Excessive crank case pressure Evo
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Cruiser
Joined: Oct 2009
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Excessive crank case pressure Evo
I'm looking for theories, hell even just ideas, on why my 1992 Evo FXR is suffering excessive crank case pressure.
Each time the shop starts her back up and rides her for 30 mins or more, pressure builds up in the crank case. It's obviously excessive pressure because it leads to the snap ring popping off the pinion shaft and fouling up the little gears. The snap rings literally gets chewed up, oil pressure drops, valves and push rods therefore not functioning right, in effect the bike stops. Very sad.
So far they have replaced the original oil pump with a high flow pump, they tested the pinion shaft and it is true, and while they were in there I had them redo the piston rings and base gaskets. The bike has had a Stage II upgrade (reshaped cylinders, new pistons, cam, adjustable push rods, etc) previously.
Now she just seems to keep throwing this blood little snap ring. Like throwing a piranha into a bowl of gold fish (not pretty). Any hints what might be going on appreciated. Oh yeah, the shop dudes are very professional, the extra work is "under warranty". But I'm approaching the stage where I worry my engine is foobar, even though they say "everything is fine except for this problem we can't solve".
Each time the shop starts her back up and rides her for 30 mins or more, pressure builds up in the crank case. It's obviously excessive pressure because it leads to the snap ring popping off the pinion shaft and fouling up the little gears. The snap rings literally gets chewed up, oil pressure drops, valves and push rods therefore not functioning right, in effect the bike stops. Very sad.
So far they have replaced the original oil pump with a high flow pump, they tested the pinion shaft and it is true, and while they were in there I had them redo the piston rings and base gaskets. The bike has had a Stage II upgrade (reshaped cylinders, new pistons, cam, adjustable push rods, etc) previously.
Now she just seems to keep throwing this blood little snap ring. Like throwing a piranha into a bowl of gold fish (not pretty). Any hints what might be going on appreciated. Oh yeah, the shop dudes are very professional, the extra work is "under warranty". But I'm approaching the stage where I worry my engine is foobar, even though they say "everything is fine except for this problem we can't solve".
Stellar HDF Member
Joined: Aug 2009
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You never mentioned the PCV system. Excessive crank pressure means that should be the first place you look. If it is blocked or improperly routed, it won't allow the case to equalize with the atmosphere.
Big Kahuna HDF Member
Joined: Feb 2006
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From: USA
+1 What he said. If the system is not blocked then make it bigger. I do believe there is a kit to enlarge the vents in the heads.
Seasoned HDF Member
Joined: Nov 2009
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From: Farmington ,MS
Need more information. What has been done to the bike? Has the crank been out? I don't believe any amount of crankcase pressure would make the snap-ring come off...sounds more like you are missing a thrust washer.
Road Captain
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From: Vancouver Island, BC
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Elite HDF Member
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From: Southern IL
thats the first thing that needs to be checked imo
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Club Member
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From: Niles Canyon Ca.
Well the Evo's went through at least 3 changes in the breather system which includes hard parts and different gasket styles so with what you've explained I'd be asking if the shop has got all the correct parts mated to the right gaskets and don't have ports blocked off . Next I'd looking at the rings for blow by to increase case pressure that much and fast . Not much else can be the issue unless somebody really screwed the pooch and got the crankcase breather gear in wrong , but that takes a total idiot to blow that one .
Thread Starter
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Cruiser
Joined: Oct 2009
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Thanks for all the replies above. I am due to meet again with the shop tomorrow, so this gives me some ideas to throw into the mix and ask what has been done, etc. Lest it is not obvious, the issue is beyond my competence to deal with myself.
Any other suggestions welcome.
Any other suggestions welcome.