Early 750 GT foam airfilter?

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Jed

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My '68 GT's airfilter is foam tube wrapped around a perforated steel flattened cylinder supported by two end plates bolted to two tubes running inside the length of the perforated flattened cylinder from the back of the airbox to the rear of the battery holder. You can see the old green foam filter here.

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I've not seen anything like this in any of the research I've been doing. The only references I can see on the interweb for GT filters are for the old paper ones and the new repo's not oiled foam ones. I figure it is a mod made sometime in the old girls history. I wonder if anyone else has come across one like this?

It's turned out to be quite useful though. The old foam tube just fell to bits when I tried to get it out so I made a new one out of open cell filter foam sheet, oiled it up and bunged it on. It's working quite well. Isabella was never really happy without the airfilter on and seems to be quite sensitive to it's lack of presence jetting wise. It was one of the reasons why she was leaning out as the revs came up. Jean Louis put me on to 118 main jets for running without the airfilter and I've got some of them but in order to fit the nice long trumpets I've got the whole airbox has to come out. I'll keep the standard jets in and the airfilter on for the time being.

The other parts of the problem turned out to be the original worn out petcocks that weren't immediately obvious as being flow restricted. Once again as the revs came out and the flow wasn't enough the fuel levels in the bowls fell and she leaned out again. With new petcock's installed, new air filter foam and the intake boots back on she's going quite well now.

:)
 
The original filter was paper.
Clem who lurks on this list did plan to have some new filters, oiled foam made up for these models.
Clem?
I have one of Clems filters on my SF2 and am very pleased.

Ciao
Paul
 
Yes I did get the Unifilter company to prototype and productionise, for the early models with the oval filter under the battery type.It was a very long drawn and uphill process, but they refused to remake the perforated steel "core" and its oval end caps.Consequently what I ended up wityh was a filter "sleeve" which can be wrapped around the existing metal core (if you still have it that is!) It is made from Unifilters pre oiled foam, and is correctly made to fit the core without stress or torture,correctly joined etc, it is also no larger then the OD of the origianal, and of course it can be washed out,use white spirit, never anything from an aerosol, in a tank, re oiled and go again, maybe ten or fifteen times.

I no longer import or deal with Unifilter, due to the operational difficulties that I continually encountered with them, missed promised deliveries, hiked prices, lies and lies and even mor lies about why/when I will get my seven or eight hundred pound order (sometimes twelve hundred) and the added worry that there has been a few cases of bikes which dont run right after fitting, mainly due to over jetting in the name of extra power (big jets must give high HP?) etc etc.The three bikes that I had here which would not go very flat at WOT, had other things wrong with them, one had a broken valve spring, once fixed he was fine, another had black gloopy crud in his tank, fuel lines and in the carbs after only about 20 miles riden,which was gumming up his carbs, the last one had been reoiled (and I think this is where the main problem comes from) and when I saw it, it was dripping oil all over the floor, I squeezed it out into a tray and was thinking about saving it, there was so much of it.Nickdav7 had one, until it was removed, by a certain well known fitter, from the dark North,oop there in sweat sock land, but before it was removed, he was regularly thrashing the granny to crank busting revs most of the times without a problem.WOT, worked OK for Nick.
I have handed the UK Unifilter franchise over to Richard Slater (Slater Bros) who stocks the 180 jota type, and the later 750 type, he can get the others to order.

I do have one single "sleeve" for the under battery 750 type, does anyone want it, paypal me ?35 for UK or ?45 for ROW.
CLEM
 
Jedzo.
Your mainjet size won?t affect your mixture until about 3/4 throttle (I have seen numerous bikes with the mainjet lying in the float bowl and the owner unaware with normal riding). The needle and needle-jet are principally in control from 1/4 to 3/4 (probably where you should be looking), and the idle system and slide cutaway under that. There is some overlap of course.
My experience with reduced fuel flow from either restricted taps or ventilation (of either fuel tank or float bowl) is that the motor dies completely and then cuts in fully as the float level comes up again, then repeats the process. Generally only happened with very wide throttle needing lots of fuel flow. Maybe others have experienced gradual leaning out, I haven?t.
For analysing your carbs use amount of throttle as your reference, not revs, put small reference dots on your twistgrip and housing for quarter, half and three quarter open.
I am a firm subscriber to good quality lightly oiled foam filtration. I have cut up and re-glued (with contact adhesive) Unifilter filters without problem.
 
longshanks, it is yours
Baskerville doubtfull
Andrea is in Royal Marsden today/tonight having another pump up
CLEM
 
some pic
this is the uni filter just wrap it around the frame of the old filter.have seen GT/ done that way works fine.I put the pic of the 650 air filter it works fine I just change it every year .
 

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Hi Jedzo,

Wolfgang does a conversion like you have - a complete kit with a perforated metal core welded to end plates and covered with a reusable foam filter 'sock' over this. Ran my '72 GT with it for many miles with standard jetting-probably still in use on the bike.
 
Thanks for that Norm, like you I'm quite happy with how it's running now with this arrangement on standard jetting. She goes well at the moment, age and mileage considered.
 
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