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Well it's been a long time coming, but now I have some success with the K2. It's running very well indeed and on the original carbs - the VHB(Z) 25 HS

I decided to have one last try and the only changes I have made are to blank off the two vacuum ports by removing the stubs and making a short screw to blank the hole. I also left the breather tubes off the float chamber breather stubs. I didn't make any other changes. I'm not sure which of these has solved the problem, but it was back to working pretty well, though with a noticeable flat spot in the mid range. I swapped the atomisers for the "home made" 260CM versions and now I don't even have that flat spot. Believe me, I'm delighted!

Previously I had closed the vacuum ports with a 2 inch length of plastic tube, blocked by a ½ inch piece of brass rod. I can't see why that shouldn't work and I can't see why removing about a 10" piece of plastic tube from the breathers should change anything either. I will see if these changes are reversible in the next day or two and I'll post the result here. With the tank in place, I couldn't fish out the breather tubes to re-connect them, or I would have done that while I was out.

Well today's ride in the sunshine, with the engine actually behaving like an engine was great fun. I do love the way this bike can hold a line through bends - I could forgive it quite a lot for that alone!

Regards to all and many thanks to all those who have helped and encouraged along the way!

Joe.

Excellent! I suspected the extra 'holes' in the HS version must be the root of the problem - though I assume my K2 had them and that was fine.

Perhaps having even short lengths of tube on the vacuum ports allowed air pressure weird resonances to build up?

I'll be most interested to learn the results of your reversion test.

Sounds like that Morini grin has been achieved

Congratulations..!! Your patience has paid off, well done for sticking it out.
Archie

Well done Joe.
Truly a good result and glad I was able to help you at least establish a baseline.
I'm sure Dave the editor would like some summarising words and pictures For ATG?
Now, as to where you can get K2 tank and fairing stickers...machine them from solid?

Be in touch soon.
George.

72degrees wrote:Excellent! I suspected the extra 'holes' in the HS version must be the root of the problem - though I assume my K2 had them and that was fine.

Perhaps having even short lengths of tube on the vacuum ports allowed air pressure weird resonances to build up?

I'll be most interested to learn the results of your reversion test.

Sounds like that Morini grin has been achieved

Those are the sort of thoughts which have been going through my mind, though I'm not really managing to convince myself. It would be a fair question to ask why I didn't try this sooner but the simple answer is that I just couldn't believe it would make any difference. Anyway, it's going well so I'm not arguing!

Archie Adv wrote:Congratulations..!! Your patience has paid off, well done for sticking it out.
Archie

Thanks Archie! I've never been called "patient" before, so I'm feeling a bit smug now!

George 350 wrote:Well done Joe.
Truly a good result and glad I was able to help you at least establish a baseline.
I'm sure Dave the editor would like some summarising words and pictures For ATG?
Now, as to where you can get K2 tank and fairing stickers...machine them from solid?

Be in touch soon.
George.

Thanks for all your help George. I am still using your 42 pilot jets, they are noticeably better than the 44 I was using before, better off-idle response even in this chilly weather. I'll order some new ones today and put them in your carbs and get them back to you.

As for the fairing stickers, NLM have a contact who makes them, so I've decided to have all the painted bits re-sprayed and new stickers put on. Meanwhile I will attend to the slightly scruffy black bits around the bike. I accept what you said about older bikes and "patina", but I think I'm just the wrong side of the line between a bit of patina and just plain scruffy! The good news is that this means I think I'll be keeping this bike for a while!

Early warning to everyone - I may be over-familiar with the carburetters, but I'm still new to the Morini in general and I've a list of questions forming in my mind......

Regards,
Joe.

The float bowl breather tubes weren't blocked were they?

Source for tank decals:
http://www.ebay.it/itm/MOTO-MORINI-K2-A ... 0708648651

Congratulations Joe! I'm sure you will find your Morini is a definite keeper - some bikes are like that.
Now, what model will you be looking for next...?

EVguru wrote:The float bowl breather tubes weren't blocked were they?

No, that was my first thought but they are clear. I'm not at all sure what they are for though. There are 4 thin plastic tubes, about 3mm bore, 2 for each carb and they run forwards along the top frame tube, just ending with an open end near the steering head. I've often seen short tubes from the breathers leading straight down, to double up as overflows, but this arrangement is new to me. Anyway, it runs just fine without them so I'm happy!

Ming wrote:Congratulations Joe! I'm sure you will find your Morini is a definite keeper - some bikes are like that.
Now, what model will you be looking for next...?

That is a very provocative question, given that I'm on the lookout for a winter project! I'm guessing the 500 is a bit more grunty on mountain roads? Not that I'm interested, you understand.