Oil is leaking between the cylinder head and block.

You need to do a block test. Sounds as if, most likely, a cylinder head gasket or intake gasket has not been sealed properly or possible crack. Go to your local autoparts store and buy a block tester with fluid and all. Sometimes you can rent the tester from Autozone or Orielly's. If this test comes up positive then I would rent a leak down tester to pin point where the leak is. Hope this helps.

Sounds to me like the head gasket is blown, but there may be sealant in the system which is making it intermittently leak antifreeze into the cylinders.

A bad cylinder head gasket will also cause a compromise in compression, which will cause a lack of power.

Time to overhaul or replace the engine's head gasket, or replace the engine with one that doesn't have a blown head gasket.

Good luck on this repair.

What color is the smoke? If the smoke is white, it's oil smoke. If it's fuel, it'll be black smoke.

Generally, black smoke from the exhast indicates a too rich mixture for one reason or the other. You said you rejetted the carb. This could be part of the problem. You also said that it's only out of the front pipe. If you rejet the carb, it effects both cylinders. If you have a vacuum leak on the rear cylinder, this could cause the front cylinder to run rich.

If the smoke coming from the front cylinder is white smoke, you may have a oil problem. It could be rings, a valve stem seal, or a head gasket leak. But, unless the smoke is heavy and the bike runs good, I wouldn't worry about it. If it bothers you, have a leakdown test run on the engine. That should tell you where the problem is. Or, just do a top end overhaul on the engine and be done with it. Have a new set of rings installed or have it bored and new pistons if needed. Also have a valve job done on the heads. This should solve the problem as you'll have to replace the intake gaskets when you take the intake and heads off.

Don't just keep throwing money at the problem. That gets expensive and is only successful part of the time. Anytime you have a problem with one cylinder only, whatever is wrong is confined to that cylinder. Anything that you do that effects both cylinders is usually useless. I would suspect a valve stem seal on your bike. You didn't say how many miles you have on the engine nor what type of carb you're running.

Good Luck
Steve

white smoke is a sign of coolant in the combustion chamber, coupled with the oilleakage points me to the head gasket

The only thing that you can do is to atleast change the head gasket and have the head and the block checked for another damage like a cracked cylinder wall or craked water jackets in head or block. Basically you need a comlete over overhaul of the engine. Good lucka andthanks for using FIX YA

sounds to me that the rings on the piston are worn out with the engine warmed up the cylinder expands a little causing blow by take the oil cap off and see if there is excessive blow by

Hi,

In its simplest terms, the head gasket is the spacer/insulator between the cylinder head and the engine block. When the piston (in the block) moves upward to compress the air/fuel mixture (against the cylinder head), tremendous pressure develops inside the combustion chamber. The pressure will find any easy means of escape to expand. If the gasket is defective, the pressure will pass through that gasket and enter the water jackets (where the collant flows through). The pressure/air bubbles will ride the coolant flow and eventually end up inside the radiator and would then be visible as you have posted.

Incidentally, the gasket may be OK but the cylinder head could be warped and the same fault would also be exhibited. This is especially more so on aluminum heads.

Both the gasket problem and/or the warped cylinder head could have resulted from a prior overheating problem.

Corrective procedure on the air bubbles would require top overhauling wherein only the cylnder head is removed. Of course once removed, your mechanic would be able to inspect the pistons and its sleeves and could decide if a general overhaul is required or stick to the cylinder head work. A top overhaul also requires cylinder head gasket replacement.

Unto the overheating problem, you may want to check the water pump, thermostat, fan, fan relay and fan clutch. It may also be to your added advantage if you would have the radiator flushed/cleaned as well as the water jackets. Some mechanics especially in warmer regions opt to completely remove the thermostat and permanently wire the fan to always be on.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.