Symptoms of a bad cam chain?

Hi,

What are the symptoms of a bad cam chain (stretched) or tensioner ?

Beside noise?

Is it possible that a out of range automatic tensioner (too much slack) create erratic idle?

I'm not skipping tooths yet but i have a grinding chain noise when low on revs around 900 rpm!

I thinking APE tensioner but before throwing 50 bucks by the window i want to be sure its that or will help!

thank you very much!

regards,
laurent

EDIT: engine has now 40k km (25k miles) cam chain change?

ELCouz wrote: Hi,
What are the symptoms of a bad cam chain (stretched) or tensioner ?
Beside noise?
Is it possible that a out of range automatic tensioner (too much slack) create erratic idle?
I'm not skipping tooths yet but i have a grinding chain noise when low on revs around 900 rpm!
I thinking APE tensioner but before throwing 50 bucks by the window i want to be sure its that or will help!
thank you very much!
regards,
laurent

Imo, 900 rpm idle speed is slightly too low.

Often, a good carb sync will significantly reduce valve train noise.
Which should be accompanied with perfect pilot circuits and correct pilot circuit idle tuning.

Good Fortune!

I still have a little bit of RPM drop occasionally (from my previous lengthy issues)... normally engine is right on 1100 rpm but sometimes after long extended red lights will drop to 800-900 rpm and start rattle like the cam chain want to go free... oil start to smokes on head (little leak) when this happen maybe its just a coincidence (RPM drop)

regards,
laurent

ELCouz wrote: ...bit of RPM drop occasionally... normally engine is right on 1100 rpm but sometimes after long extended red lights will drop to 800-900 rpm and start rattle like the cam chain want to go free....

If not done recently, would assure valve clearances are within specs.

Good Fortune!

yep,

Exhaust valves:
#1 0.13mm
#2 0.12mm
#3 0.13mm
#4 0.10mm

Intake valves:
#5 0.17mm
#6 0.17mm
#7 0.16mm
#8 0.14mm

carb sync last check was today, well within FSM tolerance.

Jettings are perfect so is idle mixture adjustment screws (confirmed with Colortune and exhaust sniffer)

Idle is around 10:1 A/F mixture which is ideal for air cooled engines (kept engine cooler with a little bit more fuel)





regards,
laurent

Also do anyone know are the symptoms of a leak in the diaphragms (BS34 carbs)

Its the only thing i didn't replace in the carbs because they cost around 150 bucks per diaphragm!! insane!

Things i've changed (only related to carbs problems) changed others part but i won't list the rest here too much items.

Brand new floats with right fuel level... check
Brand new carb rebuild kit...check
brand new main jets and pilot jets ... check
Brand new jet needle..check
Brand new carb valve needles and seats...check
brand new carb boots and intake carb holder ... check
Leaks around carbs...check
Brand new k&n filter (not pods)..check
brand new exhaust seals (for exhaust leak possibility) ... check
somewhat new gas cap(for venting problem possibility)..check
rebuilt petcock...check
new gas line..check
cleaned carbs..check

Thats why i'm asking the symptoms maybe its just that (the diaphragms or the cam chain)

regards,
laurent

the chain will have excessive play in the links, they dont stretch they wear, thats a popular misconception, and bench syncing carbs is not the same a syncing with carb stick or gauges, the chain would not cause idling issues u describe nor the valves either, check ur linkage and cable first, run some penetrating oil down the cable just to make sure, then check for intake leaks, probably a sync issue or a intake leak, and yes the new boot can leak if not clamped right, ask me how i know

Patton wrote:

ELCouz wrote: Hi,
What are the symptoms of a bad cam chain (stretched) or tensioner ?
Beside noise?
Is it possible that a out of range automatic tensioner (too much slack) create erratic idle?
I'm not skipping tooths yet but i have a grinding chain noise when low on revs around 900 rpm!
I thinking APE tensioner but before throwing 50 bucks by the window i want to be sure its that or will help!
thank you very much!
regards,
laurent

Imo, 900 rpm idle speed is slightly too low.

Often, a good carb sync will significantly reduce valve train noise.
Which should be accompanied with perfect pilot circuits and correct pilot circuit idle tuning.

Good Fortune!

what he said

I got the APE tensioner BTW a waste of money IMO

:laugh:

Maybe your clearance specs are different the KZ900 but why so high on the intakes?

One thing I learned from Plumi & Larry and through experience... The exhaust side will change on you due to heat so open them up just a tad more... This may also be due to performance camshaft upgrades. I measure my shims to keep at the following...

Intakes @ .05 to .1mm (I try to keep her a ~ .07/.08mm)
Exahust @ .1 - .15mm (I try to keep her a ~ .12/.13mm)

As for the cam chain tensioner, yup had that happen where the plunger side bolt stripped, wasn't holding the plunger securely. I tapped a larger bolt hole, inserted a bolt, she holds tight now...

Can't remember everything you did to your engine but as in my case, she does not like to idle @ any rpm under 1100rpm... She prefers 1100-1200rpm so I give her what she wants... Besides at higher rpm's, oil is pumping better thus increased oil pressure and flow up through the head...

If not recently done, would lube pivot points on timing advancer and assure it's fully and immediately closing whenever rpm drops to idle.

Also +1 on JB's advice about the throttle cable needing to be in good condition, lubed, and properly adjusted.

Good Fortune!