Opinions Please

[79XS11F]

As many likely know I am restoring my 1979 11 to complete stock configuration. I have the original complete running engine here that is in very good condition except that the compression reading are a little over the MAX spec. This likely means there is a far amount of carbon build up in the combustion chambers and on piston tops. I have a head gasket which is all that would be required to Re & Re the head for cleaning. I wouldn't even remove the valves for the job. If done I would have to use care to not displace or remove the carbon ridge at the tops of the cylinders. I am thinking that it would be nice to not have to remove the engine again on this bike.
Questions for opinions
Would you do this before installing the engine?

Can the cleaning be carried out without displacing or losing the carbon ridge at the tops of the cylinders?

Rob

[trbig]

Can the cleaning be carried out without displacing or losing the carbon ridge at the tops of the cylinders?

Yup... put the engine in and run a few tanks of Seafoam through it when you get it done. I realize opinions are like ***holes, but mine is that you don't take the head off. Leave it like it is. Sheesh... I think this is a first of hearing someone complain of too high of compression! lol.
When you get that motor tuned in right with the carbs, and you actually run it at operating temps instead of just idling around in the shop, the carbon won't be a problem.

Again... just my opinion.

Tod

[81xsproject]

I agree, don't take it apart. In the mean time, I recommend pulling the plugs, get piston pairs close to TDC but not right on, and fill combution chambers (at the just less than TDC position) with MMO, then slowly turn it over, then let up soak. When ready you can put rags over the holes and turn over with starter to blow out the MMO. More here:

Hobbyman's Crop Duster Method

[TopCatGr58]

Hey Rob,

Yeah, don't work any harder than you have too!

Aside from the fine suggestions above, I've also read of simply running the engine close to operating temps, put a fan in front of it while it's sitting, remove the intake boots/filter housing so you have easy access to the carb intakes, and then get a spritzer bottle, and some cool water, and spritz into the carbs, the water helps to crystalize the carbon and let it flake off/out.....as what I've heard and read....haven't done this technique but have seen it posted here before by more mechanically knowledgeable folks than I!
T.C.

[79XS11F]

trbig .... Is Sea-foam that good? I have never used it or seen it for that matter. I don't even know if I can get it in Canada.

81xsproject ... What is MMO?

TC ... If carbon flaks off while running what is the risk of it messing up the valves as it is exhausted?

Rob

[randy]

Yes, the water spray method is the time honored way to remove carbon. Have to keep the revs up, though to prevent stalling. And just use a mist, not a stream of water!

[TopCatGr58]

Rob,

SeaFoam IS that good, tuneup in a can, helps keep varnish out of the fuel system as well. I put in several ounces in every few tankfuls.

MMO = Marvel Mystery Oil, another great varnish/gum dissolver!

Thanks Randy for the confirmation and additional technique info, the carbon is relatively soft, and won't damage the valves as it's being blown out!
T.C.

[prometheus578]

The ol' Carbon ring dilemma...
What of it?
And yes, I've read of it. Can't recall where, though. Can't seem to find it now.
Sort of funny... when the bike was new... did it have a carbon ring? No.
Just what is the purpose then, and why can't I remove it?
"It's a ring of carbon that forms above the piston rings as the combustion chamber gets coated with carbon. If you remove it, you'll lose compression."
I see. But it wasn't there when the bike was new, and I had plenty of compression. And when I re-ring pistons, don't I re-hone the cylinder, etc which also removes the carbon ring.. yet that causes no problems.
"Yes, but you've put in new rings."
Yes, but I've also torn apart engines for other problems, and just have lightly honed the cylinders, used the existing rings, and have no problem either. And if the carbon ring is really important, wouldn't a cheaply rebuilt engine soon re-build it's carbon ring anyway, as cylinders often do? And doesn't part of two-stroke maintenence call for the occasional removal of the top of the cylinder to remove carbon... which also means the carbon ring, yet they function fine afterwards?
"But people say the ring is important..."
People say that changing your underwear everyday is important, too. So what? (talk about a carbon ring build-up!)

The ring is there, as it's at the extreme limit of the reach of the rings in the cylinder. This is where the rings can no longer scrape the cylinder walls, etc. Yes, the carbon ring build-up will tend to overlap the ring area, providing a seal of sorts on the wall, preventing gasses from slipping past the rings(if they're badly worn) at the moment of ignition, but as the piston moves downward and the pressure is still building.. why doesn't the pressure slip past when the piston is lower than the carbon ring?
If the engine is in good shape, you should have no worries.

Now then, if anyone can cite references for opinions different from this, please furnish them.

"MMO" is either someone related to Exhalted (exhausted?)Guru MRO, or stands for Marvel Mystery Oil. (Take yer pick.)
Easier to clean the carbon with the engine out, more accessable, if you choose that route.
Carbon flakes sticking to the face of the valves is a concern, but not one that happens all that frequently, but I have seen it.
Always put a fan blowing on the pipes and fins if you run the bike for any decent amout of time... unless you enjoy looking at blued pipes.
And another thought...
Most good running engines are clean anyway, have no thick carbon ring, just a little light carbon staining in that area. When people run "cleaners" through their engines to remove carbon build-up, wouldn't that also remove the carbon rings?
"Oh, the humanity!"

Please... dissenting opinions are welcome.

[jeffe]

I agree with TC about Seafoam and about spraying some water into the intake with it running. It does break up the carbon. Have done it ton several old beater cars I've owned. My dad used to do this to some of our old farm tractors. Not sure exactly how it works. I've TC theory and also that the water turn to steam in the combustion and it "steamcleans" it lose. Who cares if it works.

[webbcraft2150]

Mercury Marine sells a product call "Power Tune". Other brands available under different names but the merc stuff is all I have used. This stuff works VERY well for decarbonization of a engine. During my tenure as a marine tech and my hardheaded continuing ownership of a boat, I have used this stuff alot with excellent results. Kinda like MMO or Seafoam on steroids. Borescope exams of engines before and after have proven its abilty to clean the top end of a engine. I have seen this stuff literally have chunks of carbon coming out the exhaust after using not to mention plugs fouled out by chunks getting stuck in them. I have used it on my XS. Your posta run it thru the intake till the motor stalls out, kinda hard to do on a multicarb application. I ran the engine up to temp, removed the plugs, dumped a load in each cylinder, replace plugs and took a smoke break. "Bout 10 minutes later, I fired 'er up. You MUST do this outside or with a Cat 5 fan blowing toward the door. Engine runs rough and smokes heavily for a while but clears out. Result is a much smoother running engine with more power. Ya gotta change plugs after this. I have worked on many outboards and sterndrives that could not pull rpm in a test tank. Power Tune and new plugs made them run like new.

[trbig]

I agree with webbcraft. Johnson/Evenrude sells the same type of stuff. It comes out of the can in sort of a foam.. spray directly into the carb throat. It will try to die.. but keep it going. Spray until the motor almost dies.. then go to the next carb. Supposed to use the whole can. Turm it off.. let it sit for a while.. go back and start it up. You can not buy a smoke bomb on the 4th of July that will make a smoke cloud like this stuff will. But it will indeed clean a motor. I might be a little leary to just pour into the spark plug hole as Webbcraft stated for fear of hydro lock... but it apparently works for him. Seafoam, or even Berryman's Chemtool will work.. but Seafoam is better in my opinion.

And Pro... as bad as I hate to agree with you (Man that just kills me to admit!) With this last motor change, and before installing these 78 cylinders on my 82 motor, using used pistons and rings, I did a light honing on the cylinders and *GASP* REMOVED the carbon ring... only to find that the motor started right up and ran fine afterwards! lol. I keep looking over my shoulder for doing this taboo thing though... kinda like not throwing the salt over your shoulder after you spill it! lol Now I need to ride under my ladder and break a mirror chasing a black cat that just crossed my path.... pick up the penny that is laying there heads down, and light three buddy's cigarettes with a single match!

Tod

[TopCatGr58]

A dissenting opinion as requested!

Originally posted by trbig
I keep looking over my shoulder for doing this taboo thing though... kinda like not throwing the salt over your shoulder after you spill it! lol Now I need to ride under my ladder and break a mirror chasing a black cat that just crossed my path.... pick up the penny that is laying there heads down, and light three buddy's cigarettes with a single match!

Tod

Tod, too late, you were supposed to do this stuff yesterday, Friday the 13th!

Prom,

I wonder if it's an old myth? Perhaps thoughts about the build up of carbon decreases the total head/combustion chamber volume, like carbon on the surface of the head/valves doing the same thing, and so essentially same volume of fuel/air mix being drawn into the cylinder, and then compressed will possibly compress a little more with a smaller combustion area, like shaving the heads or using a thinner gasket.

But when removing the carbon ring on an old engine, you will now increase the combustion chamber volume, and therefore decrease the amount of compression because you'll be compressing the stroke volume into a slightly larger area which will result in less overall compression! ?

Always happy to oblige a dissenting opinion!
T.C.

[jeffe]

I read a book about the earlier years of Nascar. There was a section on how they used to cheat. One of the ways they described was to paint the top of the piston and the combustion chamber part of the the head with a heavy rough finish paint. The theory was that this would cause some carbon build up and raise the compression ratio enough to give them more HP. The beauty of it was if they got their engine inspected all these parts were hot tanked before they were measured. So who knows.

[prometheus578]

"Not really a dissenting opinion, T.C."

No.. totally agree.
Removing the carbon ring gets the engine back to it's original compression numbers.
The old myth went, that by removing the ring, all sorts of bad things will happen: compression loss, oil burning, flat tires, baldness, etc.
Ahahaha.. T.C., if you were trying to antagonize me, this was a poor attempt! The idea here was to disagree, point out facts and make me look foolish.
We seem to be in complete agreement on this issue.

Do I have to give you lessons again on the fine art of mockery and how to apply it? Where is your mean-spiritedness? I thought that being a Guru gives one the freedom, not only to instruct and teach others the errors in their ways and modes of thinking, but also to harrass and humiliate them into submission.(also good dating advice, pay attention, Hobbyman)

Again... I'm not saying that I'm right... but the "carbon ring" thing makes no sense to me.

Seriously, if anyone has any different information on the subject...
Hey, I'm here to learn new stuff, just like everyyone else.

[thewiz]

Lord of the (carbon) Ring ...

Interesting thread ... we're gonna' find out here PDQ if this carbon ridge thing is really all that important or not, Rob, cuz Canada Post says my head stud washers are in and I'm about to get real busy on it. I agree with Prom's logic though, and besides, I don't have a choice about the ridge on my motor anyway. The PO honed the cyl bores clean ... real clean .... before I got it ... far as I'm concerned, I'm lookin' at a crap shoot.

I know we're talkin' bikes here but in automotive engine rebuilding anyway, which represents the bulk of my experience, carbon ridges are reamed when re-ringing to prevent the new top ring from impacting the carbon ridge and breaking due to subtle changes in ring size/thickness and the way it sits in/on the ring land. Bores are lightly scuffed/honed so rings can more easily take a 'new bite' of the cyl wall and thus re-seal themselves.

The rings naturally enlarge the cylinder bore over time ... taper .... difficulty can come when to much of the cylinder material itself, not the carbon build up, ABOVE the point where the top ring stops is removed. This is what can cause compression loss and all the related issues as the rings may not re-seal properly.