Help with blowing smoke

I Hi guys. My knowledge is trivial compared to you gurus, but if the guides are OK, could this problem possibly be related to rocker spindles installed back to front?

MGB65B said:

I Hi guys. My knowledge is trivial compared to you gurus, but if the guides are OK, could this problem possibly be related to rocker spindles installed back to front?

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He said that they were correctly installed so that shouldn't be the problem.

In any case, I suggest a compression check. I'm thinking the bad cylinder might indicate low. The symptoms described re when the smoke appears don't really fit those typical of bad guides/seals.

How many miles did you do after the rebuild before you pulled the head off again? When installing the pistons how much oil was used to put the pistons in, as Jim said could be a ring problem as well, lots of things could be causing this problem and you could be looking for the problem in the wrong place, what oil were you using for run in period etc plays a big part, rings not bedding in on one side or broken ring?

Ashley

A leakdown test would be best. If your hearing is poor like mine is, ask someone with good hearing to help.

Glen

Ok here is what i found. There was a piece of metal in the oil drainage hole in the right inlet. Looked like a piece of the old valve guide. I flushed it out and put the bike back together. Oil is flowing better now. Major smoking issue has resolved. Just typical smoking prior to new break in. Hope that fixed the problem....

Thanks for the feedback. It is frustrating when OP's take everyone's suggestions, then leave us all guessing what the outcome proved to be.

With feedback, everyone comes away a little more knowledgeable.

Slick

What texasSlick said.
Clogged drain hole, good find.

As I said in a previous post, I have always been amazed at how small that oil drain passage in the head/barrels is. I did a lot of testing re flow some years ago when doing a rebuild and, TBH, it seemed to me that the passage was marginal at best for ensuring appropriate drainage. However, based on many years of successful operation, it obviously works though with NO wiggle room for any obstruction whatsoever.

I hope it fixes your problem though I still wonder about the fact that it was putting out a lot of smoke at higher RPM and none at idle. There is more engine vacuum at idle to pull oil past the guides/stems but maybe there was enough drainage at idle to prevent the seals/tops of the guides to be submerged in oil but at the higher RPM they were "underwater."

Please advise whether cleaning the drain hole completely cures the problem!

There really shouldn't be any smoke at all after rebuild other than initially when whatever oil you put on the rings/cylinder walls burns off. FWIW, NO oil on rings/walls during assembly is current thinking by many engine builders.

Thats great news and hope it solves the smoking problem, its great when you get to the problem and good luck with the run in, hope you get to clock up some good miles.

Ashley

Riders must predominately lean/turn right!

This case, one other on this Forum (IIRC), and a local guy in my area with a G15, had smoke from the right side only as a result of obstruction in the intake rocker box drain. One would expect flooding of the intake rocker box would cause smoke on both sides.

I suppose the phenomena is due to the drain hole being on the right. Just curious .....

Slick

Now you can begin wearing down tire treads rather than biting nails. Good fortune and many miles.

Ok Guys, here is an addendum to my smoking bike issue. Hopefully someone can learn from my mistakes. After I found the piece of metal in the drain hole, everything was fine for 2 minutes... then the oil and smoke came back. So I was frustrated as hell... kind of embarrassed to ask for more help.

This is what I had done up to the point:
New cylinder Bore, new rings, new pistons. New valves, new valve seats and Guides. I check everything that you all mentioned in the above replies. After 3 times taking the engine apart with no improvement, I decided that I would get a new head all together. I new the issue was the head because the smoke went away when I capped the oil flow to the rockers. Anyways, I was lucky that my friend Scott called (Kernel65). I explained everything that was going on and the problem that I was having. I mentioned that there seemed to be a ton of oil being pumped to the head. I measured 8 oz in 20-30 seconds.
I was getting a new head in the morning with a shipment of parts so I was planning to swap them out... But Scott suggested to check the oil flow from the timing cover back to the oil reserve. Then we started to talk about the oil pressure release valve. He suggested if the the valve was seized that the pressure would be too high to the rockers and this may account for excessive oil flow to the head.
Well guess what, he was right. The oil pressure valve was seized so the oil pressure never released. This caused oil to just flood the head and cause both the excessive smoking and oil coming out of the exhaust pipes. I replaced the OPV with a spare and POOF the smoke stopped. Actually just a little smoking is left but I suspect this is all the oil burning out of the exhaust.

So now we have another possible cause for excessive smoke and oil out of the exhaust.

Well, a round of applause for Scot everyone!

Seriously, that’s a good find. Imagine how frustrated you’d have been if you’d fitted that new head only to still have the problem.

Thanks for posting.

Thanks for the feedback. This is a win - win for all.

Kudos for Col. Kernal65!

Slick

And at the price of an unnecessary new head. Good move pardner.

Naw, The head came with another project. i will just use it for the intended bike.

Excellent discovery and thanks for the thorough post! I must admit that I tend to pooh-pooh installing an oil pressure gauge on a street-ridden Commando but having a gauge would have quickly identified this problem! I may re-think my thinking re an OP gauge!

Again - thanks for the post and complete report. Great Job!

MexicoMike said:

Excellent discovery and thanks for the thorough post! I must admit that I tend to pooh-pooh installing an oil pressure gauge on a street-ridden Commando but having a gauge would have quickly identified this problem! I may re-think my thinking re an OP gauge!

Again - thanks for the post and complete report. Great Job!

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I, too, experienced a stuck OPRV. Fortunately, I had an oil pressure gauge and immediately corrected the problem. Never understood the logic, or lack there of, of not having an oil pressure indicator. Other than a blown engine, that is. The guys that insist on a shutoff valve in the oil line feeding the oil pump and do not have an oil pressure indicator would play Russian roulette with 5 shots in a six shooter.

JimC said:

The guys that insist on a shutoff valve in the oil line feeding the oil pump and do not have an oil pressure indicator would play Russian roulette with 5 shots in a six shooter.

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Good one! LOL

This thread is an impressive display of the talent on this board!
Jaydee