serious3 Posted January 7, 2010 Report Share Posted January 7, 2010 i seem to have a misfire but it only does it in 2nd gear... it will pull hard till about 1/2 throttle then just splutter and not clear if i change up it pulls like a steam train any ideas where i start looking? the carb is spotless clean and the fuel is fresh, the airmix screw is 2 1/4 turns out( like this when i got it a month ago) was thinking of going in a half turn?? Quote Link to comment Share on other sites More sharing options...
tt5th Posted January 7, 2010 Report Share Posted January 7, 2010 What year is the bike? On the 315's up to 2000 the carb air screw should be 1 turn out. With those symptoms and a clean carb I would change the spark plug. Good luck. Quote Link to comment Share on other sites More sharing options...
serious3 Posted January 7, 2010 Author Report Share Posted January 7, 2010 its a 1998 model. carb air screw? thats the one the airbox side of the tickover screw/adjuster thing? that one on mine is 2 1/4 turns out Quote Link to comment Share on other sites More sharing options...
chewy Posted January 7, 2010 Report Share Posted January 7, 2010 (edited) got to be worth trying new plug, & checking out HT connections (it could be vibration affecting spark). We all assume everything else is clean .air filter.. is it better with hot engine ..cold engine ..is it just in present climate...i.e F cold? Edited January 7, 2010 by chewy Quote Link to comment Share on other sites More sharing options...
stork955 Posted January 7, 2010 Report Share Posted January 7, 2010 Gday, yep - what Chewy said. Higher speed misfires are usually electrical but dont rule out filthy air cleaners. The mixture screw will only affect the bike at idle and just off idle. Above half throttle and the carb is only using the main jet and needle. However a fouled plug (which can cause a misfire like this) is usually caused by mixture issues. Make sure the plug, plug cap and lead and coil connections are all good first. Cheers, Stork. Quote Link to comment Share on other sites More sharing options...
serious3 Posted January 7, 2010 Author Report Share Posted January 7, 2010 good replies and keep them coming! plug appears new but i'll change it anyway. but why does it only do it in 2nd gear from about 1/3rd throttle?? Quote Link to comment Share on other sites More sharing options...
stork955 Posted January 8, 2010 Report Share Posted January 8, 2010 Gday, higher engine load than first probably. Check the high tension side next (plug cap etc.) Cheers, Stork Quote Link to comment Share on other sites More sharing options...
serious3 Posted January 9, 2010 Author Report Share Posted January 9, 2010 (edited) right then. i went out and warmed the bike for about 15 mins and went and re set the air/mixture screw to the manual i.e. 1 turn out. it started alright but wouldnt rev in any gear just massive mis-fire and would only just tick over if the tick over screw was wound in hard.went back to the 2 1/4 turns and it worked ok and had to wind out the tick over to stop it racing. hmmmm what happens if i go another half turn out???? wonders me! result nice even tickover and pulls from rest in 2nd gear and revs out cleanly!!!! dunno what the half turn did but it seems to work perfect now. the manual says to adjust this screw till the bike revs up smoothly and adjust the throttle stop?? Edited January 9, 2010 by serious3 Quote Link to comment Share on other sites More sharing options...
john_doe Posted January 9, 2010 Report Share Posted January 9, 2010 right then. i went out and warmed the bike for about 15 mins and went and re set the air/mixture screw to the manual i.e. 1 turn out. it started alright but wouldnt rev in any gear just massive mis-fire and would only just tick over if the tick over screw was wound in hard.went back to the 2 1/4 turns and it worked ok and had to wind out the tick over to stop it racing. hmmmm what happens if i go another half turn out???? wonders me! result nice even tickover and pulls from rest in 2nd gear and revs out cleanly!!!! dunno what the half turn did but it seems to work perfect now.the manual says to adjust this screw till the bike revs up smoothly and adjust the throttle stop?? Have you got the later model carb on it? That might explain why it runs better with the air screw 3-4 turns out. Quote Link to comment Share on other sites More sharing options...
serious3 Posted January 9, 2010 Author Report Share Posted January 9, 2010 (edited) i couldnt tell you if its late or early!! only had the bike 6/8weeks and still learning all its little foibles. on mine, which is a 98, the airmix screw is on the airbox side as you look at it and in the picture in the 2002 manual i have the airscrew is on the engine side. although something just occcured to me in the fact that the instructions i quoted above were from the 02 manual and i have an 98 bike........... Edited January 9, 2010 by serious3 Quote Link to comment Share on other sites More sharing options...
stork955 Posted January 9, 2010 Report Share Posted January 9, 2010 Gday, pull the spark plug out and have a look. What colour is it around the tip? And what are the numbers on the spark plug? It seems you have some strange things happening there. The mixture screw does not affect anything much above idle, however it can give clues. Cheers, Stork Quote Link to comment Share on other sites More sharing options...
serious3 Posted January 9, 2010 Author Report Share Posted January 9, 2010 plug is an NGKBR6ES and is new it looked perfect a week or so ago a nice light tan colour not oily at all. its strange alright! thing is if i set the air screw to one turn out it runs like the choke is on all the time in all the gears, if i wind it out 3 turns it runs perfect and revs cleanly. thing is its done about 6 trips 3/4hrs at a time with the air screw 2 1/3rd turns out it was just missing in 2nd gear but it never got hot,pinked,knocked nothing. all i've done is go another 1/2 turn which has cleaned up 2nd gear. going out tommorow for a run so i'll check the plug when i get back. Quote Link to comment Share on other sites More sharing options...
tt5th Posted January 9, 2010 Report Share Posted January 9, 2010 I need to check my manual more! Sorry my bad, i got my carb settings the wrong way round. Can't remember what the setting for the earlier carb is exactly but 2 to 3 turns sounds about right. Apologies for the leading you up the proverbial garden path! Quote Link to comment Share on other sites More sharing options...
stork955 Posted January 9, 2010 Report Share Posted January 9, 2010 Ok, if the plug looks good maybe it is as simple as a mixture screw adjustment - it can make the bike hard to get through the transition between idle circuit and needle. That may well be what you are experiencing, lets hope so eh! Cheers, Stork Quote Link to comment Share on other sites More sharing options...
serious3 Posted January 10, 2010 Author Report Share Posted January 10, 2010 just about to go off for the day so i'll post later and let you know how i get on. thanks for the replies and heres hoping i dont blow something!! Quote Link to comment Share on other sites More sharing options...
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