Private shop and dealer can’t figure out this engine sound. The private shop had the engine open to look at the piston and cam bearing, no luck

dealer wants to open the engine but says that will be $1k+ just to take a look.

any ideas?

https://youtube.com/shorts/H7NwIcHzKu0?feature=share

 

Yes, don't let the dealer tear the engine down.

If that rattle is around 4000-6000 rpm and or the noise is coming from the right side cam drive your cam chain tensioner has failed. If you look here you will find the fix is to go to a manual tensioner. I know, a couple members here contacted me back in 2012 to make the kit for the KLX250 and with one member's help I got the design down and started making them.. I now also own a KLX250 so I can speak from experience too. The KLX250/300 is notorious for cam chain tensioner failure, making a buzzing noise at mid range rpm. So much so that it is my top seller. I've sold a couple thousand of them and have them in over 50 countries around the world. I am sending one off to Ireland tomorrow. As noted, I make them, not buy them and resell. I am a retired industrial tech teacher with an engineering degree and background before going back to teaching, this is my sideline and it's enjoyable to interact with riders all over the place. They've liked the product well enough to post about it and a few have even done Youtube install videos.

The replacement manual tensioner is the easiest and probably least expensive first step, and usually last step, to fix cam drive rattle. It is just getting the engine to TDC compression, then swapping out the tensioners and adjust the manual tensioner per the instructions. No removing any covers and the tensioner will last longer than the bike. The tensioner only needs adjusted if you hear light clicking. I found it would be around every 10,000 miles or more in the 30,000 miles on the KLX650, still not touched the one on my 250 or my Zephyr 550. So don't let anyone blow smoke up your tail about maintenance. You'll have to check the valves more often.

You can find information about my tensioners by doing a search for Krieger Cam Chain Tensioners and I'm usually up near the top of the page. You also can find reviews that way too. Click here to go directly to my site. The instructions for the KLX250 are on the site too. If you can do basic maintenance work on your motorcycles you can do the installation of the cam chain tensioner. The instructions that come with the kit are very detailed. If you want more information you can contact me by email at kriegercct@clems-garage.com My phone number is on the web site too, just do not call before 9:00 am or after 9:00 pm eastern time.

Contact me for the price including shipping and let me know the country where you live to get correct shipping cost.. I use PayPal for most transactions because it protects the buyer and I use the USPS flat rate shipping because it is insured and has tracking. The kits are also on ebay, but I add an extra $3.00 to help cover ebay fees. There also may be some import duties for some countries, they can't be added into my pricing, but buying through ebay they can and do include duties.

Whatever you do, try the cam chain tensioner first., if you want to get some reviews do a search in the forum for "Krieger cam chain tensioner" and see the threads and comments. You can do the same at the ADVrider forum too.