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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Oil loss through breather pipe
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<blockquote data-quote="BigEd" data-source="post: 16488" data-attributes="member: 161"><p><strong>Oil loss through breather pipe.</strong></p><p></p><p>Who did the rebuild, what work was done and how well was it done? If the rebuild was done competently and included new pistons it could be that the rings and bores have not yet fully bedded in. The timed breather should close 30 degrees after bottom dead centre measured on the rear cylinder. You can check this without a major strip down by removing the brass OP9/2 oil delivery quill and mounting a degree disc on an extension rod pushed in to the timing side mainshaft. Put a length of tube on the breather pipe and blow through it as you turn the engine. When the rear cylinder gets near to 30 degrees after bottom dead centre you should find it becomes difficult to blow. It worked for me when I checked my breather timing. I posted something on breathers last year and I have pasted it below to save you searching.</p><p> We were in Malta a couple of months ago. We flew there and then got the ferry to Gozo where we stayed at a house in Xaghra belonging to our eldest daughter. A lovely place to visit although the roads are quite bumpy in places. </p><p> </p><p> <em>“Here is my experience with my '48 Rapide, built from (what seemed like a million) battered bits that had returned from Argentina. I got it registered and back on the road last September, i.e. just over 12 months ago. I'm still getting the bugs out but having put on 10,000 miles there are hopefully not too many bugs left to sort. I used a standard timed breather set-up initially and this was pretty oily. As the new pistons and bores bedded in things improved a little.</em></p><p><em>There were/still are various weeps and drips from poor joint faces. Modern sealants have reduced these significantly.</em></p><p><em>I re-routed the breather pipe straight up and over the top of the engine and into an approximately half pint plastic catch bottle. Over two to three </em></p><p><em>hundred miles the bottle maybe collected a quarter pint of oil/watery emulsion.</em></p><p><em>The next mod was some sort of car PCV valve bought cheaply on ebay and plumbed into the rear cylinder exhaust rocker cap. Several people on list have done a similar modification. This breather was also routed to the catch bottle so that I could monitor the effect. The result is that the catch bottle now collects very little. Over the last 1500 miles it has collected perhaps two egg cups of oil/emulsion.</em></p><p><em></em></p><p><em>Summary: On my machine the PCV valve seems to have improved the breathing. </em> <em></em></p><p><em>I still have the original breather operating so maybe I could try plugging this and see if this is better or worse.”</em></p></blockquote><p></p>
[QUOTE="BigEd, post: 16488, member: 161"] [b]Oil loss through breather pipe.[/b] Who did the rebuild, what work was done and how well was it done? If the rebuild was done competently and included new pistons it could be that the rings and bores have not yet fully bedded in. The timed breather should close 30 degrees after bottom dead centre measured on the rear cylinder. You can check this without a major strip down by removing the brass OP9/2 oil delivery quill and mounting a degree disc on an extension rod pushed in to the timing side mainshaft. Put a length of tube on the breather pipe and blow through it as you turn the engine. When the rear cylinder gets near to 30 degrees after bottom dead centre you should find it becomes difficult to blow. It worked for me when I checked my breather timing. I posted something on breathers last year and I have pasted it below to save you searching. We were in Malta a couple of months ago. We flew there and then got the ferry to Gozo where we stayed at a house in Xaghra belonging to our eldest daughter. A lovely place to visit although the roads are quite bumpy in places. [I]“Here is my experience with my '48 Rapide, built from (what seemed like a million) battered bits that had returned from Argentina. I got it registered and back on the road last September, i.e. just over 12 months ago. I'm still getting the bugs out but having put on 10,000 miles there are hopefully not too many bugs left to sort. I used a standard timed breather set-up initially and this was pretty oily. As the new pistons and bores bedded in things improved a little. There were/still are various weeps and drips from poor joint faces. Modern sealants have reduced these significantly. I re-routed the breather pipe straight up and over the top of the engine and into an approximately half pint plastic catch bottle. Over two to three hundred miles the bottle maybe collected a quarter pint of oil/watery emulsion. The next mod was some sort of car PCV valve bought cheaply on ebay and plumbed into the rear cylinder exhaust rocker cap. Several people on list have done a similar modification. This breather was also routed to the catch bottle so that I could monitor the effect. The result is that the catch bottle now collects very little. Over the last 1500 miles it has collected perhaps two egg cups of oil/emulsion. Summary: On my machine the PCV valve seems to have improved the breathing. [/I] [I] I still have the original breather operating so maybe I could try plugging this and see if this is better or worse.”[/I] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Oil loss through breather pipe
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