350 airbox differences

[Db7gtgrigio]

I have just managed to acquire (at a price that was fairly eye watering....seems they are rare as hens teeth) an air cleaner assy that is in perfect condition. the only issue is, the original air cleaner for my 74 double drum Sport had a sold plastic top, whereas this one has a hole in the centre of the lid for each filter, with a hollow rubber grommet and an angled steel elbow. I presume it is from a later bike with some sort of vacuum arrangement?????

If I just get a couple of solid grommets and plug the holes I assume it will be fine?

Anyone know from what bike the one with the elbows was from and what the elbows are for. The part number and DGM number on both lids are identical.....

[Steve Brown]

Your presumption is spot on! The later air boxes had inlets there for breather pipes led from the main breather chamber. Emissions regs and all that stuff. So just block 'em off as you say.

[72degrees]

What are the numbers M 173-7019?
As Steve said, breather connections. Though I'm not sure if the later boxes were otherwise identical?

These are a significantly different shape though or perhaps this is the 500 version?
http://www.obsoletebikeparts.com/a-2824 ... ro-320137/

[penman]

Here are a few pictures which might be helpful. These are from a late (1985) 350 and show the airbox with the two breather connections to the collector box.







This airbox is significantly different to the one shown on the obsolete bike parts link, which I suspect is from a 500. The two halves of this airbox can be sealed by a rubber strip, retained by the rusty spring clips shown in the photo. Removing this seal approximately doubles the air intake area by allowing air in all around the edge of the airbox - it still goes through the filters though. This makes a big difference to the induction roar, (which I quite like!) but necessitates a bit of re-jetting to restore good performance on an open throttle.

[Steve Brown]

What are the numbers M 173-7019?
As Steve said, breather connections. Though I'm not sure if the later boxes were otherwise identical?

These are a significantly different shape though or perhaps this is the 500 version?
http://www.obsoletebikeparts.com/a-2824 ... ro-320137/

As far as I know, the 500 airbox is taller/deeper as well. I'll check when I nest get out to work on my project as it has the airbox from a standard 500 Sport.

[Db7gtgrigio]

Here are a few pictures which might be helpful. These are from a late (1985) 350 and show the airbox with the two breather connections to the collector box.







This airbox is significantly different to the one shown on the obsolete bike parts link, which I suspect is from a 500. The two halves of this airbox can be sealed by a rubber strip, retained by the rusty spring clips shown in the photo. Removing this seal approximately doubles the air intake area by allowing air in all around the edge of the airbox - it still goes through the filters though. This makes a big difference to the induction roar, (which I quite like!) but necessitates a bit of re-jetting to restore good performance on an open throttle.

The one in your pictures is identical to the one I have bought and apart from the holes in the tops same as the 1974 variant

thanks for all the replies guys, I shall just plug and play....I might add the rubber seal and see if that makes a differemce

[penman]

The one in your pictures is identical to the one I have bought and apart from the holes in the tops same as the 1974 variant

thanks for all the replies guys, I shall just plug and play....I might add the rubber seal and see if that makes a differemce

That's interesting to know. For what it's worth, with the rubber seal in it looks like this:



....and the main jet needed to go down to 98. Without the seal, I find 112 is better. If you use 112 with the seal in, it tends to go a bit too rich on an open throttle and it feels a bit flat. I'm pretty new to the Morini game and I'm finding all these carb settings can benefit from a bit of experimentation, probably resulting from changes in the fuel over the past 30 years. Having said that, if you are happy with how it's running, I'd leave well alone!

By the way, on the subject of fuel, I had assumed that with a CR of 11:1, 97 octane fuel or higher would be essential to avoid pinking. However, having filled up the completely empty tank from the lawn mower can the other day, it ran absolutely fine and I couldn't even provoke pinking if I tried. Maybe there just isn't enough difference between 95 and 97 to notice.

[Steve Brown]

By the way, on the subject of fuel, I had assumed that with a CR of 11:1, 97 octane fuel or higher would be essential to avoid pinking. However, having filled up the completely empty tank from the lawn mower can the other day, it ran absolutely fine and I couldn't even provoke pinking if I tried. Maybe there just isn't enough difference between 95 and 97 to notice.[/quote]

I thought the same when I bought my first Morini and ran it on 4 star for a few thousand miles. (back in 1977) Then as the starting became worse I went for advice to NLM. They said that the lead from the 4 star was depositing on the electrodes of the spark plugs and shorting them out. Also that 2 star was perfectly adequate, octane wise. So I switched to new plugs and 2 star and never looked back It ran better on that fuel and was perfectly happy too on the 'normal benzine' sold in Germany and Holland at the time. No lead in any of those (or probably hardly any) and I never had any valve seat problems in 100,000 miles of thrashing, rallying, commuting and even club racing. So they don't need high octane or lead or lead replacement at all. One difference between now and then I can detect is lug colour. When the bike was original and standard, the plugs were always very clean running, very light in colour and even the outlets of the silencers were very light grey. Nowadays I only see much darker silencer ends and darker plug colours. Still runs nicely though...

[Db7gtgrigio]

I just did a track day on mine so mostly WOT and red line. Did it on Aussie 95 octane with zero ethanol, bike ran beautifully. I often run it on 91 and it also runs fine.

the only carburation issue is a slight stumble just off idle.

[tobydmv]

OMG, I have been trying to synch my carbs for a week and not having any luck. The last time I pulled the carb to double check the throttle slide and jets a friggin rubber grommet fell on the ground and I had no idea where it came from. I think you just solved the mystery and i'm really amazed it wasnt sucked into the carb and into my freshly rebuilt motor....