350 K2 re-commissioning Part 2

[mad muller]

it looks like its running weak and running to hot, looking at the plugs, and its the same on both pots , if you haven't already , check fuel taps for flow , as its a usa spec , check there is no missing vacuum pipes etc causing air leaks to the carb manifolds , have you put the carb slides the right way in, the cutaways facing outwards as you look into the carb, its very low mileage which is interesting maybe its had running issues in the past, even with the carbs that are on now it shouldn't run that bad , also check the new timing belt isn't overtight causing the engine to drag this will cause overheating and poor running , to tight can be worse than to loose .

[penman]

Thanks Paul, yes I do have a balance pipe in place. It was missing when I got the bike and those two ports were just open and I assumed they were vacuum take-off ports for balancing (and very handy too!). I originally capped them, then I found out there was supposed to be a balance pipe, so that's what's there now. I could try capping them again in the interest of doing something. Hmm, my pilot mixture screws are 3 turns out, a rather rich setting, that does support an air leak theory. I think I'll have another look, maybe I've done something daft, not being familiar with these carbs - it has to affect both though. I'm a lot more familiar with Dellortos than I was a week or two ago

Regards,
Joe.

[penman]

it looks like its running weak and running to hot, looking at the plugs, and its the same on both pots , if you haven't already , check fuel taps for flow , as its a usa spec , check there is no missing vacuum pipes etc causing air leaks to the carb manifolds , have you put the carb slides the right way in, the cutaways facing outwards as you look into the carb, its very low mileage which is interesting maybe its had running issues in the past, even with the carbs that are on now it shouldn't run that bad , also check the new timing belt isn't overtight causing the engine to drag this will cause overheating and poor running , to tight can be worse than to loose .

Yes I agree, it does look to be running weak and therefore hot, but it's useful to hear someone else say it! This bike has a breather box, but that just gathers all the breathers together and exhausts into the air cleaners, so I really can't see that affecting mixture. I'd love to find some missing part causing an air leak and I'll certainly have another careful look - at this stage I really don't mind discovering that I've done something stupid! Throttle slides - will they go in the wrong way round?? Gasp! Well I have assumed they are the same as round slides and the cutaway is on the air side - i.e. not the engine side. The slides don't look worn and anyway I thought that a slide with a flat side towards the engine would tend to seal itself as soon as any vacuum develops.

The timing belt seemed OK to me. It slipped on easily enough and was "snug" rather than tight. What you say about the low mileage is interesting. This is the 3rd US import I've bought and they have all had what I call low mileage, that is 15,000 or so. But 2000??? The speedo was OK and I haven't found any appreciable wear on anything yet. It does make you wonder what put it off the road - no way of knowing unfortunately!

Hmm, one more push on the air leak theory before I spend more money with the Dellorto shop!

[EVguru]

Throttle slides - will they go in the wrong way round?? Gasp!

Yes, they will go in the wrong way round, but I very much doubt that's the case here. An idle speed of several thousand rpm is the usual result.

One other thing you could check is the fuel level relative to the jets. Just use a clear plastic container held underneath the carb as a dummy float bowl. Normally I only have a problem if the fuel level is too high (prone to flooding). One of the 'gotchas' with Dellortos is running low on fuel. The bike feels just fine, but the fuel has dropped below the idle jet and when you stop the engine stops. You get into the habit of rolling off the throttle from time to time and seeing if it hesitates upon opening if you know it's getting low.

The 258 Atomiser will make you run a little lean all the way through the main jet range. The difference between the needle OD and atomiser ID determines how much fuel comes out between them. One tuning technique involves removing the main jet entirely, so you know it's not restricting the fuel delivered whilst on the needle taper. I think it's normally only used on 2 strokes though, which have a different Atomiser/internal drilling setup.

All the jet sizes on Dellortos are in mm/100 so a 50 jet is 0.5mm. You can soft solder jets up and drill the out for custom sizes. A set of micro drills and jet reamers can come in handy.

[penman]

Paul, many thanks for the Dellorto information, all useful stuff! I think I have to take the carbs off again and make a careful check for any issue which may cause an air leak. It has to affect both carbs equally though and to be realistic, that has to exclude things like leaky rubber elbows. I have only checked them visually and made sure the jubilee clips are tight, but to cause this fault, they both need to have a hole in them. A missing balance pipe would be a lovely fault, supporting the symptoms well - but it's not missing and it's a new pipe.

I do remember starting a bike with a missing balance pipe (my fault) and it was hard to start and ran really badly - no question of it idling and it certainly wasn't rideable.

If I can't find any evidence of a leak, I think I'll have to order the bits for the UK setup. I think the plugs I originally took out of the bike might still be in the bin - if I can fish them out it'll be interesting to see what colour they are.

I will post a question on steering dampers on a new thread.

[AntietamClassicCycle]

My first K2, an '86 bought new in '88 as a leftover (identical to the one in the first post), had a terrible hole in the powerband just as you describe. A guy I met at a Guzzi rally on a 350 Sport gave me his jetting recommendations, those and removing the o-ring from between the airbox halves made it better, but still not perfect. The final piece of the puzzle was opening up the mufflers slightly. There was two baffles several inches apart down inside the mufflers, each had a 10 mm hole in the center. I simply welded a 5/8" drill bit onto a length of rod long enough to reach down inside the muffler from the outlet and drilled the holes larger. The result was amazing - no more hole in the powerband - it revved more freely and no increase in exhaust loudness.

I'm not saying this is your problem, but it sure made a change in mine. Unfortunately, I neglected to record what the revised jetting was. Oddly enough, my present '85 K2 runs excellent with just the airbox o-ring removed and a slightly larger main jet than standard.

[penman]

Hi Charlie, thanks a million for that! I think you've given me the go-ahead to change the jetting. Hearing about someone else with a smilar problem has encouraged me no end!

Since my last posting, I've stripped the carbs yet again and I can find absolutely nothing wrong, and they are clinically clean. I have removed the rubber elbows from the inlet ports and those are in excellent condition as are the connectors to the airbox. I like the air leak theory, but there isn't one. If you know your K2 jetting, I'd be most interested to hear, otherwise I will order the main jet, needle and emulsifier stated in an earlier posting.

I'm trying to remember an O-ring in the airbox - do you mean the long white rubber strip which seals the top and bottom parts together? You can be sure I'll have it apart tomorrow, if there's an O-ring I'll find it. As for the exhausts, those are the original items and the baffles are an unknown quantity to me. I'll do the carburetter updates and see how it goes.

Thanks again!
Joe.

[MickeyMoto]

Did the US (in this case, true!) version have more restrictive silencers?

[penman]

Did the US (in this case, true!) version have more restrictive silencers?

Good question, I would like to know the answer!

[AntietamClassicCycle]

I'm trying to remember an O-ring in the airbox - do you mean the long white rubber strip which seals the top and bottom parts together? You can be sure I'll have it apart tomorrow, if there's an O-ring I'll find it.

If I remember correctly (it's been 28 years!), yes, it was a white, rubber strip that seals the two parts together. The factory manual notes a jetting change depending on whether it's fitted or not (98 main with, 112 without). I'm running 115 mains as that's all I had in my jetting selection at the time.

As for US vs. world silencers: I'm not really sure, but I would guess they're the same. There are no markings on them denoting US compliance like you'd see on silencers of other Italian brands imported into the US at the same time. I believe the number of Morinis sold each year was so small, that they fell into a "loophole" that didn't require emissions compliance, only that lighting meet the standards.

A long boring story about "carburetion" issues on my '85:
I've only had my '85 since August and made it roadworthy again in mid-October. At first it ran beautifully, excellent mileage (76 mpg), no flatspots, but one warm October day a problem began to manifest itself. I was overtaking a pair of dawdling BMW riders and as I was accelerating passing them, the engine suddenly lost power. I backed off the throttle slightly and it came back to life, but with a slight misfire. Later the same day it did it again climbing a steep grade. At the top of the hill I stopped, reached down and fiddled with the carburetors thinking maybe the crossover hose had come adrift. It hadn't, but I was shocked to see the entire carburetor, rubber elbow and all, move rather freely on the intake stub that threads into the head. However the clamp was tight and the intake stub was actually turning with everything else. Moving the carb clockwise (tightening the stub in the head) made the issue go away temporarily, so I surmised that there was an air leak resulting from the stubs loosening.

I pulled the carburetors and elbows determined to tighten the stubs, but when the engine was ambient temp, they were tight. I posted about it here back then and got some excellent input from EVGuru. So, the K2 went into hibernation for the Winter and only just Saturday was roused from it's slumber. Started it up and rode it around the neighborhood a bit, pulled it onto the lift and removed the carbs and elbows as quickly as possible. Ah ha! The rear cylinder stub moved easily using a tool I had made for the purpose. Threaded the stub completely out, cleaned the male and female threads, applied thread locker/sealer and reinstalled it. The left side too was slightly loose, but the head temp had fallen quite a bit by now and it was having none of my trying to remove the stub. I got it out approx. 6 mm before it seized, so I propped the electric heat gun up pointing at it, turned it on and moved back to the rear cylinder to reassemble. After a half hour, the front cylinder head was barely warm enough to finally allow me to thread the stub fully back into place. I cleaned around it thoroughly and applied wicking thread locker and reassembled everything.

Yesterday after riding my Guzzi all day, I came home and took the K2 out for a test ride. 75 degree ambient temp and I rode it "enthusiastically" for approx. 1/2 hour in order to bring the heat up to where the issue would normally begin. Nothing. Ran beautifully the whole time, stubs won't budge. So, I'm cautiously optimistic that it's cured. Not sure if there's anything useful in all of this BS.

[MickeyMoto]

Yes, very interesting.... where in the world is it 75 degrees in April! Lucky to hit 50 here, looking at the frost on my shed roof! ....

[penman]

Hmm, that is interesting. The head looks like aluminium and on mine, that stub looks like copper or bronze, I'll have a closer look later. Needless to say, mine are tight, but with the engine cold - I'll have to check them hot as well but I can't start it as the carbs are in pieces. I've just ordered the UK jetting, hopefully I'll have the bits tomorrow. How can I heat the head up, I'll try a heat gun but I think it'll take a while to get it up to a sensible temperature. Worth a try though, especially if I can devise some way to insulate it. Pity about those cooling fins.....

[park3164]

Hi all,
This is my first post, I have a 1986 K2 ex US import, and usually just lurk as I am not the most mechanically minded. But after having the carbs rebuilt last year I know what size jets I have. The jets are idle 50 main 115 atomiser 260CM and E17 needle. These are the same sizes that were in the bike when I got it, after it likely had been stored quite a few years.
And she runs nicely with these at present on our Australian 95ROM fuel . The plugs did foul a bit, but after changing from the original B8ES to B7ES they seem pretty good now.
PS a replacement 260CM atomiser was difficult to find, until I contacted Herdan Corp in the US.
Happy roads and hope this helps your quest. And yes, it probably was 75 degrees here today in April
Fiona
Sydney, Australia

[EVguru]

Hmm, that is interesting. The head looks like aluminium and on mine, that stub looks like copper or bronze, I'll have a closer look later. Needless to say, mine are tight, but with the engine cold - I'll have to check them hot as well but I can't start it as the carbs are in pieces. I've just ordered the UK jetting, hopefully I'll have the bits tomorrow. How can I heat the head up, I'll try a heat gun but I think it'll take a while to get it up to a sensible temperature. Worth a try though, especially if I can devise some way to insulate it. Pity about those cooling fins.....

The stubs are steel. I've only ever had problems with them on early engines where the solid manifolds have been replaced, or on the Dart I had with ported heads. In both cases the stubs hadn't been installed tight enough.

Easiest way to heat the heads is ride the bike!

[penman]

Fiona - many thanks for your information. I am starting to get the picture that on the US bikes, just the carb setup was changed, maybe with more restricted silencers. So, I feel pretty optimistic about putting in new jets, needles and atomisers, which will hopefully arrive tomorrow.

Paul - thanks for that info. I will of course check the security of those stubs now I've heard the story. They must be plated with something which makes them look coppery - maybe it's rust! I'll know later. I agree that riding it is the easiest way to heat it up, but with the carburetters in pieces on the workbench I'm finding it hard to start! After 5 minutes with the hot air gun I'll probably give up anyway!

Well since we use degrees Celsius, I'm actually quite pleased that we don't have 75 degrees here. On the other hand, a bit more than the current 12.5C would be nice!