Cam timing off the mark
05-30-2007 | 09:25 AM
#1
Thread Starter
Member
Squid
Joined: May 2007
Posts: 99
From: Akershus, Norway
Cam timing off the mark
I've just changed the CCT's to APE ones and adjusted the TPS (off by 350ohms). Things work just fine, but I double checked the timing marks on both heads and as I thought I remembered from last inspection the timing on the front is off. Not by far enough for a jump of one tooth but about 2-3mm at the markings. To give a better idea, moving one tooth resulted in a least twice as much off but the other way. Rear cylinder is spot on.
I've searched a little and it seems that it's not that unusual that timing can be off on worn engines.
However this engine has had a bent valve due to CCT failure, although I think that was on the rear, so the front should not have taken damage. The thing is that the engine has a notably rougher run, with more vibrations when on power and only on power. Revving it in neutral doesn’t generate pulses to make any difference, the extra vibrations are only felt when engine is under load. I think that I can feel one cylinder giving that extra kick through the frame rattling my bones but not sure.
I'm not too worried as it has done approximately 10 k km with that vibration so there can't be anything terribly wrong, but it is strange as it used to be so smooth before the CCT failure.
Any suggestions as to what I should do with the timing and what can cause the vibrations will be appreciated.
I've searched a little and it seems that it's not that unusual that timing can be off on worn engines.
However this engine has had a bent valve due to CCT failure, although I think that was on the rear, so the front should not have taken damage. The thing is that the engine has a notably rougher run, with more vibrations when on power and only on power. Revving it in neutral doesn’t generate pulses to make any difference, the extra vibrations are only felt when engine is under load. I think that I can feel one cylinder giving that extra kick through the frame rattling my bones but not sure.
I'm not too worried as it has done approximately 10 k km with that vibration so there can't be anything terribly wrong, but it is strange as it used to be so smooth before the CCT failure.
Any suggestions as to what I should do with the timing and what can cause the vibrations will be appreciated.
05-30-2007 | 09:34 AM
#2
Senior Member
Superstock
Superstock
Joined: Apr 2007
Posts: 293
I just posted this in the KB yesterday, but if you have the valve covers off again, I would count the chain links/pins between the timing marks on the intake and exhaust cam. If correct it should be 18 links or 36 pins. If you have that, then you will be in phase and only have to concentrate on getting the timing marks as close to "correct" as you can. Mine done line up 100% either at 34k miles. Mine was doing what you described, and though I thought I was properly adjusted, a simple pin count proved I was a tooth off on my rear cylinder exhaust cam. Not sure why the book doesn't mention counting links/pins. Oh well.
Hope this helps,
-R
Hope this helps,
-R
05-30-2007 | 09:44 AM
#3
Senior Member
SuperBike
Joined: Jul 2005
Posts: 1,548
From: MN
I checked my timing when I modified my engine (15K engine). the timing was off from the marks - maybe 3 degrees at the crank. A whole link off resulted in much more, maybe even 15 if I recall correctly - you could do the math and figure it out I suppose based on link length, but it was a lot. I'd never though of counting the links, just pulling it tight from crank to exhause cam to intake cam. good idea though.
05-30-2007 | 01:46 PM
#4
Thread Starter
Member
Squid
Joined: May 2007
Posts: 99
From: Akershus, Norway
I checked my timing when I modified my engine (15K engine). the timing was off from the marks - maybe 3 degrees at the crank. A whole link off resulted in much more, maybe even 15 if I recall correctly - you could do the math and figure it out I suppose based on link length, but it was a lot. I'd never though of counting the links, just pulling it tight from crank to exhause cam to intake cam. good idea though.
For the sprocets to line up perfectly the crank end up between the FT. Actually very close to what are shown in the picture in the CCT KB log.
What did you do, just leave it there?
BTW. just red your post in the KB. The marks on the sprocets are absolutly parallell on mine. I guess that mean that the number of links must be right, right?
05-30-2007 | 03:15 PM
#5
Senior Member
SuperBike
Joined: Jul 2005
Posts: 1,548
From: MN
I actually slotted the cam sprockets so I could set them correctly according to measured TDC - I was putting in some stage 1 cams and wanted them right on spec. I would assume that if yours are parallel even after spinning the crank, that you do not have an extra link worth of slack in between the sprockets.
05-30-2007 | 03:34 PM
#6
Thread Starter
Member
Squid
Joined: May 2007
Posts: 99
From: Akershus, Norway
I actually slotted the cam sprockets so I could set them correctly according to measured TDC - I was putting in some stage 1 cams and wanted them right on spec. I would assume that if yours are parallel even after spinning the crank, that you do not have an extra link worth of slack in between the sprockets.
05-30-2007 | 05:24 PM
#7
Senior Member
MotoGP
Joined: Sep 2006
Posts: 4,138
From: Austin, Tx
It seems to me that if the piston/valve impact is sufficient to bend the valve it could also be capable of tweaking the crankshaft just as you describe - not big enough for one tooth off but off. It will cause rough running initially, higher than normal oil consumption later and eventually the engine will have to be rebuilt or replaced after months of **** performance.
Jeffers would know better what the service life of the chain is. I know he replaced his. Maybe more than once. Either way, once you crunch the valve train the whole engine is suspect in my shop. Rebuilding a Superhawk engine is one of my pet projects - just not now!
Jeffers would know better what the service life of the chain is. I know he replaced his. Maybe more than once. Either way, once you crunch the valve train the whole engine is suspect in my shop. Rebuilding a Superhawk engine is one of my pet projects - just not now!
05-30-2007 | 11:43 PM
#8
Thread Starter
Member
Squid
Joined: May 2007
Posts: 99
From: Akershus, Norway
It seems to me that if the piston/valve impact is sufficient to bend the valve it could also be capable of tweaking the crankshaft just as you describe - not big enough for one tooth off but off. It will cause rough running initially, higher than normal oil consumption later and eventually the engine will have to be rebuilt or replaced after months of **** performance.
Jeffers would know better what the service life of the chain is. I know he replaced his. Maybe more than once. Either way, once you crunch the valve train the whole engine is suspect in my shop. Rebuilding a Superhawk engine is one of my pet projects - just not now!
Jeffers would know better what the service life of the chain is. I know he replaced his. Maybe more than once. Either way, once you crunch the valve train the whole engine is suspect in my shop. Rebuilding a Superhawk engine is one of my pet projects - just not now!
If something was off balance I would feel the vibrations without load too, woudn't I?
This was a "nice" crunch. Only one exhaust valve bent and I couldn't even see a mark on the piston. I talked to a couple of very experienced mechanics and if the piston was ok the only thing they wanted me to look out for was the cups on top of the valve, the sometimes crack.
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