Top speed on a Strada?

[Johnmcnally]

Having had a couple of Stradas in the 80s I took the plunge back into Morini ownership 3 years ago. The Strada I bought is great fun around the lanes, however fitting a satnav has cruelly exposed its woeful lack of speed. Flat out it's a job to get it up to a true 70. According to my July 1980 copy of 'Which Bike' a Strada should do 93mph.Timing, tappets and carb balance are all as they should be or at least as good as I can get them.

Is lack of performance just the inevitable result of 40 years wear and tear? Were stated performance figures exaggerated? Any ideas - I'm realistic but I'd like to get it going a bit faster, at least to keep up with dual carriageway traffic.

John

[72degrees]

That does sound pretty sub optimal. My first 1975 blue Strada would get in to the 80's two up with ease.

Are the throttle slides opening fully? If I remember correctly it's possible to get the VHB carb tops on backwards and bind up the return springs. Though that should be obvious. Worth popping an intake elbow off and making sure they aren't dangling still when the cables are WFO at the twistgrip. Someone fitted a non-standard sprocket to keep cruising rpm down?

Main jets standard?

[harrymuffin]

How fatter are you now than then?

[norbert]

have you controled the fuel flow, do you know the mileage of the motor?

[danomar]

70mph on a Morini is equivalent to 90mph because it is a Moto Morini.

The difference is imagination.

And probably carburetor tuning.

[Ming]

Perhaps you have THE accurate Veglia? I think Harry may have a valid point too...

[mbmm350s]

Hi,
A simple thing it could be.
I have had this problem several times once in outside lane of M1, turned out to be a faulty electrotap.
Remove all taps and clean them out.
Try top speed test with reserve tap on.

Mark

[robint]

To check fuel flow just see how long it takes for a known quantity to flow into a container.

Some back of an envelope maths - at say 90mph a Morini is probably getting at worst 30mpg, so in an hour 3 gallons of fuel (13.5l) would be used - assuming a larger tank would be fitted of course!! So if your fuel flows out of the pipes at 13.5l/60mins or 200ml/min approx then fuel flow to the carbs should be more than adequate.

In normal use 60mph gives at least 60mpg so 4.5l/60mins is typical or around 75ml/min.

[72degrees]

My Gilera 175 has to have both fuel taps open (as recommended in the manual) , or if you hold it WFO up a long incline it runs out of steam. The one tap also needed cleaning out to be fair, but the fuel starvation on just one does eventually cut the engine completely rather than limit top speed. Try the Strada with the reserve tap on as well as the electronic main tap? Did we cover a blocked fuel cap vent?

Might be time for a plug chop.

[harrymuffin]

If you have an electric tap on only, then you will not flow sufficient fuel at anything over 70mph. If you have manual cocks then then you need a minimum fuel flow of 1/2 pint per minute from both taps at constant speeds under load. My own 507/478 would always have to have both cocks open if tramping on at well over the speed limit. If on normal 'A' roads with speeds varying up to 70's then I could get away with one open. Fuel consumption in that case would be in the 50 - 60mpg range with 28mm carbs an 130 main jets, the others would be standrd 500 sizes.
I do not see what difference that information would make to top speed as if you are not flowing enough fuel then the engine will cut out and then if you drop the clutch and the fuel has replenished the floats cut back in again. This I know from first hand experience when raacing a tart in a Golf in the upper eighties, I then ran with the reserve on to increase the fuel head and hence slightly more flow.
In any case, the speed limit is 70mph and if you are a lawfull abiding motorcyclist, then you should not be exceding this speed on public roads, unless you are a born again geriatric hooligan of your youth like most Morini ownners!

[harrymuffin]

PS. Those fuel flow recomendations came from Dellorto for the Benji Straw built 372cc racer and that would rev to 11,000rpm with a 36 back sprocket circa 1980's.

[Johnmcnally]

Thanks for the ideas. For the record I'm still 11stone, the same as in the 80's.
I don't think it's fuel starvation as there's not a faltering, it just won't get up there!. The motor has an indicated 46k but the compression has been checked and pronounced OK. I'll re-check all the relevant points and take it for a burn with both taps open.
Have the members who're getting well up into the 80s on their bike checked this with a reliable source? Veglia he say 90mph, but TomTom him say 68.

John

[harrymuffin]

What rear chain wheel have you got fitted? If you are in top with too small a cog you will be below the power band. Have you tried droping into 5th and letting it rev up to around the 8000 mark then dropping into top for a bit more? May be of interest to you, but a bloke rode his Strada up from London the scenic route, the first section on the M4 and holding up lorries, then proper roads with a couple of big down hills and complained to me on arrival that the bike would not rev with a top speed of 60ish. Checking his gearing, he had a 34 back sprocket fitted. Whomever he bought the bike from had a misguided notion that the higher the gearing the faster the bike would go! I put the correct 38 toothed cog on and had no problem in breaking the speed limit and more.

[MickeyMoto]

Both taps on...

[norbert]

With my 350 Sport motor I used 39 and even 40 teeth. I doubt wether a 38 is a good choice for an untuned strada 350.
With 501 in street frame I use 14/39.