Topic: 500 / 550 oil passage bypass line

[edbikerii]

Reference this thread: http://www.sohc4.us/forums/index.php?topic=24837.0

There is an interesting modification on CB500/CB550 engines that bypasses the notoriously leaky o-ring in the head gasket mating surface for the oil passage that delivers oil through the cylinder.

[bwaller]

I hadn't seen it done until we saw the good doctors roadracer a while back and I decided I would duplicate this mod. I know turboguzzi has also posted some pics of his external lines too. In my case the main reason for this was to avoid any oil leaks from those o-rings in the top end. I'd like to say first that I have no reason to doubt its effectiveness, but I expect there will be some negative feedback too, so even if it's only for your enjoyment here goes.

I decided to access supply from the right end of the oil gallery, this being the easiest. BUT I'm working on a frame slider type protector here because in a right side crash serious engine case damage is possible with the fittings in there.





The larger single hose is a -5 ending at a hydraulic tee. In either male taper side of the tee I enlarged the orifice and installed (interference fit) a 750 oil restrictor, same ID, smaller OD as the 500 item. The other two lines are equal length -4 hose and when attached keep the restrictors in place. These two lines end with banjo fittings.





There is an aluminum plug pressed in either end of the oil gallery in the cylinder head. The 77 & 78 model years use a larger plug and when removed no drilling was necessary to run the tap. The earlier years will need that hole enlarged first. The next step was to insert a 10x1.25mm helicoil. The banjo bolts I used needed to be shortened slightly so as not to block the oil supply orifice that feeds the cam end.

It is also necessary to block the existing oil passages. In this case I drilled the passage above the main journals, and tapped a 1/4" hole deep enough to bury a setscrew and installed with permanent loctite.





Then in the oil passage north of the head gasket surface did the same thing for a 3/16" setscrew.





That's it in a nutshell. It's really necessary to thoroughly clean any fillings from drilling & tapping. Use a small bottle brush, varsol and lots of compressed air and be sure no burrs remain. Thanks to xtalon for the coaching!

[ChevelleSSLS6]

we should have a special tech library that 'houses' useful information such as the one at hotrodders.com (another great website).  They call theirs a knowledge base.

http://www.hotrodders.com/kb/

Maybe one of the admins or site owner will catch this?
-Matt

[Bob Wessner]

Seems like the same sort of thing found in the forums FAQ's as well a Tricks & Tips.

[SEBNN]

Does anyone have an update to the link at the top?  It does not seem to work now.
Thanks

[dustyc]

Until they're fixed, you can look at the numbers in the page address and replace them in your browser.  This topic is: http://forums.sohc4.net/index.php?topic=24881.0
The one being referenced is: topic=24837.0, so just replace 81 with 37 and it will come up.

Make sense?

[edbikerii]

Since the forum was moved to a new host, I've found that you must replace the .us in the old links with a .net.  That makes the new URL:

http://forums.sohc4.net/index.php?topic=24837.0

Does anyone have an update to the link at the top?  It does not seem to work now.
Thanks

[SEBNN]

Thanks for the help, figure after 12 years of using the internet that I would have caught that.

So there is only one hole in the cam races and in the head that needs plugged?  Also, where exactly on the case do I tap in for the oil feed and on the head.  I assume that this will push the oil right into the end of the cam to lube the cam bearings.

Thanks again.

[bwaller]

The two top end oil passages are fed from the outside main crank journals. If going to external feed these two passages should be plugged in the upper case, then also in the head both sides. You can access the main oil gallery on the bottom case (see pic), right side or drill and tap into it beside the filter housing. With external lines the oil is also fed into both ends of the gallery in the head that supplies the cam with oil, same as the internal passages.   

[MRieck]

 Very nice work.

[turboguzzi]

bwaller

That bike is waaay too clean!

;-)

TG

[SEBNN]

Very nice looking job there.  Having lost oil pressure to the cam in a single cylinder Honda, I wouldn't want to repeat it with a 4 cylinder bike.  Thanks for the info, now to see if my engine will require a full rebuild so that I can get in there and do that to it.

[turboguzzi]

hi sebnn

Unlike bwaller, I didnt opent the bottom end to put plugs in the main bearing area as when I decided to do the oil feed mod the cases where already closed.

I simply plugged the two locating pins between the top case and cylinder block (those with the restrictor holes) with silicone and it worked just fine. easy peasy.

I put a single restrictor ( a carb jet...) in the end of the banjo bolt that connects to the main gallery. 

Might plug them like bwaller now that my engine is open

BTW, another good thing about this mod is that since the oil doesnt have to pass through the very hot cylinder block, it arrives to the cam quite a lot colder than in the stock set up.

TG

[SEBNN]

hi sebnn

Unlike bwaller, I didnt opent the bottom end to put plugs in the main bearing area as when I decided to do the oil feed mod the cases where already closed.

I simply plugged the two locating pins between the top case and cylinder block (those with the restrictor holes) with silicone and it worked just fine. easy peasy.

I put a single restrictor ( a carb jet...) in the end of the banjo bolt that connects to the main gallery. 

Might plug them like bwaller now that my engine is open

BTW, another good thing about this mod is that since the oil doesnt have to pass through the very hot cylinder block, it arrives to the cam quite a lot colder than in the stock set up.

TG

To make sure that I understand you, you are referring to plugging the main cam journal bearing  holes and not the main crank bearings.  Also, is the restrictor just a main or pilot jet?  Does this only go into the main line so as to prevent too much oil from going to the cam?

Also, would it be possible to take the line out from where the oil pressure sending unit is installed on the oil pump?

[paulages]

regarding the restrictors: i was able to buy blank fittings at my local oil line service shop that can be drilled to whatever size orifice you need. i'm sure these are easy enough to find (i'll post pictures eventually...). i had to cut the midsection out of the top fin on the 650 head to allow the banjo to fit.

[bwaller]

SEBNN,

One of the main ideas behind this whole external oil feed deal is to eliminate potential leaking around the o-ring captured between the cylinder & head in the original oil passage to the cam. Heat and chemical reaction eventually breaks this o-ring down and it will leak oil. Where the external oil lines feed the cam remains unchanged, we're not plugging the cam oil feed, just bypassing the original oil passage.

So plugging this original passage is essential for leak control, in my case the pics are there to show the approach I've taken.

There are oil flow restrictors to the top end partially to maintain adequate oil pressure at the crankshaft bearings, we're not trying to limit flow to the crank or the cam. On 500/550 these two restrictors are inside the locating pins between the top engine case and the cylinder block both sides. I used 750 restrictors elsewhere in the line, but obviously there are other options like what Turboguzzi and paulages are doing.

I think it would be wise to maintain the oil pressure sending unit and access the main oil galley elsewhere.

[paulages]

another potentially good location is off the main galley, just before the oil filter (i think that's where dr, tom ran his from). i decided against this for two reasons though. theoretically some of the oil could continue to circulate never seeing the filter (this would be the same case for the oil feed to the chains in the 650 case that i am replicating in my 550). i also worried that the oil lines being tapped into the case itself seem like they would stand a greater chance of working loose from vibration, not to mention running the risk of stripping at a location that would be catastrophic. the right side oil galley plug is a perfect spot IMO.

[bwaller]

Paul, I agree with your concern re tapping into the gallery beside the filter. However I'm scared $hitless of breaking the engine case at that right end location with those extra fittings in there in the event of a right side get-off. Maybe a 650 points cover would afford a little more protection plus something like turboguzzi rigged up.

I think a piece of aluminum could be welded on the outside of the case (outside of the main gallery) so that when drilled and tapped there would be more threaded material to fasten a fitting, as an option.

[paulages]

Paul, I agree with your concern re tapping into the gallery beside the filter. However I'm scared $hitless of breaking the engine case at that right end location with those extra fittings in there in the event of a right side get-off. Maybe a 650 points cover would afford a little more protection plus something like turboguzzi rigged up.

I think a piece of aluminum could be welded on the outside of the case (outside of the main gallery) so that when drilled and tapped there would be more threaded material to fasten a fitting, as an option.

i'm thinking that if you drop the bike, a little extra oil to clean up and a new fitting isn't the end of the world... i'm feeling you though. i'm planning to make some crash guards like the ones i've seen one some early 750's that mount on the lower engine mounting brackets, and protect the stator and points covers.

my line coming from the oil galley plug is a 90 deg. banjo though. maybe i'm remembering wrong, but it seems like this would tuck a little closer under the points cover than your does.

[mark]

I've been looking at this with some interest - haven't talked myself into it completely yet.

I'm wondering what the objections/pitfalls would be.. to modifying/fabricating the left side gallery plug to accept a banjo fitting. This would appear to require a small notch in the case to clear the fitting/tube, and perhaps another bit of whittling on the cover to clear the bolt head.



It looks like one would have to grind the alternator completely away before the fittings would damage the case in a wreck.

Food for thought.

[paulages]

how are you going to exit the stator cover without leaking oil?

[mark]

how are you going to exit the stator cover without leaking oil?

If oil drips out of the stator cover, it would be because the crank seal is bad. There should not be loose oil sloshing around in there. Note that there is already a notch in the cover(bottom center) to allow drainage of condensed moisture/leaked oil.


{edit: I have found an issue. The stock plug will need to be replaced with a fabricated one. There just isn't enough meat on the stock plug to keep it stable and sealed with plumbing bolted to it. Future lathe project.}

[paulages]

how are you going to exit the stator cover without leaking oil?

If oil drips out of the stator cover, it would be because the crank seal is bad. There should not be loose oil sloshing around in there. Note that there is already a notch in the cover(bottom center) to allow drainage of condensed moisture/leaked oil.

oh yeah, duh...    been working on 350 twins too much lately (wet stator)...

[bwaller]

It could be made to work, go for it. The opposite side is easy, but as mentioned a potential broken engine case is possible in a crash.

On the other hand just not crashing makes the most sense.

[DarkRider]

just wondering something how the heck does the oil get back down to the bottom of the case after? or is there some factory passages that allow the oil to return that are not affected with the external oil line mod..been wondering about line routing for awhile now given im also considering adding a turbo to my 550 project.