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n/a
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60 Posts

Posted - 20 Jul 2011 :  23:13:25 Show Profile Reply with Quote
All the problems I'm suffering from. Ordering some more idle jets and modify the vacuum pipes to clear the choke.

I also think there is an leak on the jetex system as I'm getting the usual popping on overrun. But fix one thing at a time.

Good pics to work from, must get myself organised and post some photos.
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pchristy
V4 Guru

United Kingdom
1737 Posts

Posted - 25 Jul 2011 :  12:30:33 Show Profile Reply with Quote
The 60 jet arrived on Friday, and was fitted over the week-end. The idle needle is now 1 3/4 turns open, the tickover is perfect, and the slight hiccups have gone!

Reading up on Weber carbs, it appears that the idle jet actually controls much more than just the idle mixture - it is the dominant mixture control until the barrel is about half open. This means that although you can get the tickover mixture correct by adjusting the idle needle valve, the part throttle mixture will still be wrong!

The "Rule of Thumb" is that the idle needle should be between 1 1/2 and 2 turns open. If it is more than this (mine was 3!) you need a richer jet - if its less than this, you need a leaner jet. Based on my experience I would "guesstimate" that each 1/2 turn corresponds to 0.05 on the jet.

Just filled it up again today, and its turning in 34 mpg - mostly urban motoring!



--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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john-saab
Administrator

United Kingdom
2650 Posts

Posted - 25 Jul 2011 :  12:35:02 Show Profile Reply with Quote
That's amazing timing..i was about to order a jet and thought "I wonder how Peter is getting on with his"..i turn up here to find that you posted this 5 mins ago..straaange!
Peter..do you have a part number as FRC offer 2 different style of jet.

current V4 models..'72 95 (The Flying Banana),'72 96 (Bridget),'74 95 (Veronica),'74 96 (The Brown one)NOW SOLD..destined for greater things

Edited by - john-saab on 25 Jul 2011 12:35:47
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thesaabologist
V4 Fanatic

318 Posts

Posted - 25 Jul 2011 :  17:40:45 Show Profile Reply with Quote
congrats - its sweet when these run right.

I'm running the following in my 1700:

Main jet 165
Idle jet 40
Emulsion tube F6
Air corrector 190

So called "Ashcraft" set-up. Seems to work with approx 2 turns on the idle.

---------------
1974 Sonett III
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pchristy
V4 Guru

United Kingdom
1737 Posts

Posted - 25 Jul 2011 :  18:08:49 Show Profile Reply with Quote
No part number, I'm afraid! No-one seems to list 34ICH jets specifically, but they seem to be common to some other Webers. I rang FRC and told him specifically what I wanted, and he told me he had them in stock. So I gave him my card number, and that was that!

My jets are now all as Genty's recommendations, except for the idle jet, which is richer. I'm not sure about the emulsion tube, as I couldn't find any numbers on it! But I believe the carb came off a SAAB many years ago.

I'm suprised that the Ashcraft set-up only has a 40 idle jet - mine was unhappy on a 50! But as long as the idle needle is in the 1.5 to 2 turn region, it must be right!



--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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john-saab
Administrator

United Kingdom
2650 Posts

Posted - 25 Jul 2011 :  19:43:13 Show Profile Reply with Quote
Totally agree Peter..my idle needle was almost hanging out with the 50 jet, I couldn't get the balance between a low idle and smooth low down acceleration..i had a 55 in my spare carb and that's 1/2 way out..that helps with a steady idle but i still have a hiccup when the revs drop towards idle..I sent FRC an email referring your recent buy so hopefully Anthony will know what he sent you.
I have a long drive at the weekend so hopefully it will be here by then.


current V4 models..'72 95 (The Flying Banana),'72 96 (Bridget),'74 95 (Veronica),'74 96 (The Brown one)NOW SOLD..destined for greater things
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pchristy
V4 Guru

United Kingdom
1737 Posts

Posted - 25 Jul 2011 :  19:51:47 Show Profile Reply with Quote
quote:
Originally posted by john-saab
Totally agree Peter..my idle needle was almost hanging out with the 50 jet.....


Hmm! Mine wasn't that far out - 3 turns, in fact! Are you sure you don't have an air leak somewhere? Might be worth checking the crankcase ventilation valve. These do get very cruddy, and if its not shutting at high vacuum, it will make the mixture in the manifold very lean.

I invested in a small ultra-sonic cleaner from Maplins, and gave my valve a very thorough cleaning whilst I was re-fitting things. The amount of grot that came out of it was truly amazing!

As a side benefit, I can now also clean the missus jewellery, which is keeping her sweet as well!





--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"

Edited by - pchristy on 25 Jul 2011 19:53:24
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thesaabologist
V4 Fanatic

318 Posts

Posted - 26 Jul 2011 :  09:59:12 Show Profile Reply with Quote
Great thread.

I need to get a tacho on mine (who knows what the dash rev counter is reading)- I think its idling ok around 900-1000 revs (based on the last time I tacho'ed it).

The low speed running could be smoother - especially when hot. I sorted some of the idle/low speed issues by advancing the timing.

I might go up an idle jet size and see what happens (tempting fate however - took me 6 months to get it to run with the current level of smoothness).


---------------
1974 Sonett III
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pchristy
V4 Guru

United Kingdom
1737 Posts

Posted - 26 Jul 2011 :  13:18:45 Show Profile Reply with Quote
My experience with car instruments is that they are often more accurate than we might expect! Certainly the speedos in my current cars are almost spot on (comparing with the SatNav, which has to be accurate!) whereas my modern car, which I've just disposed of, was about 5 mph optimistic at 70. And the cheap dashtop tacho in my 96 was spot on when I checked its calibration - something I wasn't expecting!



--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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n/a
deleted

60 Posts

Posted - 26 Jul 2011 :  18:42:18 Show Profile Reply with Quote
The idle jet part no. is 74409.060
Mine arrived next day, from FRC.

I needed a magnifing glass and a bright light to fine the emulsion tube no., it should be there somewhere.

Still not fitted, maybe later this week. TOO many other jobs.
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frank
V4 Fan

United Kingdom
147 Posts

Posted - 28 Jul 2011 :  21:28:33 Show Profile Reply with Quote
Hi i need to get a 60 idle jet for my Weber 34ich, could you tell me where i can purchase one? ( FRC ? )
thank you.
Frank
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pchristy
V4 Guru

United Kingdom
1737 Posts

Posted - 28 Jul 2011 :  23:36:44 Show Profile Reply with Quote
FastRoadCars! 01495 237456

They don't list the 34ich specifically on their website, but I've always found Anthony (the boss!) very helpful when I've rung. And they are VERY quick!



--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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frank
V4 Fan

United Kingdom
147 Posts

Posted - 29 Jul 2011 :  09:40:50 Show Profile Reply with Quote
Hi,
Ordered a 60 jet today.
Thanks
Frank
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john-saab
Administrator

United Kingdom
2650 Posts

Posted - 29 Jul 2011 :  11:59:59 Show Profile Reply with Quote
size 60 jet fitted and the idle is perfect..no choke on start and steady tick over..the adjusting screw now sits at 1 1/2 turns..exactly where it should be...a quick blast around the block to bring her up to temperature and she idled perfectly after an emergency stop..no stalling. I upped the revs to 900 and have advanced the dizzy a tiny bit..yet again I had to adjust the points so they are coming out and i'm going to give the electronic points a go.

current V4 models..'72 95 (The Flying Banana),'72 96 (Bridget),'74 95 (Veronica),'74 96 (The Brown one)NOW SOLD..destined for greater things
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john-saab
Administrator

United Kingdom
2650 Posts

Posted - 29 Jul 2011 :  12:04:21 Show Profile Reply with Quote
quote:
Originally posted by pchristy

I'm suprised that the Ashcraft set-up only has a 40 idle jet - mine was unhappy on a 50! But as long as the idle needle is in the 1.5 to 2 turn region, it must be right!


I wonder how long ago that was done?..fuel has changed a lot over the years so it might have been fine for 4star or U.S fuel but unleaded is a different bag of fish!

current V4 models..'72 95 (The Flying Banana),'72 96 (Bridget),'74 95 (Veronica),'74 96 (The Brown one)NOW SOLD..destined for greater things
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