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Top end tapping sound

Discussion in 'The Garage' started by Maxx650, Jul 26, 2012.

  1. Maxx650

    Maxx650 XS650 Addict

    Hey everyone,

    I've got a pretty noticeable tapping (knocking?) sound coming from my top end. It's a 79 special - mostly stock, pamco, performance airpods. Installed oversized pistons in January and had the valves recut and seated by my mechanic.

    I've taken it to my mechanic who is very good with old yams and he said that the cam chain is adjusted correctly and said he adjusted the valves but I still have this knocking noise..

    I haven't done these things myself so I don't know how the cam chain or valves actually are right now and have only taken his word. Here's a youtube video of it idling. When I'm riding it I can sort of "milk" the tapping sound between usually 3-4K rpms.

    Right now I'm assuming it's the valves. Any thing else it could be? Piston slap?

    I've watched the videos posted here on adjusting valves and would like to take a look but I don't have feeler gauges so I'll need to buy some... Would love any insight.

  2. FathomYourFears

    FathomYourFears XS650 Member

    Sounds like a mix between cam chain and valves to me. YMMV.
  3. Get some feeler gauges.
  4. I'm thinking that sounds like your camchain tensioner is missing its damper. My engine was missing that damper as well. I had a spare copper washer that I drilled to fit the tensioner shaft, and that became my damper. The copper washer quieted my engine.

    Mikesxs sells them I believe................with some rubber on theirs.

    Take out your tensioner and have a look. If its missing you could just use a copper washer as I did.

    Attached Files:

  5. Ghetto

    Ghetto Bob it!

    Man that would drive me nuts!
  6. Maxx650

    Maxx650 XS650 Addict

    Thanks retiredgentleman, I'll take a look at this. I looked around but couldn't find out for sure - will I need to pull my engine to pull out the tensioner? Or will it all slide out after loosening that nut?
  7. KeithB

    KeithB XS650 Addict

    I have a similar problem and will check for the damper washer.
    Is it supposed to go between the spring and adjuster sleeve?
  8. 5twins

    5twins XS650 Guru

    Like so .....


    You can pull the adjuster screw/spring/plunger assembly right out of the housing, motor still assembled and installed. Just remove the acorn nut cover and loosen the lock nut if you have one.
  9. Maxx650

    Maxx650 XS650 Addict

    Thanks 5Twins! I'll pull it out this weekend and take a look.
  10. DeftQuiver

    DeftQuiver XS650 Enthusiast

    Quite honestly, I've lost all trust in mechanics lately... Although I'm pretty new to the site, I've come to realize that guys like 5twins and XSLeo know these bikes like the back of their hands, and are happy to help.

    I highly recommend you use the Tech section. You can pretty easily take care of whatever you need to do using just the information found here (although I recommend a manual) and basic tools. As a side note... One tool I highly recommend is a torque wrench that can measure for low torque. You'd be surprised at how light those valve cover bolts are supposed to be torqued. :doh:

  11. chief01

    chief01 XS650 Addict

    Had a very similar noise. It was most pronounced at 2500-3000 rpm. Adjusted tensioner still no change. Finally replaced the tensioner with a hydraulic one from Germany, no change. Last week decided to change the oil and noticed that the oil was really black and full of a thick sludge in the bottom of the sump pan. Decided I needed to pull the engine. Got it out pulled and removed the valve cover. Cam was burnt, I mean black and blue burnt. Lobes were worn and pads on the rockers had grooves in them. Checked the oil tube to see if it was blocked, and it wasn't. All I can think is that the oil pump was not pushing oil. I couldn't believe that it had been running and I was doing 70mph the previous day. Don't want to alarm you but your might want to take a look at you oil.
    Last edited: Jul 28, 2012
  12. Maxx650

    Maxx650 XS650 Addict

    Chief01 - that is my biggest worry.. try to rule out some other things before I pull the head in winter.

    Also before I pulled off the locknut I checked the movement of the rod and it seemed ok - it was pretty flush with the nut and turning the engine with the kick showed about 1mm of movement which I've read is ok.

    Ok - I pulled out the assembly... and I believe the damper copper washer is indeed there. So I think that means my tensioner is ok. Any idea where to move on to next? There's a yam dealership up the road so I think I'll buy some feeler gauges and learn to check my valves. I do think the noise is coming from the right exhaust tappet cover (is that the right term?)

    Thanks again guys.

    P.S. Another question - chief01 you may be able to answer this.. how do I check that my oil pump is working fine without pulling the engine? Let it idle with a valve tappet cover off? Unscrew the top of the oil pump tube (on head of engine) and see if it makes a mess?

    Attached Files:

    Last edited: Jul 28, 2012
  13. ReycleBill

    ReycleBill Part Time Tyrannicide

    Sounds very much to me as if a valve tappet has loosened up and backed out of its threads altogether.
  14. 5twins

    5twins XS650 Guru

    Your adjuster assembly looks correct and appears to have the copper washer on it. Your cam chain adjuster method however is not the best. Easiest and best method is to adjust the chain while the engine is idling. Turn the adjuster in/out until you achieve the required 1 to 2mm of in/out movement on the rod. If the rod stops moving, you've set it too tight. If the movement is more than speced and you get a rattle like a loose valve, it's set too loose. Experiment with it and you'll see. Tighten it up too much and you'll see the rod stop moving. Loosen it way up and you'll start to hear the rattle.

    Yes, get some feeler gauges. Go to an auto parts store for them, they'll likely be cheaper. Set your intakes to .003". The spec for your model is .004" but they'll tick at that setting most of the time.
  15. KeithB

    KeithB XS650 Addict

    Thanks for the pic 5twins
  16. Maxx650

    Maxx650 XS650 Addict

    Thanks for that 5twins, I just did it on a warm engine while idling and I could create and now understand the noise of an untensioned cam chain - however my tapping is still a separate sound, much sharper and less rattle, and I think higher up. I'll be checking my valves tonight or tomorrow depending on how much my bike cools today.
  17. ReycleBill

    ReycleBill Part Time Tyrannicide

    Be sure to let us know what you find.
  18. Maxx650

    Maxx650 XS650 Addict

    I let my bike cool for about 9 hours (only idled for a few minutes to look at tensioner this morning).

    Got some feeler gauges and after watching littlebill31's excellent videos on checking valve clearances about 30 times I went through it... and everything seemed correctly adjusted.

    Tappets and rockers look normal and sturdy? A very very very small amount of 'give' on the rockers when at TDC / compression stroke which I also read could be normal [link].

    Left intake: .0025" = Go; .003" = Go (.004" = No Go)
    Right Intake: .0025" = Go; .003"= Go (.004" = No Go)

    Left Exhaust: .006" = Go (.007" = No Go)
    Right Exhaust: .006" = Go (.007" = No Go)

    I didn't adjust anything as that all seemed right to me. The link I provided above says the intakes should be set at .0024", however .0025" and .003" work for me and since 5Twins said .003" I wasn't too concerned.. should I tighten to just allow .0025" ?

    If these valve clearances look ok then what next?! Possibly my fear that the cam / lobes have worn down? Loose header? I just wish I knew!

    If the next step is to pull the header I may have to try to find another mechanic around town / take some time to pull the engine and bring it to my dad's place in Dallas since I live in an apartment complex and don't have the workspace to open an engine.

    Thanks for all the help so far guys.
  19. Maxx650

    Maxx650 XS650 Addict

    An update:

    I rode my bike to work today (50 miles round trip) and noticed that my tapping while riding has significantly decreased. I can not 'milk' it as easy as I was able to before. Also I can hardly hear it, if at all in 3rd, 4th, and 5th gears. I can still hear it on very low rpms in 1st and 2nd gear while climbing up in speed until it goes away.

    So I'm thinking maybe it is my cam chain tension as that's the only thing I've really changed? I can still hear some tapping at idle which is why I thought I had made no difference last week when I changed the tension - but I only just now rode it and realized there is a difference for the better... But still not 100% there.

    I'm going to continue adjusting my tension to see if I can get a better idle sound.
  20. Maxx650

    Maxx650 XS650 Addict

    Still not sure really where I'm getting with this.

    I think my bike sounds better when idling as compared with the first video I posted (input would be nice), however I can still milk the sound pretty well when I ride now.. I have since tried loosening the tensions a little since my last post where I described the sound being better while riding but still noisy at idle.

    Let me know if you think it sounds better compared to the video I originally posted in OP.


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