Another Carb issue

[bombhead]

Just another carb issue. If the bike is running rich (i.e backfiring, too much fuel going into the cylinder) then what would make it leaner.......turning the a/f screw inwards or outwards.

Regards

Darren
 

[Thief400]

OK Rob hold my  My tongue before I let Lose
Ok son here's the skinny, a rich engine WILL NEVER back fire on acceleration. It may pop and fart in the muffler on deceleration.
ONLY a lean mixture WILL back fire.
I know I going to get flack for saying this but someone has too
If you don't know what your doing with or know anything about carburetors don't F%@K with them. You stand a better chance of screwing them up than you do of ever fixing them.

Just my 2 cents worth and over 25 year of fixing other peoples F%@k ups

[Zhi]

Here's a helpful link for ya.
http://factorypro.com/tech/carbtune,CV,high_rpm_engines.html

2 and 1 half turns out from closed is a good starting point for the mixture screws, but if they weren't fiddled with before the problem started, I suspect that your problem probably lies elsewhere.

[bombhead]

Well that's how you earn your money by fixing other peoples f&ck up's !!
Besides we've all gotta start somewhere !!
Thanks for the advice.......anymore handy tips on carb settings would be useful as I can't afford to take it to a shop so near to Xmas !!!!!!!

 

[gsxr400 racer]

easy way to tell if its rich pull the air filter out does it rev up better? then its rich!

[bombhead]

Well at present it's not even getting to that stage. It's backfiring from the exhaust when it tries to start. Pulling the carbs out shows that there's more fuel entering the 1st cylinder than the 4th. The 4th cylinder is virtually bone dry. I've set the A/F screw back to the old settings (which were between 1 and 1.5 on the bank) but no difference !!!

 

[gsxr400 racer]

change the dang plugs and start over

[bombhead]

Dang splugs ?????
What are they ?
I've put a fresh set of spark plugs in (Iridium ones !!!) and they're getting a healthy spark

 

[interfuse]

I had zero carb experience when I got this bike and I've managed to get it running really nice. So it is possible.

BUT I've tried over countless different carb combinations that have sucked up loads of my time.

Right now I'm running 110 mains, middle clip, 2.5 turns out, and 15mm float height. But that's with a jet kit, aftermarket exhaust and moddified airbox.

It's best to start with stock settings and tweak from there. Doing one change at a time and recording the difference that it made. Getting it right can take some serious time... and alot of patience!

[jcmjrt]

Getting it right can take some serious time... and alot of patience!

...or a knowledgable person and a dyno will do the trick...

[interfuse]

Getting it right can take some serious time... and alot of patience!

...or a knowledgable person and a dyno will do the trick...

That's by far the easiest and fastest way to get it setup. And if your time is valuable then its probably also the cheapest.  

[Herr Tod]

Sidenote; did you know our B4's use (about) 17.5 liters of fuel per hour if we would run at 12000 RPM constantly? The fuelcock can handle this. I'm soon going to check if the floats can also handle this.

[TheKillerB]

Did you get the plug wires back in the correct order?  I accidentally switched two plug wires once when I was rushing to get my bike back together and it did exactly what you are describing.