Coolant Leak + Running On One Cylinder

[RobinDean]

At a weekly VinMoto garage party event, my friends and I opted to tackle the two resulting issues that are keeping my buddy from having a reliable ride ('83 Vision).

Coolant - WAS - pooling on top of the engine and one cylinder would operate intermittently (the other is constant).

Let's start with the coolant scenario:

All coolant leaks have been sealed and solved with the exception of ONE. There's a tiny hole to the top/front of the water pump. Coolant is coming out of that. What is that hole? Why is it there? What is it for? Should it be sealed? We've considered filling it with some sort of high-temp sealer but would prefer to know more first. I initially assumed that it is both an overflow and an air-intake to keep the pump working nicely. Do tell! SEE THE ATTACHED PHOTO FOR HIGHLIGHTED HOLE.

Then there's the cylinder issue:

Cold starting requires adjustment of the idle screw. Once that's been set to the stock 1100-1300 rpms, the bike warms. Three minutes in, if you give it gas, the second cylinder will kick on an "blast". Goin' around a corner and giving it gas? Not a safe feeling. Now warm, the idle shoots up to 4000-4500 (because now the second cylinder is fully active) and the idle screw must be brought down again. Sometimes there's white smoke. Sometimes there's not.

I know, I know ... it's tough to get a good sense from all of this but ... what the hell is going on with this gal?!

[jefferson]

The carb needs to be cleaned and that hole is the weep hole for the water pump. A new seal is needed.

Jeff

[Rikugun]

yup and yup  :D 

All liquid cooled engines (bike, car, scooter, truck, etc.) has a weephole somewhere on the water pump housing. Is is intended to be a visual indicator that the pump seal is failing when coolant starts leaking from it.

As far as the running issues go.... Turning up the idle isn't really the right way to go about cold starts. As you've discovered, you are creating a dangerous situation with your current  procedure. The idle speed should be adjusted to spec with the engine at operating temperature and (obviously) running on both cylinders and then not touched. If it was meant to be casually adjusted it would be on the handlebars not buried under the tank!

Admittedly, not all Visions like to idle even with the choke on when cold. This is not a car with an automatic choke or fuel injection. All I can say is baby sit the thing and and keep it running with the throttle and enrichener (choke) til it will by itself. But first, it needs to start and run on both cylinders.

The fact that it's not starting on both cylinders is an indication something is wrong. As jefferson said, more often than not it's dirty and maladjusted carbs. Have the carbs been thoroughly cleaned since your buddy took ownership? Is the tank clean and rust free? Many are not. Even a new filter can't stop fine rust from getting into the carbs and causing havoc. What are the idle mixture screws set to? Have the carbs been synced? There could also be vacuum leaks at the rubber manifolds, YICS, any plugged vacuum ports and hoses, etc.

I'd start by checking the easy stuff and work my way up to cleaning the carbs and tank.

[RobinDean]

We just replaced all of the seals and gaskets for that entire side of the engine. One of which isn't available and had to be custom made ... are we going to have to take the entire engine cover off again?

What seal are we talking about?

Diagram ... throw me a number?

http://www.yamahasportsplaza.com/pages/OemParts?aribrand=YAM#/Yamaha/XZ550RK_-_1983/WATER_PUMP/XZ550RK_%281983_MOTORCYCLE%29/WATER_PUMP_%28XZ550RK_-_1983%29

[Rick G]

The part that needs replacement is # 4 the mechanical seal. The weep hole is an indicator that the mechanical seal is leaking. If you plug the hole , coolant will end up in the oil and can destroy the engine.

leave the idle screw alone , hold the throttle at 2000 rpm , until  the bike will idle.
Both my visions  and my VX800 , will /would start on the front cylinder and follow shortly with rear cylinder. Carbs were rebuilt and tuned and synced, new plugs , fresh gas . It was/is worse in  winter. Radial air craft engines are famous for catching on one and then the others coming in. I have puzzled about this , but its not uncommon. I don't mean that its not running when you ride away, I mean it takes a second or two ,for the rear to clear its throat and get with the program.