Freshly rebuilt 750 burning oil

Back in the late sixties/early seventies I had a bit of a small business going doing mainly cheapy top end rebuilds on tired Hondas. Those little bikes would lose most of their compression by 10 to 15 thousand miles. Most of the problem came from the rings, which wore out quicker than the bores. So I would lightly hone the cylinder, slide in a set of new rings and lap the valves to get them gas tight. If I couldnt get the valves gas tight with lapping then I would send things out for a proper valve grind.
But the customers were broke kids like me, so every dollar mattered. Most of them were friends of my older Brother.

The only complaint I recall was from one fellow who was a very gentle rider. I did the standard top end freshening to his Honda 250 Dream and after a week of running it smoked quite badly. I asked him to leave it with me for the weekend.
Before taking it all apart again, I decided to give it a good thrash in the trail system and gravel pit near our farm (I was only 14, not on the road yet!) Right away there was improvment.
So I rode it all weekend quite hard, but kept the revs just down from the top and varied the rpm a lot, as you do when in the trails. I shut it down and rested it frequently so that it never got overly hot. By Sunday night the exhaust was running clean.

Glen

Small update for the day. So since switching from the 20w50 the shop provided to an SAE50 and riding in the same fashion i have been (not keep revs consistent, sprinting from 30-70 and back again) it seems the oil has helped? After a ride this morning getting on the bike pretty good the smoke was nonexistent when I got home, and the bike felt like it was pulling harder than before throughout the rpm range. I started the bike about two hours later and got MUCH less smoke on startup. I know I've heard modern oils, thin oils, and synthetic oils aren't great for breaking in motors so maybe the SAE50 is helping the rings settle in?

I used VR-1 SAE50 from the get go after the rebuild and didn't experience any smoke unless it wet sumped. I'm thinking about switching to Rotilla for the ZDPP or whatever it is and the multigrade, 15-50 I think per Comstock's recommendation. It's a bit hard to push over cold with the SAE, but when warmed up it's easy. I think they're both dino oil.

Dave
69S

kevbo82 said:

Small update for the day. So since switching from the 20w50 the shop provided to an SAE50 and riding in the same fashion i have been (not keep revs consistent, sprinting from 30-70 and back again) it seems the oil has helped? After a ride this morning getting on the bike pretty good the smoke was nonexistent when I got home, and the bike felt like it was pulling harder than before throughout the rpm range. I started the bike about two hours later and got MUCH less smoke on startup. I know I've heard modern oils, thin oils, and synthetic oils aren't great for breaking in motors so maybe the SAE50 is helping the rings settle in?

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Gravel pit time!

Synthetic oil is fine for running in a new or rebuilt motor.
There are far too many myth's about oil.
Take time to read independent essays on line about oil and learn lot's of information to help rather than hinder motor life.
We have come a long way scientifically since the 1950's. Oil is very advanced engineering these days.
Too many old bastards propagating and perpetuating myth's and crap about the good old days.
If that shit was so good then we would still be using it. Thank feck we are not.
Change it often and change the filter at the same time. Cheap insurance and peace of mind.
I would not use Diesel motor oil in a petrol motor.

plugs show rich , or damp . WHICH WONT HELP ANYTHING SEAL .

as for oils . Castrols old CRI 40 petrol / diesel / turbo oil wouldve been the best , till they multigraded it .

Synthetic two stroke oils , at least , have a ' flash point ' where they spontaeneously combust .

This temp is higher for CASTOR OIL ( of a good grade ) and CASTOR is the only oil that is ATTRACTED to HEAT .
therefore its best , for a raceing engine . Though can congeal if unused indefinately .

Darn Plugs . N3s can soot up if not given a bit of stick . Conversly N4s or more N5s could create meltdown if you thrash it .

If theres hidious ancient 6 volt coils in there , Id look at them . If it wont spark blue & white @ 1/2 in , the Ign. aint to brilliant .

You should be able to spot if the intake seals are fitted through inspection covers , with a bright torch .

On plus , Oil is Oily , petrol is sooty . Super Rich is black smoke , Oil smokes white .
If it puts out pufs of black sooty smoke , opening up - its a jetting or Ign. problem .

If its RICH you risk chewing things up , through washing the oil of the bores and ruining the rings etc ( anything they mate to . )

Chucking it on 100 octane for run in wouldnt be a bad idea . The ethanol trash would be . :x

Take a run down to your local airport and put some 110LL in it and give it the snot.

Dave
69S

kevbo82 said:

I want to talk to the shop about this again, and just wanted to arm myself with as much info as i can before doing so. I'm no expert, which is why i had someone else do the work. It seems to me like between the plug color and the smoke, it's certainly burning oil. Is there any little checks and test anyone can suggest to narrow down where the problem lies, and also any validity to the idea of the rings still seating after a few hundred miles of use?

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What's the breather situation?
Did the guy who built the engine tell you to ride it like you stole it?
Like Torontonian said, it could be gas or oil, gas stinks.

rx7171 said:

Your receipt doesn't list valve stem seals for the intake valves. They are cheap so maybe just not listed and hard to imagine an experienced shop forgetting them, however if not installed you will get smoke like that.

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YAHTZEE!

You HAVE to confirm that those intake valves seals are in place. :!:

Also, you might want to get a part number on the guides. They could have put in the earlier cast iron guides that do not take seals. Not good.

Throber said:

Synthetic oil is fine for running in a new or rebuilt motor.
There are far too many myth's about oil.
Take time to read independent essays on line about oil and learn lot's of information to help rather than hinder motor life.
We have come a long way scientifically since the 1950's. Oil is very advanced engineering these days.
Too many old bastards propagating and perpetuating myth's and crap about the good old days.
If that shit was so good then we would still be using it. Thank feck we are not.
Change it often and change the filter at the same time. Cheap insurance and peace of mind.
I would not use Diesel motor oil in a petrol motor.

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New modern motors straight out of the factory may be,but a old dinosaur with old technology, large clearances, large thermal expansion differences and older recondition methods will not like being run in on good synthetic oil.
??I would not use diesel motor oil in a petrol motor?? is this one of your myths Throber
Valve steam seals, he purchased a premium gasket set,I'm surprised he was charged for additional at all, probably been charged again for items already purchased.
Take it out, find a nice good twisty road and ride it so you scare yourself,good brisk acceleration back off for the corners.
What ever you do if you take it back to the shop he will only tell you it's your fault any way

So are there new valve seals in there or not ?

Torontonian said:

So are there new valve seals in there or not ?

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is there any way of telling? i would think i couldn't see them past the cup on the spring?
Go leafs!

If you just cant get in there to see with a flashlight because of springs 'n cups blocking a viewage , another check which has been discussed is to disable/ block the rocker feed ,go for a drive, then see if she still smokes when you idle her in the laneway. No more smoking = head problems. A constant smoke might narrow it down to rings. This will not damage the valvetrain if used to test. Look for those seals first. Go Leafs.

i took a quick peek with a flash light and mirror and couldn't see past the cups/springs to tell.

On another note, i will say that the point of this post was to learn as much as i could before taking this issue to the shop that rebuilt the motor. In no way do i feel like they're a shady business, or did a bad job, or won't stand behind their work. When i took the cover off i saw they marked the inside, which just reassures me they're detail oriented and a good shop

My toaster has a scribble on it's tag (signature) ,made in China printed below it. Poor thing died.

Matchless said:

About six months ago I rebuilt my T150 Trident engine including a plus 0.020" rebore and a set of the new Hepolite pistons & rings. These are I belive, made in China for Wassels. Before installing them I checked them for size and they all measured to within 0.0002". (two tenths of a thou) of each other. Then I weighed them. They were all the same . The machining was first rate as you would expect from modern CNC finished items. The rings also, were accurately made & didn't require gapping.
So far so good. Then I fired it up. It smoked like a forty year old Diesel lorry engine & didn't get any better over fifty miles.
I called on a couple of Triple experts for help who both told me it was the rings. I pulled the top end off , fitted a set of rings from Norman Hyde & hey presto no more smoke.
This maybe the problem you are having. I would try a set of rings from an American, British or Italian manufacturer.

Regards,

Martyn.

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I had this EXACT SAME issue with a T150 that was rebuilt by a local shop. ONE PIECE oil control rings were the culprit. Smoked like crazy. Conventional three piece oil rings cured it.

Mayby the New seal as popped off, happened to me a while ago..the new seals where "squoggy"...i machined down the guides and fitted ford cosworth..they have steel bands and fitted well. no more smoke!