Topic: K4 Engine Compression Issues

[ivanhoew]

ujeni , is it possible your tappets were too tight on the low cylinders?

[Ujeni]

ujeni , is it possible your tappets were too tight on the low cylinders?

Hmmm, not sure what you mean. Could you elaborate?

[ekpent]

His hypothesis would be that if the valve clearance was set to tight that maybe the valve was not working correctly,possibly staying open..

[Ujeni]

Ah. The valve clearances were within spec.

Now off to test valve leakage...

[Music City Metalcraft]

Always check compression on WOT.

Did you measure the cylinder bores in both directions, (in line with the crank and 90 degrees off). The bore will be worn more in the direction the piston get's pressed into the side wall on combustion. Measuring only in one direction tells you nothing.

DON'T HONE THE CYLINDERS. Unless you want the compression to go down even more. If the ring gap is within spec, it might not be after honing. Honing is removing material. If the bore is oval you just make it bigger, not round.
The rings need about 200 miles to bed in.

Turn the head upside down and fill fuel in the chambers. If it leaks through you have a valve leak.


Needless to say you should have done all of this the first time, before putting the engine in... but you probably know that by now.

[Ujeni]

Did you measure the cylinder bores in both directions, (in line with the crank and 90 degrees off). The bore will be worn more in the direction the piston get's pressed into the side wall on combustion. Measuring only in one direction tells you nothing.

Yes, I measured in both X and Y at the top and bottom of each cylinder. Everything appears to be within spec.

DON'T HONE THE CYLINDERS.

I guess the proper term is to deglaze them and not hone them. My plan is to get a honing tool with medium or light grit to do this. Sound right? Otherwise, it sounds like the rings won't seat well.

Needless to say...

Indeed 

I performed the valve seal test by turning the head upside down and filling each combustion area with fuel (also tried wd40 just to be sure). None of them leaked:



Seems as though my valves are seating ok.

Next is deglazing. Wll head out to buy that tool next.

By the way, should I be worried that the gasket surface on the head and the cylinders appears to be slightly worn below the pattern? Putting a straight edge on the surface shows a tiny amount of light in the areas where there is no pattern. Likely less than 1/100th of a mm I would guess. Take a look:

[ekpent]

If you are doing the de-glazing or hone yourself read up well and get the best suited tool. Just a little dab will do it for that operation,don't over due it.Couple different tool options,sure more experienced will chime in on the best.

[Ujeni]

Yeah, I have been looking into it a fair bit. Looks like there are two tools that are commonly used; the old-school three-arm honing tool that uses sharpening stones and the newer Flex Hone tool. I would prefer to use the Flex Hone as it appears easier to use, but I can't find any in my town or neighboring areas. I'm leaning towards the old-school honing tool.

[ekpent]

I am lucky because I give that kind of stuff usually to a friend as in Star Trek with Picard and I just say " Make it so". Sometimes the cost of the tool and the experience to use it correctly outweighs the benefit that a person can garner from building a relationship with a professional.

[74750k4]

Another trick on head nut torque is to heat the cr@p out of the head, and cylinder bank. Heat guns/propane heaters/propane torch etc. Let it cool. re-check, re-torque. Do it a few times if you're anal.

[Ujeni]

Bought the old-school Honing/Deglazing tool and watched a ton of videos on what to do and what not to do. Not hard at all! Spent just a few minutes per cylinder with a fine grit stones and had excellent results.

Before the deglazing:



...and after:



A nice cross-hatch pattern. Cool! This is why I love working on bikes, I learn new stuff all the time!

I'm still having a helluva time getting the last bits of the old head gasket off. Suggestions are welcome! 

I head up to the city to get the studs, cylinder gasket and valve cover gasket in the morning. That means I will only be waiting on the CycleX head gasket.

Thanks again for all the advice and help!

[Music City Metalcraft]

Every tool will remove material from the cylinder surface, increasing the diameter, no matter what you call it. By "deglazing" as you did you probably removed 0.005 to 0.0075, if not more, opening up the ring gap by over three times that amount. That will not improve ring seal. Now they have to bed in all over again, which will remove further material from cylinder and ring, increasing ring gap even further.

[cbr954]

If you remove .005 with a deglazing tool then you did something seriously wrong and used a very course stone, deglazing removes very little material.  Looking at the picture you can see very little material was removed because you can still see the original size of the cylinder at the top where the rings dont run.  You can see the transition from the original to the worn area.  There is no way .005 was taken off.  Deglazing is a surface prep not a material removal operation, I doubt you even took .001 off.  Stick a ring in the cylinder and measure clearance to see where you are at with clearance but it looks good to me.

[andrewk]

Looks good to me.  No way the new rings would have sealed properly in an old bore anyway.

You have to have a nice clean surface for any gasket, but especially so if you're using a MLS (the three piece metal cycle-x piece) gasket.

[cbr954]

You shouldn't and some say can't use MLS on stock surface finish it has to be finished for MLS gaskets or you can get oil seeps.  Surface finish needs to be 50 RA or finer.  The surface must be very flat also with no warping or it will not seal properly.  I like the graphite head gaskets for slightly uneven or rough finishes.  I would only use MLS if head and cylinder is machined flat and finished for MLS.

[Music City Metalcraft]

CBR954,
 think you fundamentally misunderstand the function of the tools used. What is "surface prep" other than removing material??? If you produce a cross hatch pattern in a surface, you remove material, how else would you see the pattern? Even if you 'only' polish/buff a surface, you remove material.
And the step in the ring zone will not go away, cause the tool follows the cylinder wall shape. That's why you cannot correct a worn bore by honing, 'deglazing', whatever you want to call it. And 5 thousands of a millimeter are removed very easy. Did you interpret my numbers in inches? Sorry for not adding the mm, but it's a metric bike, so I automatically think in millimeter.

Just a reminder: The recommended piston clearance is only 0.02mm, maybe 0.03mm. If you remove 0.005mm by , you increase the clearance by 15-20%.

[cbr954]

yes you remove material but it is very little.  The depth of the "hatch" is in measurable by you and me.  There is a difference between honing and deglazing.  Deglazing is used to put just enough finish on the cylinder to hold oil for break in.  Factory clearance is .01 to .04mm from factory Honda manual.  You will never notice a .005mm increase in clearance.  Aftermarket piston use more clearance and have no issues.  Either way I am done going back and forth.  Ujeni the deglazing looks good and you should be fine, always check clearances and wash the cylinders very well before assembly.

[MCRider]

My comments on the valve leak protocol. Its pretty hard to get a 360d confirm by filling the combustion chamber with fluid IMO. The arc of the valve nearest the gasket surface is left out of the test.

Better to stand the head on its edge so the ports are vertical. Then fill the ports with fluid and look for the leak in the combustion chamber. Do 4 , then flip it over and do the other four.

[Ujeni]

I measured the cylinders after deglazing. No change in measurement. They look a ton better though!

I don't mind taking another few hundred miles to break the rings in. I'm not in a hurry.

On the gasket surface, I am still looking to get the gasket remains removed. Once I finish that, I suppose I coud have them machined flat. Is that expensive? Can any shop do that or do I need to find a specialized shop?

[Ujeni]

My comments on the valve leak protocol. Its pretty hard to get a 360d confirm by filling the combustion chamber with fluid IMO. The arc of the valve nearest the gasket surface is left out of the test.

Better to stand the head on its edge so the ports are vertical. Then fill the ports with fluid and look for the leak in the combustion chamber. Do 4 , then flip it over and do the other four.

I forgot to mention that I tried it in the manner you described as well. No leaks were detected.

[cbr954]

Any competent machine shop can do the work. It is not as critical if you are going to use a standard type head gasket but with an MLS I think it is a necessity to have them machined for the proper finish and straightness, at the very least you should check the head and cylinder for flatness.  In my opinion the worst thing you can do for ring break in is take it easy on the motor.  Once it is up to operating temperature you should run it with a good load to put a load on the rings and get them seated.  Low loads has a tendency to allow combustion to leak past the rings and you will never get them to fully seat.  There are many schools of thought but do some searching about ring break in there is some good reading out there about it.

[MCRider]

My comments on the valve leak protocol. Its pretty hard to get a 360d confirm by filling the combustion chamber with fluid IMO. The arc of the valve nearest the gasket surface is left out of the test.

Better to stand the head on its edge so the ports are vertical. Then fill the ports with fluid and look for the leak in the combustion chamber. Do 4 , then flip it over and do the other four.

I forgot to mention that I tried it in the manner you described as well. No leaks were detected.

Good deal!

[HondaMan]

Bought the old-school Honing/Deglazing tool and watched a ton of videos on what to do and what not to do. Not hard at all! Spent just a few minutes per cylinder with a fine grit stones and had excellent results.

Before the deglazing:



...and after:



A nice cross-hatch pattern. Cool! This is why I love working on bikes, I learn new stuff all the time!

I'm still having a helluva time getting the last bits of the old head gasket off. Suggestions are welcome! 

I head up to the city to get the studs, cylinder gasket and valve cover gasket in the morning. That means I will only be waiting on the CycleX head gasket.

Thanks again for all the advice and help!

Keep going on the hone job! You're not done. If you look closely at the tops of the cylinders, you will see where each ring stops and reverses direction. This means those points are slightly worn, and this will create forever sealing problems. Continue to hone, using WD40 or 3-in-1 oil until the little dark rings have gone. This is the proper honing technique.

If you don't have my book, you might want to check it out. It shows this entire process, step-by-step, with these details, and what they mean to you.

You can get the book straight from the publisher at www.lulu.com, search for "My CB750 Book". I recommend the hardcover, lasts MUCH longer than the paperback.

[Ujeni]

Oh boy...disaster.....

After 24 hours of pb blaster stuff on the cylinder studs, 13 of them came out easily. The next two came out with a bit of heat and some more strength. The last was very stubborn. I let it sit pb blaster for another night. This morning, I hit the engine block around the stud with heat, gave it another go with the stud extractor and bang....it snapped off at the base!

 

I drilled into the center of the stud, but have not gone any further (didn't drill all the way through the tip of the stud I mean). At this point, there is no damage to the engine block, so I thought this would be a good time to figure out what to do next.

Options as I see them:

• Use a screw extractor. I've had bad luck with these. With all the pressure that this stud withstood, how could a small screw extractor work?
• Drill out the screw entirely and (likely) helicoil the hole. Can you heli coil a cylinder stud? I'm betting the answer is no.
• Bring the engine block to a machinist to have it professionally removed.

I'm thinking that last option is the best. Thoughts?

[swan]

Do search and you find solutions on this forum and elsewhere. I would recommend skipping the screw extractors in to hard studs and have a machinist mill it out. More expensive, but it will be done right without having to repair, helicoil etc your crankcase.