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83 GS450 cam timing

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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Hi all,
I just picked up a GS450 that the PO couldn't figure out how to start. It's funny, when those things that should go up and down are stuck, it won't run :? In the process of trying to figure it out, he pulled the cam chain adjuster off, don't ask me why, I still don't know. Anyways, I want to make sure I have them in the proper alignment with the crank and I don't have a book on this model. Is the procedure the same as an 850 with the arrows pointing inward when on T1? The same 20 tooth chain count?
Thanks a million, Bob
 
Erm, never dwelled this deeply into any engine before, but I do have a manual.

Says:
Loosen central ATU retaining bolt
Rotate crankshaft forwards til 'T' mark on the 'R' side is in exact alignment with the index mark with the index mark on the static plate. Cyl 1 or RH cyl is now TDC.

Ex camshaft into cam chain. pull forward run on chain taut (while not rotating crackshaft) Mesh sprockt to the chain so that when the camshaft is lying across the bearing housings, the 1 marked arrow is pointing flush with the upper mating surfaceof the cyl head.

Insert inlet camshaft thru the cam chain. To mesh the sprocket, count the chain roller pins from the exhaust to the inlet camshafts, start with th pin directly above the 2 marked arrow on the exhaust camshaft and cout to the 20th pin along the chain, mesh the 3 marked arrow on the inlet sprocketwith the 20th pin.

Hope that helps.
 
Brent,
Thank you for looking this up. In your manual, does it say anything about differences in the pin count for chain or shaft drive models? I have a 650 manual that states 19 pins for chain drive and 20 for shaft. I'm not doubting you or the manual, I just wanted to make sure before I button this up. Thanks again, Bob
 
On the 450's there is only the E and S and L covered in the book. The shaft (the 450A - automatic) is not discussed. Sorry.
 
OK my friend, I'll set her to 20 paces and let her rip. Thanks again, Bob
 
same for '87 450L??

same for '87 450L??

Can someone confirm that it is 20 pins between the 2 and 3 marks for an '87 GS450L??

I just bought the bike, engine starts and idles, but only has 45 psi compression when cranking. Took the head off, the cams were set at 18 pins apart.


Thanks,
Jon
 
fieroaddiction said:
Can someone confirm that it is 20 pins between the 2 and 3 marks for an '87 GS450L??

I just bought the bike, engine starts and idles, but only has 45 psi compression when cranking. Took the head off, the cams were set at 18 pins apart.


Thanks,
Jon
Click to expand...

Yes

Dink
 
Dink said:
Yes

Dink
Click to expand...

You are sure? When did they change it? My Haynes says it is 18 teeth, mine (-84) is set for 18 and it rocks!

P.S
Jon, did You count them from mark to mark or between marks? The right procedure is, that the exhaust mark #1 should be level with the head, pointing forward, and there should be 18 teeth from exhaust mark #2 to inlet mark #3, including the pins that are adjacent to the marks.
Mine had an offset of 1 tooth (both cams where out of sync) and it dropped the compression to 90PSI
 
Last edited:
Sorry, bad wording. I counted 18 pins from mark 2 to mark 3, with mark 1 pointing at the gasket surface. I changed it to 20 and the compression dropped way down. My rings and valves are in good condition, it passes a leakdown test with a perfect score, but it does have 40k miles on it. I'm going to start over and see what happens.

Can sombody post the valve clearance specs?
 
According to Haynes they are both inlet and exhaust (cold engine) 0.03-0.08 mm (0.001-0.003 in).
When checking the valve timing, did You have the ingnition timing marks correctly (the 'T'-mark aligned with the fixed pointer)? Mine has some 85000 kilometers (50 k miles) on it, the cylinders are in perfect condition and compression somewhere near 130PSI.
 
Four bangers are 20 pins but the 450 twin is 18.

Make sure you check the valve clearances per the manual procedure. The cams need to be in the specified locations or your readings will be off. When I firsted working on the GS engines I used to just have the lobe pointing away from the shim bucket before checking clearance. While this method should be okay, since the cam is on the base circle, in reality the adjacent valve pushes up on the cam which causes the cam to shift over due to clearance in the cam bearings. When you check the valves per the manual, you don't have this same issue.

Good luck.
 
Yes, I had the ignition timing marks lined up correctly when checking the cams and I also checked that the piston was at the top of the cylinder. I tried several combinations including 17 and 19 pins from cam to cam, and advancing both cams so the #1 arrow points below the gasket. So far the best results come from the book setting of #1 arrow pointing at the gasket and 18 pins from #2 to #3, that is obviously the correct setting, but I'm still only getting about 40 psi. I've also tried a different compression gauge thinking mine was broken. I'm getting 20% leakage on a leakdown tester which is well within the acceptable range.

The clearances are a bit high on two valves, but I don't think it's enough to make the compression that low.
right int. .006
right exh. .001
left int. .002
left exh. .006
My next step is to order shims for those two valves, but I'm not holding my breath.

I'm going to have an angry girlfriend if I don't have this fixed by the time riding weather returns!!
 
fieroaddiction said:
I'm still only getting about 40 psi. I've also tried a different compression gauge thinking mine was broken. I'm getting 20% leakage on a leakdown tester which is well within the acceptable range.
Click to expand...


Leakage is on the high side of tolerance, mine has only a few percents, but that does not explain that low compression. Did You listen where it was leaking? Did You remove the air cleaner during compression test? If it is clogged the engine does not get enough air.
Is it possible, that someone has messed up with the camshafts, removed the driving gear and installing it wrong way? The exhaus is propably OK, if the tachometer drive is on the right side, but how about the inlet, is it wrong way?
 
Nessism said:
Four bangers are 20 pins but the 450 twin is 18.

Make sure you check the valve clearances per the manual procedure. The cams need to be in the specified locations or your readings will be off. When I firsted working on the GS engines I used to just have the lobe pointing away from the shim bucket before checking clearance. While this method should be okay, since the cam is on the base circle, in reality the adjacent valve pushes up on the cam which causes the cam to shift over due to clearance in the cam bearings. When you check the valves per the manual, you don't have this same issue.

Good luck.
Click to expand...
So my Haynes manual is wrong? That's kinda scary... I have relied on it quite a bit.
 
fieroaddiction said:
Yes, I had the ignition timing marks lined up correctly when checking the cams and I also checked that the piston was at the top of the cylinder. I tried several combinations including 17 and 19 pins from cam to cam, and advancing both cams so the #1 arrow points below the gasket. So far the best results come from the book setting of #1 arrow pointing at the gasket and 18 pins from #2 to #3, that is obviously the correct setting, but I'm still only getting about 40 psi.
Click to expand...

One more question about the valve timing. When checking the timing, did You check that the notches on the camsafts were facing each other, level with the head. Haynes says, it is possible to to refit drive sprockets wrong way, and that prevents correct valve timing.
 
The cams are installed correctly, the notches on the ends do face each other at #1 TDC. I checked the valve clearances with the corresponding piston at TDC, that is the correct procedure isn't it?

I had checked the air filter before, but I failed to notice the metal screen below the foam element is partially plugged up. I will remove the airbox and retest. Then I'll kick myself in the head if that was the problem.
 
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