OK so berate me all you want I deserve it [bang]
So I took the bike ST3 all apart last year to do the valves and due to a number of
things never got it put back together. I finally moved to a new house and resolved
to get the bike running again and take a long trip. I need to get away.
Anyway I was working the valves over yesterday and realized I have very little compression.
I would put my finger over the plug hole to make sure I had TDC on the compression stroke and
I couldn't get any pressure to blow my finger off. What do you think? could the rings be sticking?
If I put the plugs in and turn the engine in 6th gear there is some resistance but not like it should be.
HELP I need to get away! >:(
Possibly the walls are dry and the rings aren't sealing. I'd try a little oil in the cylinders, turn it over (with a crank turning tool) to make sure the valves aren't hitting the pistons, and run it.
Thanks DP.
I'll put a bit of oil in the cylinder and crank it over a few times and finish the valve job.
Put it back together and start it up.
The pressure from combustion should knock the rings loose you think?
This was something else I was wondering about. I thought that if you take the belts off you should be able to
turn the cam pulley pretty easily? Right?
For some reason i can't turn mine by hand with the belt off it so I can slide the rockers over.
Fit a belt over the cam and use both hands to adjust the belt to get the cam where you want it in order to slide the rocker over.
Quote from: ducpainter on June 07, 2010, 08:49:58 AM
Possibly the walls are dry and the rings aren't sealing. I'd try a little oil in the cylinders, turn it over (with a crank turning tool) to make sure the valves aren't hitting the pistons, and run it.
+1 Had this problem before on older bikes I've taken apart and restored [thumbsup]
Sure sounds to me like something else may be wrong, like the timing belts being off enough teeth to mess up the valve timing, or not enough shim clearance holding the valves from closing.
I'd double check the timing and valve adjustment. I've never seen dry rings or cylinder walls result in no compression but then there's a lot I haven't seen.
If you don't have one, a compression tester is a good investment.
Could be an opener that stuck open causing all the compression to go up into the intake tract.
Can't push the valve down? Was it hitting the piston?
I checked the timing. Everything lines up.
I was goofing around and found if you are two or more teeth off on the timing the
valves will hit the cylinder when the engine is rotated.
This is on both cylinders. Not just one.
I am turning the engine counter clockwise as if the bike was moving forward correct?
What's odd is when I started this about a year ago, I had compression.
I started measuring the clearances and then my life got complicated so it sat for a year.
Now I try and get this finished and no compression. I haven't taken the belts off, at least that I remember :P
But that aside I did check all the timing marks and they all line up and the engine turns freely.
Would putting a tablespoon of oil in the cylinder and cranking the engine do anything?
Maybe pop the rings loose. I was thinking they may have a bit of rust keeping them from seating?
Quote from: VisceralReaction on June 08, 2010, 07:01:03 AM
. I haven't taken the belts off, at least that I remember :P
But just a few posts up you said the cam didn't turn easily with the belt off, which one is it?
mitt
No you are right Mitt.
I did remove the belt off the vertical cam pulley to try and
turn the pulley by hand, BUT I did make sure the timing marks were lined up before and after.
The cams don't turn, unless the belts are on it and I turn the tire while in gear.
Am I correct in thinking that the cam pulleys should turn easily
by hand when you take the belts off?
<edit>
I read what I typed and it didn't make sense :)
Quote
Am I correct in thinking that the cam pulleys should turn easily
by hand when you take the belts off?
Only if the piston is low in the cylinder. If you have the piston near to or at top dead center, the valves will hit the piston when you try and turn the cam pulleys and you won't be able to turn them.
I was talking to LT at Desmotimes and I found on the ST you can't turn the cams by hand because they
have high lift cams. He was thinking the same things as a few of us here that there isn't any
oil on the rings. I'll try so oil out tonight and post back up.