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Cam chain rattle

  1. #1
    Junior Member PaulB's Avatar
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    Cam chain rattle


    The bike is a 1987 Ninja 750R. I've got a rattle at low-mid RPM that comes in and out. (Can't tell if it's there at high revs, due to motor/exhaust noise).

    It has made this noise most of the time I've owned it (bought it this spring, about 7K miles ago). The bike runs well, extremely smooth.

    I just adjusted the valves. A few were on the loose side, so I was hoping that was the problem. Starting it up once the bike was all back together, it idled quieter than I'd ever heard it. It was beautiful. But when I revved it up the rattle was still there, and within a day it was back at idle too. WTF?

    The cam chain tensioner is the automatic mechanical type. I may pull it and reset it, though I have to remove the tank & carbs to do that.

    I'm also wondering whether maybe the chain guides inside are worn now after 15 years and 40k miles.

    Anyway, ideas are most welcome.

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    Last edited by PaulB; 08-02-02 at 01:59 PM.

  2. #2
    Junior Member PaulB's Avatar
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    Cam chain rattle

    So I'm fucked then?

    I was so impressed by the mechanical advice I've seen here that I thought for sure somebody would have some hint for me...

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  3. #3
    Freak Posting snowborder's Avatar
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    Cam chain rattle

    We use the Rochester Motorsports fix for everything like this. It is probably the cams that a scorn.

    Degs... Stones? ideas

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    2001 RC51!!!
    2007 Husky SMR 510 - no longer... blown tranny

  4. #4
    Junior Member PaulB's Avatar
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    Cam chain rattle

    I looked the cams over pretty well when I did the valves. I saw a little pitting on some of the cam lobes (sides, not centers for some reason) but I'm not a very experienced cam-inspector...

    I'm pretty sure I'm not up for paying a dealer $800 or whatever to tear open the motor and replace the tensioner guides...

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  5. #5
    Freak Posting snowborder's Avatar
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    Cam chain rattle

    I was kidding about the scorn cams, ie that is Rochester Motorsports fix for everything. Bike wont start, scorn cams, Headlight out scorn cams.

    Sounds like you've been all over it.

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    2001 RC51!!!
    2007 Husky SMR 510 - no longer... blown tranny

  6. #6
    Kosher Assassin Stoneman's Avatar
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    Cam chain rattle

    I've owned two 1985 GPz 750's. The 'detonation' was a sound in those things that I could never really get used to. But I was assured over & over & over again that it was normal with those bikes, and there was nothing to worry about. Sure it isn't just something like that?

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  7. #7
    Just Registered TLRMan's Avatar
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    Cam chain rattle

    Paul,
    Are you hearing the rattle getting on the throttle? (detonation due to carbon build up in cylinder) BTW detonation or knocking and pinging is BAD!!!!! Jay!

    or is it making the noise off the throttle or cruise? (wrist pin rap)
    You adjusted the valves, so we ar gonna rule that out..are you sure all the lash adjustments are correct?

    does the rattle sound like it's happening at 1/2 the speed of the engine? (valve related)

    Pitting on the outside wear areas of cams are norm.

    Does the noise go away when you hit the clutch when the bike is in neutral? (trying also to eliminate drive chain slap on chassis parts)
    (If this is the case it's back lash in the gearbox, or bearings)

    Another test to see if the tensioner is sour or if the guides are worn, is that the tensioner will be all the way out of it's bore.
    Check backlash on the cam chain too. Move engine crank to take up slack, then rotate backwards to see how much the crank turns before the cams do....careful, some bike manufacturers don't recommend turning the engine backwards too far, supposedly will damage the tensioner.

    It's tough for me to tell when the Tiller is making more noises than usual, cause it's always rattling!

    Either that, junk it and get a Gixxer 1000!

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  8. #8
    Kosher Assassin Stoneman's Avatar
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    Cam chain rattle

    Originally posted by TLRMan
    BTW detonation or knocking and pinging is BAD!!!!! Jay!

    Couldn't have been all that bad. The first GPz I had is still alive and kicking and the only thing the current owner has ever done to it is change the erl & filter, and replace the tires now and again. The second one I had, had over 53,000 miles on it when I got ridda it. Then some dude rode it around for a coupla years before scrapping the thing all together. But that was because he dropped it a coupla times and the plastic and shit was shitty...

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  9. #9
    Just Registered TLRMan's Avatar
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    Cam chain rattle

    A little short pinging is OK, My tiller does it when I whack the throttle with the clutch in. Maybe detonates a couple of times.
    But if it's rattling away, it's not good!
    That Kaw must of had really thick piston crowns...LOL
    Will have to write a post on Auto ignition, detonation sometime....

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  10. #10
    Junior Member PaulB's Avatar
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    Cam chain rattle

    Wow, thanks for all the responses. You guys rule.

    I know it's hard to give advice without hearing the bike or knowing what I've checked. I can rule out a few things:

    It's not drivetrain. It's not particularly an on-throttle or off-throttle thing -- I hear it mostly at idle. It's also not detonation or any other kind of combustion noise, at least not like any I've heard. It kind of phases in and out -- sometimes it's not there at idle, sometimes it is.

    Also, the fact that it was quiet briefly after the valve job makes me pretty sure it's valvetrain related.

    The chain looked really good when I had the cover off doing the valves, and had no detectable slack. I did turn the motor backwards just a tad, and didn't notice any backlash though I wasn't really looking specifically.

    It looks like pulling the thing apart, resetting the cam chain tensioner, and checking what I can check seems like a good idea.

    Thanks again. I'll post if I learn anything.

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  11. #11
    Junior Member PaulB's Avatar
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    Cam chain rattle

    Followup question, since this is really what I'm thinking about:

    I'm going on a long trip in September. Assuming that this "chuckachuckachucka" is the cam chain, would it be foolish to leave it as-is and deal with it when I get back, or am I playing with fire?

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  12. #12
    Just Registered beet's Avatar
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    mine does the same thing unless its real bad i'd go

    i think there was some guid troble on the first ones but i think they straitened it out

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  13. #13
    Junior Member Dave's Avatar
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    Cam chain rattle

    its sounds like a wrist pin to me

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  14. #14
    Junior Member PaulB's Avatar
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    Cam chain rattle

    Urk. Time to have my (good) mechanic check it out I think. After I reset the cam chain tensioner for good measure.

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  15. #15
    Junior Member PaulB's Avatar
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    Cam chain rattle

    I fixed the problem -- turns out the cam chain tensioner wasn't quite holding its position. With a replacement costing $80 and not even in stock at my dealer, I did a crafty little rebuild (details not worth explaining) that fixed the problem. The bike sounds great and I'm psyched.

    Thanks again for the earlier advice.

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  16. #16
    Just Registered beet's Avatar
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    you found a (good) mechanic

    Originally posted by PaulB
    I fixed the problem -- turns out the cam chain tensioner wasn't quite holding its position. With a replacement costing $80 and not even in stock at my dealer, I did a crafty little rebuild (details not worth explaining) that fixed the problem. The bike sounds great and I'm psyched.

    Thanks again for the earlier advice.

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