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Cam Sprocket mismatch

  • Thread starter Thread starter Zig's GS
  • Start date Start date
Z

Zig's GS

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In my efforts to get the GS850 running smoother, I discovered something that I am sure is not right! When on TDC, the notches on the right end of the cams don't face each other (not in 1 line) The intake differs with about 30degrees. Retarded. The phasing of the 2 cams is correct. (20 links) The inlet cam sprocket carries a marking - 451, but the exhaust has a marking 490 and so does the 2 spare cams I have. Is this normal? By judging with the eye, it looks as though the cam notches would line up if I change the sprocket.
Also.... according to my Haynes manual, there should be a idler sprocket between the intake and exhaust cams, not so on my bike. GS850GX.
Also... the Haynes manual tells you to measure the lenght of the timing chain and it should not exceed 157.ish mm, measured between 1 and 20 link.....and then it shows a picture of a vernier between pin 1 and 21!!!:rolleyes:
 
My guess is that someone left out the idler which is messing up the timing of the intake cam. Shouldn't be too hard to source one but you will have to remove the cam chain tensioner to install it.
 
Uhhhh... yeah, that idler is NOT optional and it is needed on EVERY GS850 model.

Man, just when I thought I'd heard of everything...
 
What baffles me is the fact that there is no provision made for any sort of tensioner between the cams. There is a piece of frictionliner inside the camcover on the inside???
 
Could they have replaced the head with a GS1000 one ? without the gear!!!
 
TeamDar said:
Could be a GS1000 shaft drive motor in a GS850 frame?
Click to expand...

Engine Number says it's 850, barrels says 840something.
It could be a gs1000 head. I have spare cams from a 1000 and the marking also says 490.
Will take photos tonight.

maybe that's why the breather cover on the cambox was not the same as the 1 I ordered. Will a 1000 head fit on the 850 barrels??
 
Yes as far as I know the 1000 head will fit on the 850. The cam chain has the same # of links, Their may be a difference in the cam sprockets
 
just looked at my aussie gs1000 st which is apart, 451 inlet 490 exhaust
 
Ok, that did not work. Will try again:o

what am I doing wrong. I uploaded the photos but they are not here?
 
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That IS a GS1000 head. Do some research I would degree the cams to make sure it is rihgt
 
A picture of the cams at TDC. If it is in fact a 1000 head, surely there are going to be some mismatching between the bores and the combustion chamber?
Wonder what pistons are hidding underneath all that!!!
 
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The 1000 valve cover has a chain guide bolted to it (small strip). Also, on the 1000 there is a U-shaped cam chain support that fits into the head under the chain bridge between the two cams. If that is a 1000 head you need that support, and the 1000 cam chain sprockets, or at least the exhaust sprocket. If that is an 850 head, you need the idler sprocket device between the cams.
 
That's not an 850 head, it's a 1000 or maybe 1100 head. The shape of the valve cover gasket area is different, on the 750/850 it is curved in the area where the cam chain runs, on the 1000/1100 is has straight sides. I am curious what else is in that engine, pistons, bore, etc. Ed's right, you are missing a few chain guide pieces.
I have both a 1000 and 850 head here, I can send a picture so you can figure out how mismatched the combustion chambers are. Also, which carbs are on the bike? The larger BS 34 from the 1000? or the BS32 from the 850?
 
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