Topic: What's a sure fire way to find an oil leak?

[Patrick]

Not the existence of one - the puddle under the bike pretty well establishes that. I'm looking for the source.

My K0 750 is driving me crazy. The damn thing runs very well and is as fast as hell, but I almost need a rainsuit to ride it. Oil is leaking from somewhere on the front of the engine and I can't figure out where or how.

First: the engine is a bore bore (810) with a hot cam. The pistons, which came with the bike, are somewhat domed ART Honda pistons which I believe are from Honda 350 and a a period correct over bore. I haven't measured compression, but this engine is a bear to kick start. I almost have to stand on the kicker and jump.

The leak appears to be on the front on the left side. I get some drainage from the fins when I put it on the kick stand and the front left of the engine is usually wet with oil. I get some pooling on the crankcase behind the left side of the top end, but so far I have attributed that to oil carried back by the momentum of the bike. The right side, front and back, are dry and beautiful.

The oil pretty much soaks the front of the left side of the motor but it does not appear to be dripping down from the top end. I have pulled the engine twice now to check the rubber pucks under the cams. They are good and tight. I rebuilt the top end twice to make sure it wasn't the head gasket and I had the bottom of the head and the top of the cylinder machined as a unit by a machinist I trust who specializes in motorcycles to ensure flatness and fit. I have replaced the oil filter with Honda o-rings to rule out the oil filter housing. I have replaced the gaskets under the alternator cover and the shifter cover and polished the gasket surfaces to a mirror like finish. I have replaced the cam cover gasket twice and last weekend I pulled the engine and replaced the cam cover itself to rule that out. I have replaced the oil rings on all the valve adjustment caps.

It doesn't leak when the bike is idling in the garage, only when I ride it, so I believe it is the pressure of the engine under load that squeezes oil out. I only have to ride it a couple miles under load for the oil to produce a small pool under the bike when I park it, so this is more than a small seep but less than a spray. The seams between the head and cylinder and the cylinder and crankcase appear dry even after a leak. The seams between the cam cover and cylinder head also appears dry. I sprayed foot powder along that seam before a ride to see if I could find a leak and it was dry afterward. It also appears dry around the casting plug in the front of the engine. The seam between the crankcase halves isn't dry, but that could be oil running down. I see no obvious visible issues at that seam either. I can see no holes in the front of the case.

This is not my only bike and it is not the only engine I have rebuilt, its just the only one that leaks oil. I have to believe that the leak is coming from between two parts that are assembled correctly, but for whatever reason no longer mate correctly. Everything seemed to fit well every time I put it together. I don't want to tear down the engine and split the cases again on spec alone, but I am willing to tear it down if I can determine where the oil is coming from and can fix it once and for all.

Have I overlooked anything? What can I do to find where the oil is leaking out? I am very frustrated by this and I am open to any suggestions.

Patrick

[mystic_1]

Clean the bike thoroughly and dry it well.  Next, hose down the suspected area of the leak with spray-on deodorant or foot powder.  Go ride the bike a bit, then look to see where the leaking oil has discolored the powder.  This should tell you for sure where the leak is coming from.

mystic_1

[MCRider]

So the question I have for you is, have any of the threads to the cam tower hold down bolts, the 2 big ones and the 2 pairs that double to hold the bearing caps on, been compromised in any way? That is are you babying them, used helicoils in them, removed the front studs and replaced with bolts down from the top?

We've had several threads about this just recently, and my personal experience makes me a reluctant expert.

If those bolt hole's threads have been compromised, oil will find its way, lord knows how, to wick itself under the cam towers and down those threads. They open to the atmosphere at about the center fin in the head. That is, you will see no oil as you describe at the head gasket or the cam cover gasket. It mysteriously appears, and the wind will blow it around.

Mine got so bad I could look into the fins with a flashlight and watch the oil drip from the bottom of one of those holes, deep in the fins of the head.

Fix, ultimately, a different head. I'm looking into having mine welded up and redrilled, as it was ported by Yosh in NJ and has sentimental value.

If none of this applies to you...never mind.  

[Patrick]

I am really wondering if it is something like that, MC. I did not helicoil any of the bolt holes in  the head and all of the cam bolts seemed to tighten down just fine, but God only knows what may have been done during the 39-years before the bike came into my hands as a basket case. I am just having a hard time figuring out what I could have done wrong to let it leak like this. A replacement head I can do if I can just nail down that as the issue. It's the not knowing that is the worst.

[MCRider]

I am really wondering if it is something like that, MC. I did not helicoil any of the bolt holes in  the head and all of the cam bolts seemed to tighten down just fine, but God only knows what may have been done during the 39-years before the bike came into my hands as a basket case. I am just having a hard time figuring out what I could have done wrong to let it leak like this. A replacement head I can do if I can just nail down that as the issue. It's the not knowing that is the worst.

I thought i was going absolutely Frickin mad when mine was doing it. I just couldn't believe what i was seeing. But my head was a swiss cheeze of helicoils and pulled threads.

So, per Mystic already, super clean your head, power washer, degreaser, etc. Set it on the center stand. Dust some baby powder in between the fins as best you can. Small travel bottles of the powder will blow little dust clouds if you practice. Start it and keep a flashlight handy. look in the fins from the side, you'll be able to see the threads of the bottomless holes that are for the cam tower studs. hopefully, you'll see oil drip from there. If not the baby powder should give some clues.

If that's where its coming from, some have indicated some luck with putting RTV on the threads of the bolts. Couldn't hurt. I suspect it would need to be clean and dry.

Sorry for the bad news.

[Patrick]

Do you ride yours like that? Did you find any way to slow down the flow? The more I look at it the more I am thinking it must be something like that - if not that exactly....

[Patrick]

Damn. I think you nailed it, MC. Got out the foot powder and sprayed it around all the suspect seams. Took it for a real short ride - just down the street to the mailbox and back. That's about three blocks, round trip. Gunned it. Parked it. The seams were all dry, but drip, drip, drip from the fins.

Now I'm wondering, since all the bolts tighten OK, whether I can just seal them with some high temp silicon around the threads. I'm also wondering if I can get to those bolts by pulling the cam cover and shifting it around without pulling the engine yet again. My birthday is coming up. That would be a great present...

Thank you. Thank you. Thank you.

Patrick

[MCRider]

Damn. I think you nailed it, MC. Got out the foot powder and sprayed it around all the suspect seams. Took it for a real short ride - just down the street to the mailbox and back. That's about three blocks, round trip. Gunned it. Parked it. The seams were all dry, but drip, drip, drip from the fins.

Now I'm wondering, since all the bolts tighten OK, whether I can just seal them with some high temp silicon around the threads. I'm also wondering if I can get to those bolts by pulling the cam cover and shifting it around without pulling the engine yet again. My birthday is coming up. That would be a great present...

Thank you. Thank you. Thank you.

Patrick

You're welcome. Like I said it was hugely frustrating to me. Until just recently i thought i was the only one it had ever happened to. Now theres a member in Spain, one or two others here and you. Misery loves company. Probably a lot of head gaskets have been changed out unnecessarily.

I think you'll have to pull the engine. I had /have a frame tube removal kit, so i could experiment trying to to fix mine without pulling the engine. You won't be so lucky. Sorry.

Happy Birthday anyway.

[mystic_1]

Your bike didn't want you to be lonely on your birthday, now you'll get to spend some quality time together! 

No way to shortcut this really, IMO.  Pulling the motor is only a few hours, pop the top, seal up pucks and bolts, reassemble, reinstall.  Could be done in a weekend.

Now I'm wondering, since all the bolts tighten OK, whether I can just seal them with some high temp silicon around the threads. Patrick

NO SILICON!  ANYWHERE!! 

You have a tube of hondabond or threebond sitting around?  Use that!  It stays in place much better than silicon.  Use sparingly.  I've read here of others using threebond on the pucks.  For the bolts I'd smear some on the shaft just below the bolt's flange and on the underside of the bolt's flange.  Just a dab will do you.  Don't use it on the threads! 

mystic_1

[Brantley]

I know I'm a bit late finding this thread, but, man, am I glad I did. Patrick, what ever came of your issue? I read your original post and seem to have the EXACT same deal going on with the K0 I just finished. I've been back inside once to retorque and redo the pucks. I have a small seep now rather than the Uncle Jed shootin' at some crude from between pipes 1 and 2. I'd like to know the outcome. Mystic, my rocker tower bolts are the earlier non-flanged ones with washers. Is it a good idea to replace 'em with flanged?

[6685]

Where is your leak coming from?  If the pucks aren't sealed correctly where would leaks occur on the cylinder head?  I rode my bike yesterday and found a unusual oil spot on the left side of the cylinder head third fin down from the valve cover.  I am clueless as to where this oil spot came from.  Could it be a leaking puck?  Thanks

[kpier883]

I know this isn't a chevy, but the guys that build them know that chevy head bolts go into the water jacket.  To seal them, they often use permatex #2 on the threads and under the head of the bolt.  I think this is a similar problem. 

[MCRider]

Where is your leak coming from?  If the pucks aren't sealed correctly where would leaks occur on the cylinder head?  I rode my bike yesterday and found a unusual oil spot on the left side of the cylinder head third fin down from the valve cover.  I am clueless as to where this oil spot came from.  Could it be a leaking puck?  Thanks

The 4 front cam bearing hold down studs are threaded into holes that are open to the atmosphere above each spark plug hold, at about the 3rd fin level. If you are getting oil there it is, in my experience, most likely those studs, are wicking oil down and out. Look in there with a flashlight you'll see the threads of the open bottom of the holes.

Many people remove those studs when working on the head and use bolts in their place when reassembling. This breaks the bond. Also many time once the studs are removed and bolts used in their place, the holes get stripped and will leak ferocioulsy. Helicoils only make it worse.

The comment from kpier is prescient. But I will add, use the studs. With some sealer. They don't have to be torqued into the head, just firmly with the sealer, and let them set up. The hold down torque then would come from nuts atop the studs and won't distort those threads in the head. Maybe that will stop the leaks. Once mine began leaking I was never able to get them to stop. But I had removed the studs, stripped the holes, and was using 1/4 28 bolts.

This time I'll use the studs as mentioned.

[6685]

thanks.