As per title.. bike picks up fine and strong, get's to a good 4K and then just stop climbing. Checked the Kokusan I get a good spark and carburation is (only) a bit on the rich side. Any suggestions?
Check the carbs are opening all the way, actually look down the throat, don't just assume they're doing it from the outside. When does it stop reving? When you're riding? In all gears? Will it go above 4k in neutral? I'm assuming you've got a carbed rather than injected one?
Yep, carbs are opening all the way up. It stops revving under load, in all gears. And yes is a carbed. Hope this helps!
If it doesn't seem down on power at lower revs I'd look at the ignition coil, they can seem fine at idle or for a blockage in the fuel lines/carb/fuel filter.
You don't mention what engine size/year etc. I would be looking at two areas, firstly fuel filtre check flow to carbs or return back to tank whichever is easiest. Then ignition ignitors, these control the advance and they do fail so if you could borrow a pair to try for elimination purposes.
944, Hi comp, large valves heads, DP cams. Carbed with 185 main, 42.5 pilot, needle 5th groove from top. Carbs are brand new. Tried to swap the ignitors with good ones but problem still there. COuld well be a fuel delivery issue but when isolating in stages (filter,vacuum tap, pump) all seems fine. Is running a bit rich but nothing which fouls the plugs excessivelly. Thanks for the suggestions, keep 'em coming!
if the engine is holding back this consistently and running fine up to 4K (with no popping or banging?) then it does sound more like a fuel related problem. So no air breather problem/Fuel pump and filter ok - fuel lines not collapsing. I am guessing you are running Keihin FCR's. If you are using more fuel than standard I wonder if the two diaphragms plus filters are causing starvation. Not had it myself but I remember a similar problem was tracked down to the tiny filter installed on the inlet pipe (on Mikunis though) being full of sand/debris.
Hi Chris, still running Mikunis as I'm waiting for a set of 41's or Dell'Orto to come up at the right price. I know the filter you mean (in the T-piece) and that's free. Which diaphragms are you talking about? the carbs or the fuel pump?
well I was only guessing but thought you might still be running via the diaphragm pump (which should be ok) and also the secondary small diaphragm near the tank hinge that I believe replaces the on/off cock effectively as far Ducati are concerned. These two plus the filter(s) could start to back things up a little for a tuned engine - just a thought.
But I wouldn't have thought so, if the carbs are opening right up.......but they might be tired, though. Have these Mikunis got the air cut-off diaphragms on the side of the carbs? They can cause problems as well. AL
Have yu checked the cam timing? I have come across this one before on a renault 16V, cam timing out by one tooth ran lovely in the lower rpm range, but the cam sensor got confused and the signal to the CPS cut the ignition hence no high rpm running.
Did the lack of revs occur before or after you modified it, has it run properly in it's current state and all of a sudden you've had a problem without having done anything to the bike?
Carbs are fine, as said I've got a pair of brand new ones, so I'm confident on the. The vaccum tap is also a new item. The pump seems fine, there's enough pressure it seems but will split it just in case and check the diaphragm on it for tearings. cam timing is spot on to the tooth. Lack of revs only just appeared but bike hasn't been running well for a while now (don't expect to be running like a IE anyway..), this seems to be an acute fit she's throwing at the moment thought..
Are the float bowls filling correctly? Think I'd be doing some basic checks, plugs, caps leads etc. Then go through the fuel system from the tank to the carbs. Check the carbs over, and I mean strip them make sure the jets aren't blocked. Then check for air leaks on the intake manifolds (use wd40). Once you're happy with all the start on the ignition system. Oh, the belts are timed up right aren't they?
Cheers for the ideas guys. As said carbs are brand new, as are the jets, but I'll split them tomorrow and see. Will also try to isolate the fuel and spark stages and see from there. I'm just running out of time and ideas as I'm off to Italy on Thurday night..
