Post by dando127 on Nov 12, 2021 6:33:07 GMT
Behave
Well, as the question says...
What's the Easiest or Best way to check crank seals?
Right the motor is an assembled running 340 that's low on power.
I need to start somewhere on it to get it back to spec.
The power seems down it winds up but then bogs once it shifts.
Compression is 125# or slightly less.
I have a 340 stock muffler on it (the one with the bigger pipe)
So before I re-build the bottom end I want to figure out if it even is bad?
I know I also have to do some clutch testing no matter what. But it should be way better then it is.
I'm open to any thoughts or suggestions
Thanks
snowcruiserman6566
If you have a can of ether just give it a shot around the crank and if motor revs up you have leaky seals.
1970TNT
CHECK THE MUFFLER FOR MOUSE HOUSES OR WHAT EVER MAYBE IN IT. THIS WILL EFFECT YOUR HP/POWER. WITH THE CLUTCH OFF CHECK THE PLAY ON THE CRANK. YOU WILL HAVE SOME IF YOU PUSH IT IN AND OUT BUT UP AND DOWN YOU SHOULD HAVE VERY LITTLE TO ZERO. IT IS EASIER ON A SINGLE THAN A TWIN.
cdem72
Ron: Does it bog when the track is elevated and you accelerate or only when you are actually driving it. It could be a wrong drive clutch with heavier weights for a larger motor, or weak driven clutch spring which may have popped out of its retaining hole. Carb adjustment, muffler problem?
olympique_mike
start with your flashlight, look behind the clutch at the seal in the 6 o'clock area, if leaking, there will be slight wetness and drool going straight down to the case. same can be done on the mag side looking through the flywheel windows, or if necessary taking off the stator. any premix motor will drool here if the seal is going. If it's shot, you will see a pool under there!
OK, that's the visual check
When a seal is leaking, extra air comes in and out so the motor will run leaner at idle, so a higher than normal idle after revving it up will indicate an air leak, kind of like when your carb nuts are coming loose. The leaner condition usually goes away higher up the rpm's so your bog sounds like something else to me.
Ok that's the seat O'pants method.
The actual wat to check crank seals is; remove the carb and block off with either a blind plate or an expandable rubber plug ( at the pool supply store), then remove the muffler and block off the same way. Now apply compressed air slowly through the plug hole using a fitting equipped with a pressure guage and shut off valve. Watch for pressure drop.
I'm not kidding, there were complete kits sold with all this stuff to do this in the '70s.
Some people like to remove the top end and fill the cases with solvent and look for leaking. I don't like this way because it can fail to find a leaking seal without using pressure.
Me, I like my flashlight.
Like 1970TNT said, an up down crank end check will tell you a lot...but you need to have the 'feel' for what is good and what is 'shot'.
Vintage Elan Guy
In all honesty, if you are doing work on the motor and you think the crank seald are leaking, just replace them. They are not a big investment to make if you alreay have the engine out and working on it.
If it's not out yet, then the methods mentioned will work to check them. Also, if you have your flywheel off, do the points and condensor too unless you know their age and condition for sure.
Behave
Thanks for the ideas & info.
Well I tried the ether on the clutch side.
At first it seemed like it may make a difference & then it didn't. Then I ran out of ether. (not much left in the can) Neither side visually look bad.
i tried running the sled again with a different stock ski-doo clutch & It is not winding out all the way & like I said seems low on power.
Holding a GPS up to my face while bouncing across the lake in light snow it read
42 1/2mph on a couple passes.
I also ran the sled with the same set-up & a 292 & that ran 39mph
again neither seem to be running well enough.
I'm going to try another idea on checking the bottom end again tomorrow.
Either try to devise my own pressure set-up. I'm thinking I may be able to fashion something from my compression checker? Or tear it apart & try the filling the bottom end method. I've not tried it but was told you can do it.
Now one other thing with the 340. It is pulsing while idling. The idle set-nut is up a bit so it is idling a little high. But any thoughts on the pulsing. It definitely is not idling even.
I'm tearing them both apart tomorrow.
As they are now neither the 340 nor 292 will be fast enough for the 100 race next weekend. very disappointing so far.
Hey where or who has seals for them these days?
lowtekrednek
on the pressure idea- be very careful!! using a vacuum pump would be much safer (thats how our local doo dealer did it when i worked there)
I'm sure the pressure idea will work as long as you don't apply too much pressure
Behave
I agree.
My plan is to try a hand vacuum pump (one you use to bleed brakes & such) It also has a meter on it. Or put a tire valve in the line & use a hand pump so I can't over-doo it.
1970TNT
LOWTECH HOW MUCH VACCUM DID YOU GUYS USE??? ONE MORE THING TO CHECK IS YOUR TRACK TENSION I TOOK A SLED APART THIS SUMMER AND JUST PUT THE TRACK BACK ON AND BOY IS THAT BABY OVAL IT IS SO BAD THE BACK SPROCKETS COME OUT OF THE HOLES ON THE TRACK. GOING TO HEAT IT UP A BIT AND SEE IF I CAN MAKE IT ROUND AGAIN
mustardbucket1
I used 3-5 inches of merc.... no more. Rotate the crank some during this procedure too. I think my '68 300 would have held vacuum indefinitely and, back together, it runs super.
Well, as the question says...
What's the Easiest or Best way to check crank seals?
Right the motor is an assembled running 340 that's low on power.
I need to start somewhere on it to get it back to spec.
The power seems down it winds up but then bogs once it shifts.
Compression is 125# or slightly less.
I have a 340 stock muffler on it (the one with the bigger pipe)
So before I re-build the bottom end I want to figure out if it even is bad?
I know I also have to do some clutch testing no matter what. But it should be way better then it is.
I'm open to any thoughts or suggestions
Thanks
snowcruiserman6566
If you have a can of ether just give it a shot around the crank and if motor revs up you have leaky seals.
1970TNT
CHECK THE MUFFLER FOR MOUSE HOUSES OR WHAT EVER MAYBE IN IT. THIS WILL EFFECT YOUR HP/POWER. WITH THE CLUTCH OFF CHECK THE PLAY ON THE CRANK. YOU WILL HAVE SOME IF YOU PUSH IT IN AND OUT BUT UP AND DOWN YOU SHOULD HAVE VERY LITTLE TO ZERO. IT IS EASIER ON A SINGLE THAN A TWIN.
cdem72
Ron: Does it bog when the track is elevated and you accelerate or only when you are actually driving it. It could be a wrong drive clutch with heavier weights for a larger motor, or weak driven clutch spring which may have popped out of its retaining hole. Carb adjustment, muffler problem?
olympique_mike
start with your flashlight, look behind the clutch at the seal in the 6 o'clock area, if leaking, there will be slight wetness and drool going straight down to the case. same can be done on the mag side looking through the flywheel windows, or if necessary taking off the stator. any premix motor will drool here if the seal is going. If it's shot, you will see a pool under there!
OK, that's the visual check
When a seal is leaking, extra air comes in and out so the motor will run leaner at idle, so a higher than normal idle after revving it up will indicate an air leak, kind of like when your carb nuts are coming loose. The leaner condition usually goes away higher up the rpm's so your bog sounds like something else to me.
Ok that's the seat O'pants method.
The actual wat to check crank seals is; remove the carb and block off with either a blind plate or an expandable rubber plug ( at the pool supply store), then remove the muffler and block off the same way. Now apply compressed air slowly through the plug hole using a fitting equipped with a pressure guage and shut off valve. Watch for pressure drop.
I'm not kidding, there were complete kits sold with all this stuff to do this in the '70s.
Some people like to remove the top end and fill the cases with solvent and look for leaking. I don't like this way because it can fail to find a leaking seal without using pressure.
Me, I like my flashlight.
Like 1970TNT said, an up down crank end check will tell you a lot...but you need to have the 'feel' for what is good and what is 'shot'.
Vintage Elan Guy
In all honesty, if you are doing work on the motor and you think the crank seald are leaking, just replace them. They are not a big investment to make if you alreay have the engine out and working on it.
If it's not out yet, then the methods mentioned will work to check them. Also, if you have your flywheel off, do the points and condensor too unless you know their age and condition for sure.
Behave
Thanks for the ideas & info.
Well I tried the ether on the clutch side.
At first it seemed like it may make a difference & then it didn't. Then I ran out of ether. (not much left in the can) Neither side visually look bad.
i tried running the sled again with a different stock ski-doo clutch & It is not winding out all the way & like I said seems low on power.
Holding a GPS up to my face while bouncing across the lake in light snow it read
42 1/2mph on a couple passes.
I also ran the sled with the same set-up & a 292 & that ran 39mph
again neither seem to be running well enough.
I'm going to try another idea on checking the bottom end again tomorrow.
Either try to devise my own pressure set-up. I'm thinking I may be able to fashion something from my compression checker? Or tear it apart & try the filling the bottom end method. I've not tried it but was told you can do it.
Now one other thing with the 340. It is pulsing while idling. The idle set-nut is up a bit so it is idling a little high. But any thoughts on the pulsing. It definitely is not idling even.
I'm tearing them both apart tomorrow.
As they are now neither the 340 nor 292 will be fast enough for the 100 race next weekend. very disappointing so far.
Hey where or who has seals for them these days?
lowtekrednek
on the pressure idea- be very careful!! using a vacuum pump would be much safer (thats how our local doo dealer did it when i worked there)
I'm sure the pressure idea will work as long as you don't apply too much pressure
Behave
I agree.
My plan is to try a hand vacuum pump (one you use to bleed brakes & such) It also has a meter on it. Or put a tire valve in the line & use a hand pump so I can't over-doo it.
1970TNT
LOWTECH HOW MUCH VACCUM DID YOU GUYS USE??? ONE MORE THING TO CHECK IS YOUR TRACK TENSION I TOOK A SLED APART THIS SUMMER AND JUST PUT THE TRACK BACK ON AND BOY IS THAT BABY OVAL IT IS SO BAD THE BACK SPROCKETS COME OUT OF THE HOLES ON THE TRACK. GOING TO HEAT IT UP A BIT AND SEE IF I CAN MAKE IT ROUND AGAIN
mustardbucket1
I used 3-5 inches of merc.... no more. Rotate the crank some during this procedure too. I think my '68 300 would have held vacuum indefinitely and, back together, it runs super.
