12 replies to this topic

[pepe]

hi guys

need help.

the car is juddddddddddering whilst driving!!! seams to accelerate ok, but when you cruise along it starts to judder. but to stop it i press the pedal on accelerate through it. also if it happens in 3rd gear i can floor it and it seams to go.

i'm running a 1275cc, hif 44, stage one, old style round filter K&N.


so is it to rich or to lean.

cheers pepe

[Big_Adam]

ooow. thats intresting. hmm...might not be the mix but to see if your mix is right. go for a drive and get the engine temp to normal. then in the haynes manual theres a section about tuning the carb. on mine theres a screw with a spring on the bottom left side of the carb (when viewed from above) push that up and the engine will either rev up meaning its rich or rev down meaning its lean then you adjust the mix,

or get the car rolling roaded.

edit.

if you just got the new air filter and stage 1 kit and never got it rolling roaded after then its probly running lean

[Grayedout]

That screw will only affect the mixture at idle !!!

The only way to get the runinng mixture right is a rolling road session !!

One quick check is to pull the choke out when it is 'juddering'. If this improves it then it's too lean and too rich if no difference or worse !

[Dan]

<<<sigh>>>

[Big_Adam]

That screw will only affect the mixture at idle !!!

The only way to get the runinng mixture right is a rolling road session !!

yes thats true. but when you don't have £30 then the screw works. made my El Gordo run alot better.

[Grayedout]

made my El Gordo run alot better

Then you were very lucky !!!!!

The cost of a rolling road session MUST be included when you budget for a stage 1 kit otherwise you will never get the best out of it !!!

[Wil_h]

That screw will only affect the mixture at idle !!!

This may be what the SIGH was for, but that's not strictly true (if atall in fact). What the screw should be used for is setting the mixture at idle before the needle is profiled for fuelling through the rev range (be that by filing or changing the needle).

[Big_Adam]

made my El Gordo run alot better

Then you were very lucky !!!!!

The cost of a rolling road session MUST be included when you budget for a stage 1 kit otherwise you will never get the best out of it !!!

so true. if your getting/got a stage 1 then you should include the price of a rolling road session. i changed my mixture after doing a few things to my El Gordo as it was running rich. i now have the mix juuust right for the way i drive. also how was i lucky. tuned my carb this way a few times. 1st time when well. 2nd time i messed it up a bit and 3rd time did it well again. i'm mearly reccomening a technique that i have used before. If Mr pepe has the £30 required then please by all means he should get his car correctly rolling roaded. if however Mr pepe or anyone else is like me and is known as SKINT then I've found that the tuning using the screw after warming the engine up works fine.

[Grayedout]

So how do you know what the mixture is like at say 3,000 rpm and 75 % throttle ???? Could be lean....could be rich......could be anywhere !!!!

If you look at the description of that screw I'm sure its titled 'IDLE mixture screw' !!!!

[Big_Adam]

hold on. what screw you on about. on a SU HS4 carb (the one i have) the idle mixture screw is completly. i'm on about the piston lifting pin (which i just figure out isn't a screw. oops) changing the idle speed won't do much.

anywho the HIf carb is completly diffrent to mine so my statment dosen't really matter as Mr Pepe will more than likely have to go to get it rolling roaded regardless. unless theres a trick to doing HIF carbs.

Also sorry Pepe for making this thread go very much off topic.

[Grayedout]

Three things then on a HS carb.......idle speed screw on the top.......idle mixture 'nut' directly underneath and then piston lifting pin underneath and to the left.

On a HIF the idle speed screw is in the same place.....idle mixture is on the left side and there is no lifting pin !

So if you are using the lifting pin then again you cannot use it check the mixture at anything but idle !!

[Wil_h]

If you look at the description of that screw I'm sure its titled 'IDLE mixture screw' !!!!

Correct, but adjusting it will affect the fuelling throughout the rev-range.

I'll repeat what I said before. "What the screw should be used for is setting the mixture at idle, before the needle is profiled for fuelling through the rev range (be that by filing or changing the needle)."

If you had the correct needle then all you would need to do is set the mixture at idle then the rest would be correct.

[Big_Adam]

aye Mr Grayedout, but it works for me. i was mearly suggesting a method of adjustment that has worked for me. might not work for eveyone but its worked for me fine till now.

setting the idel mix sets it for the rest of the range of the throttle. you set mixture at idel then it works fairly well for the rest of the range. thats what i've found thats why i recconed the method for people who have no money like myself.