Hi,
As anyone thought about or fitted an after market oil cooler. I have been looking at some of the small computer cooling radiators with a thought of fitting one in the cylinder head feed line. I know that doesn't carry a large flow but I have a 68 thunderbolt and the feed comes from the pump. The oil pipe up to the head gets hot and I am in the opinion that cooler oil might be a benefit. It's lockdown here in Scotland still and I'm bored!!!
Oil coolers were quite a thing some years ago but for the whole of the oil system rather than apart of it. Will this mini cooler have its own fan?
When stationary coolers do not really work as there is no air flow through them and unless thermostatically controlled can cause over cooling at higher speeds. One advantage is a slight increase in oil capacity.
I suppose in theory if this oil feed is cooled will the oil thicken slightly and perhaps cause a back pressure pushing some of the rocker feed oil to the tank and to some degree reducing the amount of oil getting to the rockers?
Dave.
The resistance on the rockerfeed oil pipe, being of smaller diameter coupled with the intermittent flow results in a miniscule amount actually getting to the rocker box which is fine for lubricating the rockers as intended, but would not result in much cooling of the oil as the majority of flow will bypass it. So probably a waste of time.
If most of your riding is long distance (50 miles plus) at high speeds and in hot weather, then an oil coiler would be useful, particularly on OIF twins where the original capacity was reduced for a 'styling' convenience during development, plus, they don't get much natural cooling in the spine reservoir compared to the separate side mounted oil tank.
I would try a simple check this season, if ever there will be one. Say. on a normal club run, in normal weather, feel the tank/reservoir and if you can hold your hand on it for more than 5 secs., don't bother with a cooler IMHO.
I blame the Rocket 3. It had an oil cooler so it must be a good thing. We all need one on our bikes don't we, especially those over worked outfits. I can remember at least 4 of us in one BSAOC Branch who fitted them. If you had bit of spare cash a proper R3 one otherwise it was a trip to the 'scappy' to get one off a VW Beetle.
We had them on for years. Worth it?
On my out fit I decided to run a car alternator with a belt from the crank so I took the oil cooler off to accommodate this. The intention was to relocate it as we were going to the '95 Italian Rally and it might be hot especially climbing the Alps.
Time ran out and the cooler never went back on. BSA never fitted a cooler to any twins even when sent to desert countries so why worry. I remember being stuck in traffic near Genoa and looking in the tank the oil was like strong coffee being pumped around but I put the cap back on and carried on.
Norman Hyde produced a thermostat for the triples to better regulate the oil temperature. I wonder how many actually opened in normal use. I know of one person who had theirs open after some enthusiastic riding over the Pyrenees where it was hot.
I went off oil coolers for the unsightly pipes and stuck on appearance and the lack of necessity.
When the oil gets hot whilst stationary the cooler doesn't work (a fan could be fitted), when the cooler works when moving it is not needed. On cool/cold days the oil will be over cooled so a cover will be needed and then if it warms up it will have to be taken off. I cannot be bothered with all that.
Dave.
Thanks for the replies,
My thoughts are mirrored by most as 'is it really worth it'. I live and ride in the highlands of Scotland so my bike mostly ticks along at 55mph. I do notice oil usage goes up on the hotter days and with an increase in speed (depends on who I'm out with!) Valvoline oil has brought consumption down slightly but I think a rebore is possibly the next job. I do look at the bike and as an ex mechanical engineer have a basic interest in making it better in some ways but keeping originality as far as possible. It has modern ignition, an oil filter and rebuilt engine but I did retain the plain bearing albeit renewed. I love the old bike and it will only go when I can no longer physically ride it. It does clock up a few miles through summer and regularly carries camping gear so I guess all I do ask is it is as reliable as possible.
Cheers for the replies.
I fitted a pit bike oil cooler on my Lightning 4 years ago (incidentally for the Italian rally)
The Rocket 3 cooler might have a greater flow capacity, this is good when the oil is cold. The pit bike cooler on mine was too restrictive when the oil was cold so I fitted a thermostat to the system. It would cause some back pressure and leak until the oil had warmed up, the thermostat fixed this.
On a baking hot day the engine would start getting very tappety even with 20/50 oil without the cooler, probably causing untold damage. I now run a modern synthetic bike oil, a 10/40 but with the cooler... it's never been as tappety since. But this is in the main return line, not on the rocker feed line. So just shows that with the cooler and the extra pipe
Length it just cools it enough before it's cycled round the system again.
For optimising the built in cooling capacity of the fins and airways it is worth paying some attention to the small ducts that exist between the cylinders. I am sure we all do this but it is possible for insects and flaking paint to block these passages and they need blasting out as part of a general clean. This also applies to the passageways through the cylinder head.
Too much paint on the barrels can block the very small spaces towards the top behind the pushrod tower. I have come across barrels were these have almost been blocked by unfinished casting edges. This also applies to the passages at the front of the cylinders. Make sure they are all unobstructed to maximise the built in cooling.
Dave.
Too true. When I decided to take my barrels off the Thunderbolt to clean and repaint I was horrified to see that all the internal (between cylinder) galleries were blocked. Must have been like that for ages. Being an OIF with the short front mudguard, they road dirt and mud kicked up by the front wheel found it's way into them. It took ages to clear them all out. Like bloody concrete!