650L Cam Chain, How Important?


31 replies to this topic
  • tgstoken

Posted December 23, 2007 - 05:25 PM

#1

Ok, so my new-to-me '93 XR650L has 7500 miles on it. When I start to roll on 2nd gear at low revs, I can hear the cam chain doing its "clunk-clunk" or "knock-knock" (different noise for different boys) under load. So, my question is, how bad is this? Does it happen to everyone at low revs in any gear above 1st? Do I need to fix it, or is it normal and ok. It only happens when I stress the engine on trails and lug it in 2nd and up.

  • xr650l bum

Posted December 23, 2007 - 05:35 PM

#2

What are you doing on the bike, and with what gearing? To me that sound happens when I am not in low enough gear. Maybe your engine is not idling high enough when changing gears at low speed when pulling the clutch? Need more info.

  • tgstoken

Posted December 23, 2007 - 05:55 PM

#3

Gearing is 14/48 and noise happens from stop in 2nd/3rd gear to about 1/2 throttle. Maybe I'm just lugging it too hard.

  • Butta

Posted December 23, 2007 - 06:00 PM

#4

Ok, so my new-to-me '93 XR650L has 7500 miles on it. When I start to roll on 2nd gear at low revs, I can hear the cam chain doing its "clunk-clunk" or "knock-knock" (different noise for different boys) under load. So, my question is, how bad is this? Does it happen to everyone at low revs in any gear above 1st? Do I need to fix it, or is it normal and ok. It only happens when I stress the engine on trails and lug it in 2nd and up.


You sure it is the cam chain and not detonation? That's a perfect circumstance to get detonation when everything else is correct (octane rating, motor, etc).....

  • Motosprtman

Posted December 23, 2007 - 06:24 PM

#5

chain snatch (primary) and or detonation, should run 92 octane only,

  • Whiteman

Posted December 23, 2007 - 06:48 PM

#6

Kick it down into 1st. This is not a CRF450x/r where it is fine kicking up dust in second from a stop.

  • NEKOOHC

Posted December 23, 2007 - 06:58 PM

#7

possible piston slap going on here , if the c/chain was loose you would here it on idle .

  • 2weelz

Posted December 23, 2007 - 08:15 PM

#8

Ok, so my new-to-me '93 XR650L has 7500 miles on it. When I start to roll on 2nd gear at low revs, I can hear the cam chain doing its "clunk-clunk" or "knock-knock" (different noise for different boys) under load. So, my question is, how bad is this? Does it happen to everyone at low revs in any gear above 1st? Do I need to fix it, or is it normal and ok. It only happens when I stress the engine on trails and lug it in 2nd and up.


Mine does the same thing with 2500 miles...not sure if it's the cam chain, though. I thought it was a problem at first but now I think it's normal. Remember, these are some outdated beasts!

  • Butta

Posted December 23, 2007 - 09:42 PM

#9

chain snatch (primary) and or detonation, should run 92 octane only,


WOW!!! Really?? I'm not disagreeing with you (yet), but I would be highly surprised if an AIRCOOLED 650L (stock setup) would require anything over 87 octane. I ran 93 in my YZF450 (12.5:1 compression) with zero probs.....this airhead motor with 9:1 (?) compression SURELY doesn't require as much octane.

If you are spending the extra dough on the higher octane, I think you're pissing money out the tailpipe, and losing power while you are doing it.

It's detonation......telling you to downshift and ride it like it's supposed to be ridden.

  • Butta

Posted December 23, 2007 - 09:46 PM

#10

possible piston slap going on here , if the c/chain was loose you would here it on idle .




Hmmmmmm, wouldn't you hear piston slap more after rapidly accelerating the motor and then chopping the throttle? Seems like the more you'd spin the motor the more exaggerated the piston slap would become (inertia).

I agree, if the cam chain were loose, throttle changes (regardless of motor load) would show chain noise. Since this is happening ONLY from a start in too high of a gear, my money is on detonation.

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  • 2weelz

Posted December 23, 2007 - 10:07 PM

#11

What is causing detonation? How do you fix it?

  • NEKOOHC

Posted December 23, 2007 - 10:12 PM

#12

Hmmmmmm, wouldn't you hear piston slap more after rapidly accelerating the motor and then chopping the throttle? Seems like the more you'd spin the motor the more exaggerated the piston slap would become (inertia).

I agree, if the cam chain were loose, throttle changes (regardless of motor load) would show chain noise. Since this is happening ONLY from a start in too high of a gear, my money is on detonation.


could be detonation ... could be .

detonation is caused by a rapid burn of the fuel / air mix , to overcome this you need a higher octane rating .

  • Ryanthegreat1

Posted December 23, 2007 - 10:34 PM

#13

I am getting this same noise! I have a few posts regarding my problem.

The short list of things I have done to fix it and not have solved anything:
1. Replace cam chain tensioner assembly, this includes the lever, shaft and spring.
2. Took out the clutch basket that had play in the springs in the hub and the Techs at my local honda dealer say that the amount of play in my basket is 100% normal.

I have yet to play with jetting as I think I have it fairly dead on. Starts first time every time with no throttle and will pull in 5th WFO with zero detonation. Yes I do know what detonation sounds like I had a very clear reminder when I got the bike as it was horribly lean and pinged like mad in 4th and 5th.

Jetting does kind of make sense, it is almost like its bucking but not harsh enough to be felt just heard.

Anyone have an O2 sensor near by?

  • Denn10

Posted December 23, 2007 - 11:20 PM

#14

Compression in a 650L is 8.3-1 and i would say if you had detonation it would be anywhere you were low rpms like your stating now. Try riding it and shifting a bit higher rpms and see if its still there. I know mine makes some noise when im short shifting really low in the valve train and who knows where else, its kinda just like you explained.

  • Ryanthegreat1

Posted December 23, 2007 - 11:29 PM

#15

What is considered low RPM's? The trailtech is registering 1500-3000rpm's when I get the most noise. Anything higher and the noise goes away.

Only problem with greater engine speed is it sounds like the motor is racing all the time and all I am doing is cruising around town at 30mph. This is all fine and dandy on flat level roads but as soon as there is an incline and the motor gets loaded all the bad noises return and the it is time for a down shift.

Could be all my fault and my damn tall 15/40 gearing making the jump between gears HUGE.

  • Butta

Posted December 24, 2007 - 08:13 AM

#16

What is considered low RPM's? The trailtech is registering 1500-3000rpm's when I get the most noise. Anything higher and the noise goes away.

Only problem with greater engine speed is it sounds like the motor is racing all the time and all I am doing is cruising around town at 30mph. This is all fine and dandy on flat level roads but as soon as there is an incline and the motor gets loaded all the bad noises return and the it is time for a down shift.

Could be all my fault and my damn tall 15/40 gearing making the jump between gears HUGE.


The layman's test for proper octane fuel is to climb a hill in too high of a gear and see if you can bog the motor and cause it to detonate. If it does cause some detonation in this situation and in no other (i.e. loaded motor with low rpm's includes starting out in 2nd or 3rd) then you have the right octane. If it doesn't detonate, you are running too high of an octane number and aren't fully getting the max performance out of your motor, not to mention spending more on fuel than necessary.

IF you can't change your riding style to actually use the gears to get the motor speed correct for the riding conditions, and continue to get detonation like you've been experiencing, change your fuel to a higher octane rating. While this isn't the preferred method, it will prevent your bad habit from harming the motor.

  • Ryanthegreat1

Posted December 24, 2007 - 09:21 AM

#17

I guess motor mods would be worth a mention if detonation seems to be the consensus.

103mm 10.5:1 CP Piston
HotCam Stage 1
Kibble White Valves
FMF Power Bomb
FMF PowerCore 4
UNI Filter
Dave's Mod to Carb
55 Pilot 168 Main at sea level
Always premium fuel

Also might be worth noting that at those engine speeds if I go WOT the noise seems to stop and the motor smooths out.

  • cleonard

Posted December 24, 2007 - 09:41 AM

#18

I had my tensioner and/or chain go bad. It made a weird rattling kind of sound just above idle. It was completely unlike any other noise that I have heard coming from the engine. It also reduced engine power from the changing valve timing.

No totaling odometer on my 600, but I had a lot more than 7500 miles when my tensioner went bad. It only failed with the engine running. Just sitting there with the top off, it was fine. The aftermarket cam should put a little more load on the cam chain. The tensioner is not too many $$$ and is relatively easy to install.

I get some knock on my standard compression 600 with 91 octane in conditions that make the engine hot. It is very distinctive. I expect that carbon buildup is the cause of my pinging.

  • tgstoken

Posted December 24, 2007 - 10:26 AM

#19

Sounds to me like I just need to downshift in the corners to 1st and shift back up to 2nd when things get a bit speedier. I just asked a riding buddy and he said his XT225 does the same thing if hes in too high a gear.

  • Butta

Posted December 24, 2007 - 10:49 AM

#20

I guess motor mods would be worth a mention if detonation seems to be the consensus.

103mm 10.5:1 CP Piston
HotCam Stage 1
Kibble White Valves
FMF Power Bomb
FMF PowerCore 4
UNI Filter
Dave's Mod to Carb
55 Pilot 168 Main at sea level
Always premium fuel

Also might be worth noting that at those engine speeds if I go WOT the noise seems to stop and the motor smooths out.


Yeah, that would have been helpful information......still think it's detonation due to loaded up motor and low rpms. Another poss cure would be adding weight to the flywheel, allowing more torque on the bottom end. Honestly, though, just get used to revving it more than you do now. If that makes the symptoms disappear, then it's rider induced. If the symptoms re-appear or worsen (or just plain won't go away) then we've got other probs....





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