Leak Down Test problems

[Karstan]

So, I posted last week about some problems I was having with a compression test (no pressure registering) and OldSkool recommended I try a leak down test instead. So, I'm trying that instead. Either I'm doing something very wrong or my engine has serious problems.

Here's the status:

1) Engine is removed, as are carbs, cam tensioner, and all covers.
2) I've got the engine at TDC (for #1 and 4) per this: http://www.bwringer.com/gs/tdc.html.
3) I've removed the spark plug from #1.
4) When I attach my tool and blow air into the plug-hole, all the air comes out of the intake port (where the carbs attach).
5) This occurs on all four pistons.

I'm going to go adjust the valves now as someone suggested that might be the problem I was having with my compression check. In the meantime, any other thoughts?

 

[Nessism]

You are doing a leak down test without even checking the valves first?

 

[Karstan]

Yeah, I realized as I was posting this that I was doing things in the wrong order. Please forgive the mistakes of this noob.

But now I'm running into problems with my valve adjustment. My camshafts aren't lined up properly!

According to the tutorial on BikeCliff's website, they should be able to point away from one another.
http://members.dslextreme.com/users/bikecliff/images/16valve_adjustment.pdf

No matter how much I rotate mine, this will never be possible. I have no idea how to deal with this. Help!

 

[Nessism]

Time to check the camshaft timing per the Suzuki factory service manual. Bring 1-4 to TDC, and check for alignment of the 1-- mark on the exhaust cam sprocket (it should be pointing forward to the gasket surface). Then check the number of cam chain pins between the 2 & 3 marks on the cam sprockets. Maybe the cam chain skipped some teeth.

 

[Karstan]

Thanks Nessism! If the cam chain DID skip some teeth, is that an indicator that I need to fix/replace something else?

 

[Nessism]

Thanks Nessism! If the cam chain DID skip some teeth, is that an indicator that I need to fix/replace something else?

Check timing first, adjust as necessary second, then access if something was damaged third.

 

[Homie]

So, I posted last week about some problems I was having with a compression test (no pressure registering) and OldSkool recommended I try a leak down test instead. So, I'm trying that instead. Either I'm doing something very wrong or my engine has serious problems.

Here's the status:

1) Engine is removed, as are carbs, cam tensioner, and all covers.
2) I've got the engine at TDC (for #1 and 4) per this: http://www.bwringer.com/gs/tdc.html.
3) I've removed the spark plug from #1.
4) When I attach my tool and blow air into the plug-hole, all the air comes out of the intake port (where the carbs attach).
5) This occurs on all four pistons.

I'm going to go adjust the valves now as someone suggested that might be the problem I was having with my compression check. In the meantime, any other thoughts?

Hi. Yea, you need to verify that came timing BUT first you need to re-install the cam chain tensioner that you previously mentioned you removed. Once you get the cam timing squared away make sure you are putting the piston to be checked at TDC on the firing stroke and not the exhaust to intake overlap stroke. Easy way to do this is to observe the valve action as you turn the engine over by hand. If the exhaust valve is closing as you bring the piston to TDC you're on the overlap stroke. On the other hand, if the intake valve is closing as you bring the piston to TDC you are on the firing stroke and thats where you want to be. Now, back to the garage....

 

[Karstan]

Thanks OldSkool and Nessism!

So, I got the cam tensioner and the timing problem fixed. Then I adjusted the valves (twice actually). Finally, I conducted the leak down test again. But the results aren't so great.

Valves #1 and #2 got 8% and 4% loss respectively, which isn't bad. But I still can't get ANY pressure on #3 and #4. I even tried leaking in air while rotating the engine all the way through it's cycle and NADA. So, what now? Do I have to tear apart the engine and look at the valves?

 

[Homie]

I still can't get ANY pressure on #3 and #4. So, what now? Do I have to tear apart the engine and look at the valves?

No, don't tear it apart. Lets see what we have first. #1 and #2 are good but #3 and #4 you don't get ANY pressure at all? Lets confirm a few things first: a) you got the cam chain tensioner back in, set the cam timing and adjusted the valves (twice); b) you used the exact same input air pressure on the leakdown tester for #3 and #4 as you did for #1 and #2; c) the pressure release valve on the leakdown tester wasn't accidently "on" while testing #3 and #4.

All leakdown testers have two gauges - one for the input air from the compressor and the other for the output air to the cylinder. If you are pumping the same amount of air pressure (usually somewhere around 80 psi or whatever your tester's manual says to use) into #3 and #4 and you are not getting ANY pressure reading on the output gauge of the tester something is obviously wrong. With no pressure reading on the output gauge of the tester you should hear (and feel) a lot of air coming out one of four places: the intake port, the exhaust port, the intake or exhaust port of an adjacent cylinder (blown head gasket) or the crankcase - it has to be going somewhere!

Let your compressor run until the tank is full and the auto-shutoff turns it off (its a lot easier to detect the air without a noisy compressor running). Make sure you opened the output air valve all the way open to pressurize the cylinders. If the air is going in, it has to come out somewhere. Now back to the garage try it again and listen and feel for the air because it has to be there somewhere.

 

[Nessism]

Hope you didn't try to turn over the engine with the starter while the cam chain tensioner was off, otherwise there could be bent valves now.

Did you check the valve clearances after adjusting fixing the cam timing? If so, did you find the valves on #3 & #4 really loose. If so...not a good sign.

 

[Karstan]

OldSkool -
To answer your questions: No pressure at all in #3 and #4. Cam tensioner went back in, and adjusted the cam timing (the two were actually simultaneous in my manual), then adjusted the valves. I definitely used the exact same pressure. The pressure release valve was definitely not on.

I made my own tester using this tutorial: http://www.thegsresources.com/_forum/showthread.php?t=186558&highlight=leak-down
There's DEFINITELY air escaping. I can hear it and feel it from both the exhaust and intake ports. I plan to verify tomorrow exactly how much and from where (after first double checking the valve clearances).

Nessism -
I'm afraid I did exactly that. :/ Stupid noob mistake. However, all four valves were VERY tight. Scarily tight, actually. So, I'm also worried about what kind of damage that may have caused.

 

[MisterCinders]

If you spun the engine w/o the tensioner, you probably blew the cam timing, as the chain jumped.

Since you will need to pull the cams to reset the timing, you may as well pull the head to inspect the pistons and valves for damage.

If it's any consolation, I made the same goof when I did my valves and piston rings. When I pulled the head and valves again to inspect the damage, no valves were bent. If your valves are tight now, you might have similar luck.

 

[Karstan]

Well, I re-adjusted the valves. There does seem to be a knack to it that I think I finally picked up. I re-did the leak down test on all four cylinders. The first two seem to be in great shape. The last two get 60 psi (on each) with air obviously escaping from both the intake and exhaust ports.

So, it looks like I'll be taking the engine apart?

Thanks for the consolation Mister Cinders. It's nice to know that I'm not alone.

 

[Homie]

So you re-adjusted the valves and now you are getting 60 psi? OK, now we are getting somewhere, but you still have air coming out of both the intake and exhaust ports when you test it? OK, here's what I would do next:

1) don't pull the head......yet.
2) on the afflicted cylinder's valves, back the rocker arm screw adjusters all the way off
3) rotate the engine by hand to TDC on the firing stroke and verify that the rockers are totally loose. Being that the screw adjusters are backed all the way off there should be a lot of clearance between them and the valve stems. This will ensure that the valve springs are fully pulling the valve face onto the valve seat in the head.
4) retest the afflicted cylinders with the leakdown tester. If you still get air coming out of the intake and exhaust ports you can assume you have some kind of valve problem.
5) valves could be: a) bent; b) burnt; c) have some kind of crud on the face or seat preventing them from sealing; or d) worn valve stems or valve guides which allow the valve to "wobble" and not place the face squarely on the seat to effect a good seal.

Now back to the garage and lets get this thing figured out.

 

[Karstan]

Well, OldSkool, I got a bit impatient and went ahead and removed the head. I think I may be glad I did. It doesn't look very healthy in there:

 

[Guest]

Where did everyone go? Must be dinner time... I am no pro... but with scratches on the pistons, we know something rubbed there. The gunky stuff in the head does not look like fun either... I am going to see what the boys think...
Curt

 

[Karstan]

Where did everyone go? Must be dinner time... I am no pro... but with scratches on the pistons, we know something rubbed there. The gunky stuff in the head does not look like fun either... I am going to see what the boys think...
Curt

The scratches are my crude numbering of the pistons.

 

[Karstan]

Alright, I cleaned up the valves and then, per the manual, poured gasoline into each of the intake ports and exhaust ports to see if any leaked through the valves.

Everything was tight and there were no leaks. So, either I fixed the problem, or the problem is elsewhere.

As for the cylinders, should I just clean them up and leave them otherwise alone?

 

[bbjumper]

Well, looks like it's using oil in 1,2 and 4, # 3 looks fairly normal and I can't really tell but the valves look OK to me. All of that is pretty much academic now, you have it apart, clean it up real well, inspect, measure, replace or repair as necessary. New valve stem seals, new rings, new gaskets and seals, take care of any issues with the carburetors or intake system. Put it back together properly with the use of the forum and manual. Then you got yourself a scoot that will run like new, one righteous ride.:lol:

 

[Karstan]

Yeah, that's kind of what I'm thinking. How do I get the pistons out? The manual calls for a special tool, but that tool seems to have been discontinued.