NewbieQuestions

[Bison]

Folks,
This is my first post as a relatively new owner (three months) so hello all.
My bike is a late 78 3 1/2 Sport which had been unused since 2007. I've not had the engine stripped as it started no problem and runs pretty well, but just about everything else has been looked at and repaired/replaced, cam belt, carbs, ignition etc.
Here's my problem. I can't get the carburation to run weak enough, both plugs are pretty black. I have the VHBZ25HS carbs, Pilot jet has been reduced to a 43, main jet is a 115, but I have a 112 to replace them, diffuser is a BD rather than a D, not worn, agood fit with needle in place, new needles, 17's, 2nd slot, new inlet manifolds, new air filters, carbs nicely balanced on tickover and on throttle, chokes are new with good rubbers. Ignition timing has yet to be checked with a strobe but the bike idles rather nicely, although it "sounds" rich. Two things I can come up with, it's either quite retarded ignition, or the valve timing isn't spot on. I should say the cam has been reground to L5 profile, and the previous owner, who fitted it said he had to shorten the front cyl pushrods?. The history is he had a problem with the bike not willing to rev beyond about 5000 rpm cleanly, as I've only had a spin around my pals yard I don't know if this problem has been resolved. It had diffusers from a 250 fitted and a strange mix of jets. But, one thing at a time, I would like to have nice coloured plugs!.
Many thanks in advance for any suggestions, I hope to have the small problems ironed out soon cos I can't wait to ride my lovely Morini!
Cheers,
Alan.

[mgelder]

If it's running nicely, I wouldn't worry about the plug colour until you can get it out for a good long ride.

[Unless your pal's yard is an old airfield or similer ]

[EVguru]

Black plugs is pretty much normal with modern fuel. As long as you're not sooty back, the mixture is close.

It would be worth checking the cam timing with a degree wheel. Ignore any marks on the pulleys and set the clearances to 1mm whilst checking. Timing figures are on my website and the Dutch Morini club's.

[Bison]

Thanks for the prompt replies guys. I've ordered a pair of 40 pilot jets from Eurocarb, I'll fit those and see what happens. I'll report back. I agree,. I think the valve timing would be well worthwhile checking.
Alan.

[EVguru]

The idle mixture is controlled by the jet in combination with the mixture screw, so you can achieve the same idle mixture with a range of jets. Just off idle is the progression circuit and this is much more dependent on the idle jet. Modern fuel with its high proportion of aromatics tends to make Morinis run rich through progression.

I run 43 idle jets and they're usually about right.

I'm very fussy about carb balance and the start of that process is the valve clearances which should be 0.15mm (rather than 0.1) for the L5. You need to synch the calbles as well as the stops.

Don't forget that all carburation problems are caused by the ignition and that the opposite is also true!

[swtuggle]

If they are new carbs, take a look at the number on the slides, and compare to the stock specs. The transition EVGuru mentions is off idle to about 1/4 throttle, which is affected by the slide cutout.

40s proved too rich no matter what pilot jets I tried on my 507's PHBH28s. The 50s are working well, good response and plug color.

[Bison]

Gentlemen,
A major discovery has been made, I rigged up the strobe to check the ignition timing and lo and behold it isn't advancing the ignition!. I get a flicker of movement when the strobe is flashing but that's all. That is from just above tickover to , well, shall we say rather high revs. Nothing!. This may not solve the rich running but will explain the not revving above 5000 fault!. I read the advance curve is generated in the transducers, but I do have a brand new Mz b tronics system ready to fit, Is this perhaps the way to go I wonder.
Alan

[EVguru]

Have you checked the timing and advance on both cylinders?

The advance is controlled by an interaction between the trigger threshold voltage of the transducer and the output voltage of the pickup (which increases with rpm).

I'm a great believer in the stock ignition. Both it and the charging system are frequently missunderstood, perhaps even especially by Autoelectricians (I'm an Electronics Engineer - I outrank you!).

The only bad thing I think I've heard about the MZB ignition is the difficulty of setting the timing as the flywheel isn't keyed and that it isn't compatible with the stock electronic tachometers (if your's is still working).

If you turn up to the track day I usually have spares for the stock ignition. They're never needed when I bring them, but a couple of people have had pickup issues when I don't.

[Bison]

Hi Paul,
I only checked it on the front cylinder, I'll check tomorrow night on the rear. So to repair the stock system I need to replace or repair the pickup?. The pickup is a red one, which I believe is a replacement?. Or is it not as straight forward as that?.
I have a new white faced rev counter which has an H on it, perhaps Horex?
What a lot of info and help already, thanks guys.
Alan.

[Daddy Dom]

New owner = new pictures, unless I'm mistaken??
DD

[Bison]

Hopefully there will be photo's in this reply?
Yes, it's orange!, well, they're mostly all red aren't they?????

[mantaray]

Nice bike

[EVguru]

A two into one exhaust, I should have known!

I nearly asked if it had one, but thought you'd probably have mentioned it.

It looks like a properly designed one with equal pipe lengths, but quite a few of them make it IMPOSSIBLE to get the engine running sweetly. They make sense on a parallel twin with even firing angles, but were often fitted to many bikes because they were cheap. They save the cost of a second silencer!

[Bison]

I believe it's an NLM system, Stainless Steel, been told it works pretty well. Certainly sounds and looks nice.
I do have a stock system in pretty good condition, thought I would run it with the 2 into 1 which was fitted when I bought it, and sometime in the future fit the standard system to compare running. Interesting exercise I thought.
Alan.

[Daddy Dom]

Yes, it's orange!, well, they're mostly all red aren't they?????

Nice looking bike. Looks pretty red on my screen, though. Maybe it's "Tuesday red" from the factory? Of course, that'll be only slightly different from "Friday red."
Mine's a bit cherry/orangey depending on the light.
DD