Race breed single

[dav]

At the Barry Sheene Festival of Speed last weekend there was a few Duke single racers, there was one with a few extra oil lines then standard. I can understand why he did it (to feed more oil up the top end) but is it an overkill?

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btw it was a great day out seeing all these classic racers in full flight.

[DewCatTea-Bob]

" there was one with a few extra oil lines then standard. I can understand why he did it (to feed more oil up the top end) but is it an overkill? "

____ Actually, it appears to merely be the way to see the oil pumped up, and may also have it completely diverted so that it doesn't pick-up the heat through the regular cylinder passage-way.
__ In the old-days of questionable oil-quality, that external oil-line would first go to an oil-cooler before then being connected-up as seen at the left cam-bearing support.

____ BTW, I think it's pretty-foolish to actually race with a stock-tank like that ! _ (Better to substitute a more replaceable plasic-tank during the race.)


Dukaddy-DUKEs,
-Bob

[MotoMike]

That is a handsome little Duke. Looks like he put a pretty good sized carb on it as well.

His oil line modification also allows him t use a real oil filter.

[Teckhardt]

That is a handsome little Duke. Looks like he put a pretty good sized carb on it as well.

Looks like the stack could suck in small birds flying by.

[DewCatTea-Bob]

By: MotoMike...
" His oil line modification also allows him t use a real oil filter. "

____ Now that you've pointed that out, that's probably the actual/sole reason the owner had for his external oil-line setup.
And on such a race-engine (which ought to go through an oil-change after each day of racing), an 'oil-filter' (used along with the stock oil-screen), should not be of any worth-while use. _ Furthermore, I-myself would not wish to do anything that could further delay oil getting pumped-up to the top-end ! _ And having to fill & pressurize an oil-filter canister before the oil then gets sent-onward to the camshaft, is got to be an un-positive trade-off (for a race-only engine).
So unless it's a next to impossible chore for the owner to keep his oil changed, or his chosen lubricant costs more than a new set of top-end parts,, then I believe he has added that modification for an overall (however slight) negative-outcome !


Dukaddy-DUKEs,
-Bob

[MotoMike]

I haven't seen it written but the type bearings in the Duke seem they would require high flow low pressure and from looking at the oil coming out the end of the cam It seems that is true. I would think you would need to pick your filter carefully as most automotive filters are made for plain bearing engines and relatively high pressure. I suppose the filter can serves in a small way as a cooler, but I would think that a dedicated cooler would be more at home on a race motor. positioning the filter can with the hole at the top would prevent it from draining down if that is a consideration., then the oil lines would likely be full after the initial run up and not delay the oil getting to the head. I notice that the re-routing of the return from the head to the bevel tube to hoses directly into the cases is fairly common. I have wondered if you are taking oiling away from the lower gears on the bevel shaft. just thinking out loud.

[ericpritchard]

What an intersting post - viz. the merits or otherwise of external oil lines and filter.
Firstly, there is the question of oil feed to the end of the camshaft. The standard way, as we all know, is through the crankcase and up the cylinder to the head. Some people (many racers) bypass this feed by fabricating external oil lines that run from the oil pump cover directly to the camshaft end cover (on the primary drive side of the engine) - there is already a boss on the timing side cover, so the mod is fairly straightforward. The advantage, as it was explained to me, was that the oil would be cooler with the external feed as compared with running through the hot metal of the cylinder etc.
Then there is the other mod that seems common on high performance engines - that of rerouting the oil drains from the head. I've seen three different methods - one, is a drain from the head to the gearbox - just over the third gear pinion - this, apparently is a weak spot and the extra oil helps - but I've also been told that to route the oil to the gearbox causes the oil to break down because it runs directly into the gearbox. Secondly. I've seen the oil return routed to the primary drive case - using the electrical output orifice from the alternator (assuming the racer is running total loss ignition system). The third method is to run the two drain lines from the head into the crankcase directly below - i.e. into the oil pump chamber. As for including a filter in the line - I have the specs for such a conversion but haven't attempted it because I was concerned over the additional reduction in pressure/flow.
Just to provide full disclosure - I have tried the drain method to the primary case for just one line - the other stays draining to the normal place. My current (race) engine does not use anything other than standard - BUT - I do change the oil after each race event (Kendal 40, by the way).
I would be very interested in comment on the above.
Regards
Eric Pritchard #170

[MotoMike]

I don't race and really don't run my 450 hard. spun up, but not hard. My thought is that if I were inclined to run it with it's tongue hanging out, I might consider a cooler. But probably not. These singles were campaigned successfully and quite hard for decades and the oil they used then was no where near what we have now. I think I'd still change oil after each race though.

[DewCatTea-Bob]

By: MotoMike...
" the type bearings in the Duke seem they would require high flow low pressure "

____ Right, the high-flow needed not so much for lubrication as for the need of carrying-away heat (which is the main enemy of those type bearings).


" I would think you would need to pick your filter carefully as most automotive filters are made for plain bearing engines and relatively high pressure. "

____ The resistance to flow factor certainly could be an additional concern.
I'd think a suitable fuel screen-filter would be sufficient for catching anything that the stock oil-screen let through.


" I suppose the filter can serves in a small way as a cooler, but I would think that a dedicated cooler would be more at home on a race motor. "

____ I recall a test-report (decades ago when dyno.meters were first made commercially available for testing motorcycles), which made the point that the heat-temp of the engine itself was a notable factor on power-output,, warmth was good but too much heat was bad...
So rather than try to cool the oil AFTER it's been heated, it would certainly be best to take measures to prevent it from getting so hot in the first-place ! ...
And the oil in a Duke-engine gets heated-up highest in the exhaust-side cavity for the ex.valve-springs ! _ So keeping that area of the cyl.head cooler, would be best for keeping the oil-temp down.
And the way to do that is to increase the surface-area of the head-fining (in same area), which can easily be accomplished by drilling multiple holes through the head-fins all around the (outside of the) exhaust-port. ...
__ When a hole is drilled through a fin, the fin then of course loses two surface-areas which are the Dia.size of the drill-bit - (that's actually .5D x .5D x pi [x2]), but at the same time, if the hole is made the same width as the thickness of the fin, then a new surface-area is created which happens to be TWICE that of all the original surface-area which was lost ! _ However since the fins are only about 3mm thick, any drilled holes over 6mm in Dia.size, would actually REDUCE surface area ! _ And a 4.5mm hole would increase it's surface-area only 150%, so it's best to not exceed 3mm Dia.holes (at least around the exhaust-port).
If I were doing-up a race-head, I'd do 2mm holes all-around near the exhaust-port, working up-to 4mm holes towards the intake-port side of the cyl.head, so as to help balance-out the heat-temp of the entire cyl.head.
All in positive-quest of lowering the oil-temp (as well as the working-temp of the motor) !

" My thought is that if I were inclined to run it with it's tongue hanging out, I might consider a cooler. "

____ An oil-cooler's main-purpose was to extend oil-life, (thus indirectly the motor's life as well), but today's motor-oils don't break-down from overheating as readily.


" positioning the filter can with the hole at the top would prevent it from draining down if that is a consideration., "

____ That's certainly an issue of concern which ought to be addressed !


" then the oil lines would likely be full after the initial run up and not delay the oil getting to the head. "

____ I think there would still be some added delay left, anyhow.


" I notice that the re-routing of the return from the head to the bevel tube to hoses directly into the cases is fairly common. I have wondered if you are taking oiling away from the lower gears on the bevel shaft. "

____ Probably so but not entirely, so long as the camshaft's R.tip-end hole is not plugged-off.


" I think I'd still change oil after each race though. "

____ A serious-racer would be ignorant of what may otherwise be learned if oil-changes were not done (at least over-night) between races.
__ I've never wasted the oil however ! ... I would always drain the oil into a CLEANed drain-pan and then poor it into an empty distilled-water bottle through a screened-funnel with a fresh coffee-filter/paper, so as to filter & use the oil again (in some other motor which was closer in need of an oil-change).
The purpose of the fresh filter-paper, (which of course slowed the process), was to allow for catching & noting any new metallic particles the motor was possibly creating. - A fairly useful insight to the condition of the motor !


Dukaddy-DUKEs,
-Bob

[DewCatTea-Bob]

By: ericpritchard...
" rerouting the oil drains from the head. I've seen three different methods - one, is a drain from the head to the gearbox - just over the third gear pinion -
- but I've also been told that to route the oil to the gearbox causes the oil to break down because it runs directly into the gearbox. "

____ Seems like a good/useful purpose for oil... sacrificing it's life for that of the motor parts.


" Secondly. I've seen the oil return routed to the primary drive case - using the electrical output orifice "

____ Other than making further use of an otherwise unused preexisting through-way (to the inside of the motor & oil-sump), I see no advantage to having the return-oil reenter so near to the crankcase-breather through-way, (since cooler/outside-air should not be entering in-through there).


" The third method is to run the two drain lines from the head into the crankcase directly below "

____ The function most accomplished by this simplest mod, is mainly to just help assure that the cyl.head is kept drained of oil build-up during constant high-RPM running.


" As for including a filter in the line - I have the specs for such a conversion but haven't attempted it because I was concerned over the additional reduction in pressure/flow. "

____ Beside that wise consideration, what positive effect would be expected from such thorough filtering of fairly fresh oil (which ought be kept within any well maintained Duke-motor !), anyhow ?


" I have tried the drain method to the primary case for just one line - the other stays draining to the normal place. "

____ I'd expect that the drain from the exhaust-side, would be best to so divert (so as to get that slightly hotter oil a better chance to get cooled-off).


" I do change the oil after each race event (Kendal 40, by the way). "

____ Always a good idea, especially if you take care to pay due attention to the oil's condition !
Heavier-weight oils are supposedly denser so as to absorb & carry-away potentially destructive heat.
While I don't exactly recommend for others to do so, I-myself always filled-up my emptied sumps with (in order) a half a quart of 20w50, then a full-quart of 40w, then a full-quart of 50w, and then top-up with left-over 20w50,, all Valvoline Racing-oil, (plus a couple-ounces of non volatile penetrating-oil).


Dukaddy-DUKEs,
-Bob