grib Posted June 16, 2006 Report Share Posted June 16, 2006 I am trying to track down an inlet air leak on my 240 - the engine does not return to idle very quickly when it is revved, infact sometimes I have to engage the clutch a bit to bring the revs down. I have tried adjusting the mixture screw and I have replaced the RH crank seal, base gasket, & inlet manifold gasket but there is no change. does anyone have any ideas? could it be sucking air at the carb top or throttle cable? BTW it is a new carb. Quote Link to comment Share on other sites More sharing options...
dirtmudnroost Posted June 17, 2006 Report Share Posted June 17, 2006 This information was taken from the Dellorto Tuning Manual and sounds like you may want to look at the Idle Jet; PROPER SELECTION OF THE IDLE JET Generally, if the selected idle jet is too big, the engine may tend to stall and responds to the accelerator slowly with a deaf and feeble sound, usually overcome by closing the throttle temporarily. If, on the contrary, the jet is too small, the engine responds better to the accelerator (except when it stalls when the jet is much too small), but when the throttle is closed, the speed (rpm) doesn't decrease immediately, and the speed remains high for few seconds before settling down to idle. Installation of an idle jet that is too small on a two stroke engine can be dangerous since there is the risk of engine seizure during throttle closing, especially when the engine has run at wide open throttle for a long time. Under these conditions, when the throttle closes, the engine keeps on running at high speed and therefore if the idle circuit creates too lean a mixture, the thermal load due to the overly lean combustion presents the risk of damage the engine from overheating and subsequent seizure. Cheers Quote Link to comment Share on other sites More sharing options...
cleanorbust Posted June 17, 2006 Report Share Posted June 17, 2006 The rubber between the carb and the cylinder can become rotted on Fantics; given the age of the bike this is quite likely, and leads to an air leak. It is possible to repair using latex dip if you can find some, or a new rubber can possibly be obtained. Quote Link to comment Share on other sites More sharing options...
sdc Posted June 17, 2006 Report Share Posted June 17, 2006 I had this problem on my Fantic Quote Link to comment Share on other sites More sharing options...
westyfield Posted June 18, 2006 Report Share Posted June 18, 2006 OR, your slide is just very worn and letting air around it? Quote Link to comment Share on other sites More sharing options...
italjetfan Posted June 21, 2006 Report Share Posted June 21, 2006 Hello All! i had this problem a few weeks ago on my Italjet T350, and I was about to buy a new carb, but I remade every gasket, renewed every oil seal, and lapped all gasket faces in on a surface plate with wet and dry. I also changed the carb rubber, fitted new jubilee clips, and fortunately the high revs have vanished. It only seemed to do it when it got warm. I couldn't say which part of the above cured it, but it is now like riding a diferent bike! It starts first kick, and I can leave it ticking over all trial, saving my plastic kickstart shaft! Sounds like daft advice, but make sure there can be no possible air leaks before shelling out on hardware! Hope this helps, Tommo Quote Link to comment Share on other sites More sharing options...
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