Hey there...gonna jump right in here (after introduction of course!) I just purchased a 1978 Yamaha xs650 and it runs fantastic, but.....there is a little gremlin inside trying to burst his way out with a mini jack hammer. I searched youtube and low and behold, there was another xs with the exact same sound. Here is a link posted below, hopefully you guys can help me narrow this one down for me. Thanks in advance!
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motor gremlins trying to escape with jackhammer
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pyrocentric
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The most common source of noise from these are a worn plastic front cam chain tensioner slipper. The cam slaps the aluminum slipper backing causing a "tink tink tink". If you drop the oil pan you'll likely find pieces of plastic and aluminum filings.
The only fix is to pull the engine and tear down the topend. The jugs don't have to be pulled, but you'll probably disturb the base gasket so buy a complete gasket kit anyway.
This is all assuming you don't have more serious engine damage, but generally it's just the cam chain slippers.
Before you do anything though, adjust the cam chain tension and valves. Service manual can be found here: http://dejaviews.org/xs
The only fix is to pull the engine and tear down the topend. The jugs don't have to be pulled, but you'll probably disturb the base gasket so buy a complete gasket kit anyway.
This is all assuming you don't have more serious engine damage, but generally it's just the cam chain slippers.
Before you do anything though, adjust the cam chain tension and valves. Service manual can be found here: http://dejaviews.org/xs
yup, tighten the cam chain tensioner and check the valve settings. that cleared up all the noise in my bike. you don't have to take the oil pan off you can check the oil filter on the right side of the engine and see if there are black chips in the filter screen. if so then welcome to the club! i just tightened mine up and rode it for the summer. i'll fix it this winter. of course that isn't recommended.
pyrocentric
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My engine is a 1978 and doesn't have a locknut either. Just a big acorn nut to cover it once you're finished.
Also, to adjust the valves, make sure the engine is dead cold. Pull the left engine cover, turn the engine counterclockwise with a wrench to top dead center...There's a mark on the rotor and a T on the case. Pull the valve covers. Peek in there with a flashlight and figure out on which side the camshaft isn't pushing the valves. Adjust the valves on that cylinder. Intakes should have .004", exhaust .006". Turn the engine over again to the T mark, repeat for the valves on the other cylinder.
http://www.650central.com/fsetting_the_valves_on_an_xs650.htm
Also, to adjust the valves, make sure the engine is dead cold. Pull the left engine cover, turn the engine counterclockwise with a wrench to top dead center...There's a mark on the rotor and a T on the case. Pull the valve covers. Peek in there with a flashlight and figure out on which side the camshaft isn't pushing the valves. Adjust the valves on that cylinder. Intakes should have .004", exhaust .006". Turn the engine over again to the T mark, repeat for the valves on the other cylinder.
http://www.650central.com/fsetting_the_valves_on_an_xs650.htm
if you are gonna get way up in there and do your bike the right way i recommend buying a new oil pan and filter gasket and an oil and sump filter. if the PO didn't have the wherewithal to keep his cam chain tight i doubt if he ever changed the sump filter. this will, of course, dump all your oil out so get three quarts of 20w50 and you'll be set.
Yup the sump filter is nearly guaranteed to be DOA due to the screen tearing. I pulled the sump filter on a nice 5600 mile bike. Screen torn. Made a copper cover for that area and epoxied it in. Rumor has it the MikesXS filters (screens) are just as bad as the stockers.
my mikesXS screen has held up fine so far and when i pulled the oil screen and sump screen there were so many black chips and crap in there i was shocked. amazingly though the old sump screen was in good shape. i replaced it anyways. oh yeah and when i pulled the oil pan there was a two inch section of my front cam chain guide's teflon sitting in the bottom of the pan. i was like, "heeeeyyyy, that's not where you belong."
To be clear I speak only of the sump screen. I have not heard of issues with the side accessed screens. One problem is the side screen is AFTER the oil pump so anything you find there has already enjoyed the scenic tour through your oil pump.
If it don't run for at least 10 minutes cluck it.
If it don't run for at least 10 minutes cluck it.
