Valve covers Ds blow out

[mabrown]

1983 1300 (just turned over 100,000 miles) and 2 or 3 of the valve cover 'd's blow out usually within 10 miles of startup but can happen at any time. This week they blew out after 40 miles. All you have to do is stop and push them back in and it may run for 100 to 1000 miles before it does it again. I have added a 3/8" breather to the oil fill which slowed down the frequency but did not stop the problem. I can freely bow through the new breather and hear it come out of the intake box. Messy and very annoying. Any ideas on how to fix this?? Thank you.

[MiCarl]

Are they new? OEM or aftermarket? Recently have the covers off?

 

There is supposed to be sealant under them but even without it I doubt you should be able to just push them back in without loosening the cover. Probably the best thing to do is get new and make sure they're properly installed.

[Yammer Dan]

:sign yeah that: What MiCarl said I've never had then blow out. Time for tune-up??

[gaj1917]

This also happened on an 84 that a friend of mine owns. In his case one of the D's actually ripped off. This happened on a startup after resting following a long ride. He had the cover gaskets replaced, but had at least two subsequent blowups occurred. The new D's held, but the breather hose detached. So, there was some crankcase pressure building up due to a blockage somewhere. The problem then disappeared! Mystery.

[Flyinfool]

ALL ringed engines have blow by. The crankcase must be vented to relieve that pressure. Check your vents all the way to the air cleaner be sure nothing is plugged up. THEN put in new valve cover gaskets.

 

As long as you are there, for peace of mind measure your valve clearances.

[Patmac6075]

I'll have to admit....I have no idea what valve cover Ds are? I know what the valve covers are, I know what the valve cover gaskets are, I know what the valve cover bolts are, and I can only assume we're talking about the rubber hold down washers? I've heard them called donuts and pressure washers, but not Ds....is this what we're talking about?

[BratmanXj]

I'll have to admit....I have no idea what valve cover Ds are?

 

[Patmac6075]

A picture is worth a thousand words!

thank you

[Flyinfool]

The "D"s are the first place an old gasket will start to leak as the old rubber gets hard and starts to shrink.

[Black wing]

yup sounds sounds like your crank case vent is plugged up.

[Yammer Dan]

yup sounds sounds like your crank case vent is plugged up.

 

 

:sign yeah that: That's what I was thinking. Made my head hurt!!

[mabrown]

Thank you for your suggestions. I am 100% sure the vents are not plugged. The gaskets are not old and are soft. It appears the the crankcase vapors are igniting and that is what is causing the Ds to blow out. Remember it blows out 3 Ds each time. A plugged vent would blow out one or maybe 2. A plugged vent should seep oil but it does not leak or seep any oil between blow outs. I was just hoping that someone else had found the cause of the ignition. Thank you.

[Black wing]

if you think its actually ignition in the case have you run a pressure test on the cylinders? the only think that could cause that is a blown piston or ring.

[Flyinfool]

:sign yeah that:

That would be my first guess

 

The only other remote possibility that I can think of, and I never heard of it happening is that there would be an issue with a broken wire in the stator that is causing sparks as it makes and brakes contact. Sparks inside of the crankcase could ignite oil and/or gas fumes that will be present in the crankcase. The stator and pick up coils are the only wires inside of the engine that I am aware of. I do not think there is enough current available in the pick up coils to create a significant spark. But like I said, this is purely a WAG that I have never heard of happening.

 

Check to be sure that you are running on all 4 cylinders. Start the bike from cold and check too see that all 4 pipes heat up at the same rate. Then check the voltage across the battery with the engine running, it should be near 14V with the engine at or over 3,000 rpm

[MiCarl]

...All you have to do is stop and push them back in and it may run for 100 to 1000 miles before it does it again.

 

I do not believe they should go in and out that easily.

[mabrown]

Well I have been waiting for a test ride to confirm this answer. Flyinfool's guess was right. We were to go on a trip 2 weeks ago and when I went out for the final test ride the volt meter dropped to 12. Short story the stator was bad and we left the bike at home. Well we replaced the stator and rode it yesterday with no blowouts. The last ride of the same distance before our trip had 3 blowouts.

 

Recap of the symptoms multiple valve cover D's blow out when the crankcase ignites blowing out oil and smoke. Breather is clear and there is no oil seepage or leaks between blowouts. It usually happens when you are slowing down - coming into town or up to a stop light. Cause a stator going bad. You can see the stator has been hot (covered in burnt oil deposits) but no place when you can see arcing. The blowouts came and went and now looking back they came when the stators were going bad.

 

This is my 3rd stator in this bike. This time I enlarged the oil cooling hole in the rotor bolt from .040 to .052". This should almost double the oil flow over the stator and hopefully end the stator burn out.

 

Thank you for your comments. Hopefully this can help someone else.

[bongobobny]

OK on the early Ventures, specifically the 83 and some of the 84's there was a known issue of the stator NOT getting sufficient oil on them for cooling. This was corrected with a "Kit" that was made available by Yamaha in conjunction with a TSM about the issue. Most bikes were fixed under a recall/warranty but there may be a few out there that do not have this installation. From what I remember the kit consisted of a pin and a washer affair to "sling" more oil on the stator.

 

I seem to remember reading a long time ago about someone else drilling the hole out a little...