Kirby Rowbotham oil filter conversion availability

Fast Eddie

Fast Eddie

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Folks,

Does anyone know if Kirby Rowbotham is still around and still operating and doing his rather good pressurised oil filter conversions for Triumphs ?
 

Kirby Rowbotham Oil Filter - Spare Parts?

Hello, new to the forum (and to classic Triumphs) I now have a T100R Daytona 1973 which as far as I can tell, is fitted with the Kirby Rowbotham (KR) ...
www.britbike.com www.britbike.com

"Unfortunately, it turns out that KR is no longer trading..."

That was 2019.
 
I always wondered at the logic of the arrangement, since it seemed reasonable to filter the return oil before it went in the tank, and wouldn't present a resistance to flow on the feed side.

I'm sure there must be good reasons behind it, but I couldn't work it out 🤷‍♂️
 
B+Bogus said:
I always wondered at the logic of the arrangement, since it seemed reasonable to filter the return oil before it went in the tank, and wouldn't present a resistance to flow on the feed side.

I'm sure there must be good reasons behind it, but I couldn't work it out 🤷‍♂️
Click to expand...
I pretty much agree.

The ‘but’ is that even with a return filter (ie on a Commando) you’ll still see sludge build up in the oil tank over time. So there is still ‘stuff’ in the oil.

Filtering between the pump and crank guarantees the crank getting the cleanest oil possible, especially if it’s as well as a return filter.

Of course, Triumph addressed this with the really quite effective sludge trap. Even with a filter in the system, a Triumph sludge trap still collect sludge.

So… now to the crux of my matter… I’m toying with the idea of modifying a Triumph crank and possibly removing the sludge trap altogether. Hence my thinking about the pre crank filtration.
 
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Filtering between the pump and the crank feed is good in principle, but all that high pressure external plumbing is not good.

The advantage of putting the filter in the return line is that it is simple and it does not cause problems.
 
FWIW Kirby didn't invent the idea. It’s basically common practice on many OEM engines. Interestingly, it is what Nourish did on their race engines.

The external plumbing issue is easily fixed by using the right components.
 
Fast Eddie said:
FWIW Kirby didn't invent the idea. It’s basically common practice on many OEM engines. Interestingly, it is what Nourish did on their race engines.

The external plumbing issue is easily fixed by using the right components.
Click to expand...
All good stuff, but is there an actual problem and are we actually trying to fix it?

What improvement shall we see?
 
Triton Thrasher said:
All good stuff, but is there an actual problem and are we actually trying to fix it?

What improvement shall we see?
Click to expand...
On a standard arrangement there is not really a problem to solve.

As mentioned above, I’m thinking of modifying a Triumph crank and removing the sludge trap altogether.

Why? Because the ‘normal’ place for a Triumph crank to break in race use is through the sludge trap access hole.

When you look at one, there’s no wonder, the threads create stress risers and if that’s not enough, the massive centre punch ‘whack’ certainly does, sometimes several of them on an old crank!

My thinking is to machine out the thread to a smooth bore, cut a chamfer to remove all centre punch damage, press in a purpose made plug and weld it in (laser welding to avoid any heat issues).

I reckon that’ll make for a MUCH stronger crank.

So, if I ever get around to this, the idea of a pre crank filter appeals. But, I do agree that with a filter in the return, and by using modern detergent oil, it’s certainly not a deal breaker.
 
Fast Eddie said:
I pretty much agree.

The ‘but’ is that even with a return filter (ie on a Commando) you’ll still see sludge build up in the oil tank over time. So there is still ‘stuff’ in the oil.

Filtering between the pump and crank guarantees the crank getting the cleanest oil possible, especially if it’s as well as a return filter.

Of course, Triumph addressed this with the really quite effective sludge trap.

So… now to the crux of my matter… I’m toying with the idea of modifying a Triumph crank and possibly removing the sludge trap altogether. Hence my thinking about the pre crank filtration.
Click to expand...
I removed the sludge trap from my T140 crank and fitted the OIF sump plate B25 filter along with a Morgo rotary pump. The Norton spin-on filter is probably superior, but either way it's better than what left the factory.
Another aspect of the KR version is the pump is running both feed and return in unfiltered oil, whereas the other way means only the scavenge is pumping unfiltered oil.
 
Fast Eddie said:
Why? Because the ‘normal’ place for a Triumph crank to break in race use is through the sludge trap access hole.

When you look at one, there’s no wonder, the threads create stress risers and if that’s not enough, the massive centre punch ‘whack’ certainly does, sometimes several of them on an old crank!
Click to expand...
Yes I think you could make a stronger crankshaft.
 
B+Bogus said:
I removed the sludge trap from my T140 crank and fitted the OIF sump plate B25 filter along with a Morgo rotary pump. The Norton spin-on filter is probably superior, but either way it's better than what left the factory.
Another aspect of the KR version is the pump is running both feed and return in unfiltered oil, whereas the other way means only the scavenge is pumping unfiltered oil.
Click to expand...
I run one of the ‘Charlie’s’ kits on my T140 too.

My ‘fancy crank’ idea wouldn’t be in an OIF though, so a filter in the return would be the only good option there.

Did you get the crank re-balanced sans sludge trap ?
 
Fast Eddie said:
Did you get the crank re-balanced sans sludge trap ?
Click to expand...
Oh yes!
It's running +0.060" Powermax pistons and a light '68 flywheel. I re-balanced it the old school way and it's the smoothest Triumph I've ever had.
It's very quick for a street bike, but I wouldn't race it without replacing the flywheel with a steel one.
 
B+Bogus said:
Oh yes!
It's running +0.060" Powermax pistons and a light '68 flywheel. I re-balanced it the old school way and it's the smoothest Triumph I've ever had.
It's very quick for a street bike, but I wouldn't race it without replacing the flywheel with a steel one.
Click to expand...
Interesting!

Are the flywheels universally interchangeable between 120s 140s etc?

I like the lightweight flywheel too. You’re obviously a hooligan of good taste !!

What cams you got in it?
 
Fast Eddie said:
Interesting!

Are the flywheels universally interchangeable between 120s 140s etc?

I like the lightweight flywheel too. You’re obviously a hooligan of good taste !!

What cams you got in it?
Click to expand...
Yes the flywheel is a straight swap - I happen to know a guy who has a spare ;)
Standard inlet cam, exhaust cam with inlet profile, ISTR them being either Spitfire or Thruxton profile? Memory isn't what it was when I built it.
Head ported & flowed to take 32mm carbs.
It's still remarkably tractable at low revs, and ticks over like a standard T140.

I did get hold of a Tracey Hurricane style tank/seat a few years back which would have suited it well, but I'm getting a bit old for that kind of bling.
 

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