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Discussion Starter · #1 ·
I am fairly sure that after my engine seizure scare (refer to this link for that issue), my bearings are all fine. I have put on 33 miles since it happened and I have been constantly draining, checking, and refilling oil. I have done several compression tests and the results are slightly optimistic, but not enough to make me happy. I assume that something must be damaged in there, and my best guess is some scoring on the cylinder wall. Perhaps there is absolutely no damage to anything, but I doubt that.

These are the results of my compression tests. With the bike right around operating temp I read 112 PSI in both cylinders. If I squirt oil in the cylinders I bump the results up to 140 PSI in the left, and 168 PSI in the right. Every time I have drained the oil after running, it has appeared fairly dirty. Since I usually avoid filling an engine with oil and then immediately draining it, I do not know how long oil will maintain its translucent yellow look.



What I greatly fear is that there is enough scoring on the cylinder walls to allow a lack of compression down to 110 and to encourage blow-by of the pistons prematurely dirtying my oil and shooting hot gasses at my big-end bearings.



What do you say about these compression readings and the oil? Will I be safe driving the rest of the summer, or should I consider changing the rings before riding?



This is how the oil looks with less than 50 total miles of riding and run time.

 

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I wouldn't have expected the oil to look quite that opaque and grungy after 50 miles, but I have not experienced what happened to your bike on any of mine.



I wouldn't be too concerned with the compression readings, but they should be within 10% of one another. I think 171 is the advertised compression. I suppose it is possible that as the rings wear into the cylinders a little more that the readings will go up. Are you checking compression with a warm engine, throttle fully opened, and cranked until the gage stops rising? I don't trust the push-in gages, I'm not even sure you can get one down in there tho. There are several instances where guys are running 112# compression without any apparent problems.
 

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You check compression at WOT? I didn't know that.



Your oil does look too dirty for only 50 miles. I guess, for me, the determining factor would be that noise that you have described in your other thread. Have you done the stethoscope or the stick to the ear trick to try and locate the clatter? You could also send a sample of your oil to be analyzed - it's a pretty cheap test. I am sure you can find a service on the internet.
 

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You check compression at WOT? I didn't know that.



Your oil does look too dirty for only 50 miles. I guess, for me, the determining factor would be that noise that you have described in your other thread. Have you done the stethoscope or the stick to the ear trick to try and locate the clatter? You could also send a sample of your oil to be analyzed - it's a pretty cheap test. I am sure you can find a service on the internet.
Blackstone Laboratories

416 E. Pettit Drive

FortWayne, IN 46806



I know they have an internet site and will send you (free) what you need to mail in a sample of your used oil. I believe they charge $25.00

Just because your oil looks dirty does not mean that it actually is and is unusable. The only way to know for sure is oil analysis. It will also find other trash in your oil like dirt and metal particles. Billrod
 

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Discussion Starter · #6 ·
Are you checking compression with a warm engine, throttle fully opened, and cranked until the gage stops rising?


Affirmative to all of those things. I have the screw in plug type gauge, not the push in type. I think my readings have been consistent and accurate.
 

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The compression raising when adding oil does tend to point to ring seal.However it also depends on how much oil you are squirting into the cylinder a little to much will cause the readings to be artificially high.Since both are at 112 without oil I would not be concerned the fact they are even is more important than the actual number.

Many things affect the pressure on the gage including air temp, humidity, altitude, cranking speed is very important as is throttle opening.Then you have to throw into the mix no 2 gages ever seem to read the same so the general rule of thumb is if all cylinders are within 10 percent the engine is ok.
 

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The readings on the compression look ok, as they are both very close to each other. Ring and cylinder damage almost NEVER happen the same at the same time, one will fail worse than the other, and with you getting readings the same on both it is a very good sign. You WILL get a higher reading by squirting oil in the cyclinder, even on a new engine., as even brand new engines have a bit of blow by. Squirting oil in temporarily "seals" all the rings increasing the reading a bit, as well as decrease the "combustion chamber volume" ( dependent on the amount of oil added). The problem with the twisted twins is doing a "wet" test doesnt really work well as the pistons are not "upright", so the jajority of the increase will be a drop in volume.



There is a posibility that there IS engine damage, BUT, it is also possible there is NONE. It really depends on what actually transpired to "seize" the engine. In your case, due to the nature of the fast "oil run out", the bottom bearings are probabaly ok, as they will be the last surface to run dry, with the top end being the first. More than likely the heat increase caused the pistons to expand to the point the ring gaps were closed, binding the piston to the cylinder wall. A lot of the time when this happens, either a ring or piston shell breaks, or the connecting rod shatters. However, it the endgine stops "dead" without a ring or rod busting (depending where in its travel it "siezed", you can have no permenent damage.



As your compression test indicates, you have both intact rods and rings/pistons, so chances of damage there are very small. As for the oil, have you ever had the engine apart and completely cleaned the inside walls and sump ? Did you change oil types (from Dino to full synthetic) ? It may be picking up the darker color from increased blow by gasses (but in 50 miles I doubt it) OR, it could be pulling existing crap from the inside walls. I know mine went dark VERY fast when I changed oil to Rotella T6, as it seems to break down old oil crud in the engine. If that is not it, then there is probabaly a better chance of the "dark color" being rubber seal degridation from heat , than it would be blow by (the blow by would be so severe to generate that much in 50 miles that I doubt the engine could move the bike)
 

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I've got a spare engine in my garage that I ran for a couple of years and built a couple of years ago for my present,"Bitsa" bike.It does that with the oil.I ran it overheated and blew Piston oil ring methinks.Not bothered to strip it as I already had another engine re-built ready to go in.



You can remove the right hand side pistons on these bikes without taking the engine out but it's very fiddly.You CANNOT take the left hand side ones out as you need to remove the gearbox and although you can remove the gearbox with the engine in the frame you cannot get it back in correctly.



You really need to strip the engine down and get the crank out to make the job easy.If at all possible look for a cheap running engine and then you can service the other one at leisure.This is what I have done over the years.It's teaches you the engines and they are well designed to work on once out of the frame




Repeat tip:If you take the gearbox out don't let it come apart!



I don't know the US suppliers for ring sets but David Silvers have them over here and ship pretty fast to the US,



http://www.davidsilverspares.co.uk/CX500A-1980/part_44308/



They are the same for all CX/GL500 AFAIK.
 

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Discussion Starter · #10 ·
Well, I purchased the gaskets and the rings and was set to remove the engine today. I have been driving it in such a way as to get the rings broken in properly, even though I suspected issues and knew I would be redoing it. I warmed it up to do one last compression test and lo and behold, I have 120 in each cylinder. Could it possibly be that everything is completely fine and God decided to answer my desperate pleas to just fix my bike for me? Or should I not be deceived by all the good signs and just rip it apart?
 

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If it seems to run to your expectations, I wouldn't tear in down. I would just keep running it and see what happens. Bad rings probably won't leave you stranded along side the road. It would just not have as much power as before. I'll bet 50% of our bikes are running with about the same compression.
 

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Humm....when I get my engine back in I'm tempted to run it for 80K (50 miles) and compare the oil to your photo. Maybe oil turns colour quicker than we'd all like to believe? YI've never changed oil after 80 K. Has anyone?



Anyway, I guess it's pretty good news about your bike, considering all it went through.
 

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Discussion Starter · #15 ·
Well, I decided that since the parts are on the way but everything is seemingly fine now, I'm going to drive it for a while and monitor things. I will probably open her up again this fall.



Shep, did you say that you did the "hard break in" on one your CX? What process did you follow for that? 20 miles or so of running wide open to red-line in each gear then rolling off? That was the basic description of what I found for the hard break in, but I would like to hear your process since I trust your opinion on the matter.
 

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I've used this method on all my engines and they are all good,



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



I don't run above 60 mph or 5,000 rpm for at least a 100 miles+ as well and do lots of urban gear changes slowly raising the revs I change at once I've covered enough miles.Then change the oil and filter at around 500 miles and of course re-check ALL important torque values and tappets etc inc head bolts and coolant level in the Rad.



No point doing sustained long periods at high revs until everything is happy in the engine.Also with the engines being old it's not a good idea to let them labour at low revs either so I have my idle speed set a little higher at say 1200/1300 until the engines settle then like to get them well balanced at 1100/1200 rpm


Once through this period it's basically fire-and-forget riding just doing the usual maintenance e.g oil changes/tappets/cam-chain adjust and coolant/Brake fluid change every other year and fork oil when I think the 20w heavy fork oil has gone soggy but that seems to be at least 2 years+ depending on the terrain ridden.



As you have not had a re-bore you don't have to be too critical just glean what you need from the info above and a bit of common sense respecting the engines ages and the work you have done
 

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Hard break in....Humm....I'll be interested in Shep's opinion.



I remember watching a video (years ago) about this. There seems to be a goodly amount of logic and science behind hard break-ins. I do believe it relates to new engines or rebuilt engines with new rings. From memory (please don't hold me to it)...it's how the new rings set in quicker when under pressure (acceleration) as the fuel/air explosion above the piston actually pushes down the side of the piston and some succeeds in getting in behind the ring, forcing the ring to actually expand outwards and really seal tightly with the cylinder wall as it travels down on the power stroke. Every power stroke does this, thus the greater the explosion, the tighter the ring pushes against the cylinder wall, the piston ring conforms quicker to the cylinder wall shape wearing off the microscopic bumps and groves and creating an improved seal sooner.



And, again if memory serves me well, by doing this right at the beginning with your new engine, it brings about a much better seal between ring/piston/cylinder wall and will deliver better compression over a longer engine life. Cleaner oil between changes may be a by-product as less gasses can by pass down the cylinder wall.



However, you've got to change your oil after the first 60 - 100 miles. Failure to do this could cause irreversable damage as all those little bits of shaved piston ring and cylinder wall are circulating around with that oil. These are obviously microscopic bits, but I guess they all add up to problems if not eliminated.
 

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Hard break in....Humm....I'll be interested in Shep's opinion.



I remember watching a video (years ago) about this. There seems to be a goodly amount of logic and science behind hard break-ins. I do believe it relates to new engines or rebuilt engines with new rings. From memory (please don't hold me to it)...it's how the new rings set in quicker when under pressure (acceleration) as the fuel/air explosion above the piston actually pushes down the side of the piston and some succeeds in getting in behind the ring, forcing the ring to actually expand outwards and really seal tightly with the cylinder wall as it travels down on the power stroke. Every power stroke does this, thus the greater the explosion, the tighter the ring pushes against the cylinder wall, the piston ring conforms quicker to the cylinder wall shape wearing off the microscopic bumps and groves and creating an improved seal sooner.



And, again if memory serves me well, by doing this right at the beginning with your new engine, it brings about a much better seal between ring/piston/cylinder wall and will deliver better compression over a longer engine life. Cleaner oil between changes may be a by-product as less gasses can by pass down the cylinder wall.



However, you've got to change your oil after the first 60 - 100 miles. Failure to do this could cause irreversable damage as all those little bits of shaved piston ring and cylinder wall are circulating around with that oil. These are obviously microscopic bits, but I guess they all add up to problems if not eliminated.




Good point about the oil Johhny.I forgot to mention I do drain the oil after around 50 miles of the,"Hard" ride-in part and put a new filter in even though the engines have not been re-bored.Doh!!And then again as above at around 500 miles.Oil and filters is cheap
 

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I also run my engines on Molyslip,



http://www.ebay.co.uk/itm/MOLYSLIP-...arts_Vehicles_CarParts_SM&hash=item2a122e984d



It's taken quite a few thousand miles for it to work well on my present,"Bitsa" CX500 but I now have minimal oil use and near full compression after fitting new Intake valve guides last year but has 2nd hand but decent rings.My present,"Bitsa" has always been my,"Test" bike.I mess around with it a lot as it cost me nothing in effect and was originally a donor bike for my other CX500.



It was very sad for a couple of years,







But has been back in several guises and hence is called,"Lazarus",



















I think I prefer the Red/black look
 
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