Cam chain guide
 

How do I get to the bolt holding the rear cam chain guide?

Just for future reference the right cover has to come off. I have the 351 and my cam chain is stretched out of specs. Timing marks were off by half a tooth either way I moved the cam gears. I had a severe knock when cold. The total miles are only 8500 miles. One of TNC old post says his motor was knocking like a rod but turned out to be the cam chain.

Heavy rattling is also often a sign the cam chain tensioner has failed. You see, TNC worked with me back in around 2009 in making the first KLX250/300 manual cam chain tensioner. He still has the KLX with that tensioner in his bike, but now rides a CRF450 more. I have sold several thousand of the KLX tensioners in the past 16 years, around the world, riders learning of it from this and the ADVrider forums.

A half tooth is only a few degrees and it's highly unlikely that the HyVo cam chain "stretched" out of spec in 8500 miles. That "stretch" is pin wear and that style of chain is used in numerous applications because they don't wear fast and they run quiet. Being in a constant coating of oil from the environment of the head and crank case the chains are extremely well lubricated. Ninety nine times out of a hundred (probably even better) the problems with cam drives are fixed with a manual tensioner. The reason why TNC and some others got with me about making the KLX250 tensioner in 2009. I was making them for the Kawasaki in-line 4s and for the KLX650 at the time.

One plus. Going to a tensioner to deal with cam drive noise is the lowest cost least difficult first thing to do. No engine tear down, just an easy swap of tensioners. The experience other riders and I had with the adjustment is that it will be less often than checking valves and a light ticking indicates that an ajdustment is due. That would be around every 10,000 miles on the KLX650 and even longer on the in-line fours.

I wouldn't bother with the guide unless you KNOW it is broken or worn out. in the cam drive the first thing to fail is the "automatic tensioner". The KLX250s have a history of tensioner failure that is easily dealt with by replacing the OEM tensioner with a manual tensioner at about 1/3 the price and it will work for the life of the engine. I personally bought a 250 a couple years after I started making the tensioners for them. I rode one my brother was buying and liked the light feel compared to my 650.

Like I said, unless you absolutely know the guide is bad, don't bother with it. If the tensioner is bad a new slider will not help. The tensioner is being pushed back and snapping back out over and over as the engine accelerates and decelerates. A new OEM unit might or might not work. My 650 went through two OEM units in less than 15,000 miles. The bike now has 50,000 miles with around 4 adjustments of the manual tensioner I made for it. My Zephyr 550 had one adjustment that wasn't needed after 12,500 miles, I felt guilty and did a re-adjustment that wasn't needed.

Feel free to PM me if you have any questions. If you want to do a search here, do a search for Krieger. It will bring up about five or so pages with posts, mostly with regards to the tensioner.

By the way, here was the first thread where TNC and I started working on the tensioner and I got them done.

Thanks Klx. I do have one of your adjusters on my bike. I replaced the chain and guide but the knock was a leaking head gasket. I replaced the head gasket with another new one from Bill but it was leaking too. No cracks or warping that I can find. It took me all day but I made a copper head gasket and just cranked it up with no water. The knocking is gone (for now). For some reason a small percentage of 351’s seem to have head gasket problems. Upon closer examination the water ports just seem to be too close to the cylinder. Bill has been very helpful over the phone. Hopefully the copper gasket will hold. We’ll see tomorrow.

I just didn't want you to waste time and money with something that seldom has to be replaced and usually only if broken. But i guess trouble shooting takes some steps at times to find the root cause of a problem.

Good on you for being able to create the copper gasket, I hope it does the trick and no leaks. Post up how it goes for you. I'm also curious how the water ports could be an issue. Explain a bit if you can. I'm not familiar with anything like that and would like to learn more. Never know when it might come in handy.

I've used copper gaskets on my drag engines, and I have found that a thin film of hylomar on the gasket should stop it.

thanks man. I’ll keep that in mind if I have to tear it down again

I don't know how you cut the copper gasket, but doing something like that could be extremely accurately done with a laser if laid out in a file the laser can use. Wouldn't be too difficult to do the layout with a scan of the OEM gasket then modify the bore cut. Might be something to have a few cut and then put them out in the forums for other 351 owners.

One thing to remember, the gasket should not be an exact fit. The water jacket joint may have the gasket overlap the opening. That is not a bad thing, it creates turbulence, stirring the coolant, which will aid in cooling. If the passages and mating gaskets and parts were perfect the flow would become more laminar. The coolant flow would draw away less heat, because it is not mixing. The flow on the surfaces would be hotter than the flow toward the center of the flowing coolant.

I learned that a few years back and having done a university class in fluid power, it made total sense. In most flow, like water or air through hoses, the goal is the smooth laminar flow, because speed and volume of the flow is important, like the intake manifold and port as well as the exhaust manifold and port, the smoother surface flow aids in filling and clearing out the cylinder. But with the coolant, speed of flow is not the important part, it is getting maximum cooling, getting more of the flowing fluid to contact and cool the cylinder. That takes "stirring" of the fluid on the surfaces. The turbulence of the relatively slow moving coolant stirs the coolant around, exposing more of it to the cylinder heat improving the cooling.