Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: Trigger on June 07, 2016, 07:50:42 AM
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I have many people state that the oil jet is part of the head on a Sandcast, Diecast and K0's. But, I have been removing these for years to be cleaned out properly. They are a well engineered part of the head and come with a strainer on the back and a nipple facing up. If the jet has no nipple, this means that someone had drilled it out before, trying to unblock it.
This can cause many problems as the swarf then sits in the strainer or the drill has gone through the whole part.
Here is a couple of pics:
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You are never too old to learn something new. Dont supose the later jets will fit the early head?
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Interesting Graham. Never really looked closely at mine. So if they have been butchered what's the solution other than get Rich to make them ? Those tiny strainer holes look like a challenge, although my mate in Cambridge has the tiniest holes cut in metal that I have ever seen by laser I think. Any idea of the diameter of the strainer holes?
See you got that new camera I suggested you buy BTW ;D ;D ;D ;D ;D ;D ;D ;D ;D
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I have many people state that the oil jet is part of the head on a Sandcast, Diecast and K0's. But, I have been removing these for years to be cleaned out properly. They are a well engineered part of the head and come with a strainer on the back and a nipple facing up. If the jet has no nipple, this means that someone had drilled it out before, trying to unblock it.
This can cause many problems as the swarf then sits in the strainer or the drill has gone through the whole part.
Here is a couple of pics:
Is that the head from Chromy graham?
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You are never too old to learn something new. Dont supose the later jets will fit the early head?
No such luck Bryan, I did try to get a few made some years ago but, they are over engineered and no one would even take on the job.
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Trigg, my sandcast head and one of my 69 k0 heads have a simple drilling which is diaganal and goes straight to the oil feed passage which is the stud next to the cam tunnel, so i am going to have to say not all have them as you say
pete
(http://i924.photobucket.com/albums/ad90/UK-Pete/sandcast%20002_zpsnuym5mge.jpg) (http://s924.photobucket.com/user/UK-Pete/media/sandcast%20002_zpsnuym5mge.jpg.html)
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And so the plot thickens....
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Pete that's what mine are like
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Here is mine
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Will check mine tonight .. also my mate has his early K1 in bits so will ask him to check that too. Presumably my 10/69 will be like Rich & Pete's. Interesting to see what the sandcast K1 head has.
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Yes i have checked now and all 3 of my 69 heads are like that, so with yours being the same as mine rich, and also a 69 head i think we can safely say 69 heads were much more primitive and have a simple hole drilled for oil feed, i have also read this somewhere but i am off out now so cant research it for a while
pete
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In some places they are referred to as "oil restricters" so with Honda's policy of continuous improvement maybe the very early heads without them fitted caused problems of some sort?
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Well got home and my camera is behaving like Triggers
But it looks the same as Rich, Pete's etc. Mine is 10/69 no insert just angled drilling in a round recess. Maybe my mate Chris's early K1 will reveal something. You would have thought they would have fitted some sort of insert though but the bike was rushed into production by Mr. Honda. Put a strong magnet near to my holes and definitely no steel insert fitted.
Or perhaps someone has fitted the top off a pepper pot from a dollies tea set or watering can :)
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The plot thickens Could it be PN 12238-300-300
The dollies watering can/pepper pot head :)
[attachimg=1]
SANDCAST 4/69 MANUAL NO MENTION OF OIL JETS
[attachimg=2]
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That could well be the case, as very early motors had NO stem seal on the exhaust valve guides.
:o
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This is getting interesting. PN 12238-300-300 was fitted to the late K1 and on.
I have done two sandcast heads that have the oil jet in but, on the third one it looked like Pete's and RGP's. I assumed on the third head that the oil jet had blocked, been drilled out, welded and a hole had been drilled.
It is strange that some sandcast/diecast heads have this jet and some don't, all I can put this down to is Honda had two suppliers of early heads but, that doesn't make sense.
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Or for whatever reason the bike had a replacement head fitted, either by a main dealer who would fit the later item, or by a previous owner who saw the later head looked similar and fitted okay, when it was just an "old" bike and nothing like as collectible as they are today! ::)
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;) hi guys here is my take on these oil jets.
my frame number 1017*** diecast has the simple drilling my frame number 1031*** has the big oil jets(filter underneath) i have yet to strip a k1.but I've cannibalized loads of k2s k4s k6s and f1s and f2s and they all have long thin ones like in the parts manuel :-*
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covered here too Hondaman may have a drawing
http://forums.sohc4.net/index.php/topic,154725.msg1770421.html#msg1770421
Here is mine.. Wonder what the PJ is?
[attachimg=1]
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Here is my mate in York's early '71 K1 head. Not a good photo (not taken by me Trigger ;D) Looks like O ring in the top of the oil jet.
[attachimg=1]
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That is PN 12238-300-300 jet Ash, that is the most common jet fitted from 1971 to the finish.
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That is PN 12238-300-300 jet Ash, that is the most common jet fitted from 1971 to the finish.
good boy trigg
;) we got a mate a rite know it all (we even call him the philosopher to this day) this was in the 70's he had a jock Kerr tuned f1 it was quick at the time but the top end run dry of oil,so he thought he would get more oil to the camshaft
anyways he decided to drill out the oil jets ,on restarting the rebuilt bike it lost the oil pressure to the mains and big ends and was junk ,after returning the bike too jock Kerr the guy went crackers and wiped the floor with him lol(the innocence of youth)
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sounds and looks like the jets are quite finely tuned, but are so susceptible to blocking i wonder how they developed them to get the flow and balance right
pete
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What I am always a little confuse with is that the engine evolved over the years and there is a provision in the moulding of the head head for oil jets to direct oil to number 1&4 but, were never drilled out and used.
The jets that I posted are pigs to get out as they are metal in a alloy head and if they have rusted up, then the only way to get them out is drill them.
Why the hell did they make a jet with a strainer on the back, which is very difficult to remove when the straight though hole that Pete and RGP has is so much easier?
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Still confused Graham between the two part numbers circled in red below. What's the difference?
[attachimg=1]
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I know what is the difference in the oil jets as I have both types in stock. What I am confused with is this engine was to evolve but, to put a jet in to a head that blocks is going backwards.
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I know what is the difference in the oil jets as I have both types in stock. What I am confused with is this engine was to evolve but, to put a jet in to a head that blocks is going backwards.
So what's the difference which part no is which?
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I know what is the difference in the oil jets as I have both types in stock. What I am confused with is this engine was to evolve but, to put a jet in to a head that blocks is going backwards.
So what's the difference which part no is which?
12238-300-010 is the later type used on the K1 onwards .
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Trigger, as you and hairygit point out, they are restricting the oil flow\pressure to the head.
So they must have been after oil supply for the crank mains and big ends I'd guess and as steff has two examples of close numbers but different configs it looks like their R+D was already changing the spec maybe before the very first run assembly had even started as you see the modded heads come into the production flow during that initial run so testing and approval must have happened prior to any production machines with a sign off for the mod going through after the very first heads had left casting and machine shop operations.
As to the reason, again I'd have a guess at something like endurance running, probably on a dyno, would have given them concern that under high heat and load the log of oil pressure would have shown they where too close to their own tolerance of low oil feed in the main gallery and possibly a power loss with increased friction in those circumstances to force a contingency.
The requirements of lubrication in the head are largely low/no pressure as it's more or less an oil bath system and as long as it doesn't run away too quick then it's job done form a design print of view.
But, if you need greater feed at the crank you've really got two choices, increase oil pump output or reduce leakage somewhere. If they felt they had excess which was doing nothing in the head it would at that late stage of development seem logical to restrict one to help the other area and jets seem a good solution as you could also then trim them if required without any real costs or production hold up once the casting could accommodate just a switch of a small component.
The strainer on the back of the earlier jets shows a nervousness of the jet becoming blocked and\or maybe experience from their 60's race bikes possibly.
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http://www.bkperformance.com.au/product_info.php?products_id=22179
Probably don't have any stock but interestingly described as 11 mm type so must be type with strainer underneath ;)
PN 12238-300-300