OzVMX Forum
Clubroom => Tech Talk => Topic started by: Spanish Armada on April 06, 2015, 09:34:49 am
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Just putting out there for suggestions on who to send my pre 60
Forks to to get work done springs and emulators cheers
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have a go your self. I put a set in my TT 500 they came with instructions on instillation. they make a massive difference to the way the bike rides.
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What sort of pre60 forks?
I'm doing some B series BSA ones.
Just achieving decent 2-way damping is challenging.
Emulators are a future project.
Cheers DJ.
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Daryl they r 35 mm matchy with internal damping
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Whoa! High Tech.
I haven't had anything to do with those, but they look like a pretty good starting point.
A 'cartridge-ish' top rod style, with a disk type compression damper valve.
(Pretty much what an emulator emulates ;D)
Some-one with experience and knowledge could make these work Very well.
Love to see some pics & details, please keep us informed.
Cheers DJ.
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Whoa! High Tech.
I haven't had anything to do with those, but they look like a pretty good starting point.
A 'cartridge-ish' top rod style, with a disk type compression damper valve.
(Pretty much what an emulator emulates ;D)
Some-one with experience and knowledge could make these work Very well.
Love to see some pics & details, please keep us informed.
Cheers DJ.
Daryl your lucky you haven't had anything to do with them. Over the last 12 month I have tried to help a few people sort out those Emulators in the older forks and after a lot of stuffing around with oil level and damper spring adjustments they have all gone in the bin. One of the main problems is the damper valve sits on top of damper rod which means more oil than original is needed to maintaine damping at the top of travel but that extra oil causes the fork to hydraulic on compresion reducing that all important travel. There are other issues as well that I won't go into.
They seem to work ok on the later pre85 type forks and bikes but don't believe that fitted to 7" travel pre75 forks you will end up with anything even close to carefully setup stock forks like Ceriani.
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It was the AJS/Matchless forks that were "High Tech" pre60 wise. ;)
Particularly compared to what BSA was offering back then.
These excerpts are from the 1953 AJS Manual.
As I suggested, they look very tune-able & there may be no real need for emulators,
(perhaps just a modern type progressive valve stack).
(https://s3.amazonaws.com/WEBPOSTS/OZVMX/AJS+Matchless+diag+16.JPG)
(https://s3.amazonaws.com/WEBPOSTS/OZVMX/AJS+Matchless+p52.JPG)
Cheers DJ.
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sleepy - after 2 tries finally had a set installed in my 74/75 YZB - cannot tell you how much of a difference it made.
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- cannot tell you how much of a difference it made.
Undetectable? or Indescribable?
Cheers, DJ
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I don't know how much you are willing to spend but there is a company in the UK that will make cartridge inserts for any forks.
[url][/http://www.maxtonsuspension.co.uk/url]
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I had a similar experience to Sleepy with "aussie made", read Tawain) emulators in my pre75 Betor forks. After trying several different oil weights and volume of oil, I gave up on them. Cost me a set of dampening rods as the originals were cut and custom made socket welded on as per the instructions the seller gave me to fit the emulators.
On another note, I have a set of Norton Road Holders on my B44 and they are fitted with adjustable rods. One side does compression, the other rebound. And they work! I'm not sure if they will fit the Matchy fork but it could be worth investigating.
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DJ - good (but maybe a bit tongue in cheek ;D) question - no I found a very marked improvement in performance in the front end.
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Thanks RVC. (Yes cheeky, but hopefully we are all in this for the Fun) ;D
I'd like to get some more feedback on the emulators for pre75 and particularly for Betor forks.
I had just about decided to get 2 sets, for my VMX bikes.
I have been noticing the 'hit' from the compression lock-up, more & more lately.
(I'd like to think that I'm riding faster, but honestly, I guess I'm just getting older & softer).
The Betor's are pretty sensitive to oil level, already.
If you put a bit too much in, you tend to wear it, when it blows out the breather/relief valve.
Cheers, Daryl
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Another problem with the em's is way the hold the front end up coming into a corner. The spring loaded valve takes a bit of a hit to move which is ok over bumps but when braking into a corner the older bikes need a bit of dive to steppen the rake to turn in properly. Modern bikes need the opposite to happen which is why they are good for them.
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Now. I'm starting to sound old.. "back in the day" we closed off the holes in the Betor caps.. for that very reason .. you got oil all over you.. didn't seem to affect the action with the bleed filled in..
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"back in the day" we closed off the holes in the Betor caps.. for that very reason .. you got oil all over you.. didn't seem to affect the action with the bleed filled in..
It was also often recommended, to braze a cap over the top of the damper tube & drill sideways holes, to keep the oil from blowing/blasting up to the cap vents. Later Bultaco forks had a bent steel piece that fitted inside the spring at the damper end to achieve the same effect.
As Sleepy has pointed out, when emulators are fitted, the top of the damper tube/rod needs to be covered with oil at "top-out" rather than at full compression, as normal. Lots more oil in the fork, with potential for pneumatic pressure problems.
Anybody got a good Betor emulator story?
Cheers, DJ
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The Betors I have on my B50 work a treat now. Yep, the bleed hole is filled in. I'm using Montesa King Scorpion rods that are completely stock and progressive springs with 10mm preload. 15wt oil. 190mm air gap on compressed tubes. The bike handles everything really well, much better than the drama's I had with emulators.
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Fork work? say that regularly on fine days when I'm there.