up the procedure.

Ride on

Brewster

I would agree with you Bruce. It might be best to use some Prussian blue and a soft scrub cleanser only to show the valve is making contact on the whole perimeter. Even with the very fine compound they sold me, I had a hard time getting a shiny ring on the valve. I used to lap valves on old Briggs and Statton engines when I was a kid, they were soft and you could actually see the new metal. The Kawasaki valves hardly turned another color grey.

I know Bill runs his bikes at higher speed than I do. My gut feeling would be to replace the intake springs and perform some sort of valve 'rub in' however small to show the seal between valve and seat- that would be about it.

The CRF forum had one new item to pursue, engine heat. The guys there are checking out a product called two2cool.com

It's an oil additive of 2 oz. per qt designed to reduced engine operating temp by as much as 35 degrees F. It is not a friction modifier so the clutch is supposed to be okay. It might be something to check out for riders in hotter climates where engine heat is a factor. I was checking it out for the single track 1st and 2nd gear exploring we get into. The bigger KTM's will start overheating. I've heard 400cc bikes and above should not idle. Kill the bike and use the electric start rather than idle it very long.

Something we can investigate in the future. The valve issues go deeper than materials and rpms.

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