Combustion Chamber Buildup

General engine tech -- Drag Racing to Circle Track

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cjperformance
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Re: Combustion Chamber Buildup

Post by cjperformance » Mon Jul 16, 2018 7:41 am

What oil was used ?
What does underside of piston and between 1st and 2nd ring look like?
Craig.

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Re: Combustion Chamber Buildup

Post by HDBD » Tue Jul 17, 2018 9:33 am

I didn't build or fix this. The customer repored two bolts loose and he used harley degree tightening sequence. Not sure what evidence there is regarding reversion but would certainly be willing to listen and learn if somebody could share and identify a fix.

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Re: Combustion Chamber Buildup

Post by JoePorting » Tue Jul 17, 2018 12:06 pm

Chamber and valves look pretty clean to me. Looks to have carbon buildup on the sides where there is no air flow. If it were me, I'd port the chamber by opening it up more especially around the intake valve.
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Re: Combustion Chamber Buildup

Post by Newold1 » Tue Jul 17, 2018 4:40 pm

DATS OIL in my book!

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Re: Combustion Chamber Buildup

Post by Neal Arnold » Tue Jul 17, 2018 7:35 pm

Newer Harley Chambers are not good. Some have to weld and make a nicer shape! Exh has no room to move out.

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Re: Combustion Chamber Buildup

Post by hoodeng » Tue Jul 17, 2018 8:47 pm

The evidence that has been photographed is not uncommon in a TC engine , the chamber deposits are as i would expect in a run of the mill engine ,the chamber and valves are clean and the residue is only on the crown and squish shelves of the piston ,it looks like it gets used at highway speed regularly.
The ash deposit on the piston is another thing though , the deposits present are pretty uniform and oil based ,the fact the carbon is dissolved around the outside diameter of the piston crown in this type of engine would typically indicate oil past rings ,be it bore or rings .I doubt the leaking drain to the outside would have made it into the chamber ,if it did that it would have developed a blow path from the chamber to the outside , that evidence is not on the gasket

There is what appears to be evidence of the carbon on the piston touching the head surface ,i have seen this also in TC oil burners as these areas would typically have only light residue the buildup of carbon makes it look worse .

Aside from the residue issue ,I noticed the squish clearance was set at .030" , I send out a lot of TC top ends to shops ,and get them to check squish on disassembly of engines so that i can correct it when i machine the barrels , i get them to send me the gaskets that were used to do the test , i also supply shops with metre lengths of 2ø mm soft solder and instruct them to cut the two test pieces 10mm long and place at 90° directly above the left and right of gudgeon pin and 3 mm inboard of the piston od this test procedure will give accurate results in this type of engine , i use .040" clearance as a default for customers , .030" is the minimum for this type of engine but needs to measured accurately in the first place ,,,, i have had solder test pieces returned to me criss crossed over pistons ,plaited, up to 40mm long , totally missed the squish shelf , picked up just the end of a shelf and anything in between ,,somehow the initial instruction to cut the pieces off the length i supplied 10mm long and where to place them can be interpreted in a number of ways,but nearly all guys get it right.I have seen as low as .020" and up to .050" just from test variance.

The reason i cut the cylinders is if the engine is dismantled at a later date and the person doing the job is not aware that the gaskets come in a number of thicknesses ,the default gasket in a Cometic kit is .040" and if they use OEM the gasket will be somewhere between .045" and .050" so they can not inadvertently reassemble an engine with insufficient clearance.
HDBD have you confirmed the clearance ,or was it info given to you?

I don't envy you chasing someone else's build in a later stage of the engines use,, as all is perceived as being good from the initial build , the fact the head bolts didn't make it past being torqued to spec ,being either the HD degree method or the Cometic ft lb method would get one of my eyebrows up a bit.But all of the above is only my opinion.

Cheers.

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Re: Combustion Chamber Buildup

Post by HDBD » Tue Jul 17, 2018 9:41 pm

My eyebrows are right where yours are. This builder is the type to check things so I trust the .030 squish, and torqueing the heads right with a calibrated wrench too. The chamber actually has a generous layer of carbon for this motor that only has a little over 10k on the clock. Hard to see in the photo. He is just riding it this summer then it comes down this winter and all the issues will be addressed.
Thanks for your time and advise.

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Re: Combustion Chamber Buildup

Post by hoodeng » Wed Jul 18, 2018 4:41 am

Hi HDBD,have you determined why the head fasteners were loose or uneven after torque to spec?

I have found in the past an instance where the case spigot counter bore was not as deep as specified and was holding the cylinder slightly unloaded even though the fasteners click off to spec, the other ,and i hope it's not this , the studs are moving in the cases ...

Cheers.

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Re: Combustion Chamber Buildup

Post by Tuner » Wed Jul 18, 2018 5:41 am

It is way to rich in the throttle position and load range it spends most of its time. That is how engines looked in the early '70s when the fuel changed and all the nitrophyl floats sunk in every QJet and Autolite 4300 and most others. 454s and 460s were big enough engines they would tolerate the sloppy rich mess longer than smaller engines and they would run until the carbon would fall off in big chunks and make them sound like they had a broken piston or a rod knocking. It was fun for about a year after the Arabs cut of the oil in '73 and just about every carb needed a new float.

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Re: Combustion Chamber Buildup

Post by Calypso » Wed Jul 18, 2018 3:16 pm

Many seriously think fuel washes the chamber, because you can wash parts with it... Even if black on plug porcelain is undeniably rich sign.
Apply 900,000 cycles of unclean (rich) burn on fuel wetted surfaces by running 2500rpm for just 12hrs on street, there’s bound to be some carbon residue left.

Typical Harley intake manifold is also shaped like a T. Not very ideal keeping fuel in suspension.

user-23911

Re: Combustion Chamber Buildup

Post by user-23911 » Wed Jul 18, 2018 5:20 pm

Carbon is carbon and oil deposits are oil deposits....not carbon.
Carbon is insoluble, it's a black powder.
Oil deposits are hydrocarbon.

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Re: Combustion Chamber Buildup

Post by Tuner » Wed Jul 18, 2018 5:50 pm

joe 90 wrote:
Wed Jul 18, 2018 5:20 pm
Carbon is carbon and oil deposits are oil deposits....not carbon.
Carbon is insoluble, it's a black powder.
Oil deposits are hydrocarbon.
There are no words. #-o

hoodeng
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Re: Combustion Chamber Buildup

Post by hoodeng » Wed Jul 18, 2018 7:35 pm

These pistons are from six different motors all oil burners,all suffered from a ring or bore condition ,all were corrected with piston bore service. I don't recall anyone getting back to me with alternative issues other than the ones addressed.

You could be right and i may be wrong,the oil might not dissolve the carbon, but it may well stop it from forming there in the first place, but on observation of numerous pistons that would have already had a deposit of some sort on the crown ,that deposit is now not present and there is virtually clean alloy showing on the periphery of the crown, how did the deposit clean off? Maybe its just a HD thing?

I photograph all engines and sub assemblies that come over this bench. I could add the bore shots that went with the piston crowns but my quota is over.
The photo of the Shovel head is what they look like when the gasket fails between the oil drain and combustion chamber, and is not rectified expediently.

Cheers.
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cjperformance
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Re: Combustion Chamber Buildup

Post by cjperformance » Wed Jul 18, 2018 7:57 pm

cjperformance wrote:
Mon Jul 16, 2018 7:41 am
What oil was used ? **specifically thinking flashpoint**
What does underside of piston and between 1st and 2nd ring look like?
Also do you recall the breather setup on any of these?
My 2011 103ci at 143,000km (not rebuilt since new) runs stock breather setup, runs HD360, uses no oil visible by dipstick reading and when inspected with borescope as much as I can see it is very clean, thankfully.
Craig.

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Re: Combustion Chamber Buildup

Post by hoodeng » Wed Jul 18, 2018 9:46 pm

HD360 oil is one of the best rated air cooled engine mineral oils you can buy , typically synthetic oils only protect an engine when the capability of a mineral oil is surpassed, you are obviously not exceeding that oils capability.

The TC breather system operation was unchanged from 99 to 2017 the only difference was that the first were aluminium sections ,the second was plastic [prone to warping] the third was pressed steel ,all used the same umbrellas, separators and circuitry , probably the only thing that was a bit small was the orifice in the outlet bolts ,but that only tended to be a problem in engines that were breathing more than ideal.

Regular servicing and maintenance will see you get many more trouble free miles from your bike than you have so far.

Cheers.

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