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Changing Motorcycle Valve Springs.
I have done many posts here at HappyWrench about valve assemblies. You have:
4. Measuring Motorcycle Valve Guides
However, one thing I haven’t covered is changing the valve springs themselves. Just like with changing fork springs, you want to be careful doing this job as you can launch a spring at yourself causing some major damage.
Changing motorcycle valve springs is a very easy job, requiring only a little time, patience, and an inexpensive tool designed for the job (about $20). You should also wear safety goggles and a cushioned pair of gloves.
When should you change your motorcycle valve springs? Well, when they are no longer in specification, of course! Just kidding. Take a look at your manual. Valve springs have a set inside diameter, outside diameter, and length. Generally, as springs wear out, they fall out of specification in terms of uncompressed length. Also if the springs seem tweaked or damaged in any way, you should absolutely replace them.
Below is a picture of a Harley valve spring assembly. Essentially, you have an inner spring (#26) and an outer spring (#25) that are sandwiched between two circular saucer shaped collars (#24 and #27). The valve stem itself comes up out of the valve guide, through the lower collar, up the center of the two springs, and finally reaches the upper collar.
When installed, the only thing keeping the whole assembly together are the two tiny little valve keepers located above the upper valve collar (#24). The valve stem (#28) has a notch at the top. The key is to buy yourself a decent valve spring compression tool. I have one just like that pictured below. At its most basic level, a valve spring compressor is the U-shaped bar with two rods screwed through the end openings. On the end of each rod, you put on one of those hollow looking socket things. The key is to use the biggest socket looking thing for the valve assembly at hand. You want it to sit comfortably and firmly against the upper valve collar and valve face.
Okay, so you have your valve head in front of you as well as the valve spring compressor tool with your two rods and hollow sockets ready to go. Now what?
You unscrew the rods such that you can place the valve spring compressor tool around the valve head. One hollow socket end sits firmly on the valve face and the second one sits firmly on the upper valve collar. Obviously, the valve isnt’ going anywhere, so as you tighten the valve spring compression tool you are simply compressing the springs while leaving the valve in place. As the springs shorten, the valve keepers will come loose from where they are seated. Remove them with needle nose pliers or a tiny screw driver. Put them somewhere safe as you do NOT want to lose them! Finally, loosen the valve spring compression tool slowly. With no keepers in place, the whole valve spring assembly will come completely loose and can be removed.
Place all associated parts in a marked Ziploc back (either intake or exhaust, front or rear). You don’t want to swap things around.
Installation is the reverse of the above steps. Get everything in place, compress the tool until you can get the valve keepers back into position, and loosen very slowly making sure the keepings seat against the valve stem notch. Installation takes a little more finesse than removal, but again make sure you are wearing goggles and gloves. You should be extra careful during the seating process as you don’t want to see a spring fly across your garage.
And that is the story behind changing motorcycle valve springs.
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