1978 KZ650 Smokin in the boys room

Hey Guys!!
Hope all is well with everyone!! I'm having an issue with the Old Girl smoking a bit.. When she's first warming up, no smoke, however once she's up to temp and I throttle up a bit she smokes a little.. Smoke seems to be black at times, and sometimes seems to be white maybe with a bluish tint idk, me eyeballs aren't what they used to be.. What can I do to stop the smoking? One other question, since the smoke is kinda faint could I put some engine restore in it?? I don't know if that would have an effect on the clutch plates.. I run a bit of sea foam in the tank & try to use only non ethanol mid grade when I can. Any advice or tips will be greatly appreciated as always!

Billy

Two things to look at, valve seals and rings.

If you can't be arsed to work on the engine and you can live with topping up the oil just leave it

How much oil does the bike consume? Ed

Hey 650ed!

Well, apparently not a lot, because my level doesn't really seem to change drasticaly in the sight glass. I've also noticed where some oil (i guess it's oil) is seeping out the side where those rubber things are on the side of the top end cover. what would you reccomend I do? I just want her to be ok and last me a very long time. Thanks 650ed!

How many miles on the clock now BikeMechanic73? (the bike, not you... :laugh: )

Burning oil once warmed up sounds like piston rings (why I asked how many miles it's got on it).
By this point, however, I would expect those valve stem seals to have worn considerably and be leaky/smokey too which would make it smoke more at cold-start, then at warmed-up stage... Unusual?

Those oil weeping locations sound like you are describing the cam plugs - half moon shaped rubber pieces in the cylinder head -
If so, then the next time you check/adjust your valves, you can replace those or there are tricks to using a teeeeny amount of RTV to seal the outer ridge of the cam plug. I just tried this on my '650 but so far haven't gotten the engine running to find out how well it works!

If not already done, would check for any crankcase oil contamination by gasoline intrusion into the crankcase.

Do the "sniff-test" on the crankcase oil, and physically examine the crankcase oil.

Such condition of oil diluted with gasoline might cause the reported symptoms of smoking only after warm-up, while showing an adequate sight-glass oil level of what is actually "contaminated" oil.

Good Fortune!

If you do not need to add oil it sounds like the smoke isn't actually oil burning unless it is being replaced by gasoline intrusion as Patton mentioned. That is an unlikely scenario though or you would find lots of fuel dripping from the carb overflow tubes.

Those cam plugs can be replaced without too much effort or you can try sealing them. Before you remove the cam cover you should have another gasket for it in hand in case the previous owner used sealant on it (a no-no unless the metal mating surfaces are damaged).

Have you changed the oil in the bike so you know what's in it? Be sure to use oil marked "JASO-MA" on the container when you change it or you can easily ruin the clutch plates. Ed

Hey Patton!!

I did recently change the oil & did sniff test. Did seem to have a little fuel in it.. (as 650ed mentioned "you would find lots of fuel dripping from the carb overflow tubes".) This does happen.. So is this a carb issue then?? Should I remove carbs & thoroughly clean them??

Good Fortune to you as well Patton

It does spill a bit of fuel out of the overflow especially when I move the bike while not running..

Many moons on my clock lol!! on the bike 20,300 original. I am the 3rd owner & the previous owners cared for her pretty well it seems..

Wrench Monkey,
Yeah, the cam plugs are what I was referring to.. Now when performing the rtv trick do I need to remove the cover? Also, do you suggest I use High temp or oil resistant rtv?

BIKEMECHANIC73 wrote: Hey Patton!!

I did recently change the oil & did sniff test. Did seem to have a little fuel in it.. (as 650ed mentioned "you would find lots of fuel dripping from the carb overflow tubes".) This does happen.. So is this a carb issue then?? Should I remove carbs & thoroughly clean them??

Good Fortune to you as well Patton

Not necessarily. Fuel coming out of the overflow hose (the little hose on the bottom of the carb) is the common symptom of the 3 possible problems described below. Remember - NO SMOKING or other activities that could ignite the fuel while working on carbs!

The float valve is not sealing. This may be (and probably is) just a matter of some minor dirt in the float valve and is very simple to remedy and can be done with the carbs still on the bike. Turn off fuel; drain carb by loosening big brass screw near bottom; and remove the 4 little screws on the bottom of the carb bowl. This will enable you to remove the carb bowl. You will then see the float. If you carefully remove the float you will see a stubby little needle that mates with a brass orifice; together, these two pieces are the float valve. Assuming there is no obvious damage to the needle or seat, use a Q-tip and some carb cleaner to clean the seat of the orifice and the needle. Be careful not to bend the tang that is attached to the float. This tang is the piece that the bottom of the float valve needle rests upon, and it determines the fuel level in the bowl, so bending it will change the fuel level. With the float valve cleaned it should no longer leak. To prevent a re-occurrence a quality inline fuel filter should be installed between the fuel tank and carbs. If there was damage the needle and seat should be replaced as a set; they are available.

The brass overflow tube inside the carb bowl is damaged. When you remove the carb bowl you will see a brass tube attached inside and rising toward the top of the bowl. This is the overflow tube and it leads directly to the overflow nipple on the bottom of the carb. Normally, the fuel level within the bowl rises somewhat close to the top of this tube. If the tube becomes cracked or separates from the bottom of the carb bowl fuel will flow through it and out through the overflow hose. Checking the condition of the tube is very easy after you have removed the carb bowl from the carb. Simply hold the bowl level and fill it up near the top of the tube with water or alcohol and see if it leaks. A slight crack in the brass overflow tube can be difficult to find. You can connect a rubber tube to the overflow nipple, fill the bowl with water, put finger over the open end of the brass overflow tube and blow in the rubber end and look for bubbles. If it does the best remedy is to replace it although some folks have found creative ways to repair them.

The fuel level is set too high. This condition occurs when someone has bent the float tang as mentioned above. This condition can be checked using what is referred to as the "clear tube test." The test involves attaching one end of a clear piece of flexible tubing to the carb drain hole and holding the other end of the tube above the bowl/carb joint. When the fuel is turned on it should rise in the tube to a level 2.5 - 4.5 mm below the bowl/carb joint. If the fuel rises higher than that level it may run into the cylinders or over the upper end of the brass overflow inside the carb bowl (mentioned above) in which case it will run out the overflow hose. This condition is corrected by removing the float and gently bending the tang to raise the float valve needle position. Doing this may take several tries before achieving the desired fuel level.

Correcting each of these three conditions involves removing the carb bowl. This task can be made easier if a short screwdriver bit is used, and depending on which carb you are fixing a mirror may help you locate the screws on the bottom of the carb bowl. Also, it is not a bad idea to have a new carb bowl gasket available in case the old gasket is damaged while removing the carb bowl. Ed

Now that's some detail!! Thanks Ed!! I think I'm gonna remove the carbs & give them a good cleaning & also check the all the tabs on the floats to make sure they are the same & figure out some way to do the clear tube test with carbs off the bike.. Thanks so much for everything