Cam chain tensioner bad or chain stretched?
  • Märt
    Posts: 2
    Joined: Sun Jun 06, 2021 2:20 am

    Cam chain tensioner bad or chain stretched?

    by Märt » Sun Oct 03, 2021 1:53 am

    Hi everybody. So I have a problem. I was riding one day, turned the bike off, rested a bit and when I turned the bike back on, it had a very gnarly gluncking, metal on metal sound, not high pitched, but something like nuts being dropped onto metal. (Idk). So I did some reading, that a bad chain or tensioner can cause this. So, I took the tensioner out, it goes out all the way in and goes out by itself, but when I put it back in, it's almost flush with the cylinder. Is my chain stretched?.
    I don't know hot to add images on phone, currently don't have my pc with me.
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    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Cam chain tensioner bad or chain stretched?

    by JimDirt » Mon Oct 04, 2021 8:18 am

    Welcome to the site !! \:D/

    I guess the first question is ..... What bike are you working on ??? (model and year)

    Next would be , do you know the history of the bike ?? , did you buy it new ?? , and if so (the info on what year it is would pertain to this) has the timing chain ever been replaced ?? , if it is a MX bike , do you know how many hours are on it and what was the actual maintenance that has been done to it ?? , if you have a lot of time on the bike , it is best when you are replacing the piston for routine maintenance , that would be the time you replace the timing chain as well , as it is a "wear item" just like the drive chain , it will stretch over time , especially if the bike has been raced or abused

    It could also be the the chain guides are worn as well , as that is what the tensioner actually pushes on , as opposed to the chain itself .... Also look closely at the tensioner itself again , it could be broken on the housing , and when the tensioner piston is extended , it may be going sideways when pressure is applied to it , allowing the chain to be slack .....


    The next thing to do is to pull the valve cover (again this depends on what bike it actually is) , and pushing on the chain itself from the top while the tensioner is in place , and also rotating the engine by hand back and forth to see if the chain movement is delayed from the actual movement of the crank , in other words , if the engine moves 1 inch in rotation , but it moves a 1/2 inch before the top gear moves , this would indicate the chain is stretched and has massive slack ....

    To add a image , you need a hosting site , like IMGUR or something , upload your pic to it (create a account first) then copy the link to the pic , and paste it in your post , or for a video , like from YouTube or something , just copy the link to the video itself , and add it to your post , if you copy the embedded Code the video itself will show up in your post
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho
  • Märt
    Posts: 2
    Joined: Sun Jun 06, 2021 2:20 am

    Re: Cam chain tensioner bad or chain stretched?

    by Märt » Wed Oct 13, 2021 5:08 am

    Hi, sorry for the late reply. I have a 2008 crf450r, bought it used, running, started 1-2 kick, cold or warm, its a mx bike, but I doubt it was raced because the last owner rode it for 10hours, it had worn grips and a broken holeshot device. Don't know about previous maintenance. I've ridden it for 40h, and have only changed oils, filter and cleaned the air filter, no engine work. I also had it underwater once for 5-10 min, about cylinder deep, no water got in the airbox, rode it straight home for 10-15 min after that and changed oils, filter. That was approx. 30h ago. about 5 h before the "knocking" sound, it begin to start 3-5 kick, when I checked the valve clearance(now, when the knocking sound started): Exhaust. 0.29mm(left) and 0.33mm(right), Intake. 0.03mm didn't fit in, neither left or right, so 0.0 I'm guessing. Im certain I checked the clearances right (did it like 20 times).

    pics, https://i.imgur.com/3vkGeca.jpg , https://i.imgur.com/P1WO9mv.jpg

    The chain tensioner doesn't move left/right, up/down, so I would assume its not broken in the housing. It moves out by itself.
    When I take a look at the cam chain, I can visually see that its not tight. So a new question, could i have done any harm to the bike because the chain is worn. e.g the valves hit the piston etc.

    A question about the valves, what do I need, if i have 1.2mm shims (the smallest as I've googled) and its at 0 clearance, do I need a new head, valves? what do i need to do?

    And now something that's probably dumb as ., could I add washers under the cam chain holder thing, like 0.2mm thick washers, as I see that would raise the cam, and eliminate the 0mm valve clearance issue. BUT, the cam chain would be tighter, i doubt what would be a issue, because I lift it so little. But, I think the part where the valves meet the head (idk what its called) is already worn, and the washers would be a not-so-worth-it fix. Am I wrong?

    Sorry for complicated explanation and bad english.
  • User avatar
    JimDirt
    Posts: 4406
    Joined: Sat Nov 25, 2006 6:31 pm

    Re: Cam chain tensioner bad or chain stretched?

    by JimDirt » Wed Oct 13, 2021 2:43 pm

    No you do not want to put washers under the tower ..... generally when the valves close up , you have a 1.20 shim , that is the smallest , if one of those won't bring you back to spec (0.005) , then you need new valves/a valve job .... the 08 is a great bike and is the best of that platform series ...... so it is worth keeping , unless you have the budget for a brand new or newer model year ... then I would go new (I love my 2020) ...... it will cost a few hundred or so , or a bit more to get it back going again , depending on how severe the wear is and what actual parts are needed , some dealers will say replace it all and want $1500 or more to do it , generally you do not need $1500 worth of stuff to get it going again and making it last ... , you would need the valve seats cut , new Intake valves installed (usually the Exhaust valves hold up and do not go out like the Intakes do , so most of the time they do not need replaced ) , gaskets and a new timing chain ... that's about it ... $300-$700 should cover that including labor , or save more and do the install of the head/timing chain yourself (you would need to purchase the correct flywheel puller for your bike) (you can buy a redone head from here , or have yours redone for about $500-$800 give or take)

    https://www.crfsonly.com/catalog/index. ... th/258_280

    What I would highly recommend is Stainless Intakes , it will take your valve maintenance down to about 1% or 2% rather than 50% ... I put Stainless Intakes in my 06 450X , in 06 ... I have not had to adjust them since ... The biggest killer of valves is dirt getting past the air filter ... this is the #1 cause of valve failure ... so if you decide to fix the bike , keep the air filter clean and well oiled with a good quality filter oil , and buy several filters (I have around 7 filters for my 2020 450R , and about the same for my 450X) and you can avoid this issue if not indefinitely , at least for a long time ...
    2020 CRF450R
    2006 CRF450X
    Image
    Weiser , Idaho

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