I have a 250 txt racing 2012 model and seems to have a knocking detonation noise when I blip the throttle!!! Please help me try and sort this problem bike starts first time and runs fine every time just this noise is driving me mad!! It defiantly isn't a top or bottom end noise!

are you using fresh high octane fuel

witch carb have you got on

Use a higher octane fuel:)

Could be a lean knock from either poor fuel quality or lack of fuel caused by incorrect float level height.

How is your carb set up? jetting etc...

The easiest thing to check aside from new gas is to check the fuel screw (Assuming Dellorto PHBL) setting is rich enough. Too lean and this can cause a knock on the "backside" of the blip - but will usually happen under load like at the top of a hill climb when you chop the throttle. If this is a new noise, then change the gas and clean the carb if that doesnt work.

Like the others say - partially clogged jets, Octane, incorrect Jetting, Float height, Carbon buildup, and poor fuel flow can all cause this. Hard to accurately diagnose w/o hearing it. GG's do like there Octane though.

Add may go up on the pilot jet!

Try a 50 pilot jet 122 main, jjh needle on fourth groove in and a mess with the air screw after that. Seems to be cock on

Sorry this is for the Keihin Carb not sure what you have

I had the same on my 300 I changed my fuel/oil mixture slightly and it sorted it. Maybe the same easy fix for you. ???

Sorry for the late reply!! It has got a khien carb on it!! I have lifted the needle up a setting and still hasn't changed!! Also I'm using rock oil in the bike I have changed to putoline to try that and still makes the noise!! I think next step is to take the carb off and see if the jets are clean. How far out should the air screw be (how many turns)? I havent touched this yet but think its one of the nests steps I do us normal fuel not high octane so I shall also have to change the fuel is there anything else it could be?

Thanks to everyone that sent a reply.

Best setting for air screw will depend on what pilot jet you use. Usually ends up between one and two full turns out. Change one thing at a time but carb clean is first thing to do. Tiny bit of water can stop jets working.

You could have an Air leak...

I know blown seal in crankcase, behind flywheel can cause this, getting air from sources other than carb... my 08 raga had gasket leak at base of cylinder head... so check things out, definitely sounds lean condition to me.

IF you bought from higher altitude, you MUST re-jet, takes more air in higher altitude to make the bike run very well at all, compared to low country. Low country bike will starve for AIR (choked) in Higher altitudes, which isn't so much a threat to the engine...

Example, I bought a 2001 321 from above 5500ft elevation (denver), to where I live in the 1000ft, running denver (above 5000 ft altitude) jets turned the chromed head pipe blue right at the head for about 5 inches, in less than 10 minutes, and IMHO would burn a piston rather quick in KS (near 1000 ft) FYI...

I almost posted this earlier, and thought "Naw, It wouldn't be that.....".....

My bike had a rattle that would increase in frequency as the revs would go up, and I was certain it was piston slap. Seemed hard to accept though, since the bike was only 2+ yrs. old at the time. In the process of checking stuff out, I discovered the bolt was loose that holds the fuel tank on, and that was my "Death Rattle" I was hearing. I love it when merely tightening a bolt fixes a problem I'd thought was going to be much more complicate & expensive to fix. Be nice if something like that was the source of your noise, Blacky66.

Jimmie

Well,

After reading your own story, I have to just laugh and Consider the source, Neutron, lol.

Anywho, when I hear a person say/type "detonation..." Well, a dumbass like me assumes he's smart enough to know that word and what it means, and it affects my troubleshooting thoughts, as I have assumed he's ruled other things like that, out... And, since I cannot see/hear the bike. So YEP. it Damn well could just be a rattle, hell I have seen the chain on a few bike so loose and old and dry, that even it rattles enough to be scary, on a neglected bike or dozens actually.

I mean I take my car to a mechanic, I don't use words like "detonation" I say knocking or rattling, or something generic, so they (paid mechanics) don't jump to "HIGH DOLLAR" solutions only, lol. one time it was just a loose bolt on the motor mount, go figure?