My '95 600 Monster has developed a problem, at the higher end of the RPM range (No rev counter so don't know when) it's started spluttering, almost like a misfire. It's a recent development and the only thing I've changed is the mixture which I have weakened from 5.5% to 3.5% CO at idle which is what Ducati say it should be, could it be leaning out too much up there in the rev range? Since adjusting the mixture it's been pulling much better in the midrange. I spose the thing to do is to richen it up a touch and see if the problem goes away.
Just to add that the "splutter" is below the maximum speed for the gear as stated in the handbook which I presume is correct!
JuZ, I'm not familiar with monsters but does sound a little like fuel starvation. Have you changed the fuel filter recently?
+1 my first thought, but if its only started since changing the mixture it wouldn't hurt to change back and see. Steve
Fuel filter has done about 400 miles, do an anti raindance for me so I can try altering the mixture tomorrow. The problem didn't occur until the engine was hot, for the first 20 miles it was fine, then overtaking a caravanette was the first occasion. On a side note, I presume such an old Monster does have a rev limiter?
Might also be worth mentioning the K&N filter and open exhaust I've got fitted which also makes me think it's leaning out with the extra airflow.
Juz, spluttering at high revs can be a sign of plug or HT issues, particularly if you are running the mixture at what would seem to be closer to optimum. I had similar issues with a jap IL4 which started missing at the same rpm under load which turned out to be a set of champion plugs. Check your plugs for colour and gap and have a look at your caps and HT leads and make sure the caps are seated correctly. Try swapping both plugs for old ones which worked ok to see if the problem persists - if it does that is one possible eliminated at least
how have you changed the mixture Juz - moved the clip a notch on the needle or different ones altogether or different main jets? As said, Fuel filter, diaphragm pump function or even tank breather do come to mind when you mention top end splutter.
that's what I was guessing at, so you can virtually rule out this being the cause of spluttering etc as although overlap reaches into midrange there is very little effect on the top end.
You've answered your own question here... I'd set it back to 5.5%, not only did it run better but 3.5% is too lean IMO. Don't know about M600 but my 916 'needs' 4%+ to run smoothly, too low and it will backfire particularly at idle - recommended is 4-5%. Plus although it runs 3.5% at idle it may be well different at higher speeds. Carbs may also be worn - would benefit from overhaul & setup.
I think I've probably answered my own question too, but thought I'd put it out there for other peoples opinions, incidentally the carbs were fully stripped and cleaned about 400 miles ago the same time as the fuel filter was renewed, since then it's been on a digital oscilloscope and carbs balanced.
take bike and get it set up properly on a dyno 10 mins on dyno will diagnose problems properly that will take weeks of hit and miss playing around with otherwise have carbs been dyno jetted ??? if not its a worthwhile improvement
Just an update on this. The splutteryness at high RPM didn't really come back but I had continued starting trouble with lots of popping and farting about for the first couple of miles. Friday I pretty much had the day off and did enough miles to drain the tank, I visited a Shell station and for the first time treated the old girl to some V-Power, did just 7 miles home from the filling station but it felt perkier. First cold start was this afternoon followed by a nice ride out for about 70 miles, no problem starting, no spluttering. I can only conclude that I picked up a tank of dodgy fuel.
