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Oil in combustion chamber after rebuild !

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Oil in combustion chamber after rebuild !

Posted by mike_haworth at November 18. 2017

1959 Model 50.

Ive just had the engine rebuilt, however, due to a very poor job being done on shot blasting and powder coating the barrel, I've had to pull it to bits after only 40 miles in order to get the barrel done again. I have found the combustion chamber to be very oily, although the exhaust didn't seem overly smokey when it was running. This probably also explains why there has been a black secretion seeping from the place where the exhaust pipe is secured to the head.

So, should it be this oily or not ? New rings were fitted and the valve guides were bored and sleeved. If both these jobs were done properly, where can this oil be coming from, or is this normal and acceptable ?

 

All advice/comments welcome.

Mike

 

 

 

 

Re: Oil in combustion chamber after rebuild !

Posted by Dan Field at November 18. 2017

I started a thread on the same subject, mostly my problem was over oiling from the feed to the head, but even Mike Pemberton recognises that these singles need up to 1000 miles to rn in properly.

Re: Oil in combustion chamber after rebuild !

Posted by mike_haworth at November 20. 2017

Previously Dan Field wrote:

I started a thread on the same subject, mostly my problem was over oiling from the feed to the head, but even Mike Pemberton recognises that these singles need up to 1000 miles to rn in properly.

If it's over oiling from the feed to the head I am assuming nothing can be done about it ? If the excessive oil is coming past the rings are you suggesting that this will gradually reduce as the rings bed in, and that this may take 1000 miles ? One of the problems this causes is that, even with a brand new copper exhaust seal, the oil is seeping from the exhaust port. I got it pretty tight so, is the answer to add some sealing compind to the threads ?

I'd like to think this problem will resolve over time, but somehow I doubt it ! Problems, for me anyway, never seem to be solved that easily !

Thanks, Mike

Re: Oil in combustion chamber after rebuild !

Posted by Dan Field at November 20. 2017

Hi Mike

the banjo to the head is a poor design, oil can seep around the side of the bolt or it can have 2 holes instead of one or the hole can be too big!

 

have read of this one https://www.nortonownersclub.org/noc-chat/technical1-singles-forum/132676687?b_start=30#571205994

Re: Oil in combustion chamber after rebuild !

Posted by jonathan_newton at November 21. 2017

Previously mike_haworth wrote:

Previously Dan Field wrote:

I started a thread on the same subject, mostly my problem was over oiling from the feed to the head, but even Mike Pemberton recognises that these singles need up to 1000 miles to rn in properly.

If it's over oiling from the feed to the head I am assuming nothing can be done about it ? If the excessive oil is coming past the rings are you suggesting that this will gradually reduce as the rings bed in, and that this may take 1000 miles ? One of the problems this causes is that, even with a brand new copper exhaust seal, the oil is seeping from the exhaust port. I got it pretty tight so, is the answer to add some sealing compind to the threads ?

I'd like to think this problem will resolve over time, but somehow I doubt it ! Problems, for me anyway, never seem to be solved that easily !

Thanks, Mike

Mike if it was passing the rings you would see it out the pipe especially under acceleration.  I have read several threads over the years on this peculiarity and it  seems that bedding in coking up etc eventually cures it.  Dan's comment   regarding the banjo etc is very valid. and my guess is its over oiling the top end,  cured by limiting the flow as Dan described.  Remember there was no forced lube  on this type of component for may years previous,  The Inter/Manx had nothing to the rockers outboard and an often  blocked  1/16th non pressured feed to the guides.  Some oil for sure but too much and you already see the consequence.   I  used to run formula ford "kent" engines with a heavily reduced feed hole to the  rocker box to help maintain the fuel octane level by not ingesting the excessive oil fed  up  there.

Best regards

Jon

Re: Oil in combustion chamber after rebuild !

Posted by steven lewis at November 27. 2017

Previously mike_haworth wrote:

1959 Model 50.

Ive just had the engine rebuilt, however, due to a very poor job being done on shot blasting and powder coating the barrel, I've had to pull it to bits after only 40 miles in order to get the barrel done again. I have found the combustion chamber to be very oily, although the exhaust didn't seem overly smokey when it was running. This probably also explains why there has been a black secretion seeping from the place where the exhaust pipe is secured to the head.

So, should it be this oily or not ? New rings were fitted and the valve guides were bored and sleeved. If both these jobs were done properly, where can this oil be coming from, or is this normal and acceptable ?

I have built up several M50's over the years and none have experience oiling of the cylinder. When its apart again, look at the rings and see if they show ware (polished) all the way around. especially the oil ring. i have found a few manufactures supply poor rings and i always look for quality replacements. The last 2 x ES2's i built up were dry from the start and have never showed oil on the piston top.

RGM have some multi piece oil rings , UK made that would be worth a try. 3 piece oil rings always work a treat.

Steve

 

 

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