Looking for opinions on my valves and pistons (pics)

[Audioslave784]

My 1980 850 engine has only been firing on 2 1/2 cylinders since I got it.

1 - Fires
2 - Fires
3 - Fires every two or three cycles
4 - Doesn't fire at all

The bike was a bit of a rust job when I got it, but only showed 8500 miles on the odometer (not sure I trust that).

A quick review of the posts on dead cylinders got me up to speed on the possible problems: Either fuel, spark, compression

Good spark was confirmed by switching caps and plugs between 1-4 and 2-3. Numbers 1 and 2 still fired, and 3 and 4 were still weak/dead.

Fuel didn't seem a likely suspect either - I cleaned the pilot jets and confirmed that all the float bowls had gas, and neither cylinder improved at all with higher throttle or revs, when I figured the other jets should have kicked in to help.

I then did a compression test:

1 - 90 psi
2 - 90 psi
3 - 45 psi
4 - 30 psi

Afterwords I realized that I performed the test improperly - I didn't open the throttle. Thus my numbers are lower than actual, but to me these results hinted pretty strongly at the problem.

I've never done a rebuild before, but after reading through the Haynes manual and some posts here, I decided to go for it. My plan was to change the piston rings, hone the cylinders, and inspect and lap the valves.

Now that I've taken a look at the pistons, however, the cylinders and rings all look fine to me. The pictures that I've seen of cylinders with bad rings all have a burnt look from the leaking combustion gases, but from the rings down, mine don't have a mark (except for some vertical streaks. I measured the free ring gaps with a digital micrometer and they were all between 8.5 and 8.9 mm (spec is 7 - 9 mm)

So now to my questions:
First, what do you guys think of my pistons and rings? Is there any value in replacing the rings ($100 for rings plus $40 for a ball hone)?

Second, what do you think of my valves? Specifically, what does all that black, white, and red stuff on them mean? Are any of these too far gone for a mere lapping?

Pistons 1 and 2 (good cylinders)


Pistons 3 and 4 (weak/dead cylinders)


Piston 4 close-up (note the light vertical scratches - not deep, but you can feel them with a fingernail)


Valves for 1 and 2


Valves for 3 and 4

[bwringer]

Use a ball hone on the cylinders, install new rings, and ride happy.

You'll need to fix whatever the problem was that was causing #3 & 4 to not fire, but I don't see anything all that wrong there.

Oh, and you'll probably want to use only OEM Suzuki gaskets and seals, please. DAMHIK.

[tkent02]

You need to find out why it wasn't firing, those pics ain't it. Everything there looks fine.

A non firing cylinder will get low compression as a result, because of excess fuel on the cylinder walls or whatever. Get it firing and ride it, the compression will come back up after a while.

But yeah, as long as you took it apart you may as well put in new rings.

Problem is the new rings will need a good hard break in, with engine running properly. This must be done immediately when first started up. Running it for a while as you dink around playing with ignition or carburetion or whatever will negate the chances of a good break in. A waste of a good set of rings.

Should have posted your questions before taking it apart.

I think if it were mine I would reassemble it as is, fix the non firing problem, check the compression, ride it a week or two and check it again, then put in new rings or complete top end rebuild if it were needed.

Edit, did you adjust the valve clearances before taking it apart?

Valves too tight will cause low compression numbers.

[tejasmud]

At least you are giving it a shot, have to learn some how I suppose.

"Ain't Skerd"

If it was not firing good initially that would most likely be electrical.

Low compression could have been valves if out of specification, sticky rings possibly.

Did you line up/ turn the piston rings any before taking the pics, or is that how they were?

Intake boots look original, but looks like the o-rings have been changed from the hex bolts being installed.

So, in this far. If it were me, soon will be.

Pull off the pistons clean them up. Buy new piston pin cir-clips, new gaskets, rings(8500miles?) might as well, and new valve seals. Check the valves and lap them. Hone the cylinders. Clean everything like you would eat off it (clean, clean, clean), extra clean.

Put it back together. make sure cam tensioner is set, then turn it over slowly after it is back together by hand to make sure the cams are correct. If you watch the marks and count the pins double check them. Adjust/check valve clearances.

I would turn it over by hand to get the firing issue fixed after cleaning all the connectors, possibly a coil relay mod to get 12v at the coils, check the ohms across the coils replace if needed, new wires, caps, and plugs if not already done.

Hopefully you will be running the stock exhaust, carbs, and airbox so it will fire up and be close to give it a few hours of riding.

[Nessism]

Those pistons look very good and the engine had good compression before it sat as evidence by the lack of brown blow by residue on the piston skirts.

I concur with the others, replace the valve stem seals, bottle brush the cylinder, and new rings. Normally an engine with such low mileage can reuse the rings, and you still could, but replacing them is safer.

[tkent02]

Test the valve's sealing by pouring a liquid like gasoline or some solvent in the combustion chambers. Put a spark plug in first to fill that hole obviously. Bad valves will allow the liquid to leak out right away, tight ones will keep the liquid in. The valves in your pics look fine, but what you need to see is the surface where the valves hit the seat, and the seat itself, which are both hidden with the valves closed.

You can check your valve clearances with the head off the engine. Put the cams back on and all the shims and things back in their original positions. It will tell you if the low compression was from tight valves. Don't rest the head on whichever valves are open at the time, rest it on blocks or something.

[Audioslave784]

Wow, I was sure the problem was a compression leak. Looks like I was chasing the symptoms and not the cause. But on the bright side, last week I didn't know how to rebuild an engine, and this week I do, so all in all I'd say that's a win.

A little more background on the engine. I adjusted the valves a month ago and set all the gaps to the upper end of the spec. I also replaced the intake boot o-rings (but not the boots) and put on the fresh screws. I am running stock exhaust and airbox. The bike was actually running pretty well on it's 2.5 cylinders (I can't wait to feel how she pulls on all 4). I took it for a few rides around town, one of which lasted over an hour, but cylinder 3&4 didn't get better for it.

I didn't believe the problem was electrical, because even after I switched the 1-4 and 2-3 ignition and plugs, cylinders 1&2 fired fine and 3&4 were still intermittent/dead. Is there something I could be overlooking here?

I am actually thinking now that my reasoning behind disregarding the electrical and fuel problems might not have been sound. If the cylinders had low compression from the constant stream of unburned gas, is it possible that a charge with both good fuel-air mix and a good spark still might not fire?

Either way my next step will be to pour some gasoline in the combustion chambers and test for valve leaks (thx Tkent). I'll also order new rings and a ball hone, inspect and lap the valves, and throw in some new oil seals. Might as well learn how to do it all now and get it over with.

If the valves on 3&4 leak like sieves then hopefully I can solve the problem before I get the engine back together. If not then I'm pretty much back to square one (although it sounds like I should read up on testing the ignition coils). Next time I'll make a damn post BEFORE jumping into a major rebuild.

Thanks for the help, I'll post updates when I got em.

[Big T]

Since you have the head off, it's easier to prop the head up (with the intake boots vertical) and pour gas into the boots, as see if gas comes out around the valves

Turn head 180 degrees (exhaust ports up) and test those valves

It's a lot easier to see the leaks with the fuel running into the combustion chamber, rather than out

Also, check your cam chain guides while you're in there. While you engine has low miles, plastic parts tend to age and get brittle

[chef1366]

So you just swapped coils?
Looking back at your first post you only switched spark plug caps and plugs? Did you swap coils?
Maybe you have bad wires on the #3 and #4. I would've swapped 1 and 4 and 2 and 3 to see if the problem went to 1 and 2.
One coil fires 1&4 and the other 2&3.
If the issue still prevails after the rebuild it may be good to get some good coils.

[Nessism]

I wouldn't bother with that leak check business since there is going to be carbon and gunk on the valves and seats. Scribe numbers into all the valves so you can get them back into the proper hole after you take everything apart. Decarbon the head and valves (make sure you don't loose the numbers) and then inspect the valves and seats to make sure everything is in good shape. Assuming everything is okay, lap the valves and slam in new seals. Leak check then if you want but if everything check out well, and the valves lap in well, you don't need to.

[chef1366]

Valves seat after the first couple of lifts. They get hammered in.
Make sure you get all that lapping compound off before reassembly.

[Audioslave784]

Chef - I didn't really explain myself well here, but what I did was swap the wires between 1-4 and 2-3 first, tested the engine, then I swapped spark plugs and tested again. Neither of these swaps changed anything.

I just rested the head on the exhaust side and poured gas into the intake boots. Watched the valves for a couple of minutes, no leak. Flipped the head and poured gas into the exhaust side. Again no leak. I already built a PVC valve spring compressor and bought some lapping compound, so I'm going to try and lap the valves this morning anyway while I've got some time.

[tejasmud]

Make sure you get all that lapping compound off before reassembly.

I have read this a few times about making sure the compound is cleaned off due to it will cause pitting. The abrasive in the compound can't be good for an engine. Makes sense to me.

[chef1366]

I have read this a few times about making sure the compound is cleaned off due to it will cause pitting. The abrasive in the compound can't be good for an engine. Makes sense to me.

Shoot, I don't need to leave lapping compound on my head to hammer it. My valves were so hammered they were almost as sharp as razor blades on the edges.