Mechanical question –

Factual Questions
1

My bike (85 Yamaha Maxim 700) was running relatively fine. The valve cover gasket had been in need of replacing for a few years due to a very slow seepage of oil around the corners. Brought it into the shop to have a couple of unrelated problems taken care of (RR’d clutch cable, oil change) and had them replace the gasket. Rode it home, all seemed somewhat well.

The next day I was making a couple adjustments (brakes, idle speed) when in putting back and forth on my street (no faster than 10 – 15 mph) oil came out under pressure from one of the spark plugs. Strong enough to splatter on my arm. (ow!)

I have to call the shop in a couple hours and ask them about this. Can any of the TM out there give me a hand and tell me if and how the replacing of the gasket and the new high-pressure oil leak are related? If it is going to be leaking like that, I’ll have to have it towed back to the shop, and if it is something they should have seen before they gave the bike back to me, they should at least share in the towing cost. I hope someone can help. Thanks.
Rhythmdvl

Once in a while you can get shown the light
in the strangest of places
if you look at it right…

2

Wow! I’m confused about some items:

It came out of the spark plug? or the hole?
This also should have made the bike run like hell as the oil fouled the plug, in addition to which you should have observed smoke from the tail pipe as it pushed oil into the hot exhaust pipe.

My first instinct is to say you blew the head gasket, and my other thought is that you cracked the head near that particular plug.

Beyond that, I’d have to look at it, and in any case, from what you described the shop as doing, they’d have no idea that it was going to happen, as they didn’t give it a tune-up or change plugs or anything.

I’d start by examining the head and case very carefully, and then the plug in question to check for oil fouling and condition of the plug threads. Next, do a compression check on all cylinders. It’s also possible that with a blown head gasket, you pumped pressure into the crank case, which would account for it coming out under pressure.

Another possibility would be broken piston rings, with the same result, except you’d have noticed rough running and noise as they scraped the cylinder walls.

Let me know what you find; I’ll be interested to hear what happened.

Hope that helps!

VB
I’ve performed a complete diagnosis of your car. It’s broken.

  • A Wally original!
3

Mechanics rarely accept blame for the failures that occur after they work on something. Most of the time, it’s not their fault.

Does it actually come out of the spark plug? If the bike runs fine, it is unlikely to blow oil out the spark plug.

Or does the spark plug stick out through the valve cover, hemi engine style. It is possible that the oil return drains are blocked, either by pieces of the old gasket or by gasket sealant. The valve area could fill up with oil and eventually spray out though any hole it can find in the valve cover, such as around the spark plug.

4

First to dispel a bit of confusion - it to be oil coming out from behind the spark plug. The side of the plug’s wire had oil on it, and there was a bit of splattering on the tank in line with the plug.

That it did not seem to run poorly struck me as a bit odd, but I noticed it a few hundred feet from my house, within a minute or two of shutting down for the day. (had to meet some people and have not started the engine since it is raining cats dogs and protestors here in DC). It had only been running for a few minutes, enough to adjust the idle and run up and down my block two or three times.

::horrified wail::

I’ll be taking a good look at it later this evening (after I do my taxes) or tomorrow night depending on the weather. I can do everything on my own except the compression check. Pleaseohplease don’t let me find a crack!

As for broken rings… it did need the idle adjusted, but I had been thinking of doing that before I brought it in. I can’t say if it was that much worse yesterday, but it certainly was not running at its prime. No strange noises though.

Just read Starfish’s comment. I totally understand mechanics being defensive. I used to work at a body shop and we’d get blamed for all sorts of things we had nothing to do with. (e.g., how does bodywork on a rear quarter affect someone’s engine?) I don’t necessarily want to call them up and demand that they come get the bike, but it is also good to have some idea of the possible causes, etc… The plug sticks up through the valve cover, and again, I wrote the OP wrong. Oil is coming from the sides of the plug, not the plug itself. So, I am going to hope that it is something more along the lines of plugged return drains. It is a good shop, so if it is that they will probably take care of it for me. Again, thanks for the input, and wish me luck!

Rhythmdvl

Once in a while you can get shown the light
in the strangest of places
if you look at it right…

5

Motorcycle mechanics are usually broke too, not that it’s an excuse (far from it!) I used to be a Yamaha mechanic. It’s been a decade, but I think I still remember…

The 700 Seca/Maxim was an air cooled, DOHC, right? If I recall correctly, the gasket was a rubber gasket that fit into a groove running around the valve cover and mated to a flat surface on the head (the 1100s were the ones with a paper gasket… right?) The valve cover is held on with …eight?.. bolts that have big cupped washers under them and gaskets under that. Even on a high mileage bike, like this one may be, I can’t see how you could generate a lot of pressure on top of the head unless the vent was clogged.

The area under the valve cover is open to the bottom end through the cam chain’s opening (the divider between the inner sparkplugs at the middle of the engine.) This opening is just under one inch wide and several inches long and has a chain running through it to turn the camshafts. If there was enough trash to clog this area, it would have already gotten caught in the cam chain and the bike would not run.

Now, running from the airbox (where the air filter is) to the engine is about a 3/8-1/2" tube (IIRC, on the Seca/Maxims, it runs to the valve cover.) This is the engine breather, where blowby (the gases that get past the rings) goes to get burned through the engine again. I’ll bet that either this hose was pinched or kinked when the bike was put together or the breather tube was clogged inside the valve cover (the pressure would have pushed out any clogs in the airbox.) The blowby would raise the pressure in the engine, causing the oil leak at the gasket.

This should be an easy fix; let me know if you get fed up and want to do it yourself. Regardless, I’d check to make sure that the valve cover gasket is soft. If it’s new, it will be, as the gaskets harden with heat/use.

One other problem that I could see with this one is that they may have used the old valve cover bolts when they put the new gasket on but didn’t use any gray Yamabond valve sealer. Yes, I’m recommending this one type of goop by name. The valve cover bolts are designed to bottom out, and they have gaskets on them that get hard and will not seal. The gray Yamabond will seal the gasket and bolts like no other sealant (ie, Permatex, etc. Don’t even think of silicone) will. There is an aftermarket equivalent, though, and it’s the same stuff. I wouldn’t bother with replacing the bolts. The Yamabond will replace it; new gaskets all around may not. Come to think of it, I’ll bet that this is the real problem.

Valve cover leaks were fairly common on these engines. I learned about this stuff from the older mechanic at the shop where I worked. Yamaha’s Genesis engines were new when I left the business. They use a similar setup for their valve covers, but, being water cooled, they may not have the same problems with the gaskets hardening and shrinking. It’s entirely possible that the mechanics at the shop you went to didn’t know about these problems.

Anyway, I hope that this helps.

6

(b)(i) … (/i)(/b)
Can’t nest UBB, can we???

FWIW, this is the light gray stuff. It never dries hard.

I suspect that this is a case of the mechanic not knowing about this particular problem. Turnover is high, so you can usually forget about having an ‘old man’ at the shop, and in the Eighties I never heard about a mechanic going to factory training. Think about how many people feel about mechanics. Sure, there are some real losers out there, but even the good (or at least earnest) ones don’t know everything, but take a lot of shots. The best gift you can give a mechanic is trust. If that isn’t warranted, then at least give them a little respect.