6 replies to this topic

[WALLYROVERS]

hi first time on site. 

i had my carb refurbished few weeks ago its a su hs4 since i put it back on car not run well at all .

i can get it running roughly adjusted carb to peoples recommendations to no avail , if its sort of ticking over and i pull choke up with finger it will stop.

cheers

[bpirie1000]

Check the gasket is not leaking.

From what you describe about the choke it suggests the mixture may be wrong.

Who refurbished the carb. There are so many bits that need to be precisely adjusted for the carb to run properly and smooth. Setting needle, setting float, setting idle,etc...

Is the jet all clean and fluid able to flow through..
WHAT ARE THE SPARK PLUGS LIKE.

[WALLYROVERS]

new jet with rebuild  got new needle fitting kit yesterday fitted it  . just the same . carb was refurbished by reputable company came back looking new.

i have text him couple of time he gave me information how to get to a good starting point with tune .i have tried three needles AAA  AAC   AAU

plugs black sooty .got illumination electronic ignition .its been on seven years or more. new dizzy cap ht leads 

also new vacuum advance . old old not working.

 

 thanks

[68+86auto]

Stop changing the needles. Since you can't even get it to idle properly, it's NOT the needle.

Reset the settings as per the SU instructions.

Now it should run.

Check that the mixture is close to the factory specifications. Don't just mess with the adjustment until you think it's right. Follow the procedures. It is best if you have some way to read the mixture. For now just make sure it isn't way too lean or rich.

Now you need to adjust the timing. Just because you've had it like that before doesn't mean it's right. Especially since you have replaced the vacuum advance unit. The replacement vacuum units are the wrong length from what I've seen.

Only once the ignition system is perfect do you tune the carb. PERFECT, nothing else.

Once the ignition is perfect, adjust the idle mixture. Again, this needs to be done by test equipment or at least a tachometer and the rpm drop method as prescribed in the manual. People have a tendency to set it way too rich. For some reason even the MOT HC limit is way higher than a reasonable level.

Once the idle mixture is set, you can check it at higher rpms. The mixture adjustment above idle is by needle changing, NOT the jet adjustment.

Edited by 68+86auto, Today, 12:20 PM.

[bpirie1000]

Would also ask how old the fuel in the car is?

Edited by bpirie1000, Today, 01:27 PM.

[Chris1275gt]

I don’t know how experienced you are with the mini engine. I wasn’t at all and I couldn’t interpret the noises the engine made so purchased a Gunsen colour tune plug and easily set the mixture good enough for it to run apart from mot tweaks for the last 5 years. I’d put the original needle back in and clean the plugs and go from there. Once the you’ve set the mixture leave the nut alone and go from there.

[gazza82]

If you are killing it by adding a bit of choke and plugs are sooty it is far too rich.