Hey all dunno if anyone's been following my progress but I got a Weber onto a 3F block and head, just running into a problem now which seems like blocked jets maybe?

Basically I went for a drive round to check it, and after going along at 60mph on an A road I went into 2nd. Started stuttering and jerking like it wasn't getting enough fuel, but if I slammed my foot to the floor, plently of power after a bit of jerking, it picked up fine...

Running these jets:

1st stage

idle 45

emulsion F22

main 117

air 155 (i think)

2nd stage

idle 70

emulsion F30

main 125

air 200

Thing is, it seemed ok until this happened and once I drove it afterwards... I think its just crap in the carb blocking the jets tho maybes?

Edited 12 July, 200719 yr by Narrow_Lane

I had this probel, I kept cleaning the jets out.

In the end I stripped the carb down to bolts and pieces. I took a can of Carb Cleaner and blasted everything so clean that it looked new again, inside every venturi, arteri and thread.

It appeard to be clean but it has never had a blocked jet since.

Yea I'm reluctant to do it, but looks like I will be doing the same sometime.

It did it again today, when I was testing its speed (on a disused airfield). Weird thing is its always the 1st stage that has the problem... But yea blocked jets sounds like the issue, bloody fleabay carb "perfect working order" my arse!!

Hey all dunno if anyone's been following my progress but I got a Weber onto a 3F block and head, just running into a problem now which seems like blocked jets maybe?

Basically I went for a drive round to check it, and after going along at 60mph on an A road I went into 2nd. Started stuttering and jerking like it wasn't getting enough fuel, but if I slammed my foot to the floor, plently of power after a bit of jerking, it picked up fine...

Running these jets:

1st stage

idle 45

emulsion F22

main 117

air 155 (i think)

2nd stage

idle 70

emulsion F30

main 125

air 200

Thing is, it seemed ok until this happened and once I drove it afterwards... I think its just crap in the carb blocking the jets tho maybes?

Those main jets are WAAAAY too big for a polo engine, that looks like a golf set-up or something

This is more like it should be:

1st stage

idle 45

emulsion F22

main 100

air 175

2nd stage

idle 70

emulsion F30

main 115

air 160

Yes your problem does sound like blocked jets though

Edited 13 July, 200719 yr by hypojam

if it's way to big, you'll be over fuelling the engine and bigggegeggring it iup!

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Did you find out what carb it was mate. Check this pic out:

can you see the number the arrow is pointing to? You need to have a look on yours and see what it says. In that PM I said it's probably 24/25 and it still looks that way based on your main jet sizes. The F22 wants replacing with an F30 on the first stage.

Did the problem clear up after you floored it? Could have been a blockage they happen to me all the time, although not so much with the bigger jets, the 100 tends to be worse than the 105. I run this in my derby

Idle 45

Main 105

Emulsion F30

Air 160 (IIRC)

Idle 70

Main 115 or 120

Emulsion F30

Air 165

I'll have a look, and find a local dealer for weber rather than fastroadcars so I can chat to the guys there.

Yes I know the jets a bit big, but I don't have the time or money to sort them at the mo... The problem does seem to be blockage, I pulled out 1st stage and blew through them - it cleared up after that :)

Emulsions ain't cheap lol, £12 each

Dude...

Main jets are only like £2 each, the amount of fuel you will save by just changing the first main jet will cover the cost of the jet within one tank full of petrol.

The main jets are fine if the venturis are 24/25, you may even need to go up to 120 on the first stage if it's venturi is 24mm. The main jet size is actually more to do with the size of the carb rather than the size of the engine (within reason) the idle jets are more critical, and those are alright. Just get rid of that F22! it'll be over fuelling on part throttle rather alot. £12 is about right although I think I paid £10.50 from fastroad cars. It was well over a year ago however.

Yea ok lol

Got 45 mpg to london and back so it's not far off!! And I can beat an 06 plate Mini One

It is a 24/25 yea. I'll order an F30 2moro. Should be ok on 117 it's not much difference in size.

Also you think the 200 is too big for the second stage air?

And the problem was blockages the carb must've had crap in it, cleared the jets twice on the way 2 london, was 100% fine all the way back :) :) :)

45mpg!

Christ... the best I've ever got is 35

Lol I think its more like 40 come to think of it, but I was impressed anyways. Taking it easy tho, only got 4 gears atm :roll:

I was getting that with mine on similar settings, I never quite figured out the second stage jetting to the point I was happy with it, so I tended to stay off it, which must have helped the mpg a bit. :) So I cant be much help. The first stage was great though. I could get 50+ on a long run. I think the trip to mania and back last year I averaged well over 45mpg.

What gearbox did you go for? GT that's pretty damn impressive if it is a gt box. I think your urban figues might be a bit worse, because of the F22. It might be worth sucking it and seeing however, as if it aint broke dont fix it!

Using an 8P, don't feel the need for a different box, as I have 165/60/13s and enough power to keep me happy for the time being!

5th gear 2moro I hope :)

yeah I've never been a big fan of the gt box myself either. It's fine on a standard gt but as soon as you start modifying it becomes too short for day to day use. I have an 8p on the derby and most of the time it's fine. 4th is a bit long but once the 1.6 is in there it'll be reet.