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Discussion Starter #1
Bike History:
1) Purchased Used
2) Previous Owner put a new ring & piston in it before I purchased it.

Bike Current State & Problem
1) The bike sits a lot
2) Recently, my son rode the bike after the bike had been sitting for about 4-5 months.
3) Put new gas in, and my son rode for about 10 mins before the bike "smothered" out. Almost seemed like it was flooding. He wasn't riding hard.
4) I pulled the plug, and it was wet & black.
5) I cleaned up the plug, reinstalled the plug and it started but then smothered out again the same way.
6) Since that episode, been thru the carb and all clean, no issues and made no adjustments.
7) Can do the exact same procedure, clean up plug & reinstall, and the bike will run shortly,..then smoother out with white smoke out the exhaust.

Is this a crankshaft seal that suddenly went bad?

Thanks for any help.
Joe
 

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Hi Joe. A few of the usual suspects can cause your trouble. Crank seal or coolant leak are contenders. I would start by checking for obvious coolant leak with pressure test of cooling system. If you don't have a method available you can remove radiator cap from COLD radiator and fill to top and operate kick starter while carefully observing fluid in open radiator opening for air bubbles while cranking. You can also do this with a running engine provided you maintain steady rpm and do not allow engine speed to drop suddenly. You can test until motor warms up but careful during test, radiator can overflow and puke hot coolant all over. I would suggest testing compression as well. Sometimes a compression test on cold engine with radiator cap removed will indicate leakage also. Could be a crack or defect in cylinder or cylinder head or engine gaskets or cases, but a common failure is improper installation of cylinder head sealing o rings. Have to test carefully, but don't be surprised if it's a simple coolant leak from a twisted or pinched o ring. If you remove cylinder head for inspection be sure to move piston to BDC and inspect cylinder condition also. A lot of sellers will put a new piston in a scored cylinder and motor runs good until it warms up and scored cylinder galls the new piston until it seizes and sputters and stalls until motor cools off. That's another dirty trick to watch out for. Check back as needed for help. Lots of good folks here with helpful advice. Good luck
 

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Discussion Starter #3
Thank you Augie. Here's a link to a startup after I cleaned the plug and "aired" out the cylinder. I did do a quick check for bubbles a few moments ago in coolant, but no luck. I'll try running it, but I don't think it will run long enough to get warm. As you can see from this video (hope it works), that it quickly dies. Yes, I had my Sunday clothes on : )


Thanks,
Joe
 

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Well at least you were wearing proper footwear Joe :oops: that's a healthy puff of killer smoke yez got there. Have a look at transmission fluid level and see if she's low on fluid, but I kinda suspect a coolant leak into cylinder. Hard for me to see it from here. I'm hoping our forum friends here study your post and video and offer an opinion here. Stay tuned, some of our friends here are on another hemisphere and time zone. Probably hear from them soon.
 

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Welcome to the forum.

A decent amount of smoke!

Water smoke (steam): White and will disappear quickly (as the steam is warm and when cooling down will be gone).

Oil smoke: Will hang around for some time and best way to get rid of it from a garage/workshop in to open windows and doors...

I concur with Augie:
  • Check head gasket (O-ring) if you diagnose water steam.
  • R/H crank seal if oil
  • Have someone just resently filled new fuel after mixing in oil in to the fuel?? (Could be heaps of oil in the fuel... Mix should be 40:1)
  • Compression seems OK. She starts easily enough. You could have heaps of oil or water inside crank case that, as soon as you start the motor, gets splashed around and ends up on top of piston. Now just to figure out how it gest there!
  • Also check oil level in transmission. Should not be able to get in to the crank, but if the level is stoo high and you have a worn crank seal it won't help the situation.
If you still struggle come back and together with all thw other brains on this site we will find a solution for you!
 

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Discussion Starter #6
Thanks fellas for the replies. I will check these items as you have recommended. I've did some more research and found an idea that I thought might help me focus in on the problem. Would like your input. For troubleshooting purposes, could I drain the oil from the crankcase, run it for 45 seconds to 1 min to rule out the crankshaft seal? If it still smoothers out with exhaust smoke, then focus on the coolant leak? Maybe that would tell me it's not sucking gear oil?
I honestly can't tell if it's steam or oil smoke. The smoke lingers around but it's very light.
 

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Yeah. I have drained transmission fluid for testing purposes with no future transmission troubles(that I was aware of) but the trouble with troubleshooting a leaky crank seal is you would have a crankcase full of previously leaked trans fluid inside and you may continue to get some smoke when running. You may not see a complete elimination of smoke. A reduction in smoke is usually an good enough indication. You can also drain coolant for testing also. Draining trans or coolant testing should be done for a minute or two. You can ride the bike to test but you should ride gently and no more than needed. Good luck
 

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I know what you are doing. Here some short-cuts for you...
  • If you have a leaking crank seal you will have a build-up of oil inside the crank case (around the crank), so even if you drain the transmission oil out it will take some time to burn all the oil off from inside the crank case.
  • If you have a leaking head gasket ( O-ring) your spark plug will be wet, but not with oil. And if there is water getting in, it is being blown out through the exhaust as it does not stay in the crank area.
But if you really want a short cut, here: If you start the engine from cold it will take a short while befor the cylinder gets hot and the water is needed to cool it all down. So if you drain the radiator and motor from water you will have approx 30 seconds before your motor starts getting hot. If the motor was cold in the video and you now empty all the water (and it is the water that is causing the issue) then there will be no smoke inside the 30 seconds...

You can obviously do the same thing with the oil, but as mentioned, if the seal is damaged you will have a build-up of oil around the crank and it will take some time to burn it all away.

If this was my bike I would replace the head gasket O-ring (as this is a relatively simple, cheap and quick task) and start the bike. If there still was smoke coming I would know that it is oil smoke. But as oil smoke stays around and has a different smell than steam, and steam will disappear fast, surely you can figure out what it is? How about this: put your hand behind the muffler and allow the smoke/steam to go on to your hand. Then when it gets too hot to keep your hand there turn off the motor and taste what is now on your hand... or you might be able to easily see if it is water or oil.

EDIT: @augiedoggie while you posted I was still writing. But we are both really only confirming the same path to take.
 

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Discussion Starter #9
Here’s a video of the bike with the coolant drained. It must be the crankshaft seal? I noticed the smoke did linger a while. I’ll go ahead and replace o rings while into the head. Also, I’ll attempt to post some photos of the cylinder walls as well so you all can have a “look-see”

 

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Yep. Looks like engine oil. Also if you take the barrel off fit a new set of piston rings while you are in there, even if it looks like the bike has good compression.
 

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Discussion Starter #11
Got it tore down to the seal. Please refer to pics as I have a couple of questions.

1) Is this the correct seal depth? I cannot tell from the online manual that I googled.

2) The metal ring that houses the o-ring on the crankshaft has a visible “wear ring” from the crankshaft seal. I can’t hang a finger nail in it. Should I replace this ring too with only a visible wear ring? Any experience with this?

Thanks again,
Joe
 

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Discussion Starter #12
One more issue of interest,..found about 1/8 cup of oil drained out of the exhaust pipe when I pulled from the head and layed it to the side. Didn’t notice it until I had turned back to look for a tool, and saw all the jet black oil on the floor.
 

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Looking good Joe. The oil was probably accumulating in exhaust port and exhaust valve area. Clean it up as best you can with rags and contact cleaner. The rest will burn off. The ridge on seal ring/spacer sleeve shown can be an issue. If you have access to a lathe you can polish it smooth without worry. If not it's best to replace it. Probably unable to reverse it because it should have a chamfer inside for the o ring on bearing. Best to replace o ring also. Have to fish it out with a pick or a hook. You can replace crank seal and install sleeve afterwards to make installation easier. Be sure to lubricate seal ID with grease or 2 stroke oil(I use grease) dry seal will fail quickly. Be sure o ring is on crank before installing sleeve. Check back as needed for help.
 

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Not much to add to Augies comments. Apart from:
  • Do NOT fit a seal that is not made with steel as the outside as they will not stay in place once you get the motor running and will get blown out (ask me how I know...). But if you replace the seal with one like in the picture you are OK.
  • Replace the steel spacer as where the seal goes it will now be smaller in diameter. This is not needed to be done every time you dismantle the motor and fit a new seal. But once there is some wear (and not only a shiny mark from the seal) I tend to replace them. For a few dollars it is a good insurance policy. And I hate stripping down motors because I did not do the job properly in the first place!
  • Replace O-ring also.
  • Yep, the seal depth is OK.
Regarding the oil in the header pipe/muffler. That would be the oil that was not burnt up in the cylinder. I recommend you also re-pack the muffler as the packing would be quite oily by now.

And if the bike still smokes when you start it dont panic, as it will be oil that is still left inside the crank area. But it will be gone very soon.

Come back and let us know how it all went when done!
 

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Discussion Starter #15
Fellas,..motor back together. (That was fun) Still smothers out in a cloud of oil smoke. Gotta be oil or too much fuel, because all coolant is gone. Is it the carb? (Keep in mind, this thing purred like a kitten until it sat for about 6 months. My kid then got it started & rode it for 30 mins. While he was riding, it smothered out in oil smoke as it is doing now.)

I can pull out the plug, blow it off, blow in the cylinder/head to evap the gas/oil, and keep repeating this process you see in the video all day long.
 

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Hmmm... so you replaced the r/h crank seal. Did you also replace the steel spacer and O-ring? And did you try to pour out the oil from the crank area? And if so, was there any in there??

She starts well so I am still leaning towards oil somehow getting in to the cylinder/crank area. All bolts that keep the two motor casing halvs together are on the left side of the motor. If the issue is transmission oil getting in to the crank area it could be the gasket between the two motor halves and there is only one place where the gearbox oil is on the other side of the crank area (see attached pic) apart from the crank seal you have just replaced. The two bolts that keep this area tight are unde the stator plate. How does your engine oil look like a short time after you have replaced it? As the motor only runs for a few seconds after you have cleaned the plug the oil should not change colour at all. If the oil gets black quickly it would indicate that oil gets in to the crank area and back to the gearbox. We have never had this issue, but if the bolts that hold the two cases together are loose in that area then maybe that is where the oil comes in. Or the gasket could have had a damage when fitted and with bolts that were not properly torqued this area of the gasket could now be damaged.

As you can see, I am still leaning towards engine oil causing this. But I would still check the reeds to make sure they are OK. And also that the float level in the carbi is OK and the needle valve that stops fuel from getting in to the carbi is OK and does it's job and closes when the bowl fuel level is right.
93191
 

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Discussion Starter #17
I elected not to replace the metal spacer since it was only shiny. Probably shoulda got one. I realize there is probably a few tenths of a thousandth that it might be worn around the circumference. Furthermore, I know it was recommended in this thread, but I took a chance. So yes. It's possible it's still leaking around that area. I will get a new one. The crankcase below the piston & rod is now clean as well. I poured as much out of the engine as I could, but there really wasn't that much. There was more in the exhaust pipe.

I'm wondering though about the carb. The needle valve & float are adjusted properly. However, I noticed some "safety" torx screws holding part of the housing together within the float bowl. Is this something I should disassemble? Is there a gasket in there that's causing the carb to flood after starting?
 

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Discussion Starter #18
Oh, the housing within the float bowl that I'm referring to has "safety torx" headed screws holding it together.
 

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I think your shiny description of the spacer is adequate. As long as it is not grooved it should be fine. Make sure it is fastened tight. Loose nut will allow oil to pass underneath spacer sleeve. The safety screws you refer to are removable, but be careful not to round out the screw head. Best to heat screw head with soldering iron(not a friggin torch) before removal attempt. The heat expands and grows the screw head off the surface and relaxes surface tension for easier removal. The part you are removing is a jet plate(I think) it uses a small spaghetti seal(formed o ring) inside it. The o ring sometimes degrades and shrinks and allows a rich running engine that refuses to run well. Usually makes carburetor impossible to jet.
 

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Ah yeah. Forgot to mention. Carburetor jet plate o ring is available from JD jetting for your kehin carb
 
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