Compression issue after rebuild

[madwoodman58]

I am so depressed.

I had some oil leaks around my cylinder and head so I figured I would just rebuild the top end while I was at it. I have an 82 GS1100GL with 14000 miles. I had rebuilt most of the lower end and drive train last year and wanted to get everything matched up. I have a K&N air filter in the standard box and V&H 4 into 1 exhaust.

So I bought all the OEM gaskets and rings, took everything apart, cleaned it up like new, got every bit of carbon off the pistons, cleaned and rebuilt the carbs with new rings and OEM gaskets, put in new jets sized off the schedule on BassCliff's site (two sizes up on the main, one on the pilot. New hoses, etc.

I followed all the instructions, took my time and did everything the right way. I got it all back to gether and it was beautiful. Started it up and it ran! Took it for a ride int he neighborhood and it would bog down at about 3000 rpm and I had to really get on it to get it to jump up to 4500 rpm. It had no power and couldn't really push the bike.

I double checked everything. Went through the carburetor tuning procedure several times. Nothing changed.

I just checked the compression. :-( A consistent 90 psi +- 3 all the way across. Ran the wet check and it went up to 120.

DO I really have to buy $200 worth of gaskets and take th ewhole thing apart again and hope I get it right the next time? I've never really had a problem with my repairs working before (thanks to everyone on this board for holding my hand), but this is a real kick in the teeth.

I have put a total of about 18 miles on the bike between all my test rides since the rebuild.

Is it possible it is something else? The PO had a 140 main jet in it that I dropped down to a 120. Seemed weird, but I was trying to set everything correctly, "by the book".

Please help me before I go run into a wall (at 2000 rpm).

[Big T]

Are those compression number hot or cold?

Throttle held WO during the test?

Honed the cylinders?

Was it running well before you took it apart?

[gearhead13]

Are you sure you got the cam timing right? If its off a few teeth that could lower compression.

[madwoodman58]

Compression numbers are warmed up, idled for about 10 minutes first.

Throttle was wide open.

Cylinders were honed before I replaced rings.

It was running well before I took it apart, just pesky leaks in the gaskets.

I thought I had the cam chain right. The guidance as to the line on the cam pointing "to the top of the gasket" isn't real precise, butmtheremarent to many ways to do,it. I wil check that when I take it apart.

[SqDancerLynn1]

I would bet the timing is off a tooth

[gearhead13]

The exhaust cam sprocket arrow on mine points more to the aluminum surface. Are you using an actual Suzuki service manual?
Did you check the ring gaps before install?

[almarconi]

It is very easy to mess up the timing if you are not careful. The crank can move just a bit while the cam chain is off and this will throw off your measurements. It does not take much to be off one or two teeth. Getting the line on the sprocket lined up with the gasket surface is only the first step, you also need to count the cam chain pins to make sure they are in the proper position. The manual has a picture of how its supposed to look.

What about the cam chain tensioner? If its not working properly this will not allow the engine to rev properly.

You made no mention of adjusting the valves, are the clearances in spec? This will give a false compression reading if the valves are not adjusted properly. It's very possible that the rings may not have seated yet.

Are the head bolts tightened down using a torque wrench?

[madwoodman58]

Yes, I'm using the service manual I downloaded from BassCliff's site and I was very careful to count the links between teeth. Of course, I'm hoping I did make a mistake or the rings aren't seated yet. That's what I'm looking for so I may not have to take it down to the base again. If I should run it another 20 miles before I start checking things, I will. I just didnt want to damage anything.

Cam chain tensioner was installed according to the service manual and appears and feels to be working properly. All head bolts torqued to spec.

I do need to check valve clearances again. I think I'll take the cover off and check the timing chain and valves first and go from there.

[Nessism]

Make sure the 1 mark on the exhaust cam sprocket points at the gasket surface. Sometimes it looks like the 1 is above the gasket surface but that's okay (if you move the chain a tooth, it will be further off below the gasket surface).

What you describe with the bike not liking to run at high rpm doesn't sound like a compression issue. Most likely your carbs are jacked up somehow, or the cam timing is off. A 140 main jet sounds too big, so wondering if those are aftermarket jets of some sort (Dynojet brand for example)? Maybe put them back in and see if the bike runs better, like before?

[Steve]

..., you also need to count the cam chain pins to make sure they are in the proper position.

And it's VERY easy to mis-count those pins if you are not careful.

I can't (won't, actually) tell you how many times I mis-counted pins on the cam chain before I finally realized that the pin directly over the #2 mark on the exhaust cam sprocket is not ZERO, it is #1. Yes, you start counting with that pin, not the one next to it.

Cam chain tensioner was installed according to the service manual and appears and feels to be working properly.

It is also rather easy to mis-read directions for the tensioner.

In a nutshell: compress the plunger, lock it in place, install tensioner. Release set screw so plunger is free to move, turn set screw in until it stops, then back it out 1/4 turn and use lock nut to keep it there. Too many times, people will stop reading at "let it move, then turn the screw in until it stops". If you don't back it out that 1/4 turn, the plunger will not be able to move to take up any slack.

.

[tkent02]

put in new jets sized off the schedule on BassCliff's site (two sizes up on the main, one on the pilot. New hoses, etc.
The PO had a 140 main jet in it that I dropped down to a 120. Seemed weird, but I was trying to set everything correctly, "by the book".

Once you check the cam timing, put the old jets back in. If it was running perfectly with the 140 main jets, put them back in and ride it hard. There is no book, every engine, pod, and pipe is different. Those jet sizes are only rough guidelines to get you in the ballpark.. The compression will come up once the rings seat. To seat the rings, open the throttle. Once the rings have seated, fine tune the jetting but for now open the throttle.

http://www.mototuneusa.com/break_in_secrets.htm

Your compression numbers are what you might expect with unseated rings, and those numbers, though low, will not cause the lack of power in a certain RPM like you have. That is a jetting problem.

[Big T]

Plus 1 to all the above

If your cam timing, cam tensioner and carbs all check out Ok, then go ride it a few hundred miles and see what happens. Lots of varying RPMs to seat the rings

[Maddevill]

If he had 90psi dry and 120 psi wet he has a compression issue. No amount of re-jetting will fix that. So, I say take care of the compression problem first, whether that be running it in more r taking the top end apart again.

[almarconi]

I can't see spending all that time and money replacing rings,etc without taking the head apart. The head should be stripped, cleaned up, measured, parts replaced if needed, new valve seals, lap in the valves and assembled. If your going to all that trouble might as well do it right.

[madwoodman58]

That was the process I went through the last time. Now everything is new.

I'll check the cam timing and the valve clearances first. Then I'll try the old jets. Then ride it for a while. Then tear the whole stinking thing apart again.