Topic: damn 'F' model

[CB750F2]

Does anyone know the original ID of those oil restrictors? Apparently it was common practice here to drill out those restrictors one number drill size bigger. I would be very wary about doing this because more oil at the top means less available for the bottom and it probably wouldn't prevent blockages anyway. Pat

[Terry in Australia]

I've got a couple of heads sitting on my bench pat, so I'll check it out tomorrow. The K0 heads didn't have "pull out" jets, but rather, just a drilling in the casting, so it'll be interesting to compare the size of the holes in my spare K0 head to say, my spare K2 and F2 heads. Cheers, Terry.

[scondon]

 How did the word "restrictor"  ever get lumped on these oil jets. Certainly the orifice is smaller than the passage it sits in, but it is a "jet" nonetheless and is intended to "increase" velocity? of flow through the cam towers(isn't it?). Maybe even to insure that this pressure build-up occurs inside the two main oil passages in the cylinder/head rather than at the base of the cam tower where keeping a good seal can be more difficult.

  Cam towers have some pretty small oil passages in them and I would put just as much attention into cleaning and clearing them as I would the oil jets, especially if the towers have been sitting on a shelf or in an exposed engine for very long.

[Terry in Australia]

Their actual technical name is "Orifice, oil control" Sean, (according to my parts manual) because they control, or "restrict" the flow of oil into the head, allowing the maintenance of oil pressure to the crank as well.

The term "jet", while common parlance, can also confuse, as some folk could make an incorrect assumption  that somehow the "jet" causes some oil "atomisation" which of course in this case, it doesn't. Cheers, Terry.

[bwaller]

I imagine the oil flow upstream of the "device" would result in less (but still ample) volume at an increased pressure, but certainly downstream would also build pressure because of the restriction in the passage.

 Sean is right, for sure the oil passages in the cam towers are definitely smaller so reduced volume is needed whereas in the bottom end more volume is required to satisfy all the larger oil feeds. Sorry though, my vote is still to call it a "restrictor"!

Maybe I'm just full of $hit.   

[MCRider]

I've got a couple of heads sitting on my bench pat, so I'll check it out tomorrow. The K0 heads didn't have "pull out" jets, but rather, just a drilling in the casting, so it'll be interesting to compare the size of the holes in my spare K0 head to say, my spare K2 and F2 heads. Cheers, Terry.

Terry:  I have the old style and new style as discussed here http://forums.sohc4.net/index.php?topic=38682.0   I speculated about drilling, but have never really known anyone to do so and would only do it myself if someone I knew and loved told me it was OK.    While volume may go up, seems it would drop oil pressure.

My smallest numbered bit was too big to go through either. They appear to be very close if not the same. I can see where the removable orifices make it easier to clean and holds a larger O Ring up against the bottom of the cam tower. The O Rings on the old styles were tiny.

Maybe one of my wifes sewing needles will go through. Certainly some compressed air would.

[CB750F2]

Ron, thanks for the message. I think that if one was contemplating drilling out the restrictors it would be important to know their Honda designed diameter otherwise you could be drilling out a restrictor that has already been drilled. Hopefully Terry finds this info from his spare heads. Pat

[SD750F]

My 1978 F3 engine is ready to assemble. Back from the machine shop yesterday and here is what I had done.

Top end taken apart and cleaned. All four exhaust valve guides replaced. All valves reseated and checked. All springs checked are are well within tolerance. The one missing oil restrictor looks like it will be provided by one of the members. and the bottom head surface flatten.

Cylinders honed and cleaned. Top head surface flatten to mate with the top end. I will take a brass rifle bore brush to clean the head stud holes including the oil supply and returns.

Pistons have be re-grooved so I can now use standard K series rings. Pistons were steam cleaned to remove all the carbon that had blocked some the of the oil holes around the oil ring groves. I really like the replacement difference between a custom $200 per piston compared to $20 per piston!

My total machine shop bill, $271!!!

Case opened to remove all slug and some glass beads that got inside during initial cleaning. All oil seals replaced and stainless steel hardware installed throughout the case.

Soon it will be time to slide the frame down onto the completely reconditioned engine! Yahoo! I think I will be riding yet this year before snow begins to fall!

Scott

[scondon]

Their actual technical name is "Orifice, oil control" Sean, (according to my parts manual) because they control, or "restrict" the flow of oil into the head, allowing the maintenance of oil pressure to the crank as well.

The term "jet", while common parlance, can also confuse, as some folk could make an incorrect assumption  that somehow the "jet" causes some oil "atomisation" which of course in this case, it doesn't. Cheers, Terry.

   "Restrictor" it is then    For me it's just the association this word brings to mind.

Restrict:    confine, bound, limit. Circumscribe,restrain, regulate, impede

     Anything that impedes or limits flow to the cam would be bad right. One would either want to remove or modify this restriction or even make an elaborate device that would insure enough oil got to the cam


Control:  Power of directing. power of restraining. means of restraint. means of regulating. place where something is overseen.

     Some how I feel better with this

Jet:   Stream of water water,steam, gas, flame, etc. shot out esp. from a small opening. Spout or nozzle for this purpose

     This makes me feel simply fantastic


    In the United States we have learned to change reality with proper choice of words.   Control Jet!!!!!!     Awesome

[Terry in Australia]

Maybe I'm just full of $hit.   

Well I know I am, and I'm always surprised by how many folk here think that they're NOT full of Shiite!