Author Topic: Stretched timing belt....?  (Read 2424 times)

Offline LT South Africa

  • Jr. Member
  • **
  • Posts: 79
Stretched timing belt....?
« on: March 05, 2017, 05:39:44 am »
Hi guys.

So I've plugged some leaks on the bike with new seals.

I'm about to install the new tappit cover seal and plug seals.

Might as well check my valve settings.

While lining up the cam timing sprockets with the bottom, I notice light shining in between the chain and sprocket teeth. See pic's attached. I'm thinking that the chain might be stretched. But I'm not absolutely sure. The timing chain and teeth of the sprockets look to be in good condition and not worn at all. Any advice...?

Offline Summit670

  • Full Member
  • ***
  • Posts: 480
  • Country: us
Re: Stretched timing belt....?
« Reply #1 on: March 05, 2017, 09:06:49 am »
The service manual spec says camshaft chain std lenght is 158.8-159.2mm 20 link length and service limit is 161.5mm
Arctic Cat M8 163 rules

Sleds, Dirt Bikes, ATV's, Street Bikes, Mountain Bikes.  Heck, I guess if it has handlebars I'll give it a try.

Offline MAN OF BLUES

  • Arena
  • Sr. Member
  • ****
  • Posts: 2887
  • Country: 00
  • WHISKEY.Tango.Foxtrot.
Re: Stretched timing belt....?
« Reply #2 on: March 05, 2017, 02:59:53 pm »
That's not looking good at all to me... also appears the plastic follower down inside the engine tower is worn also, the one the chain tensioner forces agains....
Does this bike have a manual chain tensioner installed????? This... is the exact reason I am sooo against those manual adjusters....
If not, id still measure the dinstance between links and compare to the spec in the FSM....

On another note....
CAREFULLY remove ALL of that goober RTV sealant, and don't drop any in the valve area... that is wayyyy sloppy and when this stuff migrates to the wrong places, it will shut off your oil flow... and you will be replacing an engine... the ONLY place RTV should be used, is in the crescent shaped cutouts at the ends of the cam shaft areas where the cover gasket seals... NEVER use RTV in this manner for a replacement for a poorly sealing gasket.

Best of luck.

46 YEARS OF KAW.....  47 years of DEVO..

Offline LT South Africa

  • Jr. Member
  • **
  • Posts: 79
Re: Stretched timing belt....?
« Reply #3 on: March 05, 2017, 09:19:37 pm »
Thank you. I actually did remove all the sealant. Replaced with a new tappet cover seal.

Came ex Japan and I had to wait 5 weeks for it.

No. The tensioner is still the original spring loaded tensioner.

I will measure as per summit670 advice above.

Offline RFH87_Connie

  • Arena
  • Full Member
  • ***
  • Posts: 944
  • Country: us
Re: Stretched timing belt....?
« Reply #4 on: March 13, 2017, 06:54:34 am »
I think it's normal for the cam chain to sit like that on the gears (seeing light).  It doesn't look right (not seated like we think it should be), but is OK and designed that way as far as I can tell.  Mine looks that way as I recall, but I can't find a picture of mine.  It made me feel uncomfortable too.  I did find one of SISF's videos and screen shot it below.  Anybody else have a verification picture?
“I can truly say I had rather be at home at Mount Vernon with a friend or two about me, than to be attended at the seat of government by the officers of State and the representatives of every power of Europe.” - George Washington

Offline jacksdad

  • Jr. Member
  • **
  • Posts: 31
Re: Stretched timing belt....?
« Reply #5 on: March 14, 2017, 01:31:16 pm »
I've rebuilt a few engines, and the hy-vo chains always look to be sat 'too high'. Thats the way they are meant to be, I did think the experts on here would have confirmed this.  ::)

Offline LT South Africa

  • Jr. Member
  • **
  • Posts: 79
Re: Stretched timing belt....?
« Reply #6 on: March 14, 2017, 08:16:08 pm »
Thanx guys. That puts my mind to rest.

Offline RFH87_Connie

  • Arena
  • Full Member
  • ***
  • Posts: 944
  • Country: us
Re: Stretched timing belt....?
« Reply #7 on: March 15, 2017, 05:30:20 am »
By the way, most C-10 owners just use the starter to "bump" the motor when checking the valves.  Just hit the starter to rotate the engine slightly so the cam lobe is facing up and away from the rocker arm where you want to check the valves.  The back side of the lobe is perfectly round so it leaves a large rotational margin for checking the valves.  Check a set or two of the valves, and rotate the engine slightly again by tapping the starter button until you have checked them all.  This way you don't have to keep the taking the side cover off.
“I can truly say I had rather be at home at Mount Vernon with a friend or two about me, than to be attended at the seat of government by the officers of State and the representatives of every power of Europe.” - George Washington

Offline MAN OF BLUES

  • Arena
  • Sr. Member
  • ****
  • Posts: 2887
  • Country: 00
  • WHISKEY.Tango.Foxtrot.
Re: Stretched timing belt....?
« Reply #8 on: March 15, 2017, 04:24:52 pm »
By the way, most C-10 owners just use the starter to "bump" the motor when checking the valves.  Just hit the starter to rotate the engine slightly so the cam lobe is facing up and away from the rocker arm where you want to check the valves.  The back side of the lobe is perfectly round so it leaves a large rotational margin for checking the valves.  Check a set or two of the valves, and rotate the engine slightly again by tapping the starter button until you have checked them all.  This way you don't have to keep the taking the side cover off.

I'm just asking, kinda like SISF does on occasion,
I'll ask this:

Why does the service manual specify using the timing plate numbers for TDC and confirming the somewhat horizontal (but slightly higher) position on the cam lobe as the position to check clearances?

46 YEARS OF KAW.....  47 years of DEVO..

Offline RFH87_Connie

  • Arena
  • Full Member
  • ***
  • Posts: 944
  • Country: us
Re: Stretched timing belt....?
« Reply #9 on: March 16, 2017, 07:23:51 am »
If I remember sometime back a few years, one of the heavy users on this site said the cam lobe is round on the back side.  I think it was during the time when the modified cams were being created.  Perhaps it was SISF, T-Cro, or maybe someone else.  Please don't misconstrue that I am saying they did say it because I'm not going to dig for it on the forum.  I would tend to agree with this, but have not ever put a set of calipers to it.  At this point SISF should actually know if this would be correct due to the fact that he has re-designed the stock cams for his "Torque" grind.  Maybe he's listening and will put it to rest.  I can't find the mention in the shop manual anywhere where you refer to "the somewhat horizontal (but slightly higher) position on the cam lobe as the position" to use when checking the valve clearance.

I did find this in the shop manual, and it would be the specific method to use.  Notice it says it "may" result in improper adjustment.  My opinion is that many don't know where the cam needs to be when checking the valves, so following the manual exactly is the best way for these individuals.  If I'm wrong about the back side of the lobe not being "round", I would gladly retract my recommendation.  I would probably do the valves the same way though on my own bike.  Are you going to tell me you pull the plate off each time and line it up by the marks?
“I can truly say I had rather be at home at Mount Vernon with a friend or two about me, than to be attended at the seat of government by the officers of State and the representatives of every power of Europe.” - George Washington