Author Topic: Cam Cover Blow Out  (Read 1156 times)

cvincer

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Cam Cover Blow Out
« on: August 01, 2019, 09:37:25 AM »

Sitting at the traffic lights, engine idling, I heard a slight  'puff'  and the engine stopped.  Started it up again, but a few minutes later I could smell hot oil..& pulled over.  The problem was one of the 'plugs' of the cam cover gasket had blown outwards, causing oil to blow out the side.

Simply loosened the cam over bolts, pushed the 'plug' back in, & carried on home where I cleaned the oil off the bike.  I then got on it & went for a 10 minute ride, red-lining it in the lower gears several times........with no blow out.   Any ideas why the blow out happened at idle??

The photo shows the plug after put it back in place.

fret not

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Re: Cam Cover Blow Out
« Reply #1 on: August 01, 2019, 01:29:16 PM »
Excessive internal pressure.  I don't know why.  The cam covers each have a vent that goes to the air box, and one is larger diameter than the other.  I substituted the large vent cover from another motor for the small vent cover, so both covers now have less restrictive breathing.  I'm not sure if this is enough to prevent the blow out problem, but it should at least improve the situation a bit. 8)
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

Inheritance

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Re: Cam Cover Blow Out
« Reply #2 on: August 03, 2019, 07:47:43 AM »
On an unrelated note -- is that a stock Reg/Rec and was there enough slack in the wires to mount it over there? I really need to consider doing this but splicing/soldering sounds like an expensive mistake for this job.

George R. Young

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Re: Cam Cover Blow Out
« Reply #3 on: August 03, 2019, 02:08:17 PM »
The Kawasaki Concours has a similar shaped valve cover gasket and recommends a dab of silicon seal on each gasket lobe to prevent this blowout.

fret not

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Re: Cam Cover Blow Out
« Reply #4 on: August 03, 2019, 04:18:20 PM »
This issue is what the 3 Bond (Hondabond, Suzukibond, Yamabond, etc.) is good for.  It seems to resist oil pretty well, better than(most) silicone.
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

injuhneer

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Re: Cam Cover Blow Out
« Reply #5 on: August 03, 2019, 11:13:08 PM »
Excessive internal pressure.  I don't know why.  The cam covers each have a vent that goes to the air box, and one is larger diameter than the other.  I substituted the large vent cover from another motor for the small vent cover, so both covers now have less restrictive breathing.  I'm not sure if this is enough to prevent the blow out problem, but it should at least improve the situation a bit. 8)

Might one of the vent tubes be obstructed?

These half-round seals do age. They can harden or shrink causing exactly what happened.

Some old Maserati engines have this problem. I make a half-round aluminum plug with an o-ring to replace those. Maybe I'll give it a shot on the XZ.
- Mike O
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fret not

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Re: Cam Cover Blow Out
« Reply #6 on: August 04, 2019, 03:57:36 AM »
You wouldn't have by any chance a table top CNC would you?
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

cvincer

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Re: Cam Cover Blow Out
« Reply #7 on: August 04, 2019, 04:43:02 AM »
Re all the replies:-

Inheritance ......yes it's an OEM reg/rectifier. The lead from it that connects to the one coming from the stator has been extended.
                         Think I cut the lead of a dead reg/rectifier I spliced it onto the lead from what is now the insitu reg/rect. Simple
                         job with the soldering iron & some heatshrink.   I've also put an heatsink on the engine to take away heat from
                         the stator...make sure the securing bolts you use don't foul the moving parts inside the engine.

Walt M............. No, the hose was fine.

Fretnut.............It is the rear cylinder with the larger diameter hose.  Sounds like you've put a rear cam cover on the front cylinder.
                         Where did you vent it to??  (any pics?)
 

Had thought the problem might have been related to a 'wasted' spark, but today decided to install a new cam cover gasket, and was amazed to find the exhaust camshaft had sheared......why I've  been able to happily ride around on it for the last few days can't understand.  Only having 1 exhaust valve opening must explain the blow out.   I've drained the oil but not bits of metal + nothing on the magnetic sump plug....but then again never found the 'pecker' missing from an accelerator jet. Wonder if the sheared cam had something to do with the carb balancing problems detailed in an earlier post?

Anyway, I've got a spare camshaft so will get on the road again sometime.  Thanks for the replies.

.

Walt_M.

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Re: Cam Cover Blow Out
« Reply #8 on: August 04, 2019, 07:16:45 AM »
Well, that's a new one. How many miles on this engine?
Whale oil beef hooked!

Prophet Of Doom

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Re: Cam Cover Blow Out
« Reply #9 on: August 04, 2019, 07:22:44 AM »
Only having 1 exhaust valve opening must explain the blow out.   
That would do it.  Half the exhaust would increase blow-by significantly I would think.
Never heard of that happening before.  You are very lucky it happened with the valve closed.

cvincer

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Re: Cam Cover Blow Out
« Reply #10 on: August 04, 2019, 10:29:02 AM »

   86,000 kms

pinholenz

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Re: Cam Cover Blow Out
« Reply #11 on: August 04, 2019, 05:41:28 PM »
That is astounding. Its hard to believe that the engine kept running let alone being able to redline!
Only one '82.5  eXtreme Zen 550

injuhneer

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Re: Cam Cover Blow Out
« Reply #12 on: August 04, 2019, 07:17:22 PM »
You wouldn't have by any chance a table top CNC would you?

My machines would need a very big table. LOL
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injuhneer

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Re: Cam Cover Blow Out
« Reply #13 on: August 04, 2019, 07:22:08 PM »

   86,000 kms

Interesting failure.

If the ends of the fracture are bright then the failure is recent and stress related. Like when the bearing caps are replaced or swapped without line boring. If the ends of the fracture are dark grey then the fracture has been in the making for some time.

The cam looks good otherwise. Definitely could be repaired.
- Mike O
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pullshocks

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Re: Cam Cover Blow Out
« Reply #14 on: August 07, 2019, 02:45:51 PM »
It happened to me while I was on a trip .   Vent hose was in place and unobstructed, so I never understood why. Fortunately it happened a few blocks from my hotel and I was able to work on it in the parking lot.  I wrapped a bunch of tie wire to hold it in place.

Full write up here:  http://ridersofvision.net/rovforum/index.php?topic=13288.0

I can't believe 8 years have gone by.

Walt_M.

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Re: Cam Cover Blow Out
« Reply #15 on: August 07, 2019, 03:59:03 PM »
But, did you have a broken exhaust cam?
Whale oil beef hooked!

pullshocks

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Re: Cam Cover Blow Out
« Reply #16 on: August 08, 2019, 01:25:49 AM »
The gremlins threw a lot of stuff my way during 5 years of Vision ownership, but not a broken cam shaft.....

Prophet Of Doom

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Re: Cam Cover Blow Out
« Reply #17 on: August 12, 2019, 12:06:24 AM »
The gremlins threw a lot of stuff my way during 5 years of Vision ownership, but not a broken cam shaft.....
Does anyone here have a gremlin bell on their visions?
If there ever was a bike that needs one this is it.

cvincer

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Re: Cam Cover Blow Out
« Reply #18 on: August 12, 2019, 09:42:43 AM »

Here's a couple of photos of the camshaft.

The new cam is in the REAR cylinder but the bike won't start. FRONT cylinder tries to fire, but nothing from the REAR.  Can't understand the problem, lining up the valve timing marks is simple....& whatever is wrong withe the REAR, the FRONT should be firing....the bike running on a single cylinder.

Seems to be a mistake in HAYNES. ...when it talks about valve clearances, it says that at TDC on the compression stroke, both the front & rear cylinders will have their cam lobes pointing up, whereas on mine the REAR has it's lobes lying almost flat opposing (Inlet/Exhaust cam lobes) each other and looking at the diagram of 'Cam Sprocket's in HAYNES ...how could the rear have the lobes upwards?

The XZ service manual makes the same mistake...plus when talking about valve timing for the REAR cylinder, says the lobes at TDC on the compression stroke should be facing each other, whilst the accompanying diagram shows something different.

Anyway, don't know why mine won't start;  at the weekend I'll try a rain dance & then maybe a lump hammer.

injuhneer

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Re: Cam Cover Blow Out
« Reply #19 on: August 16, 2019, 09:34:16 AM »
There was another thread that covered the cam positions for timing. I would have to find it but maybe one of the long-time members can point you to it.

The manual must be incorrect. At the absolute minimum the difference in angle of the cams relative to each cylinder TDC must be at least 70*.

If the rear cams are drastically out of time it seems there should be ignition firing through the intake or exhaust when cranking.
- Mike O
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