Ok I will try to explain it to you but I doubt you will comprehend any of it.Yes it will bleed primary compression ,it will also suck just as much air as it displaces,possibly more,since the carb can only meter the fuel air ratio by the air that flows through it the mixture will now be too lean on that cylinder since unmetered air is now present with no additional fuel in it.I really hope you also believe that front case is sealed up that tight,it only takes the slightest leak for air to get in there ,that could be around the wire grommet,starter o-ring or the front cover gasket.Now if you have total loss like a lot of people run here there probably is some air getting in the front cover due to sealing problems at the grommet area.You also cannot change the volume area of the crankcase without it having a detrimental affect on engine performance.As Ricky Ricardo would say LUCYYYYYYY you gots some splaining to do!BTW I am not into flame wars at all but when I see someone post something that is just totally wrong and ridiculous I will call them on it.
Well let this be the last of what has become a little annoying flame war. To discredit my abilities and flagging BS on what you have not yet experienced leaves you a giant hole in credibility from me. It's not to say you don't posses
strong diagnosis skills.If it were not for differences in opinion there would be no enlightenment, mistakes and speculation lead to answers. Because you have not experienced this anomaly I have suggested does not mean it doesn't exist.
My comprehension of two cycle engines is fairly thorough having competed at the professional level of grand prix motorcycle road racing for a number of years. Having prepared and ridden machines myself that awarded me one AMA pro racing 250 GP win with an entire budget that would not have bought my competition a 1/2 seasons worth of tires. Having made chicken salad out of chicken droppings I know what works and what is not necessary. Receiving multiple club national championships and many AMA/WERA national podiums in addition to a seasons best finish of 2nd in the 99 national championship. I have had association with the some of the best two stroke tuners from this country as well as the UK. I have beaten their machines with skills I learned and a determination that I still apply to my daily work here at my shop.
The anomaly you have yet to experience has troubled my twin carbed 1994 sea doo explorer. My shop being gifted the machine as a support vessel to transport all our gear to the sand bars off our coast here in Charleston. The boat developed an air leak. Immediately after firing up the boat after sitting for a few months it revs up to about 4,500 rpm sustained and no adjustment of the idle speed adjuster would effect it. There was no way to make it idle without running at this high rpm. I removed spark plugs from engine and had come to find the front cylinder spark plug had captured the front/flywhhel side
crank seal spring. This spring wedged itself in the chamber of the spark plug around the porcelain. I proceeded to flush the boat out running the garden hose in an attempt to see if I could remedy the high rpm's. Had I not cooled the engine off it is likely the air leak would cause the front cylinder to run lean enough that it would heat up and possibly diesel run away on me. I have had such instances where the spark plug caps are removed, the kill lanyard pulled
and attempted to close off intakes with rags. The engine continued to rev out until it finally cooked itself. An over heated seizure that still pumped up 135 lb's compression when checked after the melt down. Having the need to test a customer machine out in our local pond complete with over 1200 alligators in less than 15 acres the explorer would have to be brought down to the water to act as a safety in the event the customers boat had any electrical issues.
Well low and behold the explorer is launched and once under a load with the now front crank seal spring missing guarantying an air leak the engine fires off both cylinders just fine at idle at runs steady at 2000 RPM or so. Accelerate away from the dock and machine actually works just as normal. Pulls away clean with no hesitation and still revs out to top speed. Mind you the 650 engine is not the most ideal engine size for this craft as every where you go it's running at wide open throttle. While over the water test riding the explorer we pull the new plugs out and would you believe the burn on each plug is identical. Running this boat on 60:1 premix and oil injection it has continued to run this way for the past 7 weeks or so. No signs of detonation and no loss of speed, but a significant loss in power when the boat is loaded with 3 or more people on board. Operating my shop as a one man band I have had little time to do any repairs on my own machines. Owning 8 personal jet ski's and this explorer there is always something to be repaired and working 6 days a week does not afford me the time to pull this engine. I do have a 720 engine I am building to replace the 650 in the boat now so I will continue to use the weak 650 with the leaky crank seal until it's finally bad enough not to pull us and our gear around.
This explorer when under a load is simply bleeding off primary compression into the stator cover causing a lean mixture and not enough fuel to get the engine revving out. This air leak due to the damaged front crank seal has not caused the engine to seize. Mind you it has been in operation for better than 7 weeks and still ticking. So yes a leaky crank seal can cause a significant loss in power, but if it occurs beneath a properly sealed stator cover in can not suck in an unlimited source of air to allow the mixture to be lean enough to cause seizure. If you are mixing a MACHO COMACHO 60:1 synthetic poppy seed based super happy fast go go lubricant in your 185 lb cranking superjet or the like then such an air leak may pose to be a significant problem. Tuning a screamer and tuning a dinghy are two completely different animals.
So with all due respect to yourself and my abilities there is such a scenario of a leaking front crank seal that will function without detrimental engine damage. I am NO BS artist. I would never speak of what I don't completely understand. If something is suggested, regardless of how far cast out there it may be, a simple difference of opinion will aid in completing the speculative evidence that will lead to a proper diagnosis. In this case scenario the front crank seal leak has not caused engine failure only a lack of performance.
Our opinions may vary but I will soon have this 650 engine pulled and can provide you the pics to detail what I am writing about.
You can call BS all you want but the anomaly exists.
