Author Topic: Top end "oil jet" question. (Read 2786 times)

Obsidus · « **on:** March 25, 2012, 10:59:07 AM »

So a few weeks back I threw my camshaft due to lack of lubrication on my '78 SOHC. I replaced it, but I has question. Now, if I read the shop manual correctly, there is a diagram displaying the flow of oil to the top end of the motor through only two ports. These ports are located just to the left and right of the tunnel, right?

After I had removed the towers and holders, I shot air down the jets since I figured that one side was clogged up. At one point, I was able to feel air coming out of the opposite jet when I put my finger over it. This is good?

Would compressed air have been enough to free up a clogged jet?

MCRider · « **Reply #1 on:** March 25, 2012, 12:05:05 PM »

Quote from: Obsidus on March 25, 2012, 10:59:07 AM

So a few weeks back I threw my camshaft due to lack of lubrication on my '78 SOHC. I replaced it, but I has question. Now, if I read the shop manual correctly, there is a diagram displaying the flow of oil to the top end of the motor through only two ports. These ports are located just to the left and right of the tunnel, right?

After I had removed the towers and holders, I shot air down the jets since I figured that one side was clogged up. At one point, I was able to feel air coming out of the opposite jet when I put my finger over it. This is good?

Would compressed air have been enough to free up a clogged jet?

I've seen and read about many such failures and endured one myself. I've never seen one on an engine that hadn't been opened up and worked on, though i suppose that's possible. Mine was such. Was yours?

usually its debris in the jets on the top of the head, in the locations you mention, you are correct. Blowing air down would force the debris down but not out. Though it might break it up and rearrange it so it can get past the jet and get caught in the filter.

Usually, removal of the head is called for. then when you blowout the jet the debris can leave the engine and you're good to go. Since you've already dislodged the debris and sent it to the netherlands... well...

Obsidus · « **Reply #2 on:** March 25, 2012, 12:46:24 PM »

Quote from: MCRider on March 25, 2012, 12:05:05 PM

Quote from: Obsidus on March 25, 2012, 10:59:07 AM
So a few weeks back I threw my camshaft due to lack of lubrication on my '78 SOHC. I replaced it, but I has question. Now, if I read the shop manual correctly, there is a diagram displaying the flow of oil to the top end of the motor through only two ports. These ports are located just to the left and right of the tunnel, right?

After I had removed the towers and holders, I shot air down the jets since I figured that one side was clogged up. At one point, I was able to feel air coming out of the opposite jet when I put my finger over it. This is good?

Would compressed air have been enough to free up a clogged jet?
I've seen and read about many such failures and endured one myself. I've never seen one on an engine that hadn't been opened up and worked on, though i suppose that's possible. Mine was such. Was yours?

usually its debris in the jets on the top of the head, in the locations you mention, you are correct. Blowing air down would force the debris down but not out. Though it might break it up and rearrange it so it can get past the jet and get caught in the filter.

Usually, removal of the head is called for. then when you blowout the jet the debris can leave the engine and you're good to go. Since you've already dislodged the debris and sent it to the netherlands... well...

Pretty much. It had an R2 shaft in there and I replaced it with an R1.

And are you implying I've caused more work for myself or that I may have got this right? I think the only way I would know for sure is if I take everything apart again.

MCRider · « **Reply #3 on:** March 25, 2012, 01:48:50 PM »

Its a tough call. Curious, did you use a silicone based gasket sealer on the rocker box gasket? Or oon the pucks?

As to what to do next. If you want a dependable rider, and depending on the answer to the above question, you may want to pull it apart.

Sorry you burned up a R1 cam, assuming it was from an early CB. There were R1s from later CBs that were nothing special.

lucky · « **Reply #4 on:** March 25, 2012, 01:54:12 PM »

"So a few weeks back I threw my camshaft due to lack of lubrication on my '78 "

What does that mean? "Threw my cam"

Brantley · « **Reply #5 on:** March 25, 2012, 02:36:25 PM »

I had a jammed up/ chipped starter idler gear that I lived with for around a year... I didn't know why the starter kept hanging up, and it fired on the first kick most times anyway so I lived with it. Finally got off my ass to restore creature comfort and removed the alt cover to find CHEWED gear and plenty of small metal bits. I used a magnet to retrieve what I thought was all of it and changed the oil. The next weekend: big, spectacular, smoky overheating. Anyone for charred rocker arm? I would find the cause of yr blockage rather than hoping you got it and doing the whole burnt cam procedure again.
So, Ron, did you mean "opened up and worked on" anywhere or just the top end?

MCRider · « **Reply #6 on:** March 25, 2012, 02:47:25 PM »

Not so much sidecovers, unless silicone is used. Mostly top end and such.

Obsidus · « **Reply #7 on:** March 25, 2012, 07:20:10 PM »

Quote from: MCRider on March 25, 2012, 01:48:50 PM

Its a tough call. Curious, did you use a silicone based gasket sealer on the rocker box gasket? Or oon the pucks?

As to what to do next. If you want a dependable rider, and depending on the answer to the above question, you may want to pull it apart.

Sorry you burned up a R1 cam, assuming it was from an early CB. There were R1s from later CBs that were nothing special.

Ya know, I'll have to check on the sealant. The only area I've applied sealant to is an itty bitty rip in the cover gasket. I've still got a couple weeks before I can start riding it legally anyway, so I'll probably end up doing the top end/head work and pulling the oil pan for shavings and sludge. It's my first build, by I want to do it right and be able to ride without having that in the back of my head. Thank you for your advice.

Quote from: lucky on March 25, 2012, 01:54:12 PM

"So a few weeks back I threw my camshaft due to lack of lubrication on my '78 "

What does that mean? "Threw my cam"

Basically means it got all muffed up. Learning most of your mechanics from your Southern family, you pick up slang like that.

Bodi · « **Reply #8 on:** March 26, 2012, 08:19:45 AM »

There's a largish oil gallery coming up through the barrels, and a part with a tiny orifice between the head and barrel. The blockage happens when a bit of crap comes up in the oil and blocks that tiny orifice. Blowing down from the head will dislodge it, but it's still in there and will come back up and naturally end up in the orifice again.
The question about silicon is because if silicon is used as a sealant, tiny blobs get squeezed out of the gasket surface and eventually come loose, floating around in the oil. They should get caught in the oil filter but with a dirty filter and thick cold oil the filter bypass valve can open occasionally, letting crud through. These bits of silicon can and do clog the head oil orifices and sometimes even the main bearing oil passages.
I would remove the head and clean out the oil passages thoroughly. And inspect the main case gasket surface: if it's sealed with silicon I would split it, clean the silicon off, and reseal with Threebond 1194 or Yamabond. You can even try Permatex but it makes a heck of a mess and Threebond is generally preferred. Threebond 1104 was the best I think, but is discontinued, probably some carcinogenic component.

Tanqueracer · « **Reply #9 on:** March 26, 2012, 01:27:15 PM »

What kind of oil were you using prior to this event?

Obsidus · « **Reply #10 on:** March 26, 2012, 05:02:12 PM »

Quote from: Tanqueracer on March 26, 2012, 01:27:15 PM

What kind of oil were you using prior to this event?

Unknown. It's a motor I picked out of a trailer from a local shop that has a large stock of them and builds chops for customers.

Obsidus · « **Reply #11 on:** March 26, 2012, 05:10:23 PM »

So these oil jets sit to the immediate left and right of the tunnel....and they sit right under both holders, right (positions in the red circles in my attached pic)? I ask because I just find it to be a peculiar place for something that supplies oil to something as critical as the camshaft. I might do it today but work beat the hell out of me. I'm gonna pull it all on Friday. While I have the head and all that off, what's a good solution for all that carbon that will no doubt be on my pistons? Isn't there some sort of gel or what not that you coat the tops with and it burns it all off on ignition?

Tanqueracer · « **Reply #12 on:** March 26, 2012, 05:26:02 PM »

Don't assume it was the oil jet that caused the failure. The part may have failed and shed enough large (or small depending on your point of view) pieces that clogged the jets. I'd examine the parts very carefully to see if you can make a determination as to what came first.

MCRider · « **Reply #13 on:** March 26, 2012, 05:41:14 PM »

Quote from: Obsidus on March 26, 2012, 05:10:23 PM

So these oil jets sit to the immediate left and right of the tunnel....and they sit right under both holders, right (positions in the red circles in my attached pic)? I ask because I just find it to be a peculiar place for something that supplies oil to something as critical as the camshaft. I might do it today but work beat the hell out of me. I'm gonna pull it all on Friday. While I have the head and all that off, what's a good solution for all that carbon that will no doubt be on my pistons? Isn't there some sort of gel or what not that you coat the tops with and it burns it all off on ignition?

As to the orifices, you are correct about their location. From there the oil travels into the cam blocks on either side of the can chain under great pressure. THen it squirts out of each cam block at specific locations to oil the cam bearings, internally, and the lobes of the cams, and the rocker arm followers, externally. If you follow the path you'll see what a complete design it is.

MasterChief750 · « **Reply #14 on:** March 26, 2012, 05:43:34 PM »

chem dip carb cleaner will clean off the carbon on the pistons, but may take a few treatments. depending on how thick it is just let it sit for 24 and scrub it with a nylon brush and repeat as necessary.

Obsidus · « **Reply #15 on:** March 26, 2012, 07:31:23 PM »

Quote from: Tanqueracer on March 26, 2012, 05:26:02 PM

Don't assume it was the oil jet that caused the failure. The part may have failed and shed enough large (or small depending on your point of view) pieces that clogged the jets. I'd examine the parts very carefully to see if you can make a determination as to what came first.

I assume it was the oil jets because only the right side of the camshaft was ruined. The other ends, lobes and all, were peachy clean and there was an obvious presence of oil there. However, the right side was bone dry.

MCRider · « **Reply #16 on:** March 26, 2012, 08:24:50 PM »

While all posiblities should be examined, the oil orifice is always the most suspicious. usually when it clogs the cam seizes in the bearing (usually just one side involved) and snaps in half. Really cool.

When the orifices are clear and working, I've never heard of a top end valvetrain failure. Camchains, but not for lack of oil.

Obsidus · « **Reply #17 on:** March 26, 2012, 08:48:56 PM »

This one actually bored itself into one of the holders. Made the most god awful metal-on-metal screech I have ever heard.

Quote from: MCRider on March 25, 2012, 01:48:50 PM

Sorry you burned up a R1 cam, assuming it was from an early CB. There were R1s from later CBs that were nothing special.

I burned an R2, and replaced it with an R1. Silly.

lucky · « **Reply #18 on:** March 26, 2012, 09:05:41 PM »

Quote from: Obsidus on March 26, 2012, 05:10:23 PM

So these oil jets sit to the immediate left and right of the tunnel....and they sit right under both holders, right (positions in the red circles in my attached pic)? I ask because I just find it to be a peculiar place for something that supplies oil to something as critical as the camshaft. I might do it today but work beat the hell out of me. I'm gonna pull it all on Friday. While I have the head and all that off, what's a good solution for all that carbon that will no doubt be on my pistons? Isn't there some sort of gel or what not that you coat the tops with and it burns it all off on ignition?

Don't worry about a little carbon on the pistons. It gives you higher compression.

crazypj · « **Reply #19 on:** March 26, 2012, 09:08:59 PM »

You can unscrew the block off and check for 'bits' in oil gallery
It's common for people to fit an oil pressure gauge in place of the plug

Obsidus · « **Reply #20 on:** March 26, 2012, 11:06:38 PM »

Quote from: crazypj on March 26, 2012, 09:08:59 PM

You can unscrew the block off and check for 'bits' in oil gallery
It's common for people to fit an oil pressure gauge in place of the plug

You mean the plug next above the points housing, just behind the jugs?

And what 'block'?

Bodi · « **Reply #21 on:** March 27, 2012, 04:41:02 PM »

It's a "block off" plug because it vlocks off the main cross-engine oil gallery. The right plug screws in, I think the left one is held on by the alternator cover (not 100% sure for a 750). This gets oil from the filter and feeds all the bearings and the head. If you have chunks of crud in there... not good.
Losing one side of a cam pretty much points directly at a blocked oil control orifice.
The advice to look at other damage, I believe, was to figure out where any orifice blockage came from. The main gallery is supposed to be pretty darn clean, only filtered oil should get in. Finding any junk in there points to some previous problem that should be checked out. Simple abuse - not changing oil and filter - will allow detritus to get in when the filter bypass opens. Mismounting the filter can do it. A failed filter can as well, there was a report of bad aftermarket filters a few years ago.

Obsidus · « **Reply #22 on:** March 27, 2012, 10:02:04 PM »

And this should be done after oil is drained?

ekpent · « **Reply #23 on:** March 27, 2012, 10:37:50 PM »

One other tid bit to keep in mind by looking at the pic of your cam end, and I assume the aluminum holder also got it as bad, is where is all that metal now that was removed ? Drop the oil pan and see how much is down there and check the galley plug also. Just sayin'

crazypj · « **Reply #24 on:** March 28, 2012, 08:29:03 AM »

As Bodi said, the screw in plug just above and to left of points cover.
It would also be a GOOD IDEA to strip oil pump and check it as metal bits can cause rotors to crack
You will also need to flush tank, there will be sludge at the bottom

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Author Topic: Top end "oil jet" question. (Read 2786 times)