Hi everybody,
I have discovered that both cam lobes (all four) in my 12,500 mile '07 are well below the remove from service specs in the manual and the auto tensioner was out about 75% so the cam chain is probably due for replacement too. The manual states that if the cam chain needs to be replaced, the cam sprockets and the crankshaft should also be replaced! I checked the parts diagram and sure enough, there is not a separate sprocket on the crankshaft for the cam chain. So, my question is...what have others done in this situation (other than replacing the crankshaft)? It seems to me that I should either replace the cam chain, use the existing cam sprockets, and leave the crankshaft in service or replace the cam chain, also replace the cam sprockets with new parts, and also leave the crankshaft in service. I truly do not see the need to replace the crankshaft unless i see appreciable wear or damage to the cam chain drive sprocket on the crank once I remove the primary gear and have good visual access. However, opinions from those who have experience will certainly be appreciated. Thanks, and enjoy your holidays!

 

Are you reposting after three years? Click here cams worn out ? Regardless, here is my answer.

The auto tensioners are junk. There is no way the chain is worn out with 12,500 miles. The HyVo chain is known for strength and that they run quietly. I have the same kind of chain on my KLX650 with 35,000 miles and they are just fine. My 20,000+ mile KLX 250 has the original chain in spite of the tensioner not functioning properly. If you look at the tensioner you will see a pattern of wear on the plunger teeth, on the underside you will see the shaft is polished from pushing in and out tens of thousands of times, every time the engine decelerates. The chain goes under tension on the back side on deceleration, the pressure will cause some tensioners to snap back over the tooth, rounding the tooth slightly and allowing it to happen easier and easier. Mine was pushing in about .375".

Replace the cams and put in a manual tensioner, I have been making the tensioners for about 12 years now after having riders here request them. They do the job quite easily, seldom requiring any adjustment. It has been around every 10,000 miles for my 650 and then takes about five minutes to do so.

 

Thanks, and no, this is for my 2007 model. That was for my 2009 which is long gone. You are probably right though and I actually have not measured the cam chain for wear. I was just assuming it was worn due to the position of the auto tensioner. I did purchase your manual tensioner for my 2009 and I should probably get one for the 2007 just to increase the bike's reliability as I invest in a complete top end overhaul. Please refresh my memory about how to order your part for the bike-thanks, Mike.

 

I will PM you my email address. I still don't understand how/why a cam would wear out in 12,000 miles And it has happened twice with you. I'd have a reputable dealership service department check them out for wear, can't cost more than a couple bucks if they even charge you for it. There is no way I'd replace the chain or sprockets. Even a common drive chain that is exposed to the elements doesn't wear out that fast. If the cams check out good I'd say put them in, put in a manual tensioner (that is probably lower cost than the side cover gasket if you swapped out chains) and run it.

 

Well, I don't know that much about the history of this bike's maintenance as I didn't get it until it had about 11,500 miles. I measured the cam lobes myself with my fairly new digital caliper but I did not check them with another measuring tool (or one that has been officially calibrated) to verify. I will check them against one of the calibrated tools at the hangar when I return there on Wednesday. I will also measure the cam chain for wear (measure the distance between x amount of pins while stretching the chain) to confirm whether it is actually worn. After what you mentioned about how long they usually last, I now doubt it needs to be replaced. Thanks for your advice-I appreciate it.