Oil coming out breather tube!!!!

[grubsie]

Curious as to why this is happening. I know that it is typically attributed to ring blow by. When rebuilding, I had the cylinders bored .025 (1st over) along with new rings. pistons and rings from Thailand, Never again!) Funny thing is that the shop that bored the cylinders asked for the rings as they told me that without the rings, they couldn't do the job. Got the cylinder back and installed it along with lapping the valves in the head
After getting the bike up and running, i never checked the compression until now that the oil and smoke is spewing out the breather hose. The camshaft chain side is 131 lbs and the other side is 76 lbs (even if I add oil to the cylinder)

Needless to say, I tore down the engine and found that top ring and bottom ring (Oil ring) were stuck. The middle ring was fine. I got the rings free and working smoothly in their respective slots. re-assembled and did a compression test off the bike using the battery with the starter. No difference in compression readings.

Took the top end off again, took the valves out ( a real party blast out then in again) Re-lapped the valves. After installing them, I filled the chambers with laquer thinner, then checked the level after approx 1 hour.
The cam chain side that had 131 lbs compression was about 4/5ths full. The other side that had 76 lbs was at 1/2 full. The leakage on the exhaust side was just slight wetness where the guide is in the exhaust ports. The intake side had fluid draining out when I tipped the head.
The leak test test was better overall than other engines than others I have run with no problems with compression. Put the top end together again and the readings were the same again.

Decided to put it back on the bike to try running it again. Oil satill coming out the breather tube. I did notice that the cylinder with 76 lbs had what sounded like some cylinder slap noise.

I will tear it down again and check the the ring end gap on that cylinder as I do not have the gauges to check the bore and the piston. The cylinder looked good when I had it apart (some glazing) but looked good. The piston in that cylinder seemed sloppier than the 131 lb side.

I think I already know the answer to this question, but can valve leakage cause oil and smoke to come out the breather tube? How can I tell weather I have a cylinder problem or valve problem?

[Spokes]

Oil will come out of the breather tube if you don't have the baffle plate & gasket installed.

Make sure the rings are installed correctly. You can install them upside down.

Make sure the ring gaps are staggered on the piston, example: top ring gap at 11 o'clock middle ring at 3 o'clock and bottom ring at 7 o'clock.

Search eBay for Honda Brand Rings. I too fell for Thai rings...once..junk to start with.

I also buy Honda pistons from eBay.

Cylinder or valve problems can be determined by adding oil in the cylinder then checking compression. If the compression goes up suspect rings if not suspect valves.

At the very least, buy new Honda rings, install them as above and find the missing baffle plate and gasket.(IMO)

[Nige1100s]

Not sure if your Thai rings are the same but with the genuine honda ones the top and second rings are different and didn't fit the way I expected. The one with a beveled upper edge is the second ring while the plain ring is the top ring. I guessed and got it wrong then found the manual and had to take it to bits again. Worth a check.

[VegeKev]

Hey Grubsie,

Nothing like a challenge....

It may not be surprising that the machine shop asked for the rings as they may have just wanted to be certain whether or not they were coated....chrome, moly or just plain. The harder the ring the coarser (grit) the hone needs to be in order that the ring is fully seated (square to the cyl. wall) by the time the hone pattern is worn away....eg chrome plated 2-stroke rings may require a 240 grit as compared to plain rings where you could getaway with 320 or even 400....

When you lapped the valves, did you check that the seat was concentric and complete on the valve seat?...whenever I play with seats its always a good thing to check using Bearing Blue (oily blue ointment?) lightly smeared on the valve face and then pop the valve in the guide and seat the valve with finger pressure.....DO NOT twist the valve otherwise you'll just draw a line around the seat!
Pull the valve out and check to see that you have a blue line all the way around the seat. Other than using a vacuum tester, this the best way to ensure a good seal.

Interested what made the rings get stuck in the first place? was it a side clearance issue with the piston ring lands? or was it end gap?

Cheers,
Kev.

[grubsie]

Wish I had measured things after getting the re-bored cylinder and also checked the compression after initial assembly.

I did that "assume" thing once again and e all know what that means.

After tearing the top end down again, I found some pretty scary measurements. The cylinder that had 76 lbs had all ring end gaps at .041" (Yikes) The other cylinder with 131 lbs had all ring end gaps at .031" (Still not good) I could slide a .010" feeler gauge between the piston and cylinder wall on the 76lb cylinder and .009" on the 131lb cylinder. The bores look good except there appears to be a lot of glazed spots.

I know I am not the sharpest tack on the planet, but this engine has less than 100 miles on the rebuild and the ring end gaps and piston clearances are all beyond wear limit specs. Like I said, wish I checked these things after getting the parts back from the machine shop. They also had the rings installed on the pistons and top ring and middle ring were reversed. At least I fixed that before initial assembly.
I think it is time to find a new machine shop.

Oh well, at least I can tear down and re-assemble the top end in my sleep now.

Ordered .50 over pistons and rings today. I know that the ring end gap minimum is .008", but am a little concerned about the where the piston clearance should be on a fresh re-bore. The manual I have says between 0 - 008". I know it can't be zero. What would be considered (like brand new) clearance.

VegKev,
As far as the stuck ring goes, for some reason there were little burr-like edges along the inside edges of the ring that were causing the ring to be tight. I filed them down and the ring moved freely again.

Also, when I lap the valves, it's just to make sure the seats are clean so I only do some light lapping. I have never used the blue stuff. I'll have to look into that.

[VegeKev]

Hey Grubsie,

If you can get a 0.010" feeler gauge down beside the piston then the bore would have to be nearly at the 0.50mm spec anyway!.....assuming that the bore is not tapered or out of round.
On a air cooled bore, and if the piston has a steel expansion control ring cast into it (most modern cast pistons do)....on a bore this size absolute minimum 0.001" / maximum 0.0025" clearance. If I was doing the honing it would get 0.0015".
Forged pistons get a bit more.....as do cast pistons without a control ring.

Kev.

[grubsie]

Got the .50 over pistons and rings yesterday and dropped them off at a shop that came highly recommended. They called me this morning to inform me that I have to go to the next over size .75. Just so happens that the work that previous shop did left the cylinder bores convex. Tighter in the middle than the top and bottom of the cylinder. In order to clean it up, they have to go larger than 2nd over. They said it was caused by improper honing. They think that the previous shop didn't bore, just honed to get the pistons to fit. So just ordered .75mm pistons and rings.

Just goes to show that you have to be careful who does the work.

[grubsie]

Finally got the the engine back together. Took 3 times for the seller on ebay to send the correct size rings. Machine shop did a stellar job on the boring. They actually marked each piston and ring set to it's corresponding cylinder as the pistons were were just a tad different in size. I check the ring clearance in each cylinder and they were dead on at .008".

Re-assembled the top end and did a compression on each cylinder. 1 was at 135lbs and the other at 133lbs. Mounted on bike, put the rest together and 2 kicks it fired up. Sounds great, much quieter than when I did this the first time. Carb needs to be dialed in, but took it out for a quick spin. It sounded like a whole new bike and seemed much stronger. And most importantly, no more oil out the breather tube.

Now, for whatever reason, new issues with the carb. It revs up fine and comes back down to idle fine, but if I let it idle for a little bit, the the rpms drop and the engines sputters and gasps when I try to rev it. Once it catches, it revs fine and returns to idle fine until I let it idle for a short time.

Took the carb apart (again) and cleaned, flushed and compressed every jet and hole. Re-checked the float level. Re-assembled and re-installed. Same problem. Checked for air leaks and found none. Even checked the mating surfaces on the carb and spacer and they were fine. I also tried new parts from the Keyster KH-0035 carb kit that I bought when I 1st took on this project.

Also, the choke does not seem to do it's job. I tried starting it this very cool morning here. Set the choke to close the carb opening and kicked it over. 1 little sputter. Tried a few more times and nothing. Set it 1/2 way and kicked again and nothing. Tried again with a litle bit of throttle and it fired right up but would barely idle. The idle would not change no matter where I set the choke. If I set it to full choke, the engine would die. I had to let the engine run for a while with the throttle slightly twisted until the engine warmed up for it to idle without dying. I found that turning out the air screw from the original setting before I tore the engine apart from 2 turns out to 4 turns out, the engine seemed to not want to stall as much but it does not idle as smooth as it did on 2 turns.

It just seems strange to me that before I tore the engine apart, the original carb settings worked fine even though the top end was junk. Now with a good top end and without touching anything on the carb initially, there are problems with the carb.
Funny, the choke worked fine before.

Any ideas? If only I could get this little bike to runs as good as it looks.

[Larzfromarz]

A shot in the dark here Grub- I don't have full trust in the Keyster kits supplying the correct jets. Which jets are you running? Honestly it sounds like a lean condition-

PS: the vacuum created with the bad cylinder could be significantly different than with a good cylinder. It's a guess but that might have a bearing on the current situation regarding carb performance.
L

[grubsie]

Hey Larz,

I was thinking it was a lean problem also. The keyster jets are the same size as the original Main #100 and the slow #40. I have the original jets back in since the Keyster ones didn't make a difference.
Also, there is only 2 lbs difference in the compression of both cylinders now with the re-bore. There was 55 lbs difference before the re-bore and the carb worked perfectly then.

Guess I am going to try cleaning the carb again and pay special attention to the slow jet and it's passageways in the carb.

Still, I don't know why the choke will not work.

[Larzfromarz]

I'm thinking more of the vacuum created (much less in the weak cylinder vs now with a good cylinder good vacuum) and the effects on how the carb worked then vs now. Spokes will probably know the correct jet sizes- I've got to track them down cause i don't know-
L

[VegeKev]

Yep...I agree with Larz. Too rich not too lean. Increased vacuum draws more fuel. The fact that the choke makes no difference is a tell....already above 14:1 so decreased air makes no difference...also the extra 2 turns out on the AIR screw.....

U're getting too much fuel at idle from somewhere....

Have fun

Kev.

[Larzfromarz]

Thanks Kevin,
You made the point clearer than I did.
L