Author Topic: Backfire at start-up after cam/timing/valve tinkering  (Read 4543 times)

Offline MikeD2001

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Backfire at start-up after cam/timing/valve tinkering
« on: February 12, 2006, 08:53:18 PM »
As I mentioned in a previous post, my cam chain tensioner came loose while riding one day.  Long story short, I took out the exhaust cam and reinstalled it in the process of trying to get everthing back together.  I believe everything is lined up... when the signal generator rotor is lined up with the pick-up coil, the intake sprocket has "3" pointing up, exhaust sproket has "2" pointing up, there are 24 pins between their respective arrows.

http://www.snapfish.com/slideshow/AlbumID=35129455/PictureID=1079981071/a=41464894_41464894/t_=41464894

http://www.snapfish.com/slideshow/AlbumID=35129455/PictureID=1079981071/a=41464894_41464894/t_=41464894

http://www.snapfish.com/slideshow/AlbumID=35129455/PictureID=1079981071/a=41464894_41464894/t_=41464894

http://www.snapfish.com/slideshow/AlbumID=35129455/PictureID=1079981071/a=41464894_41464894/t_=41464894

http://www.snapfish.com/slideshow/AlbumID=35129455/PictureID=1079981071/a=41464894_41464894/t_=41464894

However, the previous owner installed '89 GSXR 1100 cams and degreed them at 104.  I'm not exactly sure what "degreeing them at 104" means, but do I need to compensate for this somehow when adjusting my valve clearances or with respect to my sprockets/chain/timing?  Now, according to my Haynes manual, the cam notches should be pointing away from each other at this position, with both the intake and exhaust lobes also pointing away from each other, leaving both #1 valves closed.  However, the notches on my cams point toward each other.  It's my understanding that the notches are removable, and I'm thinking that they were possibly just installed wrong leading to my confusion but actually (in this case) don't have any bearing on my timing.  I'm getting a very loud backfire when I attempt to start it (which I've done twice now).  I don't think it will run as it is, but I haven't even tried to let it go beyond that.  I don't think I'm 180 degrees off, but is this possible with what I've described?  If so, could I correct this by removing the timing chain from the sprockets, turing the crank a full turn, and replacing the timing chain?  Any help would be greatly appreciated!  I am going insane with this unseasonably great weather in Oregon, and all my buddies telling me how much fun they're having riding!
Mike D
'01 1200 Bandito

Offline Red01

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Backfire at start-up after cam/timing/valve tinkering
« Reply #1 on: February 12, 2006, 09:44:52 PM »
AFAIK, the notches are cut into the end of the cam, so they're not removable.

With the stock cams (and I'm 99% sure the GSXR cams are the same in this regard), the notches will be pointing away from each other when #1 is at TDC on the compression stroke. With the cam chain connected and the crankshaft turned 360*, the notches will be pointing towards each other since the cams will only turn 180* and #4 will be at TDC on the compression stroke (#1 will also be at TDC, but on the exhaust stroke).

The 5* timing advancer and cam timing shouldn't have an effect on setting your valve clearances, but if you want to be sure, just be sure the cam lobes on the valves you set are pointing at the outer edge of the valve cover flange to straight up and perpendicular to that flange.
Paul
2001 GSF1200S
(04/2001-03/2012)
2010 Concours 14ABS
(07/2010-current)


Offline MikeD2001

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Backfire at start-up after cam/timing/valve tinkering
« Reply #2 on: February 21, 2006, 03:27:21 AM »
Thanks for your help, Paul.  :congrats:   Things seemed to make much more sense once I realised #4 isn't #1 and vice-versa  :idea:   I got her running again, thank God!  However, I am now having a high idle rpm problem that I didn't have before.  I replaced the air filter with an identical OEM one, and a similar inline fuel filter to the one the previous owner installed between the tank and carbs.  I also adjusted all the valves.  The box was modified by the previous owner with an approximate 3-4" square hole.  The fatory stage 1 jets are suposed to still be there.  It also has a holeshot mid pipe and carbon figer M4 slip-on.  The only things I believed I changed were the filters as mentioned and the valve adjustments.  Unfortunately, the bike seems to be little off all around.  Could the colder weather (40's F) than summer (80's F) have that much effect?  I know I rode it last fall and in summer evenings when the temps were in the 50's and didn't notice any difference in performance.  I am perusing previous posts on this board and others for answers, but any suggestions would be awesome.  Thanks.

-Mike
Mike D
'01 1200 Bandito

Offline Red01

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Backfire at start-up after cam/timing/valve tinkering
« Reply #3 on: February 21, 2006, 02:09:08 PM »
Can't you just turn the idle down with the thumbscrew?

The cold weather will tend to make it run leaner.
Paul
2001 GSF1200S
(04/2001-03/2012)
2010 Concours 14ABS
(07/2010-current)


Offline MikeD2001

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Backfire at start-up after cam/timing/valve tinkering
« Reply #4 on: February 22, 2006, 01:18:02 AM »
Oh, have I played with the idle knob!  It seems that once it gets at that higher idle rpm, about 3000,  it decides that either it will idle there or not at all... I adjust it all the way down, up, and everywhere inbetween.  It seems to respond to my adjustment, then after a short while, it returns to the high idle.  I remember detaching the idle knob and bracket to help get at the cam chain tensioner, but I don't think I somehow really messed up it's functioning, could I have?  I'm not sure.  Thanks again.

-Mike
Mike D
'01 1200 Bandito

Offline Red01

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Backfire at start-up after cam/timing/valve tinkering
« Reply #5 on: February 22, 2006, 10:01:07 AM »
Be worth double checking.
Paul
2001 GSF1200S
(04/2001-03/2012)
2010 Concours 14ABS
(07/2010-current)