Hi guys, Happy new year and all that. Hope everyone in the southern hemisphere is out, enjoying this awesome weather. So as the title suggests, I am having trouble starting the bike when it's hot. It starts fine from cold (haven't had any problems with that since I did a once over on the head last year). So anyway, the bike gets to normal operating temp or just over and then I turn it off when I've finished my ride. Then when I go to start it again (while still warm) it stutters and will idle about 100 RPM at half throttle, anything below half throttle and it just dies. It sounds like it's overfuelling in a big way. I had a pretty big backfire after trying to start it today at the top of the Port Hills and then just push starting it. Any ideas guys? Cheers, Hagen
could be leaky needle and seats in the carb, or maybe the pressure relief in the tank causing the carbs to flood. To give you an idea for about half an hour after i ride i can hear the pressure venting from the tank as the vapour is heated by the cooling engine. Perhaps try releasing the fuel cap and leaving it open after a ride and see if the problem persists.
Try turning off the fuel tap just before you stop the engine and see if that makes any difference. Don't forget to turn it back on when you restart...
Thanks guys, I knew someone would have some good suggestions. I will try them out when the weather is back to being nice here. It could well be the tank not venting properly and forcing fuel in because it makes some weird breathing noises after I switch it off until it cools down. I think the vent hose is pretty old and full of crap so maybe I will replace that. But as it is, I have no problem opening the tank lid every time I stop. Might look a bit weird but I'm sure it won't be as bad as having to push my bike down the hill to get it going again. I hope it's not the carbs. I spent about $500 getting second hand ones and getting the shop to tune them up.
As much as its unlikeley my fzr had a similar problem and it turned out to be spark plugs and leads. if all else fails give it a go.
Mine used to do it (not sure now) and I worked out that it cleaned up easier if you held the throttle so it was only just open.
Yea it eventually goes if you give it half throttle then slowly release the throttle til it almost dies then go back up to about half throttle and around again. But the low revs etc do not sound very good so I'm not a huge fan of doing it. I'm thinking it could be something as it is feeling kind of flat after 10k RPM and I could only manage 180kph the other day instead of 195-200. Not on public roads obviously. I'm going to have to wait til I shift to do open her up or anything. I will try plugs, leads and maybe even take the dreaded carbs apart. Cheers guys.
mine had the same problem, quite often it would die at a set of lights idling whilst hot.. often it would do the same thing .. Start > stutter @ low rpm > touch throttle = Dead. I used to leave it stuttering for a few minutes till the RPM's picked up (usually when it picks up i choke it) and runs beautiful afterwards =/ seem's to be a common issue.
It only appears to be a problem in the 3LN which has different, more aggressive, cam settings and different carbs. I am theorising that it could be a problem combination of cam timing, valve adjustment, exup adjustment, exhaust temperature and muffler mods. All these things modify engine airflow, and with the engine and exhaust temperature at a certain point, an unwanted resonance may cause a problem.. Remember that these engines have a huge overlap of time when the inlet and exhaust valves are both open. Great for high RPM airflow. When conditions are just right (or wrong), opening the throttle butterflies gives no extra airflow or vacuum to open the vacuum slides and perhaps an unwanted return pulse of air pressure is entering the combustion chamber from the exhaust system. Good theory but not easy to prove and I could also be totally wrong. <!-- s:-? --><img src="{SMILIES_PATH}/icon_Eyecrazy.gif" alt=":-?" title="Eye Crazy" /><!-- s:-? --> Hopefully someone can play with this and prove me right or wrong, I would certainly like to know..
