Cam chain tensioner modification, mechanically inclined only
Posted: Fri Mar 25, 2005 11:18 am
If anyone hears their cam chain rattling at idle and low rpm, here's a method I used to modify mine for a few more miles before getting a new chain. First, make sure the carbs are in synch, as this will aggrivate the noise if they aren't.
Older Japanese bikes, especially kz's switched to an automatic cam chain tensioner to reduce the amount of maintenance and adjustment necessary. The problem is, the automatic tensioners have about 1/2 inch less adjustment capability than the old manual ones.
Fortunately they are easily removed. Many of the kz models can be swapped with the manual ones from an earlier year, but you lose the automatic feature. What I did instead was remove the automatic one and disassemble the parts. BTW, do not turn the engine over with the tensioner removed!! To disassemble this, a set screw must be removed. The purpose of this screw is to limit travel of the tensioner, preventing it from springing into the engine. After you modify the plunger, this screw is used to hold it in place during installation. More on that later.
I used a drill bit of the appropriate diameter, and welded it to the small end of the plunger, extending its length. Then I cut the bit off 1/2 inch beyond the weld. Now you have a longer plunger. You must grind a flat surface into it to match the original area for the set screw. This will be self-explanitory when you see it. Just leave enough of the drill bit unground to leave a lip for the screw to catch on. smooth everything to prevent catching after installation. When you reinsert the plunger and springs, there will be a ball-bearing cam you need to hold in place aginst the tension of the larger spring while you tighten the set screw. This cam is to prevent loosening of the adjustment, and is what makes the system automatic. Once you've reassembled the tensioner, reinstall it in the engine. Get a new gasket, or make one if the old one was damaged during removal. If you don't put the plunger in far enough, the unit won't seat and you'll have to reassemble it again. No big deal, there are hardly any parts in there, just make sure you hold it until the screw is tight. once the unit is reinstalled and both bolts are tight, slowly unscrew the set screw just enough to hear the tensioner snap against the chain follower. That's it. your tensioner will now take up cam chain slack until it runs out of length. By that time, you will need to replace the cam chain.
I didn't include pics, because I don't think most guiys will do a job like this unless they have enough mechanical ability and welding confidence to do it. If you have those two things, you will find it self explanitory after reading this and taking the tensioner out.
If you have to ask "what's a cam chain tensioner?", you probably shouldn't try this.
Older Japanese bikes, especially kz's switched to an automatic cam chain tensioner to reduce the amount of maintenance and adjustment necessary. The problem is, the automatic tensioners have about 1/2 inch less adjustment capability than the old manual ones.
Fortunately they are easily removed. Many of the kz models can be swapped with the manual ones from an earlier year, but you lose the automatic feature. What I did instead was remove the automatic one and disassemble the parts. BTW, do not turn the engine over with the tensioner removed!! To disassemble this, a set screw must be removed. The purpose of this screw is to limit travel of the tensioner, preventing it from springing into the engine. After you modify the plunger, this screw is used to hold it in place during installation. More on that later.
I used a drill bit of the appropriate diameter, and welded it to the small end of the plunger, extending its length. Then I cut the bit off 1/2 inch beyond the weld. Now you have a longer plunger. You must grind a flat surface into it to match the original area for the set screw. This will be self-explanitory when you see it. Just leave enough of the drill bit unground to leave a lip for the screw to catch on. smooth everything to prevent catching after installation. When you reinsert the plunger and springs, there will be a ball-bearing cam you need to hold in place aginst the tension of the larger spring while you tighten the set screw. This cam is to prevent loosening of the adjustment, and is what makes the system automatic. Once you've reassembled the tensioner, reinstall it in the engine. Get a new gasket, or make one if the old one was damaged during removal. If you don't put the plunger in far enough, the unit won't seat and you'll have to reassemble it again. No big deal, there are hardly any parts in there, just make sure you hold it until the screw is tight. once the unit is reinstalled and both bolts are tight, slowly unscrew the set screw just enough to hear the tensioner snap against the chain follower. That's it. your tensioner will now take up cam chain slack until it runs out of length. By that time, you will need to replace the cam chain.
I didn't include pics, because I don't think most guiys will do a job like this unless they have enough mechanical ability and welding confidence to do it. If you have those two things, you will find it self explanitory after reading this and taking the tensioner out.
If you have to ask "what's a cam chain tensioner?", you probably shouldn't try this.