One of the first lessons in Performance 101 is that bigger is not necessarily better. Installing big cams, jets, carburetors, EFI throttle bodies, injectors, and valves — you name it — can easily decrease torque and horsepower. My 2007 TC 103 pushes over 100 hp, and it runs great with the upgraded 50mm throttle body and matched injectors. The stock 2007 46mm stock throttle body is bigger than what went before. My choices from Harley-Davidson were injectors from the 50mm throttle body or those from the 58mm one. Okay, I reasoned, the H-D EFI is an automotive Delphi system. I was going to go to a GM dealership and then check the performance car shops looking for bigger injectors. I asked Steve to get the part numbers off the CVO 110 EFI throttle body and the two injectors (there’s one to feed each cylinder). As he wrote down the part numbers he exclaimed, “Boss, they’re the same as yours!” The 2007 CVO 110 throttle body part number is #27708-06, and the injectors are #27709-06A. My 2007 TC 96 throttle body is #27708-06, and the injectors are #27709-06A. The 2008 CVO 110 part number changes to #27605-08 because of the servomotor that is integral with the throttle body for the throttle-by-wire control on the 2008s. The 2008 injectors are #27609-01B, which indicates a change from the injectors in use since 2001 to 2005 (#27609-01A). I think we’re going backward again. But let’s get back to the situation at hand. I turned to my head wrench and said, “Okay, Steve, so the 2007 CVO 110 has the 50mm injectors and body?” “No, boss, they’re identical to your stock TC 96 46mm throttle body!” he replied. The 50mm throttle body part number is #27623-05 and the injectors are #27654-06. I thought Steve was nuts, so we both checked, and he was right, as usual. I made a wrong assumption. I assumed the throttle body and injectors were bigger than the 46mm used on a 2007 stock TC 96 engine.
Now I was exasperated! Why would H-D do this? To save a few pennies like with the pushrods and rubbing rocker arms? No, I thought, this has to do with emission restrictions. Well, at least I had my answer. I went into a 2007 Screamin’ Eagle catalog and ordered a 50mm throttle body with matching injectors. The 50mm throttle body and injectors are part of my Band-Aid strategy to assist in the two major fixes that would resolve Chris’ CVO 110 overheating problem, which is the cause of the symptomatic blowing head gasket. Gas cools combustion temperatures by lowering the air/fuel ratio. These will only work on the 2007 CVO, but not on the fly-by-wire 2008 models that require a servomotor to activate the throttle plate. Each Band-Aid is not a solution in itself, but further insurance Chris will have no more overheating problems. Other Band-Aids will be the addition of the Harley-Davidson cylinder head fan (#91550-00C, chrome; #91531-00D, black) and a quart-larger oil tank. Both will help combat excessive heat. I could not use a 2008 catalog because the only upgrade offered is the monster 58mm for-racing-only body (#27623-05 and #29915-08 injectors). In my opinion, the 2008 catalog is much thinner due to emissions-control crackdowns.
Rear Head Oil Leak
When the rear head gasket lets go, the leaking oil stains the cylinder fins immediately behind the return oil passage. The oil return dowel pin attempts to ensure that the return oil stays within the confines of the oil passage. On each cylinder-head combo, the front dowel pin’s function is for head-to-cylinder alignment. The rear dowel does double duty of alignment and oil return. Oil drains from inside the rocker boxes, down through the head, cylinder, and engine case and into the gearcase compartment. The head gasket currently in use is the second-generation multilayer system (MLS) that H-D hoped would rectify the oil-leaking situation. This three-in-one gasket has a metal center with a rubber, Viton-coated metal gasket on either side. The two metal rings, each on a gasket appendage opposite each other on either side of the bore, hold the multilayer gasket together. This gasket will not tolerate a rough or warped gasket surface. Cross-hatching in the cylinder indicates that there are very few miles on an engine when this gasket lets go. The cylinders are fine-honed with cross-hatching to assist piston ring break-in and for oil retention on the cylinder walls. Above the cross-hatching is the area where the piston and rings change direction at TDC of the stroke. This piston-ring stop and reverse direction area wears faster than the rest of the cylinder bore because of the sudden change in piston direction. Above the travel area of the top compression ring in the cylinder is a small black band, which is carbon build-up from the combustion process.
Conclusion
Next month I’m going to get into the controversial stuff: head gaskets and supposedly separating cylinder liners.
Donny Petersen
Tattoo Tony’s Heavy Duty Cycles
Toronto, Canada
www.HeavyDutyCycles.com 
Techline-Feb09-H-D 110" CVO -Part II: The valve springs and other issues (concludes) 
Linear Mode
