Wildguzzi.com
General Category => General Discussion => Topic started by: Stephen Hill on October 23, 2017, 03:06:34 PM
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As part of cleaning out the oil sump for the first time, I dismantled the oil pressure relief valve. And discovered that it was missing a washer that would change the relief pressure.
Using air pressure, I found the valve was blowing off around 45 psi.
Factory specs are 54 to 60 psi.
Adding a missing washer and an extra shim, it now blows off at 56 psi.
I am not impressed with faces of the valve: they are grooved with machining marks (both the piston and the seat). Which probably explains a fair amount of leakage prior to the valve blowing off.
Question #1: Anybody cleaned up these faces to try to reduce leakage?
Question #2: Is setting a blowoff pressure using air a reasonable procedure? Pressurized oil would be closer to the operating conditions, but hard to accomplish, messy, and should produce the same result, in my opinion.
BTW, I generally followed this procedure, but did not bother dripping any oil into the valve as part of the procedure.
https://www.youtube.com/watch?v=V91Z_KkKraI
I disagree with the guy in the video that the piston/bore clearance is relevant here.
Thoughts??
Stephen Hill
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http://www.thisoldtractor.com/moto_guzzi_loopframe_oil_pressure_relief_valve.html
The testers shown are for non-filter engines, but can be easily modified so that the filter-engine OPRV will screw in.
I sometimes find it necessary to lap the valve in with valve grinding compound. It's easy to apply if you buy it in the little squeeze tube from Permatex(?).
I clean the valve thoroughly (especially after lapping) and squirt oil into it before testing.
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I was a mold maker in another lifetime, so have some diamond lapping compound. Used that. Pressure went from low 20s to mid 60s after lapping.
I used this High Tech Tester.. :smiley:
(https://farm5.staticflickr.com/4443/37181432103_ccc5acd79d_c.jpg) (https://flic.kr/p/YDAyoc)2-009 (https://flic.kr/p/YDAyoc) by Charles Stottlemyer (https://www.flickr.com/photos/107188298@N06/), on Flickr
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Thanks Chuck. I like your high tech tester. Much more sensible than mine.
The thread on the valve body is an oddball: metric, and by memory measures 12.75 OD. Nothing I could find on a "standard" metric table of threads".
To make my "manifold", I step drilled a brass fitting and overdrove a 1/4 pipe tap, which is nominally smaller in diameter, but uses almost the same thread form as the valve body. Managed to get two threads out of the deal before I ran out of tap length. Held 60 psi no problem........
Ever find yourself in the middle of a dumbass solution you have devised but there is no going back?
Stephen Hill
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Thanks Chuck. I like your high tech tester. Much more sensible than mine.
The thread on the valve body is an oddball: metric, and by memory measures 12.75 OD. Nothing I could find on a "standard" metric table of threads".
To make my "manifold", I step drilled a brass fitting and overdrove a 1/4 pipe tap, which is nominally smaller in diameter, but uses almost the same thread form as the valve body. Managed to get two threads out of the deal before I ran out of tap length. Held 60 psi no problem........
Ever find yourself in the middle of a dumbass solution you have devised but there is no going back?
Stephen Hill
I first was going to <cough cough> *buy* a tap and make a fancy manifold. Being a er.. frugal..Guzzi Guy, though, "Hey, it's only gotta hold 60 psi.." 5 minutes later with a piece of garden hose, a couple of clamps, and Bob's your Mother's brother. :smiley:
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M14 - 1.5 threads. Nothing "oddball" about that.
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I was a mold maker in another lifetime
Well that explains a lot - is it still only treatable, or did all my donation to research ever lead to a cure ?
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Well that explains a lot - is it still only treatable, or did all my donation to research ever lead to a cure ?
It's still not curable, but now I only make fungus. Thanks for caring.. :smiley:
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Oh - that helps explain why you're such a fungi ....
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<rimshot>
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Antieham writes: M14 - 1.5 threads. Nothing "oddball" about that.
I measured the OD on the valve body thread for my 1976 LeMans. Definitely nowhere near 14 mm. Closer to 12.75. I couldn't find that in any metric table I looked at.
Stephen Hill
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Antieham writes: M14 - 1.5 threads. Nothing "oddball" about that.
I measured the OD on the valve body thread for my 1976 LeMans. Definitely nowhere near 14 mm. Closer to 12.75. I couldn't find that in any metric table I looked at.
Stephen Hill
Uhh, how did you measure that? Calipers? (pretty close) Micrometers? (right on the money) Scale? (open to interpretation.) :smiley:
Charlie's seldom wrong..
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Uhh, how did you measure that? Calipers? (pretty close) Micrometers? (right on the money) Scale? (open to interpretation.) :smiley:
Charlie's seldom wrong..
Here it is with HF calipers. I used an M14-1.5 tap from my brother's Gearwrench set to tap the hole in my tester.
(http://thumb.ibb.co/md9zBR/OPRV_2_001.jpg) (http://ibb.co/md9zBR)
(http://thumb.ibb.co/g2vQJ6/OPRV_3_001.jpg) (http://ibb.co/g2vQJ6)
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The bike's back together, so I can't measure it now. Measuring the wide end of the 1/4 plug tap I used, yup, the valve probably measured 13.75 mm. I guess I expected it to measure closer to 14, which is why I didn't go chasing a tap.
Regardless, job's done. Thanks all for your assistance.
Stephen Hill