Jets



  • I'm doing a big rebuild of the bike whilst its off the road waiting for the new head gasket and tyres to arrive. It hasn't been very good low end power. Opening up to WideOpenThrottle quickly will actually make it stall. Checking the jets shows I'm on 17.5 pilot and 210 main. I've heard a lot of people going as big as 240 main with the full dep system (which I have). My spark colour is good though ( autumn brown). Now I'm planning to open the airbox up a little so will get a bigger main jet just to stop in being to lean - but has anyone ever heard of a 17.5 as the pilot jet!? The Haynes manual says it should be 22.5! Why would someone have gone smaller?



  • 210 main? Your bike must be an early one or an early carb
    On later models the std main is 240 I think
    Also later dts have a 28mm carb early ones have 26mm
    Hope this helps



  • @yammad said in Jets:

    210 main? Your bike must be an early one or an early carb
    On later models the std main is 240 I think
    Also later dts have a 28mm carb early ones have 26mm
    Hope this helps

    Incorrect. The later DT's ran 210 main.

    If you are going to open up the air box then low end performance will suffer. But yeah up jet to suit.



  • Sorry I stand corrected
    Wouldn't want to mislead anyone
    There was a difference in carb size over the years wasn't there ? Or have I got my wires crossed ?
    I've worked on so many bikes over the years I get em muddled up



  • @Calum ah, OK. Thanks. So low end suffers if letting more air in?..... Why is that? My low end is already pretty bad but the last owner(s) has mullered the mixture screw... I've just spent 3 hours carefully drilling it out and ordered a new one for £10 so should be able to get that sorted a bit better. So my 2005 model should be on a 210... Maybe it should be on a 17.5 too. Not impressed with the Haynes manual - it claims to cover my later model but misses out loads of needed info and specs on it.



  • @yammad cheers mate. Easy mistake as there are so many models of this bike and they switched just about everything over the years!!!! No idea what carb I have - I know its a flat sided mikuni but isn't the one used on most of the dts



  • I think u were right to question a 17.5 I only have the manual that goes to 1991 and in there it's a 22.5
    Maybe somebody tried to correct a jetting issue and got it wrong 😉



  • 94-1999' models run 210 Main Jets with the TM28ss

    Later Models 99'-05' onwards - Main Jet 240. TM28ss

    Pilot should be a 25. for 99' onward models, but I think perfect for the earlier Pre 94-99'



  • @Darty thanks again guys. Ordered the right jets. Should run like a dream when I get it set up properly



  • DOH! didn't look at the back of the haynes manual (pg140) where they added later bike models. From 2004 onwards the main jet was 210 and pilot was 17.5 - so my bike was set up correctly! Problem now is my jet needle is a little bent and shows excessive wear on the bent side which means I need to replace my needle and needle jet ( 5j40 and q2m(939) ) but I can't find those anywhere on the web.