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SU damper

Started by _lxhatch_jim_ , Jul 17 2007 11:36 AM

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18 replies to this topic

#1 _lxhatch_jim_

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Posted 17 July 2007 - 11:36 AM

Lads, could someone with SU's let me know what type of oil they use in the dampers? I've heard motorbike fork oil is a good weight.

More importantly, how do you know exactly how much to put in? I've been told about three different amounts. Apparently you fill it until the screw cap of the damper sits half an inch above the dome, and then push te dampener in. Does this sound right?

Any general tips would also be helpful.

Cheers
Jim

Edited by lxhatch_jim, 17 July 2007 - 11:37 AM.

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#2 Litre8

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Posted 17 July 2007 - 12:14 PM

Depends on the application. I used to use ATF in the dampers on my XU1. Fork oil is probably pretty heavy so may result in slow throttle response.

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#3 orangeLJ

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Posted 17 July 2007 - 12:46 PM

i use sewing machine oil in mine. My mother hates it cause she can never find the stuff when she needs it. The proper stuff to use is this really light gear oil, if i remember correctly, have a bottle at the workshop, will look when im down there next.

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#4 _lxhatch_jim_

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Posted 17 July 2007 - 01:01 PM

Thanks boys. I've been using singer oil but I think not enough of it. I'll add some more in this evening. Apparently there shouldn't be any "play" on the damper when you lift the needle piston.

I've got a problem with the revs not dropping after acceleration. I've made sure the linkages are all in free, working order so it's not that. It's like the throttle is stuck open, but after a quick depression of the pedal it drops down again.

My initially thoughts were that the jets aren't centred perfectly but then the problem is intermittent. The piston hits the bridge cleanly too. I'm at a loss.

Has anyone experienced this before? I'll work it out eventually, just a matter of persistence. I've only just got them on and running so these teething issues are inevitable.

Cheers
Jim

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#5 V-SLR5000-P

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Posted 17 July 2007 - 01:37 PM

If the needles are not centred and hang up in the jets you should have problems on acceleration too, as the mixture would be too lean until the needles lifted out of the jets. Sounds like the throttle blades are not closing fully, the airflow will also keep the dashpot/needle lifted. I would try pushing down the throttles next time it happens to see if one or more carby is not closing properly. Maybe you just need stronger return spring/s.

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#6 _draglc_

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Posted 17 July 2007 - 01:39 PM

The more oil, the longer the 'piston things' (mind blank sorry) take to drop, also depends on the weight of the oil, ie how thick. Thinner oil will drop quicker.

Could also just be dirt or crap in them, take them apart and give them a quick sand with some very fine sandpaper, and wash them in carby cleaner or petrol.

A1

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#7 _gtrtorana_

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Posted 19 July 2007 - 07:57 AM

I don't use any oil in my CD strombergs and never had an issue. I have seen Holden documents stating not to use any oil but it may be different for SU carbs.

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#8 _draglc_

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Posted 19 July 2007 - 02:20 PM

yes you can also use no oil, the 'pistons' will rise faster, and rattle more at idle.

everyone ive spoke to recommends having some kind of oil in there, but obviously its personal preference.

A1

Edited by draglc, 19 July 2007 - 02:21 PM.

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#9 _lxhatch_jim_

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Posted 19 July 2007 - 03:18 PM

Lads, I've got mail that claims 10-20 weight is the go (depending on application, climate etc) and that as long as there is no free play when you lift the piston, there is enough oil.

Apparently there are also dampers that have a ball joint like hinge where the damper rod meets the screw in cap. This allows the damper to centre in the bore correctly at all piston heights.

Thanks for your help

Cheers
Jim

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#10 _why-psi_

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Posted 19 July 2007 - 06:21 PM

sewing machine oil in winter, makes it a bit more driveable. no oil in summer, makes a snappy throttle

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#11 orangeLJ

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Posted 19 July 2007 - 07:22 PM

i cant stand the f*cking tapping on idle though! little bit of oil helps quiten em down.

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#12 _jklumpp_

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Posted 23 July 2007 - 01:40 PM

I was told by Midel Singer oil was very close to original SU oil, & a fraction of the price... & Don't use ATF, as the oil should get thinner with temp (acts as a sort of choke when engine is cold)
As for how much, The oil damper (rod you remove to fill the oil) acts as a dipstick - oil should be just over the damper at the end of the rod.... if damper is just covered when engine off, will always be in oil (piston rises with revs)... hope that all makes sense....

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#13 LC-069

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Posted 04 July 2009 - 04:43 PM

Hey guys,

i require oil for my reco triple SU's.

Anyone used this oil and what is the difference between the two, dashpot and damper??

http://www.penriteoi.../su_dashpot_oil

http://www.penriteoi...l/su_damper_oil

Cheers

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#14 rodomo

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Posted 04 July 2009 - 05:01 PM

This is from your top link:

SU DASHPOT is suitable for use in pre
1940 SU carburettors, which do not
incorporate a damper in the dashpot
assembly. Removing the dashpot cap can
readily identify this type of carburettor,
as there is no damper rod on the
underside.

SU DAMPER is suitable for post 1940
vehicles using SU and Stromburg
carburettors incorporating a damper in
the dashpot assembly. The damper
assembly is attached to the cap and be
seen when the cap is removed.
SU DASHPOT SU DAMPER
Viscosity @ 40oC 15 68
Colour amber green
Environment, Health