Author Topic: To Needle Roller or Not?  (Read 978 times)

Offline Lukey

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Re: To Needle Roller or Not?
« Reply #15 on: 02.12. 2020 17:54 »
Many thanks for all your replies, seems a mixed opinion whether to have it done or not!
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Online Rex

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Re: To Needle Roller or Not?
« Reply #16 on: 02.12. 2020 21:34 »
If in doubt, don't do it! There'll be something to spend the money on with the bike rebuild soon enough. *eek*

Offline 1957 A10R

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Re: To Needle Roller or Not?
« Reply #17 on: 08.12. 2020 22:06 »
It's your bike you've to decide. I can only speak for myself. Back in 1998 at the International BSA Rally I spook with Steve McFarlane (the man who started SRM and took over the conversion from Devimead) to convert an engine or not. What do think he replied? He has started a new business again were he does the conversions again too. Well his reply was: when I tell you to do the conversion I'm speaking in favour of my business. When I tell you to stick with the bush, I'm speaking against my business. But in theory their's nothing wrong with a good bush. When you think it will be possible to go faster with an engine with a conversion something else will break and the conversin will be blamed. The only advantage with the conversion is, is you enlarge the intermediates between rebuilds. These are Steve words in 1998 not mine.

Offline Rocket Racer

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Re: To Needle Roller or Not?
« Reply #18 on: 09.12. 2020 00:53 »
Think about your use case and your budget.  Is it a keeper? No point doing it while leaving in the original conrods or conrod bolts to fail. With clean oil a bush will run for the life of a set of pistons.
The bush can still cope with high revs and abuse. The bearing conversion should last longer. A mate who ran his SR motor dry (split the rocker feed down by the oil tank) and is replacing rods and pistons needs to do nothing to the combination bearing, its still good (the oil seal needed replacing) .

A fresh bush can be a cheap solution, the conversion isnt. I have so far done conversions on two motors, leaving the third a bush. Sold one of those motors so will be doing another conversion. I will end up with two race preunit twins with conversions and a stock road bike on a bush and original low mileage rods. I also have a spare bearing so I can revisit the stock motor in a few years.

Its your money how do you want to spend it.... BNR clutch, nova 5 speed, carrillo rods, paint job, chrome, TLS brakes...  *eek* the bush isn't a cut and dried good or bad option but is nice to have if the budgets available
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Online metalflake11

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Re: To Needle Roller or Not?
« Reply #19 on: 09.12. 2020 06:56 »
There seems to be an assumption that the conversion is ridiculously expensive!.....It isn't!

As Truckedup said earlier, to do the bush properly isn't cheap by the time you've paid an engineering shop to set jigs up etc. I bet there isn't much difference in price by the time you've finished.

The needle roller bearing is about £80, how much is a bush because you can offset that cost. Last time I looked (a few years ago, granted) the actual engineering work at S.R.M. was only £250.

It's not even that hard to do yourself if you have decent engineering skills and the equipment. The Australian Beezer Bill(?) plans are still on the interweb somewhere I think.

Different strikes for different folks, but after 42 years riding the same bike, if I had to go back to a bush main bearing, I'd sell up and buy something else to see me out.

What's left of life is for riding not messing about in a shed.
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Online Black Sheep

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Re: To Needle Roller or Not?
« Reply #20 on: 09.12. 2020 07:58 »
Each to their own... I'm more than happy with plain bushes on our Star Twin and A10. I hope to see out my riding days on them. And the Velo and the Douglas...
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Online Swarfcut

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Re: To Needle Roller or Not?
« Reply #21 on: 09.12. 2020 09:22 »
   With the standard design I'm amazed the big ends actually get any lubricant, given the small hole into the crank, rotating past the feed holes and oil in the bush.  I know its under some pressure, and   the same concept as on millions of vehicles around the world, it works. I suspect that oil mist and splash play some part, and how these engines still perform with the crank well blocked, until that fateful last run. Has anyone modified this design to retain the bush but improve the supply to the crank? Say a halfway house end fed arrangement, but keep the bush? More oil holes in the bush or crank? Oil scoop of sorts in that crank journal radial groove?

  In my estimation the real benefit of the roller conversion is  to ensure a positive oil pressure to the big ends, however using the combined bearing also has the advantage of positive crank location and less demand for lubricant to this bearing, so more oil to the plain big end journals.

 So, horses for courses and it really depends on the use the bike gets, and again whether its a keeper. Clean oil and a cleaned out sludge trap means the original design is more than adequate for pottering, but regular hard use and enthusiastic riding style point in the direction of a conversion.

 Steve M's words ring true, and at the end of the day as always the benefits and peace of mind need to be weighed against the costs and hassle.


Offline bikerjohndavies

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Re: To Needle Roller or Not?
« Reply #22 on: 09.12. 2020 09:30 »
I also believe that with regular oil changes and the way we ride our cherished bikes that the original setup is more than adequate.  Here is the link to Beeza Bills timing side conversion that metalflake11 mentioned for those with the skill to do it themselves.
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Online muskrat

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Re: To Needle Roller or Not?
« Reply #23 on: 09.12. 2020 19:36 »
G'day Fellas.
The only problem I had with the conversion (BSA-Bills type) was the oil seal in the bridge to the crank. It blew out two or three before I converted it to a bush. No problems since.
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Offline Gearbox

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Re: To Needle Roller or Not?
« Reply #24 on: 26.12. 2020 08:41 »
Just my experience, I used to race a sidecar in the early 80's, initially an a65 with an a10 crank to give 750. End fed engine, lasted 2 seasons before it was sold. Replaced with a good A65 motor, end fed (Devimead) and tuned well. Fitted with a cast iron oil pump. Reved to 9000 give or take on the cable driven tacho. Used a lot and never had a problem. Same bottom end was treated to a Devimead short 750 conversion, A70 crank and corillo rods. 840cc, Pulled like a train for a season, till the barrels lifted on the long straight at Snetterton. Bottom end was fine, except wrecked barrels, pistons and rods., We did put oil filters on each motor as well.
Properly done, the bottom end is pretty tough.
Speaking to my local engineering company (T and L Engineering, near Bedford, who have done these conversions) they comment that for normal road use, the plain bush is fine if done properly and the roller bearing is something that gives you peace of mind.
My A10 motor had them sort out the bush and crank end float.
No definative answer, but suspect its how just how it fits in your head. If I was building the motor from scratch, I suspect I would opt for the conversion, but with mine newly done, its a case of riding it and regular oil changes.
Need to investigate the fitting of an oil filter on mine though, Imagine that this addition would increase engine life.