BikeBoy.org - 996 Strada Eproms 3: Ultimap UM222 eprom and valve clearances

996 Strada Eproms 3: Ultimap UM222 eprom and valve clearances - Written 05/08

Summary: A little more discussion on 996 eproms and the Ultimap UM222 eprom based on some recent info and questions that get asked.

The Ultimap “996 single injector” UM222 eprom has a deservedly rather good reputation, and it’s the only eprom we run in the 996. Our 996 with modified cam timing eproms are all based on the UM222. Many people who fit them make claims of the eprom fixing lots of running problems they’re having, but in our experience, the only real thing the single injector per cylinder UM222 should fix over a dual injector UM191 or UM221 or any other dual injector eprom is the roll on misfire at 3,500 RPM. Any other benefits I’d put down to bad baseline set up with the previous eprom personally. Our 996 bikes ran great with the other eproms when set up right, apart from the roll on misfire.

The 996 Strada 3,500 RPM misfire is a very unique and wacky thing. On a bike that does it, it is a totally repeatable phenomenon. You cruise along at 3,500 RPM and whack the throttle open. The bike goes duh – duh - duh – duh - duh – duh - duh and then takes off. It’s very specific – they don’t do it at 3,000 RPM or 4,000 RPM or any other RPM.

It only happens on bikes with Strada cams – none of the 996S (Euro spec, SPS cams) bikes ever did it, and it happens regardless of cam timing. Neither of the factory single injector per cylinder 996 models (ST4S and S4R) do it either, although they did have different inlet cams. It’s one of those things you need to experience to appreciate, and I think a lot of people who haven’t experienced it really don’t understand how wacky it is, they just think it’s some sort of surge or the like.

A side issue that contributed to the frequency of the misfire is the gearing of the 996. With the new 1.84 primary drive ratio and 15/36 gearing, 3,500 RPM was right around highway cruising speed for those who live with 100km/h or 60mph open road speed limits. So people rolling on from highway cruise speeds would be stuck in the middle of it. Change the gearing and you’d also help reduce the problem.

I was talking to Pete Smith at Epicycle a while ago about something or another and we got onto soft rocker closing springs and effects on idling which led on to ST3 and some minor (and odd) running issues that the heavy closing springs fixed at specific RPM and how that related to experience I’d had with my 851 and how on the early 851 it was very valve clearance influenced and Pete said that he’d been able to get rid of the 996 roll on misfire by pulling down the exhaust closing clearances to around 0.05mm, regardless of eprom.

This on reflection correlated with what a customer of ours had said previously, which I hadn’t been able to make sense of. He’d had his heads done elsewhere before the UM222 was released and the head work fixed the misfire for a short time. But then it came back. His bike got one of the first UM222 we fitted, and his feedback after we fitted it was that it ran very nicely in general, and maybe a little better than it had with the UM191 previously fitted. And that the misfire was gone – which was the whole aim of fitting it.

Pete also commented that you know when the clearances have opened up because they start misfiring again. Flip the collets over, new collets or a shim change and they stop. Simple as that.

It’s also worth remembering here that the Ducati specified valve clearances were opened up quite a bit in ’97 or so and that 0.05mm is tighter than the 996 manual recommends, whereas 0.05mm was specified in the 851 and 888 manuals. I queried the later specs when they were released and was told “that’s what they say to do” so that’s what we sort of did (we ran them on the tight side of the late specs, still bigger than before though).

So there are then two known fixes for the 3,500 RPM roll on misfire. Why these two totally different solutions work I have no idea. Nor do I have any idea of the cause.

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