Topic: damn 'F' model

[superchode]

guess the engine ailment:

http://www.3cpu.org/gallery/750_repair/750_head%20aug08.jpg?size=orig

[eurban]

Top end oil starvation on the 1-2 side.

[bwaller]

a certain little blocked restrictor.

[superchode]

eurban's the winner! not even 10 minutes... nicely done.

now to fix it.  still torn between fixing the F head up (valve guides and seats have been done) and replacing the top end with a K head.

[SD750F]

Concerning the restrictor. My 1978 F3 engine has one installed on one side while the other side has no restrictor. Tell me should I have the one removed or the other installed??? I have been looking through my maintenance books and can not find anything about it.

I should add that I have APE HD studs that will restrict the delivery of oil to the top end because of the wider diameter in the supply path. So I want to make sure that I will provide enough oil to the top end without flooding. I would imagine this is the reason for the restrictor(s) in the first place to balance the entire oil delivery system?

Scott

[NWrider]

Can you directly replace an F head with a K head? I was under the impression they were different enought that they didn't interchange directly due to oiling or draining differences. I'm have the understanding the pistons will have to be replaced as well.

If there is a change over, I'd sure like to understand what it takes, assuming I don't have the correct info.

[WFO]

Iam going to say it's missing the cover to keep all that oil in there 

[fixahonda]

Wow! That valve gear looks like it got hot!

I've never seen the "F" problem before. Good luck sorting it out.

[Bodain]

Can you directly replace an F head with a K head? I was under the impression they were different enought that they didn't interchange directly due to oiling or draining differences. I'm have the understanding the pistons will have to be replaced as well.

If there is a change over, I'd sure like to understand what it takes, assuming I don't have the correct info.

You can. It will fit, but you will have more grief than you can shake a stick at. There are draining differences.
If you go K. You must do Pistons, Cylinders, and Head.

[Terry in Australia]

That's it guys, you need to do a whole "Top End" rebuild, not just the head. If it's just an oiling problem though, the K head won't fix it, they have the same issues.

Shortly I'll be posting pics of my new external "Top end Oiler" kit that takes oil from one of my oil cooler adapters, and sprays it onto the exhaust side of the cam, (the hottest side) so with one of these installed, you'll have a lot less to worry about it happening again. Cheers, Terry.

[eurban]

Wow! That valve gear looks like it got hot!

I've never seen the "F" problem before. Good luck sorting it out.

No this is not the "F" problem.  That would be valve guide wear, largely due to valve angle.

[Jerry Rxman Griffin aka MuthaF'er]

Don't you be cursing our beloved F models (at least the ORIGINAL F's)

[superchode]

ok, ok, i take it all back.

i do have a question about the oil orifices, though... the manual says to remove oil o-rings and orifices after removing the cam towers.  can you actually get the orifices out at this stage (ie. without taking the whole head off)?  i can't see if or how they are removable.

amazing what a contrast there is between the left and right sides of this engine.  one side was being oiled perfectly while the other was tying out and heating up.  both orifices look identically clean, though.  i'd love to get them loose and have a real good look.

[05c50]

When I rebuilt the top end on my 750a, I was able to get the restrictors out after removing the towers.
 I have a couple of questions. Do you have any idea how long the engine ran in this condition (hours,miles)? Did you recently have the engine apart? It seems that most of cams that wear like this are caused by gasket sealer getting into the restrictors. I'm just wondering out loud-what would cause your restrictor to plug up?

.........Paul

[superchode]

so i should be able to just grab the restrictor (with the head still on) and pull it out?

motor was rebuilt fairly recently... i didn't use any gasket sealer, though... just the gaskets themselves.  something got in there, i'd expect.  have to get that restrictor out to find out.

[05c50]

It's been a few months since I did the engine, but I'm pretty sure that I used a sharp pick and pulled the o ring and restrictor out after removing cam baskets. Let us know what you find plugging up the hole.

........Paul

[superchode]

ok, pulled them out.

oddly enough, the well oiled side didn't look much different from the un-oiled side.

definately small bits of something in both orifices.  the side that cooked happened to get the main passageway blocked.  should work fine now, too bad i'll need another set of towers and a camshaft. one or two of the hot rockers should be replaced as well.

[05c50]

If it were mine, I'd try to flush  out the oil passages and maybe pull the pan to clean out any debris before I replaced any parts. Just a thought.

.......Paul

[MRieck]

You have make absolutely sure those upper case oil feed holes are clear....another member recently had a problem with that.

[joeb]

I am running a K head on my 78 836 and to keep the oil from pooling in the head area I had a valley cut on the bottom of the cylinder to connect the oil drain hole that is blocked off by honda to allow the oil to drain faster from the head.

[SD750F]

Well I am getting the idea without hearing it specifically that you should remove the restrictor(s) in the top end oil gallery on a "F" engine? Is that correct?

What do you think Terry? Anyone else? I am at the point with my rebuild were it is the perfect time to do the right thing.

Scott

(see my question early in the thread)

[Jerry Rxman Griffin aka MuthaF'er]

Definitely not. The only real issue with a F head is only with the 77/78 F and it pertains to valve guide wear. This is due to the more "extreme" valve angle relative to the cam (as compared to the original head used on all other including 75/76 F's) and the ensueing additional stress causing the guides to wear prematurely.

[bwaller]

Definitely not. The only real issue with a F head is only with the 77/78 F and it pertains to valve guide wear. This is due to the more "extreme" valve angle relative to the cam (as compared to the original head used on all other including 75/76 F's) and the ensueing additional stress causing the guides to wear prematurely.
[/quote

+1.   Most definitely not. Again, the restrictors are there to maintain adequate oil pressure to the crank and bottom end. I wouldn't even consider enlarging them.

The restrictor size is adequate. Obviously the problem is that people are not meticulous enough when rebuilding if these are blocking with any kind of crap. Sorry but lets be honest. If there was no restrictor the rest of the passageways upstream are small enough to be blocked with the same crap anyway.

Terry's plan, I believe, is to just add a little extra.

[bryanj]

Been there, seen the video, shrunk the Tee shirt.

Most common cause--------

lumps of old cleaned off gasket falling into oil pathways

[Terry in Australia]

What Bryan said, very common that the "blockage" was introduced by either a "bodger" slopping silastic over old gaskets, or a well meaning rebuilder leaving a few gasket scrapings in the cases.

My "TOE" is intended as an "enhancement" to the OEM oiling system, and definitely not as a replacement. It's been speculated in another thread that the OEM jets (restrictors) could be removed or "bored out", but I wouldn't attempt it, the person who suggested it certainly hasn't tried it either........... Cheers, Terry.

[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!