G'day, and help!

Flash · Post by **Flash** » 10 Nov 2008 09:40

G'day, I've just taken the plunge and bought my first Morini - a 1975 3 1/2 Sport. I'm located in Perth, Western Australia and whilst I'm not unfamiliar with motorbikes (particularly older, pre-1970 British types) this is my first Italian machine and thoroughly look forward to throwing it around some corners!

I consider myself very lucky to have been able to get a Morini vee twin at all here in Perth, let alone the exact model I wanted (drum-brake), but unfortunately I purchased it as an unfinished project and it's thrown up its share of foibles! I've ironed out most of the bugs, but I'm at my wits end at the moment because the darned thing just won't run properly and I'm hoping some of you learned fellows might be able to guide me in the right direction. The scenario is as follows:

The bike will rev fairly well in first through to fourth gear, but at 100 Kph (roughly 6-7,000 rpm) change into fifth and she won't rev, just coughs and splutters and refuses to pick up any more power. It also takes a few gos to get it started but I think that's just a knack I haven't picked up yet. My primary concern is the lack of power - for a bike capable of 100 mph she struggles to break past 60 mph! I can't do a proper plug-test with the (dare I say it?) awkward positioning of the ignition key, but after a decent run they come out quite black and sooty, indicating richness.

I'm running Strada carbs with the slightly smaller main jet and I've checked and cleaned all jets/needles/pipelines and floats; they haven't been balanced yet but the slides are opening equally. I initially used 98 octane fuel but was told it was rubbish and subsequently turned back to 95 (no discernable change in the engine). Ignition has been timed on the front cylinder with a strobe light and I'm regularly getting a nice fat spark with the recommended plugs. The engine was rebuilt (although not by me) and can thus be considered 'tight' and not bedded-in, if that makes much of a difference? The rubber inlet manifolds between the carb and head are okay, although one has been temporarily repaired where it had split (soon to be replaced). The airfilter housing and elements are second-hand but the elements appear to be quite clean and barely used.

Basically I'm baffled why it is that I'm getting fuel and ignition but no performance - what have I overlooked that could cause such a dramatic power failure?
I'm sorry to debut on this forum with only questions and cries for help, but I can only hope that maybe we can figure this out and I can talk more about the joys of riding such a fine machine!

Thanks and regards,
Flash

3narf · Post by **3narf** » 10 Nov 2008 10:34

Hello

What plugs are you using? I would always advocate NGK BP6EVs, although as others have pointed out they tend to mask other ignition problems...

I fitted the ESs once and my bike wouldn't rev past 7000. Putting back the EVs (or Denso ZUs) sorted it.

Could be a cheap fix; worth trying first, anyway!

dougi · Post by **dougi** » 10 Nov 2008 14:42

i have a 1978 3-1/2 sport. the problem you are having sounds like the same problem i had with my 3-1/2 when i got my 3-1/2 a few months ago. replaced spark plugs BP6ES, plug caps and turned out to be the float hights were the problem ! it pulls cleanly until about 95 mph in 5th gear and is happy to sit at 60-70 mph in top gear 6th. i am happy with that !!

Flash · Post by **Flash** » 11 Nov 2008 12:46

Thanks for these suggestions, I will change the plugs and re-check the float levels and see what happens. The reason I'm not convinced it's the floats at this stage is that it revs highly with little problem in fourth and only has difficulties in fifth and top - i.e. if it were draining the bowls I'd have assumed the lower gears were equally affected. Nevertheless, leave no stone unturned eh?

Thanks again,
Flash

Flash · Post by **Flash** » 16 Nov 2008 13:08

Through the process of elimination I've now come to the conclusion that the bike isn't performing properly because it is running far too rich. Needless to say the inference is that it is either getting too much fuel or too little air, but I wonder if anyone else has had a problem like this?
I wouldn't have thought it's being choked by the air filters, but is this perhaps a possibility with Morinis?
Otherwise the problem is with the main jet, but unless they've been reamed out the main jets I have are the smaller Strada jets (112). Whatsmore, I have the North Leicester siamesed exhaust and it has been suggested that it should run adequately on jets up to 180 with this system.
Or as a final supposition the problem might lie with the petrol - 95 octane premium unleaded - so I wonder if anyone else has had issues with modern fuels in these bikes?

Thanks again,

Flash

3potjohn · Post by **3potjohn** » 17 Nov 2008 06:43

And you say you checked the carbs-including the choke circuit?How are those o-rings?

Jem · Post by **Jem** » 17 Nov 2008 20:39

First observation - changing gear (from 4th to 5th) does not affect the behaviour of the ignition or the carburettors. But going faster needs more power which only shows at the higher speed.
What transformed my '77 Sport was swapping the original floats for new ones. With the old ones it was impossible to be sure that the height was right (& I strongly suspected they were porous); the replacements are a completely new design, & material - it is not possible to adjust the height, they're right from the factory.
Double check all the jet sizes & needle settings (middle groove); are all the jets in the right places and screwed home (I know it's an insulting question but the way the main jet fits in the nut the holds the float bowl on has confused some people).
Third, it is difficult to tell by eyeball that filters are flowing properly - try taking them out and running the bike (take it gently!).
Oh, lastly, my own cock-up! The left hand carburettor faces backwards...is the slide facing backwards as well? I could get my Kanguro to start & run but only very rich...

Good luck!

Flash · Post by **Flash** » 30 Nov 2008 13:21

Thank you all for your advice and suggestions. After much toying and researching I've come to the conclusion that I simply need to downsize the main jets. I was informed by a local Moto Guzzi mechanic that he had to do this to all the older model Guzzis thanks to the changes to petrol in the recent past. This information combined with the old process of elimination means I'll be tinkering with jet sizes for a few weeks (they're not available here in Aus so they'll be coming from England or Italy), so any suggestions in this field would also be greatly appreciated. I was thinking of starting with 100s, 105s and perhaps 110s and see what happens.

Thanks again, I'll keep you posted on the progress.

Flash

dougi · Post by **dougi** » 30 Nov 2008 23:16

here is a webbsite in the uk i get my 3-1/2 sport Dellorto carburetor parts from.
http://www.dellorto.co.uk/default.asp
i hope it helps