Gas in crankcase mystery

Did I buy a trashy parts bike or is this the best bike I own? I have a rather rough '81 Maxim 650, and bought a great looking, cheap, but dead '83 Midnight Maxim 750 so I could use the front end on the 650. But it ain't dead. It started easier and sounds better than my old 650. The young PO ran out of gas eight months ago. He says the bike worked fine til then. He filled the tank. The bike would not start. He parked it. I bought it off CL. He said he thought he had blown a head gasket or something, he didn't really know, but the bike was dead. I took it home in my truck.

The crankcase was full of gasoline. The tank was EMPTY. I read a great thread on here: <http://www.xjbikes.com/Forums/viewtopic/t=15369/highlight=shaft+leak.html>. That sounded like what I was looking at. The airbox even stinks of fuel. I changed the oil and after sitting for 8 months it fired right up and purrs like a kitten. However, there is dirty gasoline dripping fast from, as best as I can tell, the little vent hole in the forward end of the left silencer and from the forward end of the left mid-pipe shield (I think). The exhaust is white, foul and thick from both pipes. I let it run for several minutes and the dripping is tapering off somewhat, but the smoke is still white and thick.

I am guessing that the PO put the petcock on prime, filled the combustion chambers, which kept the bike from starting, then filled the crankcase and pipes from there. But I wonder how after 8 months there is still fuel in the pipes. Or maybe it's not the petcock but a stuck float and I am just repeating the procedure that sunk the PO? Any advice on how to proceed would be much appreciated. Is there a way to assess the float issue without pulling the carbs? Is there another cause I am failing to even consider? This 750 is in so much nicer shape than my old 650, I am really hoping this is a viable bike. Thanks in advance for any help. -Dan

 

Pull the carbs, fix the stuck float, and clean them.

Bench sync and set the float levels.

Get the valves in spec.

Do a compression test.

Put the carbs back on, do a running vac sync.

 

WOW, fast reply. Thanks. Does that mean that you think it DOES sound like a stuck float issue? And that there is no way to assess or fix WITHOUT pulling the carbs? I would like to get a read on this quickly and cheaply so that I can confidently sell the 650 to get money to do a full on carb rebuild and front brake rebuild on the (hopefully?) sweet new Midnight. If I had to guess, I would say that maybe these carbs have been rebuilt once because all the rubber around them looks and feels quite supple still. -Dan

 

I wouldn't sell the 650 until the 750 was tagged and running.

You can assess the floats quickly by putting the bike on centerstand and doing a "clear tube" sighting on all 4 carb bowl drain ports, it will be obvious that some will settle-out about 3MM below the gasket parting line, and the "culprit" carb(s) will be alot higher. You can also use a rubber mallet, shoe heel, dead squirrel, to rap on the carbs to dislodge and re-seat the float needles.

But actual service (adjusting floats, polishing pivot pins) requires carb removal, and , if the're off, you do a full service anyway.
Good luck !!

 

A carb cleaning is indicated by the crankcase contents. You will have to clean them at a minimum, rebuild them worst case. Depends upon what you find when you open them up. "Liquid rebuild" is NOT a solution to this problem. Do it once and do it right and you will have years of happy experiences to enjoy. Try to short-cut this and you will be nashing your teeth and pulling your hair until you do it right.
Hang on to that 650 until you sort this Midnight out. They are pretty much the same bike (although not exactly in a few places) and you can use the 650 as a reference as you plug away on the 750.

 

I don't think it's a stuck float...I'm 99.44% POSITIVE it's a stuck float.

Chances are you can lightly tap the offending carb and un-stick the float temporarily.

But that would only be half-assing it.

The bike sat for 8 months with residual fuel in the carb passages. When a bike runs dry, it doesn't run completely dry.

After a couple of months the fuel that was in the passages evaporates, but not before it turns your carbs into a gooey mess.

To add to Fitz's list:
Check operation of petcock. Probably ok but still something you want to check.
Change the oil filter if you didn't change it when you changed the oil.
Check/replace air filter if it is dirty/gas soaked
Change the spark plugs while you're at it. My guess is that they are fuel-soaked

 

Thanks to all. That sounds like concensus on following up on the stuck float theory. So I should find out what that means exactly. Is it that the float can't rise to close the needle? If so, I would assume that that could be the float isn't pivoting on it's pin/axle, hence the "polishing pins" reference from TimetoRide? Or is it sometimes that some crap is keeping the needle from seating? I'm guessing that's something I'll just have to go in to find out, right? Is the white exhaust consistent with the carb issue theory?

Robert: What is the difference between cleaning the carbs and a full rebuild? I assume a liquid rebuild is a SeaFoam treatment?

TimeToRide: Thanks for the quickie assessment tip. That will be my next step. As soon as I can locate this "dead squirrel" tool. Chacal maybe?

 

One more rookie question: To do the clear tube test for fuel height, is that with the engine off? Petcock on Prime?

 

It could be debris, or some rust. Your next step is to read the 3 looooong carb write-ups on this site, and get mentally organized for a rebuild.

"To do the clear tube test for fuel height, is that with the engine off? Petcock on Prime?"
That will work. You are also in need of a new filter and oil change if you didn't do that.

 

My guess on the white smoke would be water. You'd be surprised at how much moisture they can collect just from sitting outside for a short time. By outside I mean anywhere that isn't heated.

Mine blows white exhaust every time I start it after a rain even though the bike gets covered. Once it warms up and gets hot enough to evaporate the moisture, the smoke dissipates.

 

Thanks for the replies. Left inboard carb sends fuel up the clear tube way high. And on any carb the airbox drain pipe is dumping fuel as long as I'm on Prime. Prime bad. I guess it's finally time I went to the church of clean. Prep an area tonight and pull them tomorrow or Friday.

The white smoke is unlike anything my 650 has ever put out and I store it outdoors in the Great Northwet. I will hope it's a product of all the fuel that is everywhere on this bike thanks to one bad carb. Still, if this $300 "parts bike" gets on the road for a carb overhaul, I will be one happy camper.

 

Test the Petcock.

Part of the problem is that your Petcock is likely to be "Leaking-by".

THAT, ... combined with Improper Float Heights and/or Leaking Floats will Flood the Crankcase with Fuel.

 

Yes, and yes, and bike propped up so carbs are LEVEL front to back AND side to side; you'll be testing all 4 carbs.

Keep in mind, adjustment will require pulling the rack.

OR you could pull the rack to begin with, and do it right; on the bench and after properly cleaning the carbs as well.

Or, you can take shortcuts and do it over and over until you DO take the time to do it right. Seems to be the more popular course of action these days.

 

We would all be happy if you were able to rescue another "parts bike" from disappearing and being lost in the wind forever.

 

They ought to call "Parts Bikes" , ... "LABOR Bikes"

The reason its a Parts Bike is either:

The Owner can't wrench and do his own labor
The cost of LABOR is out of reach for the PO.

 

Cleaning the carbs is just that, a basic tear-down and cleaning. No spliting of the rack.
Full rebuild means tearing the carbs apart, spliting the rack and replacing all of the soft parts (shaft seals, float needles, etc...).
And you are right about the liquid rebuild, precisely what I was referring to.
Good luck, it sounds like you are on the right track.

 

And remember-- NO DIPPING!!! DO NOT submerge the rack or a "whole" carb in carb cleaner; the throttle shaft seals are trapped in there and can be ruined in the process. Carb bodies can only be "dipped" if completely stripped first which is not always 100% necessary.

 

Thanks to all for the advice on this. I pulled the carbs and found a little chunk of nasty on the #2 float needle seat. Cleaned that out and had the carbs back on by noon of the first 70 degree day we have had in 250 days. My "parts bike" will now blow my good bike off the road any day of the week. Looks like I'll be selling the 650. I will do a full rebuild come winter, but they actually looked quite good inside. Thanks again.