3 replies to this topic

[KLMOC]

Hello I have always worked with injection in the 5 years being on the mini scene. My family member has just bought a 998 carb mini and I am pretty sure its running to rich as it runs ok and starts ok on choke etc. But while running and revving it has a little black smoke and has a distinct misifre quite a bit. I am guessing it running SU HS4 but thats all i know.

It has stood for two years and only been started at idle and on and off the trailer so not sure if it needs a good run

I was going to borrow a colour tune kit and see what the results come up with. If it is rich. How do i adjust the mixture?
I have heard the mixture adjustment is underneath? a type of thread and nut. which way do i screw it up or down for leaning? until i get a nice bunsen burner blue from the colour tune.

Edited by KLMOC, 25 April 2013 - 11:28 AM.

[cal844]

yes its a brass coloured nut. its located inside the spring on the bottom of the piston. you could take the carb off the engine and give it a rebuild. (kits are available)

[iwatkins]

Could probably do with a good run with fresh fuel to decoke it before you try tuning it.

If it is a HS4, it is the nut under the spring under the carb. Looking from above, turning the nut clockwise will richen the mixture, anticlockwise will weaken it.

Also check the dash pot has oil in it as that's often a cause of misfires under load.

Cheers

Ian

Edited by iwatkins, 25 April 2013 - 07:18 PM.

[KernowCooper]

If its been standing a long time then before adjusting the mixture check the needle valve and the float level while its apart as both those could be causing a rich mixture.