Thread: Ironhead Oil Transfer Valve
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Old 7th April 2012
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Originally Posted by IronMick View Post
There is a scientific answer to this question and many many many opinions, all based on some measure of expertise. Some claim the nn years of experience, others similar years of experience working in oil analysis labs. Some are "mere" personal opinions like, jeeze man you could put Mazoilla in there and not have problems. Then there is the do what is in the FM crowd, and those who say that is old info and does not apply to modern oils.

Is this a reasonable summary?

There is no correct answer. Choose your favorite measure of expertise and do what they say.

I would run the same in both for the models with the transfer valve, and HD Formula+ for the newer ones.

scientific answer you want?
im ur huckleberry.

the purpose of the transfer valve is to keep your garage floor clean.

its an oil control device. to control the oil in order to keep it in your bike.

im being vague for a reason- to help you keep an open mind.
there is so much speculation- some times the myth becomes the reality. dont take me wrong here, im not being elitist.

im sharing my experience so it wont get lost as i get more feeble. no other reason. i seem to have collected a decent stash of usable every day insights. i dont own that. we do. i amassed it while gettin paid to learn it.
paid by other ironhead owners.
you guys.

the valve is a part of a bigger system. a system that we often break down into its components. then we deal with the 'target component'. often losing sight of the big picture. its our nature as mechanical guys. pin point the prob then bring the hammers of hell to bear on it.

if we can let go of that instinct for a moment this will make perfect sense.
so you want to think big picture here.

i read a million posts about this little part.

from those posts heres what we know:
1) fact: if you blow thru the valve it only allows flow from primary to engine. fiction: that means its a one way check valve. bad assumption. it allows flow one way only when pressure is different one side of valve to other. see #2.
2) fact: when taken apart carefully as not to bend the triangular reed we find no spring that 'checks' the valve when pressure differential is absent. so its allowed to 'leak' in state of equallibrium. fiction: theres some thing missing from this valve. thats why its not checking and allowing leaking oil into my primary as i found when i left the pri cover off an saw the trail of oil from the valve.

if you dismiss the assumptions and stick with what we can prove this truth emerges- valve is one way when engine running. but not when engine is static. then its relaxed. and oil leaks from motor thru it.

3) fact: oil is leakin out of your valve when primary cover is off. its leakin when primary cover is on too. fiction: theres only supposed to be a small amount of oil in the motor so theres sumtin else wrong too. what could that be? ahah its gotta be the check vavle in the oil pump leakin. and this is the spot you go off course chasing ghosts.

because when your motor is not running oil is leaking into before it even gets to the check valve.

you are told to inspect the check valve in response to any noticeable change that increases oil exiting thru breather tube. because a check that leaks will shorten the time it takes to fill motor enuff to puke.

even a perfect sealed check cant stop oil thats gettin in thru a different path.

if we slow down now and think we get to this- in order for the pump check to leak, oil has to get to the tank side of pump check. in order to get there its gotta sneak past gear clearance in pump. whitch it obviously does. but is the only place this errant oil can go? hell no. on way to check it finds clearance here

where the breather valve fits thru the upper oil pump housing.

where it leaks into the space between breather sleeve and housing exiting at the first place it can. the bottom of slot in upper housing.

now its filling the breather passage that leads to crank case. this passage is located lower than the floor of cam chest.

so oil is now filling the crankcase not the cam chest. the factory made sure that it happened like this. they wanted this unchecked oil to stay out of the cam chest. so your bike is less likely to puke.

they didnt want the oil to just sit in the case sump either. because it would just end up in the cam case soon after bike was started.

they wanted to somehow 'transfer' it to a reservoir. allowing it to reenter engine in a controlled volume that the return pump could handle without being drowned. (now is the correct time for ahah)

look at the position of valve compared to breather passage. its about even.

go back to 1st case pic. note that the floor of camchest is about even to bottom of pinion race.
now look at the position of breather passage in regards to floor of cam chest. chest floor is higher, breather passage lower. crap flows downstream.

so oil flowing unchecked into pump from oil supply line leaks clear thru engine into primary before it can start to fill cam chest. on primary side though theres plenty of room to fill with the errant oil. .

the transfer valve 'transfers' "pre pump check" oil leakage out of the motor and into the primary.

where it reenters engine on startup in a controlled volume that the return pump could handle without being drowned

in other words it 'transfers' it back to engine when bike starts.

this is the improvement refined from the 52-54 siphon tube that used the same valve guts.

it does makes perfect sense dont it?

and now given some thought you will see why the valves arent used on the racers.

the 77 style oil system did away with the unchecked supply leakage. so there is no reason to 'transfer' what isnt there.

its name is absolutely 100% correct its the transfer valve.

are any of you still holding on to the idea theses are simple bikes?
are any of you thinking the factory 'didnt get it right' with this part?
i hope not.

after all im not teaching this to you. it was you guys i learned it from.

big picture my friends, keep an eye on the big picture.
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