The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: renos-a10 on 31.01. 2011 10:34
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Hi all ,
Yesterday i start my BSA A10 ( 1960 ) ... all fine .I make a ride and all sound great.
Somebody know that oil must but in form and how much?
Thanks
Renos
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Hello renos!
BSA recommends SAE20, I found SAE30 to work better for me and on smooth modern roads.
Each fork leg contains 225cc.
Cheers, Markus
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Thanks Markus. I buy SAE30 . I think the guy who buy my BSA he didn't but something in forks *conf*
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BSA,s were known for having soft front suspension and this was always dealt with by using thicker oil. I would put SAE 30 or even higher oil in them. All the best.
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Putting the oil aside for a moment... Bear in mind that there are two types of fork springs, it is easy to get the wrong sorts as one sort is for side car pulling, (a firmer spring) the other being solo. (softer) I currently have side car springs in my forks and although nice and firm as a solo rider there is the occasional knock when going over bumps or potholes. I really should revert back to the softer solo springs.
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Hi LJ,
Mine does that too, a "clonk" just sometimes, not consistently..
As I haven't had the bike long (well, at least before pulling it to bits!!) I presumed the previous owner had done something wrong as he said he'd rebushed the forks..
Will start by emptying out whatever is in there (he put grease in the primary area so who knows....!!) and replacing with maybe SAE30.. I must admit I hadn't considered the springs - are they easy to tell which type you have??
Thanks,
Adrian
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BSA,s were known for having soft front suspension and this was always dealt with by using thicker oil. I would put SAE 30 or even higher oil in them. All the best.
I'm changing the oil in the forks. I already have monograde SAE40. What do you reckon?
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Too late; I've done it.
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I use tractor universal 10W 30 in the forks. It's great for hydraulics and gives supple suspension. SAE 40 does seem a mite heavy.
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Oh well, I'm off to Derbyshire this weekend for my next BSAOC camp. So, along with two rideouts and the return journey I'll be covering about 250 miles over the weekend. I may be changing the oil in the forks next week!
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well GB,
You never know if you dont try.
Who knows, it may be perfect.
Or they may be so stiff you pogo-stick to the camp.... *smiley4*
Lee
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Have tried many grades of oil from 10 to 90 in the forks but didn't really noticed much difference. Have 30 grade gearbox oil in for the moment and will probably stick with that.
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The clunk on extension is a BSA feature, most pre A65 damper rod types do it sometimes - it was often commented on by magazine road testers. The bushes clash because there is little damping on rebound.
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The bushes clash because there is little damping on rebound.
..or none *eek* This is one of the reasons that I chose to use a Conical (OIF) type front end
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I got so fed up with the clunk I got a local engineer to convert my late A10 forks to accept the A65 damper rods. That worked fine no clunk but the usual mudguard split developed so fitted complete A65 damper rod forks with stronger mudguard mounting (and 1958/59 SR front mudguard) to my A10. Clunk gone no mudguard splits.
Tried the Eddie Dow conversion before that. Helped with compression damping but not with the extension damping, still clunked.
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Interesting – mine rattle like a witches teeth. I’d assumed that I just needed to put in an Eddie Dow type upgrade. Just that otherwise the bike handles so well I could never quite bring myself to part with the cash.
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With the Eddie Dow conversion on compression the damper is immersed in oil with a column of incompressible oil beneath it the damping coming from the oil being force through the centre drilling and clearance between damper an fork tube.
On extension, above the damper is a column consisting some oil but mainly compressible air so much less effective damping on this stroke.
Rattles often caused by top bush to circlip gap which needs shimming.
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top bush to circlip gap which needs shimming.
Oh yes another of those tasks we all look forward to ;)
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The clunk I get is the plunger units bottoming when I hit a pothole! Anyone devised a buffer solution for that?
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Oil damped plungers as in this BSA patent filed in 1949?
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Oil damped plungers as in this BSA patent filed in 1949?
Flippin-eck, where did you find this? I presume the design was not used as plunger suspension on the 'A' series was quite short lived. Do you know if damped plungers were ever fitted to other machines? What about Ariels?
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Fit new springs if the plungers are bottoming. It's important to keep rear plungers well greased. You should never see rusty plungers!
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Fit new springs if the plungers are bottoming. It's important to keep rear plungers well greased. You should never see rusty plungers!
New springs, well greased.
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After using SAE40 Monograde oil in my forks I can report no ill effects.
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Hi All,
At this stage I would imagine that most BSA's running have had the fork stanchions replaced at some time *????*
If there is oil in the forks, the fork bushes should not clash on extension, because there is oil trapped between the upper and lower bushes as the forks extend
Early forks did not have the two oil holes in the stanchions
I found some "new" bushes recently that the top edges were chamfered *eek*
These would not work as the circlip would not hold them solidly in place, I machined off the chamfer and added thicker shims. Thin shims are waste of time anyway*ex*
I know that people have had different experiences with the Dow type dampers!
Julian,
There's a ball valve in the damper that allows oil to flow through on compression, the ball closes on extension
forcing the oil down around the outside of the valve body giving rebound damping
in the "normal" forks the damping is achieved by the oil being forced in an out through the holes in the stanchion
to the ever changing space between the bushes
I added extra oil so the damper valve is submerged on extension
Thinking out loud *conf2*
Was the TD damper rod length calculated to work with the longer TD fork bushes that make the overall fork length
2in. shorter *????*
The TD top yoke restores the ride height
A design flaw on BSA forks is that water can easily get trapped in the seal holders and sucked into the forks *problem*
Regular oil changes are a must *ex*
John
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A design flaw on BSA forks is that water can easily get trapped in the seal holders and sucked into the forks *problem*
Regular oil changes are a must *ex*
Left fork drained an emulsion of oil and water
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For me, the issue with the Dow dampers on extension is that the oil is not confined above the damper - oil and compressible air above so as the forks extend I think oil drains around the valve rather than be forced through, giving limited damping.
The circlip and shim issue can be solved using the widget from A65 damper rod forks, it bears on top of the top bush and the oil seal and when oil seal holder screwed on retains bush and eliminates any gap and the chattering.
The parts book calls the widget a spacer and it is part 68 5134.
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any chance of an assy. pic/parts book pic of this Julian, I cant picture it?? thanks
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First, sorry for my negative view of Dow type dampers I am sure others have had more positive results.
photo of spacers attached.
BSA issued some guidance on fork servicing. Photos attached.
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7 and 1/2 ounces or a Coca-Cola bottle full.
Things were better then.
Lee
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thanks JUlian, are they a straight add in or are mods required, I haven't finished putting my '56 forks together so maybe its a good opportunity...do you know who stocks them too? cheers
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You may need to fettle. Slide the top bush into the fork leg and check that the spacer bears on it.
Top bushes vary in thickness of flange. You can see in the photo. When assembled as above the spacer bears on the bush on the right, but use the bush on the left there is a gap which would need a shim. You may see a small gap between bottom of oil sealholder and fork bottom with a spacer fitted.
I would think that any ofmthe big dealers might have the spacer.
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HI All,
Julian,
On my SR and other BSA's that I have fitted the damper to, I increased the amount of oil volume so the damper valve
sits in the oil at all times
I found that I had to reduce the oil viscosity to 10 weight
It was only in the last few days that I got to thinking about the rod length on the TD damper and whether the length
was to suit the forks with longer bushes fitted ???
John
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First attempt at pattern Dow dampers was that the valve did not quite reach the oil. Used more oil but still not happy.
Second attempt was an auto jumble purchase of a complete kit - yoke, extended bushes, complete dampers etc. No longer have either but memory is that the second set had longer rods. Worked fine on compression but stll had the clang on extension, tried more oil, thicker oil but it still happened and I thought that perhaps what was happening was that on extension, oil was being drawn through the 2 drillings in the fork shafts from the space between the bushes.........
Anyway I really wanted them to work but could not get them to work as I wanted so first my local motorbike enthusiast engineer converted the A10 fork bottoms to accept A65 damper rod internals, this worked fine but splitting mudguard and some corrosion to studs resulted in me transplanting a complete set of damper rod forks from a 1968 Lightning which was a lot more expensive unfortunately.
Has anyone sen or used the Webco dampers in second photo. Sorry about the quality. Looks like they screw in to replace the bottom bush retaining nut. Seen in the 1961 Webco catalogue.