90 650SJ-Blowing out rear crank seals

[quickSX/XP]

I recently bought my friends Superjet and I am having a problem with it. We put a good used crank in it as well as new rings and reeds and we took it out last summer and it ran great for about 20 minutes then it started running bad and it would hardly even rev up, anyways we pulled the hood and seen that it had blown the new rear crankshaft seals out. So I bought the ski with the seals blown out and figured we had gotten a set o defective seals and the large vacuum leak created the no power/ backfiring condition. Anyways i put new seals in it and fired it up and it sounded like a sick dog, the exhaust was poping really bad and it was backfiring through the intake and it would hardly rev up, After a minute or two it went pow and popped the rear CS seals out again.
I am thinking maybe a bad CDI causing it to fire the rear cyl. at the wrong time or twisted crank??
Does anyone have any ideas or suggestions, or have any of you guys seen these symptoms before??

[ February 29, 2004, 10:35 PM: Message edited by: quickSX/XP ]

[Technical Support]

You can check the crank easily - do that first. Yes the CDI is suspect, although you also need to check the reeds, and go through the carbs. Anything to make it backfire can blow the seals out.

[quickSX/XP]

Here I am almost a year later and I thought I had this one fixed. The crank seemed in phase(when #1 was at TDC, #2 was at BDC) I tried a CDI last summer and did the same thing(blew the crank seals, but it barely even ran maybe 20 seconds) so I saved this one for winter. I had planty of other skis to ride. The stator plate coils ohmed out ok but I still suspected the pulse coil. So I pulled the stator plate and with my fluke hooked up to the pulse coil I tapped and wiggled the wires the resistance went crazy. I thought bingo! the glue was partially seperated with the coil of wire was bear and coming apart. I put a new coil and split the case put the seals back in. Checked out the entire elec. systems connections, wires everything. It has new rings, reeds, rebuilt carb. Took it out today and it ran awesome...For about one half hour they in a split second it had no power. Got to shore and both rear crank seals blew out again... Could the charging or lighting coil cause this. I am scratching my head on this one...

[quickSX/XP]

As per Clymer manual. Unless it is wrong... I packed the lips of the seal with marine grease and installed the rear single lip(has arms) followed by the rear double lip seal. when the crank was sitting in the upper case with the seals installed the the seals were in there respective grooves. I checked this before installing the lower case. I did not hear a backfire. It was running great, then like I turned a light off it lost most of its power. ???

[BULLRAIDER]

Here is a funny item....the clymer manual, is dead wrong...at least on my copy I bought, the seals on my 1100 triple are shown real nice going in the engine case,one problem.....the seals in the picture and the description are backwards....guess what happens when you pop for the good (yamaha) seals, and they are backwards, and ride around a while?, I thought I did something wrong, so I got new ones and really looked at that book again, found out the book is backwards,I went to the yamaha shop with the book to make sure, and sure enough..... I called Clymer and asked them about it, (I wasnt too happy)....get this....I was told to look on the inside cover for the part in small print that says"this is only as a reference, they can not be held responsible for typo or misinformation, real good .....on your 90 sj, be sure and check the spark plug end caps they UNSCREW, and is very common for them to be broken down to the point where it is corroded, the ends are replaceable, or just cut back about an inc and re-install them, ..Just a free try....hope this helps

[ March 01, 2004, 07:04 AM: Message edited by: bullraider ]

[Technical Support]

Use case sealer on the outside lips of the seal. Use alight coat of grease on the inside. The legs on the seals face outward.

[John Kubiak]

On the 650/701 Yamaha engines, the pulse coil does not have any effect on the ignition system until about 2500 RPM's, at which time it provides a signal to the CDI unit to switch from base timing to the "mapped" program for higher RPM performance and responsive operation.

Also as there is one coil firing through both spark plugs, the timing will be off for both cylinders if it is off for one.

[ March 01, 2004, 08:43 AM: Message edited by: John Kubiak ]

[Mpeavler1]

Jeff is correct....once apon a time not to long ago I rebuilt my 1100 raider and did this 2 times due to incorrect Yam manual as well....I was installing them wrong and a call to TEXAS to Mr. Jeff pointed this out to me and I flipped the seals around and now the ski has about 70 hours on them seals..and they have not moved an inch. YOU MUST make sure that you are putting them in the correct way and in the correct order! ALso make sure you have nothing in the groves where the seal rest. Also something noted here you may want to check to make sure you pump is properly aligned and it's not twisting the seals out due to out of alignment...this could be why the last crank went out

Cheers,
Mike

[Technical Support]

Unless you had a big backfire, I doubt it. How exactly are you proping and installing the seals?

[quickSX/XP]

I installed the inner seal with the arms facing out(the only way it will go) Then I installed the outer double lip in its grove with the spring facing out. I did not silicon them in this time. I did the last time with no luck. I have never done that to any engine until this 650 came along. Just curious what coil does the CDI use under 2500 rpm. Could a coil that is breaking down intermitently cause a bad enough misfire to blow the rear seals. Although it did run quite well. If the front crank seal was set up the same way it might have blown out for the same reason but since the stator is right in front of it it has no where to go. Should it matter if I am using a 62T CDI. That is what was in there since 95 or 96. along with several other mods. Also the couplers are lined up correctly The last crank was the original and the pump has not been out in years. I appreciate the input, several minds are better than one...

[Technical Support]

Silicone has NO part in building an engine.

[quickSX/XP]

Silicone IS used to seal the cases... I use ThreeBond "Silicone Liquid Gasket" 1211 or Yamabond(also silicone). 1211 in this case. Unless... you thought I was using the same silicone that one would use in the bathroom. Anyways...back to the thread. Input regarding a possible cause and solution to the problem stated above is greatly needed. Was the info. aforementioned regarding the installation of the outer rear seal correct?? ---spring facing out

[Technical Support]

Yes, typically when I hear someone refference silicone, they mean the 100% silicone used on pumps. You have no idea how many people think gaskets can be substituted by it...base, head, exhaust, intake...yep, seen it ALL.

[quickSX/XP]

Tech support Does it sound like I installed the seals right. Any other suggestions?

[Technical Support]

I don't recall off the top of my head which way the springs are, but I know the legs go out - I believe the springs face in. I can double check in the AM.