Compression test.

[courier11sec]

110,140,90,110. Bummer...
Not sure if I want to rebuild or replace the bike.
Even in tip top shape I'll still have a heavy slow bike. I love the thing, don't get me wrong, but I shouldn't have a car that's faster than my bike if you ask me.

 

[49er]

Ray

Those figures are sad. Because #2 is close to mormal check that the valve clearances aren't too tight on the other pots. If your car stomps on your 850 then your bike needs a good tuneup or you're driving something exotic.
My 850 had 110-125 and was getting harder to start when left for more that 3 days between runs. It still performed well but I decided that it needed a freshen up.
On strip down the rings were worn and the bores were marked and slightly oval. The markes have been caused by the bike being stored for several years by a previous owner. When I pulled the cams, the lobes had light rust pitting on them.
I'm fitting new o/s pistons and raising the cr.
These bikes are SPORTS TOURERS. If you want something that kicks butt, buy a lightweight 16 valve job. If you want comfort and average performance and handling, give your 850 a top end rebuild. This is assuming that the bikes mileage isn't excessive.

 

[courier11sec]

I was thinking I'd rebuild this one for putting around on and look out for a liter bike to go fast on. The car runs high elevens, so it's not like the 850 is worthless, but now I know it needs rebuilt and I'm the kind of guy that can't just put it back together and ride it that way. I might offer to sell it back to the previous owner now that I've improved it quite a bit. We'll see.

 

[courier11sec]

Good call on the valves. I pulled the valve cover and checked it out today. Sure enough, the valves are too tight. Couldn't manage to get the shims out with nothing but a couple of screwdrivers though. Guess I'll look around for a tool.

 

[Tom MLC]

This may be a tad bit late, but did you check the compression with the engine warm & the throttle wide open? Sorry to insult you if you're thinking DUH..of course I did! Anyway in case you didn't, you will find different results. I too had poor compression results on my 1000 after she had been sitting for a few weeks. I got 110/90/95/130. But I didn't panic. After I got her back together and running in the garage I checked again. 130/135/135/140.

Sounds like you've already done a tear down. I hope it wasn't a waste of time.

 

[courier11sec]

No offense taken, it was a good question. engine was warm when I did the compression test. Throttle was not wide open. I suppose I should have thought of that to make sure the feild was as even as could be.
Still the tight valves have me thinking I could luck into just a valve adjustment.
Now if only I could find a danged valve adjustment tool around here.

 

[Guest]

No offense taken, it was a good question. engine was warm when I did the compression test. Throttle was not wide open. I suppose I should have thought of that to make sure the feild was as even as could be.
Still the tight valves have me thinking I could luck into just a valve adjustment.
Now if only I could find a danged valve adjustment tool around here.

throttle must be wide open or it'll throw off the results

 

[Guest]

Find a shop or dealership that carries MotionPro stuff. They can get the tool you need... about $30.00. Or you can order one online. I think it's called the Suzuki tappett tool.

 

[mark]

throttle must be wide open or it'll throw off the results

Totally agree with this. A compression test without a wide open throttle means little. I'm surprised your numbers are as high as they are with a closed throttle. Mine were in the 50's.

 

[49er]

Z1 Enterprises, Inc stock the Suzuki Shim Changing Tool (#KL35-2628) for $27.00.

Contact: sales@z1enterprises.com

Cheers
Ian G

 

[49er]

Ray
I have tried to send the previous post twice. Where you see a smile at the end of the part # substitute an eight.
Cheers
Ian G

 

[courier11sec]

New results with throttle open
150,135,130,150

 

[mark]

New results with throttle open
150,135,130,150

Those are O.K. numbers. Once you get the valves adjusted you could see even more improvement.

 

[courier11sec]

I'm not happy with the drop in the center two cylinders, but with the valves so tight, I'm apt to think it will improve as well. We'll see.

 

[jetta90]

Let me share my little story.................................just bought a 1984 GS750 E with 66,000 kilometers (41,000 miles or so). Ok shape but needs some attention................................
compression check yielded 107, 100, 100, 105 - engine cold, throttle wide open (more on this in a moment), valves NOT adjusted and on the tight side.
Updated compression check now gives 130, 120, 126, 126 - engine cold, throttle wide open (again, more on this in a moment), valves adjusted properly.

It will make a difference once your valves are adjusted and it will also make a difference checking compression when the engine is warm versus cold. I will check next with warm engine.

OK, now for the "more in a moment" bit.............................there i was doing the first compression test and looking at the results with great dissapointment, so I figured I should adjust the valves to spec to get accurate results. Makes sense. So, I adjust the valves and test compression again but I get some improvement but not quite what i expected.
Repeat the compression check on all 4 cylinders with not much change.
Well, now I'm really starting to be upset with this recent purchase, not that it cost that much but darn it would be nice to get a break once in while!!!
If I don't happen to glance at where the air intake snorkel is located ........
WTF - just to be sure nothing would get in I had stuffed a rag in there !*@*!*&@&!*&*&** nice and tight !!!! Definately one of those DOH !! moments
a la Homer Simpson. How embarassing.
Anyway, compression test with valves adjusted, cold engine and no frieken rage stuffed in the intake is 130, 120, 126, 126.

 

[Guest]

Anyway, compression test with valves adjusted, cold engine and no frieken rage stuffed in the intake is 130, 120, 126, 126.

Now try it with the engine warm. They will go up even more.

 

[49er]

Your story has a familiar ring to it. I managed to forget to remove a small piece of rag from an inlet port on a race motor a few years back. The thing started roughly, then cleared and roared into life. Didn't realise what had happened until I found that I had only removed three rags. Cleaver stuff.
I'm not sure if your air box is similar to the 850's. If so, the reason that your figures didn't rise when you removed the rag from the airbox intake is probably due to the fact that some air is drawn in directly through holes in the bottom of the airbox. At cranking speed, the airflow would be low enough to enable sufficient unrestricted air through to the cylinders. You may even have an unsealed end cap on the box.
Checking cylinder pressures when the engine was hot increased my readings by 10psi from the cold readings.
At the end of the day, the cold pressures are what influence how well you can restart an engine that has sat for more that 3 days, especially in the winter. Engines that have sat for days are usually hard to start with the throttle fully open. One exception is when they have been flooded.