 Techline-Jan.09-H-D 110" CVO -Part I: The head gasket oil leak & other issues (cont.)
My Take On The 110
I have been investigating the reports of a CVO 110 rear cylinder leak since Day One. However, Internet claims need verification. The writer may fervently believe his problem is widespread, but is it? Is the problem diagnosis correct? If I cannot see it for myself or hear it from a known and respected source, then how can I write about it?
At Heavy Duty Cycles, we work on Twin Cams up to six days a week, year in and year out. I do get to see the problems firsthand, sometimes before anyone else. Some dealers profess not to have heard about the problem at all. Maybe they did not sell any because the CVO Screamin’ Eagle models are the most expensive Harley-Davidsons and only available in limited quantities. Alternatively, maybe the ones they sold have no miles on them, which is certainly possible with some segments of the nouveau riding population. However, after a deluge of commentary, I knew there had to be some legitimacy to customer complaints. I did not feel comfortable writing this article until I had personally seen a malfunctioning CVO 110, taken it apart, diagnosed the problem, and repaired it to my satisfaction. One thing is clear: the Harley-Davidson approach is not working. My approach will.
I went through the 1999 to early-2000 cam bearing debacle. It affected more bikes than this current malady because the rear cam ball bearing in the cam support plate was in every Twin Cam manufactured at the time. The CVO 110 is a limited-edition motorcycle, and only available in certain models at that. I do not mean to demean this problem in any way, as the percentage of bikes affected may well be higher. The early rear cam bearing problem could easily occur as early as the CVO gasket issue, but might also not develop for many more miles. As Jerry accurately says, the problem is one of an oil leak, and not a compression leak. As for a replacement head gasket blowing again after a test ride, I can only say that the technician may not have checked for a warped gasket surface. The types of gaskets in use in the 110 demand a very smooth surface in order to seal properly, which, in my experience, does not occur often.
The head and cylinder mate just below the head’s exhaust port. The cooling fin below the port is the top fin for the cylinder. Two studs with nuts attach the exhaust pipe to the head’s exhaust port. Organized mechanics always rethread nuts back onto the original parts, to prevent loss. The baked-on oil stains are on the otherwise polished cylinder fins below the exhaust port. The oil originates from the return oil passage that begins in the head cavity that’s enclosed by the rocker boxes on top of the heads. The breather apparatus located between the two rocker arms in each head separates oil from the oily mist, which travels up the inner pushrod tubes and into the heads. The descending pistons force air out of the bottom end (flywheel) compartment, through the rollers of the pinion bearing, into the gearcase, and up the hollow pushrod tubes into the heads.
The separated air vents out the breathers and into the air cleaner housing, where it can be sucked back into the engine on the intake stroke and burned. The separated oil returns to the gearcase by way of the oil passageways in the head, cylinder, and engine case. The return oil must pass by and through two sealed surfaces, which are the head gasket (between the bottom of the head and the top of the cylinder) and an O-ring (between the bottom of the cylinder and the engine cases). Each head-to-cylinder and cylinder-to-engine cases juncture has a hollow dowel pin that protrudes into both mating surfaces to ensure oil does not leak out. The base juncture uses an O-ring from 1999 to present around the hollow dowel to ensure further that the oil stays inside the passage.
Interestingly, the use of the O-ring (#11273) also seals the dowel supported by a head gasket from 1999 to 2003. H-D eliminates its use from 2003 to present. All I can say is that the use of an O-ring around the dowel pin works, and we use them on all years, where possible, at Heavy Duty Cycles. The oil leak in question begins as seepage outward from the dowel pin. Compression is still sealed inside, as the gasket does not blow inward.
Rebuilding A SE 110
The oil leak was evident as soon as a customer (Chris) brought his CVO 110 in for repair on his own dime. Many readers have complimented their dealer response as adequate in their e-mails and discussions with both American Iron Magazine and me. They aren’t blaming the dealers, as owners can see dealer frustration. However, Chris was not one of these. Chris, a gnarled, grizzled graybeard who has ridden his whole life, gave me one strict guideline to follow, “Fix the thing. No more problems. I bought this bike to ride.” His out-of-town dealer had repaired his 110 twice already, insinuating that Chris had caused the oil leak from the rear head gasket. The dealer’s third response was threatening to kick Chris out of the dealership for complaining too much. I mean, after all, he had about 5,000 miles on his machine. Why should he expect more? When Chris cooled off, I suggested, tongue in cheek, that the real problem might be that he rode his bikes too much. Smiling, he told me to stick it where the sun don’t shine. I felt sorry for Chris, but was excited to see and diagnose the problem myself.
The 4-3/8"-stroke flywheels on Chris’ CVO were in excellent shape. The pinion shaft runout was 0.0005". Chris’ sprocket shaft measured in at 0.001"runout, with both flywheel rims the same. Chris has a nice flywheel assembly any mechanic would proudly install. However, a nearby dealer had a CVO 110 in the shop with a staggering 0.025" runout on the pinion shaft. This occurs when the flywheel halves scissor by shifting on the press-fit crankpin, one in front of the other.
Now, I don’t yet know whether this scissoring problem is a result of the extra torque generated by the TC 96 and CVO 110 over the TC 88s and their bigbore counterpart the TC 95, or if it is due to a relaxation of the 0.007" interference press-fit straight crankpin in the flywheel halves.
Perhaps it is a combination of the two. And perhaps the extra heat generated by the closed-loop EFI stoichiometric 14.7:1 air/fuel ratio aggravates the press fit, expanding the flywheel body around the crankpin. Certainly there are reported air/fuel ratios on the rear cylinder approaching a blistering and destructive 16:1 on the rear CVO 110 cylinder.
No matter, the Heavy Duty Cycles machinist “Marvelous” Martin tacked the crankpin with TIG welding to the power (left) side flywheel on Chris’ CVO 110 using a stainless steel rod, just to be safe. We did the pinion right side also, but one would think this not necessary since it only drives the oil pump and the valvetrain via the cams. The crankpin was tacked equidistant on four sides in a crosshatch pattern. Steve, my head wrench of almost 30 years, ground the top of the welds, careful not to fool with their integrity. There is too much money involved to fool around.
The stock SE 255 cams were also in excellent shape, as was the cam support plate assembly and oil pump. However, one future problem may well be the ovaling of the cam support parent-material bearings. Moment Arm Force exerted on these bearings is exacerbated by the SE 255 cams and 110" motor. This is compounded by my desire to put a set of higher-lift, longer-duration, overlapping cams into the 110. The 110 is begging for a performance mechanic to release more horsepower and torque!
Steve and I installed an S&S 585G gear-driven cam setup. With the stock rocker arm ratio of 1.625, these cams deliver a .585" valve lift. However, we increased the rocker arm ratio to 1.675, which effectively increased valve lift to .603". Chris now has a cam which will give him some more bottom end oomph, with the overlap increased from a paltry 13 degrees to a respectable 40 degrees, and a duration increase of 34 degrees on the intake cycle and 25 degrees on the exhaust cycle for better top end.
Article concludes in the next thread. Check back issue for pix and extra information. |
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