Air leak front bearing. What to do?
07-28-2010, 03:24 PM
#16
No no no no no no... hold it here for a few seconds... If the front bearing actually IS leaking that means you get TOO MUCH AIR in the engine.
Not the other way around with to much fuel going OUT of the engine.
It's simple: IF the bearing leaks too much you get air into the engine in two ways.
1. Air through the carburator bringing fuel along with it.
2. Air through the front bearing NOT bringing fuel along with it.
And this equals a lean condition with high temps and bad performance!
Not the other way around with to much fuel going OUT of the engine.
It's simple: IF the bearing leaks too much you get air into the engine in two ways.
1. Air through the carburator bringing fuel along with it.
2. Air through the front bearing NOT bringing fuel along with it.
And this equals a lean condition with high temps and bad performance!
but im not gonna try to make too much sense of it, if its hard to tune and seems like its leaking then change the bearing most times that cures it.
07-28-2010, 05:01 PM
#17
My 454 does the same thing. I thought it was because of the pinch. When the cooling head is off it will push the sleeve up and I have a little over a gallon on it. I just said screw it and ran it. Like you mentioned it smokes like it is running rich but temps stay in the 280 to 290 range. I really like the motor though, it has great power and ides like a champ. Just runs hot!
07-28-2010, 05:44 PM
#18
My 454 does the same thing. I thought it was because of the pinch. When the cooling head is off it will push the sleeve up and I have a little over a gallon on it. I just said screw it and ran it. Like you mentioned it smokes like it is running rich but temps stay in the 280 to 290 range. I really like the motor though, it has great power and ides like a champ. Just runs hot!
07-28-2010, 06:36 PM
#19
The cheap SH based engines like the 454 love to run at 270+ degrees. That's just were they run. Don't last too long either.
If you did have an air leak somewhere, the engine wouldn't run well and would be very inconsistent. An engine that runs well, but runs hot is not a sign of an air leak. Usually if you have an air leak you will get a long run-on after high speed runs and a high idle. Take it one step further to a seriously huge air leak and your engine will run lean no matter how you tune it and will exhibit the earlier symptoms as well.
As Klimpen717 posted, when you have an air leak, air is being brought into the engine in two places. Via the carburetor with the correct fuel/air ratio as normal, and through a leak. This extra air coming through the leak knocks the fuel/air mixture out of balance creating a lean condition.
If you did have an air leak somewhere, the engine wouldn't run well and would be very inconsistent. An engine that runs well, but runs hot is not a sign of an air leak. Usually if you have an air leak you will get a long run-on after high speed runs and a high idle. Take it one step further to a seriously huge air leak and your engine will run lean no matter how you tune it and will exhibit the earlier symptoms as well.
As Klimpen717 posted, when you have an air leak, air is being brought into the engine in two places. Via the carburetor with the correct fuel/air ratio as normal, and through a leak. This extra air coming through the leak knocks the fuel/air mixture out of balance creating a lean condition.
07-28-2010, 10:59 PM
#21
Tech Regular
so if its only air being pulled in then why do you see oil and fuel on the chassis and fly wheel? ,seems like same amout of air but fuel, oil leaking out throws off fuel air ratio
but im not gonna try to make too much sense of it, if its hard to tune and seems like its leaking then change the bearing most times that cures it.
but im not gonna try to make too much sense of it, if its hard to tune and seems like its leaking then change the bearing most times that cures it.
That will happen when the vacuum inside is low at idle.
It's actually true that a leaking engine will leak OUT more fuel also.
That happens when you get an air leak and you tune richer to compensate for the extra heat, that doesn't help of course and you richen it a bit more.
At idle you will now have an excessive amount of "extra fuel" and since idle gives the lowest possible vacuum the fuel will try to escape somewhere and that leaking bearing is the only way out.
There is not much arguments when running with a leak, EVERYTHING will be thrown off the charts. Nothing will add up and you will just scratch your head and become frustrated.
07-28-2010, 11:24 PM
#22
What about crankcase pressure at full throttle? wouldn't it blow out fuel if the front bearing was leaking?
07-28-2010, 11:54 PM
#23
I didn't say that fuel can not escape out of the engine.
That will happen when the vacuum inside is low at idle.
It's actually true that a leaking engine will leak OUT more fuel also.
That happens when you get an air leak and you tune richer to compensate for the extra heat, that doesn't help of course and you richen it a bit more.
At idle you will now have an excessive amount of "extra fuel" and since idle gives the lowest possible vacuum the fuel will try to escape somewhere and that leaking bearing is the only way out.
There is not much arguments when running with a leak, EVERYTHING will be thrown off the charts. Nothing will add up and you will just scratch your head and become frustrated.
That will happen when the vacuum inside is low at idle.
It's actually true that a leaking engine will leak OUT more fuel also.
That happens when you get an air leak and you tune richer to compensate for the extra heat, that doesn't help of course and you richen it a bit more.
At idle you will now have an excessive amount of "extra fuel" and since idle gives the lowest possible vacuum the fuel will try to escape somewhere and that leaking bearing is the only way out.
There is not much arguments when running with a leak, EVERYTHING will be thrown off the charts. Nothing will add up and you will just scratch your head and become frustrated.
07-29-2010, 08:00 AM
#25
Overly rich needle settings usually during run in fills the crankcase with excess oil , when you ramp up the rpm's you pull a vacuum/pressure pulse through the crank but pressurize the crankcase , the extra oil has no where to go but the path of least resistance , where would that be ?
07-29-2010, 08:21 AM
#26
Tech Regular
Thats absolutely correct. The oil will try to escape through the front bearing.
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