Why is only one pipe smoking???

[MikeH1A]

Not sure what is happening with my J model Buffalo so any advice appreciated. When she starts ( usually easily on the button) there is a large volume of smoke (and I mean large) but this dies away after several minutes and the choke being turned off. When riding, the smoke definitely settles except for one pipe. This is from the right hand cylinder (as you sit on the bike). As I ride, there is a consistent (but not overwhelming) amount of smoke that comes from that one pipe - nothing from the others and this will continue throughout the ride. If I pull the plugs, the left and centre ones are a nice tan colour whilst the right one is black and wet. I have backed the oil pump off a bit. She does not seem to be using oil from the tranny as oil easily comes out if I undo the screw on the side of the case. In terms of two stroke, it looks as though I used about half a litre on today's ride which was 220 KMs.

Keen to hear your thoughts. Should I be concerned or just ignore it? The latter approach has served me well in life to date LOL

[Suzsmokeyallan]

I believe your check valves in the CCI lines need inspecting as some could be weeping or stuck open and that will cause the excess smoke on start up after the bike has sat for a while.
The right cylinder excess oil situation and oily plug could mean the crank seal has begun to fail by the primary drive gear on the right side and its sucking a small amount of oil from the transmission from that seal into the right lower cylinder.
A simple leak down test for that cylinder will tell you it has or not and its worth inspection.

[pearljam724]

Allan, after much reading on here. I've yet to hear how you actually inspect the cci check valves. What is a good method ? I understand they should only allow air flow one direction and not the other. But, which valves go what direction ? What tool do you use to suggest inspecting them with. Or unlike the oil check valves, would it be ok to use a very small amount of compressed air ? I was considering buying new ones, but would like to avoid that possibly if I can reassure that mine are fine ?

[Vintageman]

The check valves holds at a few PSI. If you use compressed air only use 5 -10 psi. If you can set air pressure under 3 psi it should hold. If you suck on the banjo with check valve you can feel it break open, unless you have weak lungs

I think this is the issue not the crank seal since smoke goes away. Also if you use a 2 stroke oil with a distinct smell you can tell by the scent of the smoke. Gear oil has a different smell.


I have found that a lazy man's leak down test can be performed in reverse. If it leaks significantly you will know it

You can apply a hose to crank case vent and blow into it. It should hold pressure for a long time (10s of seconds). Then using another hose into each carb side of cyclinder with piston up and listen for air leak (place hose to ear).

Note that if the sprocket seal is bad or the round metal bushing is worn the seal rides over air leaks out there, Don't panic. Fix the leak around sprocket and test again.

[tz375]

My first thought was that one of the check valves on the right cylinder is leaking when the bike is sitting and the bottom end has excess oil and some of that is in the exhaust now.

The comment about oil coming out of the level screw did throw a wrench into that thought process for a moment. With the bike level, and the drain screw out, the oil should weep until it's at the correct level. If oil is dribbling out every time you check, the implication is that the oil level is too high and that could be masking a leak down of trans oil.

That suggests two things. First, let the oil weep until it stops and that way you have the right oil level. More important though is to do a leakdown test on the bottom end. Vintageman is correct that you don't have to have a leakdown tester. You can simply take the hose from a compression tester and screw it into the right plug and pump it up to around 6-10psi. No higher or you risk damage to oil seals. Turn the motor so that the right piston is close to TDC. Some air will leak past the rings and out of teh intake or exhaust, so do not freak out if you here some hissing out of either orifice.

To do a leakdown test you really need to remove the pipes and carbs and block those off with rubber expanding plugs which you can get at the hardware store.

If you hear any air leaking out of the crankcase breather, the seals are shot.

Just as likely and easier to fix is the possible oil pipe leak. I use a simple gravity check. Remove the oil pump and octopus (oil distribution system). On the bench, fill all the lines with oil from the pump end. Hang the octopus up above a catch tray and leave it there for a while and watch to see if any of the lines drain down.

Under no circumstances should compressed air above say 10 psi be used on the oil lines when cleaning them.

[pearljam724]

I meant to refer to the SRIS check valves mounted under the crankcase. Not oil line, check valves. Got the CCI and SRIS part mixed up, lol ! So, still looking for an answer to the SRIS.

[MikeH1A]

Many thanks for the helpful thoughts and suggestions. I had wondered about my oil level being a tad too high. I did drain and change but there must have been some left lurking in there. I've opened the check screw twice now and oil readily oozes out. So, I shall follow the suggestion of opening it and letting it weep out until it stops. Then on to the next options you mention.

Thanks again, Mike

[MikeH1A]

Just checking something guys. I pulled the oil level screw out and let her sit on the main stand for the oil to dribble out and settle at the right level. HOWEVER ... so far I have collected 270ml of oil and it hasn't stopped coming out. The flow is less but it is still seeping out. How could it be this much over the correct level or is this symptomatic of something else going on? Now I'm a bit scared to ride her in case there isn't enough oil in there.

Your thoughts please.

[tz375]

If the bike was more or less level, it means that it was over filled before. When filling the bike with oil, it takes a while to find its way to the clutch cover and to start to weep out. If you just fill it until it weeps and then cap it, it will have too much oil in the trans.

[Suzsmokeyallan]

Yes but normally when its overfilled and you give it a few blasts the excess oil vents out the breather and runs down and out by the hole at the oil pump cover.
Have you seen any oil running out by the pump cover Mike?

[MikeH1A]

Hmmm, can't say that I have Allan. What are you thinking of with that line of enquiry? I changed the oil myself and thought the old stuff had drained - but perhaps not. Would it be possible for around 300mls to remain in the bottom after draining? If it wasn't overfill, why would there be so much coming out at this stage?

Thanks for all thoughts and assistance.

[tz375]

There is a considerable difference between "Initial fill" and "oil change" quantities though I can't find the reference at the moment. So it would not be unusual to have 200-300ml remaining after "all" the oil is drained.

There is some windage where oil wraps around the gears and is flung off causing an oil mist and very slight pressure rise in the trans. Add to that a smaller than stock air pocket and heat gently and oil may well seep out of the breather. That isn't an all bikes do it type situation though, and oil breathing out is more likely to be caused by shot crank seals allowing a pressure rise in the cases.

That's why it's a good idea to do a leak down test.

[Suzsmokeyallan]

As this thread progresses its apparent lots of the ideas presented can be used for deciphering the issues and through those test results a solution can be reached.
Therefore the leak down test would be the best place to start in so much as it will confirm if the cranks seals are good.
If that test fails, then you automatically will know the crank needs a rebuild before anything further is done.
If the crank passes the test then you will need to look at CCI line check valves and the oil pump as well SRIS lines and those valves as you next area to check.

[pearljam724]

If a guy overfills his crankcase intentionally for rebuild reasons. And the motor is lying on its face where the exhaust ports are located. Is it normal for oil to leak out one of the exhaust ports ? I assume it's normal because of the overfill ?

[tz375]

No. There is no way that oil from the transmission should be able to reach a combustion chamber or exhaust port unless an oil seal is out of place on one side of the primary drive gear.

Could it be oil that you put on the crank or pumped into the inlets or through the oil feed lines that pooled and is now dribbling out?