31csr engine strip ~ posting 2

lawrence · Post by **lawrence** » Mon Mar 15, 2004 11:52 pm

Hi
I have stripped my 1961 model 31csr engine. The camshafts seem a reasonably snug fit in the bushes. Do these need replacing as a matter of course? I recently rebuilt a Bonneville engine and had a real struggle getting the new cam bushes honed. The new ones had exactly the same play as the old ones and I then read that it was practically never necessary to replace them ;o(. Are the AMC ones the same?

Also, the oil filter is a wire mesh assembly. The manual says to replace it with a felt one. Are these available? I can’t see them in the spares list.

The engine has obviously had an oiling (lack of oil) problem by the state of the big end shells and even though the speedo reads only 27 thousand miles it is on 40 thou undersize shells, ie fourth regrind.. All the oilways are full of a jelly-like sludge (mind you, it hasn’t run for thirty years). Any suggestions for special attention?

Thanks

Lawrence [}:)]

Eric · Post by **Eric** » Thu Mar 18, 2004 11:23 pm

Before making any suggestions what amount oversize have the cylinders been bored out to? Clean off the top of pistons they should be marked up with the amount oversize. There is no felt filter replacement for your engine keep the one you have but more on that later. The speedo has probably been replaced or repaired, maybe more than once, or perhaps it stopped working for a long period of time.

lawrence · Post by **lawrence** » Sat Mar 20, 2004 8:14 am

Thanks Eric. Will check my pistons Monday night and post details

Ta

Lawrence [}:)]

lawrence · Post by **lawrence** » Sat Mar 20, 2004 7:38 pm

+40 and they look how I feel after diging the garden ;o(

Lawrence [}:)]

Biscuit · Post by **Biscuit** » Sat Mar 20, 2004 8:16 pm

Pistons with blisters!!! wowee!!!

Eric · Post by **Eric** » Sun Mar 21, 2004 12:00 am

Lawrence from the information you have given us so far I would suggest your bike has done at least 60,000 miles, as it has had two re-bores. [:p] The crank may not have had 4 re-grinds to get to 0.040 undersize, it could have needed more than -0.010 in the past to restore it to round (mine did last time), or perhaps the right size shells were not available, forcing the then owner go to the next downsize. [:(] I suppose its not surprising that the oil ways have a jelly like sludge after all this time, but check out the oil ways in the crankshaft very carefully as these can tell you quite a lot. [;)] Oil feeds in through the centre web then travels outwards to each big end journal. To achieve this apparent miracle the crank is drilled from outside to in, leaving a redundant oil way beyond the journals that becomes the sludge trap, closed of by the infamous countersunk head screw. [;)] It is possible for accumulated sludge to fill up the trap area and restrict, or even stop oil getting through to the journal from the centre web, so this can be a cause of oil starvation. [:(] You can only determine this by assessing the amount of sludge you remove from the crank during the cleaning up process. This sludge will not be jelly like but similar to solid cast iron and will almost certainly require a long series drill of the appropriate size in a hand drill to get it out. [^] Then its pipe cleaners and anything else you can think of to clean, clean, and clean every oil way in the engine until you are more than satisfied they are completely clean. If you don’t have one, find a friend who has a compressor and some high-pressure air to help you out, this is almost an essential. [8)] Whilst the gauze oil filter you have is useless for filtering oil to the degree required, it was often completely ignored during routine servicing and could get clogged up enough to restrict oil flow to the engine. The felt filter was even worse in this respect and still did not actually filter the oil to the degree required. [:(] The oil pumps have to be in good working order and perhaps you should contact a specialist about these. [:)] You should also consider having the crank dynamically balanced after it has been re-ground. [:)] And the possibility of adding some proper oil filtration. [:D] In the ideal world the oil should be properly filtered before it is used in the engine, so that only the most microscopic particles of dirt are allowed to pass through to the bearing areas. If you consider how a shell bearing works it relies upon a microscopic film of clean oil under pressure to maintain separation between the bearing surfaces. [;)] The oil is in effect the replacement for the rollers or balls used in other types of bearing. [^]

lawrence · Post by **lawrence** » Mon Mar 22, 2004 7:11 pm

Thanks Eric, much appreciated. I will definitely get the crank balanced. The difference it makes is incredible. Thanks for the oilway cleaning tips.

Lawrence [}:)]

lawrence · Post by **lawrence** » Wed Mar 24, 2004 11:12 pm

Thanks for the tip David!

Lawrence [}:)]

Eric · Post by **Eric** » Wed Mar 24, 2004 11:57 pm

I was not aware that Andrew engineering did the felt one, but would ask you to consider AMC stopped using the felt one because it could clog completly and prevent any oil from reaching the engine. It was re-introduced for a short while, probably because someone on high insisted they were better than the gauze one. In this respect they were right it is better but still not good enough to filter oil properly, but it can easily block completly. Malcolm Saggers is the man to talk to about oil filtration.