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Need Help Timing a 1981 GS1000GL

  • Thread starter Thread starter csbutler3
  • Start date Start date
C

csbutler3

Guest
Hello, I'm having a hard time getting my bike to fire. It ran before, but not well and it leaked a little oil so I took apart the top end to have it cleaned, had the valves conditioned, rebuilt the carbs and replaced the starter clutch; I have fuel and spark but now the bike cranks but no longer has compression. The piston and rings are good and the valves are not bent, which makes me believe that the valves are not closing when they are supposed to.

I put the bike back together according to the Clymer manual word for word (meaning I set the timing mark T for cylinders 1 and 4 on the advance govenor and pistons are TDC, Cams lined up where they supposed to be and have 20 links separating the 2 and 3 marks on them) the only thing i see potentially wrong is that at TDC the advance govenor has already passed the firing mark; I see another mark on the govenor (it looks like an F?) that makes the pistons a little bit below TDC and has not passed the firing mark. I plan to work on it again soon but I really need help. So my question is:

How would I go about setting the timing for this bike so that I have compression?

I hope I explained well enough to paint a picture, but if you need any more info, please let me know! All the mechanics I've talked to say that timing a DOHC Suzuki is a booger, and in my case, they're right! Thanks in advance for your assistance! :D
 
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Have you adjusted the valve clearances correctly?
If not the valves can be held slightly open all the way around the crank rotation and not allowing any compression at all, or rather letting the compression all escape through the intake and exhaust. If your valves were ground and you used the same adjustment shims as before, they are all too tight now.

Your ignition timing has nothing to do with the compression, valve timing would have to be completely wrong to not have compression.

Timing a DOHC Suzuki is a completely straightforward and simple task, your "mechanics" are full of schit.
 
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I dont like to ask this but how do you know the motor has no compression. I would do as Tkent says. Take tappet cover off and recheck the valve shim clearances and make sure they are within spec. Timing being incorrect will not affect compression.
 
Suzuki_Don said:
I dont like to ask this but how do you know the motor has no compression. I would do as Tkent says. Take tappet cover off and recheck the valve shim clearances and make sure they are within spec. Timing being incorrect will not affect compression.
Click to expand...

Tkent, when I had the valves conditioned the machine shop who did it for me placed the valves back in, so I have not checked the clearances which makes me agree with you along with Suzuki_Don

No worries Suzuki_Don, each question will help find a possible solution. I dont have a compression tester and unfortunately I'm not able to buy one at the moment so I took out the spark plug out of each cylinder one at a time, plugged the hole with my finger and cranked the bike; the cylinder isnt blowing air like its trying to push my finger out or at least make a hissing sound like air is rushing past my finger during the compression stroke. As for the valve shim clearances I will have that checked out ASAP.

That also reminded me, at one point with the spark plugs in and the carburetor removed, I covered the hole that connects carb to cylinder with the palm of my hand at the number 4 cylinder and when I turn the bike via advance governor it sucks my hand at one point then almost instantly pushes air back out, I dont think thats normal so hopefully you or someone can shed light on whats happening there. BTW I appreciate your quick responses!

Also, hypothetically speaking and out of curiousity, what if the bike had compression, spark and fuel yet didnt fire? Is that a possibility?
 
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valve jobs raise the tip of the valve stems.
sounds like the valves are all to tight and hanging open..
gonna suck trying to check valves that you cant get a feeler gauage in.
after a valve job i always bench shim a shim type head before re-installing the head.
if this is the case, install several size smaller shims and adjust as per manual spec.
 
blowerbike said:
valve jobs raise the tip of the valve stems.
sounds like the valves are all to tight and hanging open..
gonna suck trying to check valves that you cant get a feeler gauage in.
after a valve job i always bench shim a shim type head before re-installing the head.
if this is the case, install several size smaller shims and adjust as per manual spec.
Click to expand...


Well 3 people say its the valve shims that are no longer adjusted properly since the valves were conditioned so it sounds like we have a solution! (I hope lol) That was fast... :D

I will check the valves out sometime before the end of the week (hopefully correct the issue at the same time as well) and give everyone an update when I get a chance
 
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csbutler3 said:
so I took out the spark plug out of each cylinder one at a time, plugged the hole with my finger and cranked the bike;
Click to expand...

CAUTION::hand: Be careful doing that after you have the valves adjusted.. These are ferocious machines and could suck you entire hand into the cylinder on the power stroke :)
 
Okay, I finally got around to working on my bike again and during my absence I found out my valves were only cleaned up and lapped, there was no grinding work involved so I do not think the shims need to be replaced.

tkent02 said:
Your ignition timing has nothing to do with the compression, valve timing would have to be completely wrong to not have compression.
Click to expand...

Could anybody please explain to me, as detailed as possible, how I would set up cam timing correctly so that the valves are closed on the compression stroke? I have a feeling that I'm not doing this part correctly, even with a Clymer manual. Thanks again for taking the time to help out a super novice like myself =)
 
Please don't just think the valves don't need adjustment. Please measure them and know for sure.

But, to answer your request, is sounds like you did it correctly the first time. Set the timing marks on the end of the crank to the T1-4 mark. Align the #1 mark on the cam chain with the front edge of the head. Start counting cam link pins at the #2 mark, continue to the #3 mark on the intake cam. Note that there are not 20 pins between the marks, there are only 18. :eek: That is because pin #1 is at the #2 mark and pin #20 is at the #3 mark, so only 18 pins are between the marks. I stress this because I started to make that mistake the first time I tried to set the cam timing. :oops:

Another reason to stress checking valve clearance is that the specified clearance is very small. As the valve wear, it becomes less, so it does not take long to get to ZERO.
Example: the Kawasakis I used to ride called for .006-.010" clearance on the intakes, .010-.014" on the exhausts. The Suzukis we are dealing with call for .001-.003" on all valves. Keep in mind that .003" is only the thickness of a piece of paper. Most feeler gauge kits only go down to .0015 because the metal is so thin, it bends very easily.

.
 
You might have set the cam timing 180 degrees out of phase. It's easy to do.
I suggest you pull the #1 plug out, stick a screw driver down the hole, and rotate the engine while looking for the 1-4 T mark as Steve suggests. Once you have the mark aligned, with the screwdriver verifying you have #1 at TDC, check your cam timing again.

Good luck.
 
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