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Post by bamaboilermaker on Nov 29, 2020 16:51:15 GMT -5
I have been working on a few XL2's lately - points models. On one saw from 1976, I did the standard, lines, filters, duck bills, etc. Happy to see it fired on 5th pull and ran real strong after carb adjustment. One thing I noticed was that the oiler was not working. Stripped saw down again, replaced oil lines (again), rebuilt saw, fired on 2nd pull. still no oil on bar. Stripped saw down again. removed oil pump, suspecting bad diaphragm. It looked like new! Cleaned out passages and re-installed. Spun flywheel w/ drill. Still no oil. Replaced entire pump assy from a scrap saw (diaphragm looked worse from parts saw). Spun it up again. No oil on bar. Pressure tested oil tank system all good. Needless to say, I was scratching my head on this one. Saw itself appeared to be a very low hour saw with excellent spark and compression. As a last resort, I removed the oil inlet from the casting to clean it out. I saw that the hole that it goes into was oblong and not round. I pulled out a casting from the parts saw and found perfectly round!! Maybe this is the reason this saw was so low hours? I assume that pressure from diaphragm was escaping thru unsealed area under the inlet. I put the cleaned inlet port back into saw, sealed it with RTV, will let it sit for 24 hours before rebuilding and testing. hopefully this fixes it.  |
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Post by xl130 on Nov 29, 2020 16:55:10 GMT -5
Is it possible that the line is getting pinched between the oil tank and crankcase when you tighten the recoil down?
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Post by bamaboilermaker on Nov 29, 2020 18:43:48 GMT -5
I thought about that first. On original rebuild I used the harder fuel / oil lines from Home Depot (😕). Replaced w normal tygon. The lines not pinched , as verified by spinning flywheel on bench without case.
Hopefully the RTV trick will work and another saw can be returned to service
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Post by ken8831200 on Nov 30, 2020 6:45:14 GMT -5
Only problem I might see is most RTV will swell when in contact with oil or gas. I might try something like JB Weld.
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Post by bamaboilermaker on Dec 1, 2020 13:10:03 GMT -5
An update for anyone interested. I initially did vacuum testing and passed. Last night I did pressure testing and never could open the check valve to allow for oil to flow to the bar connection. Trouble shooting the entire system, I found 3 different oil pump diaphrams and tried on the system. Same result, no oil flow. Suspecting that the check valve ball / spring was broken / damaged which was blocking flow, I inserted a drill bit into bore and to my surprise, check valve moved under spring load and allowed oil to flow with system manually pressurized. I then pulled up Leon's shop manual 5th edition and referenced all of the critical dimensions in the oil pump system. I broke out the calipers and went to laying out the critical components of the system compared to the design tolerances. I found that the head of the pump body was at ~ 0.012", just shy of the allowed max of0.015". All 3 of my diaphragms were just a hair short of the minimum spec of 0.620". I then inserted the drill bit and measured the length of stroke needed to touch the check ball and then again at what stroke was needed to open the valve. I found those dimensions to be 0.586" and 0.697" respectively. XL2 OIL PUMP CUT SECTION.bmp (770.92 KB) In order to test the theory, I plan on cutting a #53 drill bit and one of the diaphragm pins to create a combined total length of shaft = about 0.695". This should allow for the check valve to open and flow oil to the bar. my hope is that I do not create a leak path to allow for bar oil to enter combustion chamber on the pump side of the diaphragm. I got nothing to loose on this saw. Pretty interesting to get into the details of this system, never had one not work. I personally think this saw never had a functioning oiling system from the factory.  |
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Post by sweepleader on Dec 2, 2020 23:36:03 GMT -5
Interesting research. Normally check balls in pumps are operated by hydraulic pressure of the fluid, the fluid pressure being high enough to overcome the spring pressing one the check ball.
I don't think I would have guessed that the pump shaft operated the ball.
Nice work.
I would be concerned that the loose drill bit might not retract with the diaphragm and thus block the flow of oil refilling the pump.
Also, does the arrow in the tube at the top of the diagram return to the oil tank? If that was blocked full of oil, it would prevent the diaphragm from moving toward the check ball stopping the pump.
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dann757
Collector wannabe
Posts: 11
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Post by dann757 on Jan 26, 2021 18:05:04 GMT -5
This is very interesting and just what I'm trying to fix on my 1975 XL2 Auto. I put that saw away years ago and got a renewed interest in it. Sentimental reasons, that saw helped me gather firewood. Greatly appreciate Leon's , the saw is running thanks to his carb kit. I got as many oiler parts as I could from him too. I just rebuilt the oiling system. I fired it up and it seems like it's blowing bar oil into the crankcase. The pump diaphragm seems like it might be OK, I know those are basically unavailable on earth. I was trying to get some nitrile nylon diaphragm material for a possible attempt to do some microsurgery and replace the diaphragm!
Getting close but no oil to the bar. I put a drill bit into the pump body hole and the ball moved under spring pressure. Seemed like that hard line tube was functioning. I got the oiler insert, ball and spring from Leon's. Has anybody extracted the fitting. I imagine the oiler insert must be tapped out from the fitting side.
What causes the bar oil to blow back into the crankcase? Thanks for any replies or input.
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Post by undee70ss on Jan 26, 2021 18:30:00 GMT -5
This is very interesting and just what I'm trying to fix on my 1975 XL2 Auto. I put that saw away years ago and got a renewed interest in it. Sentimental reasons, that saw helped me gather firewood. Greatly appreciate Leon's , the saw is running thanks to his carb kit. I got as many oiler parts as I could from him too. I just rebuilt the oiling system. I fired it up and it seems like it's blowing bar oil into the crankcase. The pump diaphragm seems like it might be OK, I know those are basically unavailable on earth. I was trying to get some nitrile nylon diaphragm material for a possible attempt to do some microsurgery and replace the diaphragm! Getting close but no oil to the bar. I put a drill bit into the pump body hole and the ball moved under spring pressure. Seemed like that hard line tube was functioning. I got the oiler insert, ball and spring from Leon's. Has anybody extracted the fitting. I imagine the oiler insert must be tapped out from the fitting side. What causes the bar oil to blow back into the crankcase? Thanks for any replies or input. Duckbill valve in oil tank, when it is damaged or missing bar oil will get sucked into crankcase. Another possibility is the the oil line are connected to the wrong ports. |
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dann757
Collector wannabe
Posts: 11
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Post by dann757 on Feb 19, 2021 19:14:36 GMT -5
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Post by protocol1 on Jun 7, 2021 21:24:16 GMT -5
The check ball in the oil pump discharge is opened by oil pressure developed by the stroke of the pump plunger rod. If the pump does not pump oil, then there is probably air in the pump preventing unseating the check ball, and/or the oil supply and pulse hoses are misconnected. Correct operation of the oil pump does not require adding any custom parts to the pump. Nice drawing regardless!
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