mattholmes Posted February 7, 2009 Report Share Posted February 7, 2009 after some advice i have a 08 4 stroke that for some reason wont rev smoothly ticks over fine have drained the fuel and filled with fresh just in case of any contamination and also stripped and cleaned carb twice and still no luck as soon as you try throttle it coughs splutters and backfires any advice welcome Quote Link to comment Share on other sites More sharing options...
big john Posted February 7, 2009 Report Share Posted February 7, 2009 (edited) Try putting a new NGK CR7EB spark plug in, usually cures it! Big John Edited February 7, 2009 by Big John Quote Link to comment Share on other sites More sharing options...
mattholmes Posted February 7, 2009 Author Report Share Posted February 7, 2009 tried new plug it didnt make any difference also checked cap to make sure that was fine, bike was running fine for about 20min previous then went slowly down a fairly long bank just using engine braking taking it steady then the at the bottom when i started to throttle away the problem started ?????? Quote Link to comment Share on other sites More sharing options...
helloyes Posted February 7, 2009 Report Share Posted February 7, 2009 Mine used to do this try a 110 main jet and get a Jitsie idle screw (makes adjusting easy) Then adjust for best idle, i found if there was a big change in temp i need to ajust this. - Hope this helps I also added a twin air filter and cut some of the baffles out of the exhaust, it now revs and revs and is a total joy to ride ! Quote Link to comment Share on other sites More sharing options...
stork955 Posted February 7, 2009 Report Share Posted February 7, 2009 Gday, what colour was the spark plug that came out of it? ( Around the business end, on the centre electrode) Cheers, Stork Quote Link to comment Share on other sites More sharing options...
peterb Posted February 7, 2009 Report Share Posted February 7, 2009 Hello Matt, I don't know what type of carb is fitted but the problem does seem to be carb/fuel related. If you have a DellOrto with an accellerator pump attached (like the Scorpa 4T) then these carbs are prone to accumulating dirt in the pump area, which is basically a small diaphragm inside a housing on the LHS of the carb. Needs a complete strip and thorough clean out. If it is a Keihin carb, these must be run with an inline fuel filter as there is no filter fitted in the carb. If not the carb, then the problem is likely to be electrical though I have not heard of any problems with the 4T motor. Good luck, PeterB. Quote Link to comment Share on other sites More sharing options...
mattholmes Posted February 7, 2009 Author Report Share Posted February 7, 2009 the plug did seem very black and coked up Quote Link to comment Share on other sites More sharing options...
big john Posted February 7, 2009 Report Share Posted February 7, 2009 OK Matt, sorry, you didn't say on your first post that you had changed the spark plug for a brand new one. However, what position is your fuel tap in, it should be set so that the long plastic tip is pointing down as per the manual. I have heard of some who are riding the bike with the fuel tap set wrongly. Big John Quote Link to comment Share on other sites More sharing options...
rlracer Posted February 8, 2009 Report Share Posted February 8, 2009 As stated by helloyes the jitsie fuel screw is a must as far as helping to get to the fuel screw. Was there any water in the bottom of the bowl ? All passages clean ? Is there a tear or a pin hole in the top of the diaphram ? Maybe unhook the kill switch to see if it still does it. Just some things to look at. John were you thinking the fuel valve may not be opening all the way when the bike is started ? Quote Link to comment Share on other sites More sharing options...
mattholmes Posted February 8, 2009 Author Report Share Posted February 8, 2009 thanks for all the advice going to have a look monday night going to get a jitse screw ordered and check everything thats mentioned will keep you posted Quote Link to comment Share on other sites More sharing options...
helloyes Posted February 8, 2009 Report Share Posted February 8, 2009 Just remembered the vent pipe from the top of the carb has a rubber boot pushed over it. These perish so check this, its at the top on the right as you sit on the bike. Mine went as did my mates, i just made a nylon bung. The bike runs odd if this vents to atmosphere. Quote Link to comment Share on other sites More sharing options...
mattholmes Posted February 8, 2009 Author Report Share Posted February 8, 2009 cheers helloyes hopefully with all this info should be able to get it sorted will keep you posted Quote Link to comment Share on other sites More sharing options...
mattholmes Posted February 11, 2009 Author Report Share Posted February 11, 2009 problem sorted turned out to be either the stator or cdi both changed at same time to save re-building bike and stripping back down have to say both items changed under warrenty so just labour to pay cheers for all the advice though Quote Link to comment Share on other sites More sharing options...
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