Difficult question to answer

[Bison]

Folks,
Never having had a ride on a Morini I don't really know what to expect from my 1978 3 1/2 Sport. Just been out for a ride of about 20 miles and here's my impression. Surprisingly torquey, mid range is good, nothing really happens at top end of rev range, in fact the power delivery is very linear, is this your impression too?. I was kind of expecting a wee surge at higher revs, around 7 to 8K?, slightly cammy perhaps, am I wrong in expecting this?. The bike is running Shell V Power, 40 Pilot, stock needle and position, 115 main. Busso silencers on a stock looking but stainless exhaust. MZb ignition system, std gearing.
I realise everyone will have a different answer to this but would love to hear your opinions
Here's my other impression, it's absolutely a hoot to ride, I had forgotten how much fun a small lightweight bike could be, I'm running in Pirelli Sport Demons and have to say they are very very good. I've got twin discs on it too and you can really stuff it into a corner late.
Big smile on face!.
Alan.

[72degrees]

I always found a Sport needed to be really revved to make decent progress. Sure it has a Sport cam? I'd expect a noticeably increased eagerness once over 7000.

The most disappointing Morini I ever had was the 350 K2. Now that really did have a linear power delivery. Not the bottom end that my 75 Strada had, the top end of my 79 Sport or the grunt of my 375 with L5 cam. I kept thinking that the K2 would come on the cam and it never did. Still a good bike and it made a surprisingly competent two-up tourer with massive Givi panniers but a bit anodyne.

[EVguru]

Restrictive silencers will take the edge off the top end and I suspect the Bussos and Sitos fall into that category. My Sport really sings with it's 'Riservato Competizione' LaFranconis.

I've said time and time again, a Sport engine is torquier than a GT/Strada, which I'd put down to the higher compression. Sport engines didn't always get the right internals and you might have low(er) compression pistons. A few extra degrees of ignition advance at high rpm can make a difference too.

[Bison]

Hi 72,
Thanks for your reply. It has a reground cam as supplied by NLM, I checked the timing with a disc, certainly the valve duration is the same as the Sport, didn't measure the lift. Interesting, a wee punch at around 7000, hhhmmm.
Paul, yes, I think you've hit the nail on the head, the silencers are providing nice backpressure for low and lower middle range, but restrictive at higher revs. Unfortunately my option is to fit the 2 into 1, and I know your feelings about those, and I just got the jetting sorted beautifully for the stock system. Where did you get your Lafranconis?.
I wrote Busso, they are Sito, sorry.
Alan.

[mgelder]

The black chrome Sitos on my 350K Sport were noticeably restrictive at the top end compared to EVGuru's LaFranconis, and the short megaphone style exhausts I'm running now certainly feel and sound like they give a little lift at the top end.

Still blummin' loud though.

[shameless plug]
Re-packing the pipes: http://www.realclassic.co.uk/morini_clu ... _play.html
[/shameless]

I'm still using standard carb settings as it seems to run ok. It feels like it 'comes on the cam' a bit above 6 or 7k rpm, but there's no powerband like you get with a two stroke and no rush of top end power like you get with a large diplacement engine. It's all relative, though; if I want to go fast I've got a bike that's more powerful than four Morinis...

[EVguru]

I think that if you drill some holes in the back of the silencer around the main outlet it bypasses the mid baffle.

My 'comp' LaFranconis came with the bike and are pretty rare. Even rarer is the NOS pair I have in boxes.

Two smokes excepted, backpressure is rarely of any benefit, but low backpressure should not be obtained at the expense of exhaust gas velocity. A straight through silencer is good, too large a pipe diameter is bad.

[boris tarpit]

. . I've got those on my 420 . . last time I was at Matlock somebody asked me if the turbine baffle in the end actually spins . . .

[Bison]

So then, assuming for the sake of expenditure I fit the 2 into 1 NLM system back on to give it a try, any suggestions as to jetting?,
Alan.