Saturday, July 7, 2012

Crank Seals Blown on Yamaha Waveraider

1995 Yamaha Jet Ski will not start without starting fluid.Also the crankseals blown out of its case.

Used waterproof lube in the seal inner surface.And used Black RTV gasketmaker to seal the cracked crank case.

BUT STILL SAME PROBLEM IS THERE.

WHY THIS PROBLEM OCCURS?

This is due to the pressure leaking in the crank case.And Hydro locking Problem.

OK,CAN YOU EXPLAIN IN DETAIL?


  • HOW PRESSURE LEAKS WHEN PROPER SEALANT IS USED AND 
  • WHY HYDRO LOCKING PROBLEM OCCURS?


Yes i will explain you with complete detail and information.

You first issue the pressure leaking.
This is because of the use of black RTV sealer for the mating surfaces of the cases. The problem is, silicone based sealers are not impervious to other petroleum products such as gasoline. That means gas will dissolve the sealer and leave you with no sealer between the cases and air leaks and pressure leaks in your cases.

Your second issue is rear crank seals blowing out of its case.
The first  cause of that is hydro locking the engine.
NOW what is hydro locking? The above detail will explain it to you.

Water gets trapped below the piston and when the piston comes down it pushes the seals out because the case volume has decreased and a liquid can't compress so the seals get pushed out. The water enters below the piston problem is very much noticed on raiders.
Raiders are terrible about getting water in the bilge and if flipped over and then uprighted in the wrong direction ingesting the water into the engine. That produces the hydro lock and blown crank seals.

HOW TO IDENTIFY IF WATER IS GETTING INTO THE SYSTEM?

Is it possible you are getting water in the engine like the details mentioned above.
But also you look at your reed cage for the rear cylinder when you split the cases. If it hydro locked, it usually damages the reeds as well. So if the reeds are damaged,you know that there is hydro locked due to water entering there.


OK,ALSO I NOTICED LEAN CONDITION?

On this issue,i suggest you get the compression tested.as you mentioned it will start with starting fluid but not without that.This indicates low fuel pressure.The compression test done for all the 3 cylinders.
The test should show the 120 psi on all cylinders.If its 110 to 120 psi then its ok.
If any of the cylinder shows less then 90 or Zero Psi then its the problem.


CAN A BLOWN CRANK SEAL CAUSE LEAN CONDITION?

YES definitely it will cause lean condition problem.
It isn't blowing the crank seals out that would cause the seizure. However, a lean condition because they are blown could. You have the air leak at the seals and also reduced to no crankcase pressures to run the fuel pump which could lean out the mixture as well. No matter what, low compression on any cylinder will not let it run.


This details will help.
Thanks.