I had my '02 F4s' valves adjusted a few weeks ago during a service. The bike is much more responsive and feels noticeable more powerful and crisp.

However, it seems prone to occasionally have small backfires when closing the throttle and letting the rpm drop down. It's not very loud, but sort of like those "quite" farts. :) Is this normal?

-- Allan Gibbs (Phoenix, Arizona) (Agibbs996@aol.com), September 20, 2002

Answers

Mine do the same, this has to do with the fuel injection set up: too rich when you shut off, and the gas burn in the exhaust pipe.

This also happen when you re-jet carb for racing.

Nothing to worry about.

But I don't beleive this is approved by DOT and EPA in the US. ( I am in the US) Probably the first bike in the US were set lean to meet the standards, at the cost of few horses, then they must have shipped bike with the better mapping to get the power???

-- o (okthomas@tir.com), September 20, 2002.

I experienced a little of this when I had my CRC open pipes installed. It also idled roughly. Some minor tweaking of the programmable chip had the bike running smooth as stock.

-- Chris Eden (biospeck@mindspring.com), September 21, 2002.

F.I. SYSTEMS ARE PROGRAMED TO SHUT OFF FUEL AT CLOSE THROTTLE FOR ONLY A FEW SECONDS AND THEN INJECTS FUEL TO KEEP CYLS. COOL ,SO THE UNBURNED FUEL IS LOOKING FOR OXIGEN . THE MORE OPEN THE EXHAUST THE SOONER IT LIGHTS UP . BIG BEAR DAVE FERRARI TECH.

-- BIGBEAR DAVE (BIGBEARDV@CS.COM), September 22, 2002.

Figured I'd resurrect this old thread.

I had some really big backfires at the track. I wish someone would have told me if fire was coming out of the exhaust. I would brake for this one corner right when the bike was hitting the limiter in 3rd. Then I would chop the throttle, blip it as I downshift to second and then I would be on the brakes for a few seconds. As I rolled back on for the apex, I would get a backfire big enough so that I could feel a bump through the seat. I'm sure it was entertaining for the people behind me!

I got passed by a GSX-R 1000 that had lots of fire coming out the exhaust on downshifts too. Must be an injection thing.

-- Andy Ruhl (quadreverb@yahoo.com), November 09, 2002.

It's been about two months since the service, the good news is that I'm not getting any backfires. The bad news (well not really) is the bike's feeling more like it did before the check up.

I'm not complaining, since the bike is holding up pretty well and running even better now that the weather's in the 70s. Sounds like the MV likes the colder weather. I know I do. :)

-- Allan Gibbs (Phoenix, Arizona) (agibbs996@aol.com), November 10, 2002.