bwellervt

Hey Guys, So, I'm working on my old XS500, this being the same bike I posted about earlier with the missing tappet adjustment screw and bad vibrations. As expected, the screw wound up somewhere bad: the LH crankcase cover. Destroyed the balancer chain, broke the idle shaft bracket into 3+ pieces, and sheared the teeth right off the balancer drive sprocket that is built into the crankshaft. The helpful soul who responded to my last post mentioned that I could run w/o a balancer. Is this a crazy idea? My other, and more preferred option is to replace the crankshaft and get that balancer spinning again. I've already got a replacement balancer chain and idle shaft bracket. Anyone have a crankshaft for my XS500C they could part with for a reasonable price? Thanks in advance for any advice or help finding parts! -Ben

Thanks for your advice Jim! I'll be finding that screw. When I do I'll epoxy it to my keychain as a reminder of the work I've caused myself! --Ben

Pictures as promised... No good happening here.

Whoo Doggy! So, I jumped into a tear down of the left side crankcase cover... Certainly found a problem there. Opened the cover, and found two chains in there. The frontmost chain was intact. Behind this chain was a second chain. This chain is completely destroyed, and the respective sprocket on the crankshaft is done. Still searching for the screw that must have caused this. I've got some pictures to upload after I scrub my hands. The plate behind the rotor is cracked. Anyone know what this is called? Also, anyone have the specs for the thread that is just inside the rotor? I'd like to bodge together a puller and get the old rotor out of the way. Looks like I've got a hell of a project on my hands. Any and all help is appreciated. I'll be posting updates as I get along here. Thanks. --Ben

Hi Jim, Thanks for the reply. I think I'd have to agree... I'll be draining the oil and pulling both covers and the sump. When the bike is warm the oil light remains off (it is working!), no flashing. Current symptoms are the vibration that I mentioned, and poor performance (like one intake valve isn't functioning) after she gets to full temperature. Still puzzled, but getting the engine apart might reveal the solution. That screw can't be doing anything good in the motor. Thanks again. --Ben

Hey All, My first post here. Thanks for having me. My bike is a '76 XS500C. BACKGROUND: So, down to business: I recently had a break down on the way up a twisty mountain road here in VT when I shifted into a false neutral between 3rd and 4th during a pass. Over-revved the motor, and blew out 3 of the 8 valve tappet adjustment screws on the rocker arms. Limped her up and down the mountain, got closer to town, tire locked up as expected. Grabbed clutch and coasted her into a country store to call a buddy. FIRST STEP: This was all two weeks ago. Since then I pulled the valvecover... Found 2 of the 3 adjustment screws, and 3 lock nuts... That's right, 1 screw is MIA in my mill. Fished and fished, drained the oil, flushed and flushed again. No screw has surfaced. I found a slightly longer adjustment screw from a more modern Yammy to fit. Slapped it all together. Set clearances x8 valves. Locknuts tightened down good. (Can't fit my torque wrench in the tight space, though!) Valvecover back on, new oil filter, new oil. PROBLEM: Started up the XS after putting her back together. Sounds great. Some valve noise, but sounds like everything is working as it should. The bike starts easily and quickly now. After warming the bike up, I took her for a rip down the street... At 5500 - 6500rpm, the motor produces severe vibration. Enough to numb the hands almost instantly. SUSPECTED CAUSES: - bad job setting valve clearances (doesn't seem too likely to me) - bent valve(s) - balancer issue (Is that part of the balancer I see through the oil fill? If so she ain't moving with the motor!) - loose motor mount Any input will be greatly appreciated! The warm-weather riding season is short in Vermont, and I want to get out and ride. Thanks a lot. --Ben