125cc thumpstar issues

Hey i have a problem with oil leaking from the exhaust manifold, a lot of smoke also, and revs so high sometimes wont turn off? Help please

Hi, by now you might have solved the problem, but if not.  You might have an air leak, or bad seal in that area,  I also think the oil is coming from your valve adjusting cap, cover, which is very near the exhaust outlet. if not that, and the smoke is coming out right at the header, where it exits the head, then it might be engine damage, but I do not think so, or the oil smoke should be coming out of the end of your exhaust pipe too.

  The common issue with HIGH IDLE and not shutting off is from an AIR leak located between the carburetor outlet and to where the intake manifold attaches to the head. There are two gaskets there, one or both leaks. This is how you test that, start your bike, put some gasoline in a squirt bottle or even eyedropper and squirt it at the joints of the intake manifold, if the RPMS JUMP up, or you get major misfires, when you do this, that is where your air leak is.  Be careful, the gas can ignite if you are not careful, do this outside with fire extinguisher near by.  Also check to see if any of your carburetor adjusting screws has fallen out.. it does happen. You have two of them, one for idle, the other on bottom of float bowl for air fuel mixture. Also check to see that your throttle cable is not binding on anything and half way pulled out for some odd reason.   GOOD LUCK.. post again if you have more problems.

Thanks heaps for reply will get dad to try that, this is a picture of where i am leaking oil from it drips off this screw ImageUploadedByThumper Talk1399860545.764543.jpg

Hi, thanks for the picture, it really is a good thing to always do.  This does not look good. I am a bit puzzled the oil should not be leaking from there.  Check the inside of the tail end of your exhaust pipe, if  you get a black oily residue on your finger, that is NOT good.  But its not bad news yet.  you need to check your head gasket, while the engine is running for little wisps of air puffing out from around the head gasket.  My head was loose and required re-torque, to 8-10 foot pounds, NOT MUCH. This number was given to me by SSR people, and I do not think it is right, but the bolts that hold on the head are LONG, and go all the way from the top of the head to the transmission case, if you OVER tighten them, one might break and that is a bad, bad thing, so be careful to not over tighten the 4 head nuts.  If you do not have a torque wrench, maybe buy one, but if you do not want to, tighten it this way: get a small 6 inch 8 or 9 mm wrench, I forget which without looking it up in my note book on the bike, (you should start one). now with that small wrench choke up on it close to the nut to be tightened and pull with medium muscle power. that is about 6-8 foot pounds. (your goal is 10 foot pounds) of the nut turns and feels like it is tightening, that is good, now hold the wrench normally and tighten it one last time with medium muscle force, if  your dad does this, tell him to use less power on the wrench, this will get  you close,  Now this will not heal a bad gasket, but it sure will help, and might solve the possible problem.  I am thinking that the oil is being sprayed towards that nut from the head gasket.  IF NOThing is seen leaking, or no air puffs are detected, its not the head gasket, but you should check those four nuts anyway.  Remember to check the nuts on the valve adjusting cover plate.  Tighten same way.  if this does not help, it is possible the carburetor is really messed up, and needs a rebuild or to be taken apart and look for something amiss, like the Main jet came loose, or clip came off needle jet clip groove, (that is located inside the carb top slide, where the gas cable goes)..My clip was in the middle groove, it ran great that way.  Clean the carb in and out with gas or carburetor cleaner spray.  note: sometimes the screws holding the float bowl on are really hard to crack loose, try not to strip those screw tips. Any hardware store will have replacement screws if  you do mess one up, you can drill it out or grind it off.  I know, it could be a problem, but hey, its a motorcycle, a machine, and all machines are problems sooner or later.  Grin........ This should all take you about 1 or 2 hours with carburetor disassembly, maybe 3 hrs. Note, if you have an impact driver, use it on the bottom carburetor screws this might prevent stripping them.  EVERYONE strips one, try to be different, ha ha.  I wish I could hear it running, that would tell allot, usually does.  Miss firing, some sputter, it wont rev up smoothly, all indicate carb and maybe valve or piston problem.  Once it is right, it should idle with occasional miss fire, and rev up smoothly to wide open, (in neutral) with no sputter until you max out the revs.  Tell me more of what you discover,  We might have to look elsewhere for a solution.  note: the valve cover plates use rubber "O" rings to seal them. Check it for damage. If you find any, you need a new "O" ring gasket, or can use gasket sealer (oil resistant) until you get the part. Bike owners need a few good tools, not many tho.  The torque wrench, and carb cleaner, and gasket maker, plus new spark plug should always be around. Buy a NGK spark plug, stop using the stock plug. Note on plugs, when you remove your plug, and it is oily, or black with burnt oil, its the spark plug and carb.  Good luck I think you will need some.

also, replace the header exhaust gasket, it obviously leaks.   A good running motor will not drip oil at exhaust.   Carburetor, spark plug, exhaust gasket look like a minimum work load to fix this one.

One more thing, you said you get smoke out of the exhaust pipe.  This indicates bad rings, if your bike is under a year old this is not normal, if over 3 years old, it can happen. Also, very important, check your oil level, if over filled it will do this exact thing.  they only hold about 3/4 of a quart at the most, the book says  .6   (point six) of the contents of a quart bottle.  or 60% of a quart. I added a little more because oil was not seen on the dip stick while bike was level. Always check oil on level ground, if you cant, do not add any until you can.  If the engine was running, let it cool down, and wait about 15 minutes at least for the oil to drip down into the cases, Then measure it.  NOW I am out of ideas..  good luck

I had this same exact problem with my SSR 125, and it was the exhaust valve seal gone bad letting oil into the exhaust and combustion chamber. New head gasket, valve seals, and exhaust gasket should fix your issue.

A similar thing happened to me when I got my bike, the oil was not leaking out of the exhaust port though, it was coming out of the exhaust. The cause was that when I got the bike, I didn't oil the air filter and the engine got dusted. I replaced the piston and rings and it still goes hard today. The way you tell if this is your problem is by letting your bike idle for 5mins, after that revv the engine and if it blows a cloud of blue smoke, your piston rings are bad, you can probably get away with replacing the piston and rings without boring it like I did, just make sure you run in the engine very slowly, don't exceed 3500-4000 revs for 3-6 hours. Also change your oil, because if your engine got dusted, some dust will have got into your crankcase, you should also get a new air filter if needed, if you are in dusty conditions don't be afraid to put a lot of oil on your air cleaner.

Good Luck.

Edited by ________jake_____

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now