More Carburettor Woes! Help1

[Jack]

I have a problem with my SEI, it will accelerate so far and the it just goes "bwarrrrrr" and bogs down, before eventually clearing. It never seems to run clean from then on though, it feels restricted.

The bike is equipped with Dellorto PHBH26 BS carburettors.
The main jet is 120: the idel jet is 43; the atomiser/emulsion tube is 264T; the float needle valve is 200. The cold start device jet has no identifying marks and the throttle slide just ha 40 stamped on the bottom. However it's still attached to the cable/cap assemble so I can't see the top of it.

I have already ordered some choke seals on the advice of Tom, who was spot on, they are completely shot. Thanks Tom.

However, I was wondering if anyone else had any thoughts; for instance could it be the fuel pump? I experienced something very similar on a 750/4 I sorted the other year, which have a perished accelerator pump diaphragm. So could it be the fuel pump perhaps, are they prone to vacuum leaks etc? Any suggestions welcome.

Secondly, when I managed to get the air filter box off I noticed that the carb manifold ports were a bit damaged. I discovered that K&N do a cone air filter that will fit. Has anyone done this, is it a good idea, what jet upgrades are required, are there any problems/drawbacks etc?
I treated my Commando to a K&N and had to uprate the jets from 220 to 260.
It run well now though, in fact it has never started, idled or run so well - ever!
So I am a K&N convert really.

Any advice would be appreciated.
Thanks.

All the best
Jack

[3potjohn]

I have a 350 that has never missed a beat in over 13 years and a 501 that I cannot get to run smoothly. Its right around quarter to half throttle. That gets to around 4500rpm and then goes all horrible. I tried going down the A30 at the crack of dawn and cutting the motor at this rpm and coasting into a layby to examine the plugs. Looked a bit whitish.At low speed it seems rich.
So things to check include fuel flow to carbs, float height/ fuel volume in floatbowls, air leaks at manifolds, any evidence of muck or water in the float bowls. Blocked carb passageways can be an issue. Does it happen with both taps open?
Is this after replacing the enricher ( chokes)?
Other things to check might be plug caps and connections.
Best of luck
John

[SupermotoDave]

Fuel pump?
The general recommendation and received wisdom is do not fit K&Ns, Morini’s like the air box and people hunt high and low for them if they are not fitted.

[harrymuffin]

I have K&Ns fitted to a 507 5speed. The carbs are 28mm and have no problems with flat spots right through to my imposed 7500rpm limit. At around the 3500 mark she pulls like a steam engine with the front end gently lifting. I did through experience on a SEI with K&Ns fit a half shroud over the front facing carb mainly to stop the water being sucked in and filing the float bowl with water with heavy rain and road spray. I have one also fitted to the 507. Just wondering if this rough running is at speed as it could be the super charging effect of air into the forward facing carb that pressurises the float bowl and hence maakes that cylinder go rich hence eight stroking. Tyr the bike in low gear - 2nd and see if it happens, it is only when you tend to go up to around the 40mph that this happens hence a shroud on this one too. There is no point on doing a plug chop now as there is no lead in the petrol which is what you were looking at. Also check your ignition timing, if retarded the plugs run too hot and will slow the engine down and not spark at the right time, gained from experience on bikes and cars.

[simonnorthroad]

I've always (35 years) had pancake not cone K&Ns on my 500 but mounted vertically on the end of the carb-to-airbox rubbers up.under the tank. No problems and the Late, much missed Phil Smith of Weevee said it was the best performing 500 he'd ridden.
Part of me wonders if once the air has pushed through the pleated paper of a K&N into the Venturi whether it matters much if the filter is facing forward or back.
Riding in the rain is a very different matter though!

[Jack]

Thanks for the replies chaps, very helpful.

To be honest Dave, I had presumed that the front tap was a small electrical fuel pump/fuel tap.
I have just found a thread posted on the board about replacing this tap with an MZ ETZ manual tap. Does anyone know what other, if any, manual fuel taps can be used to replace the electric one?
I had always turned on the other fuel tap, assuming it was the main fuel tap, no, I know...
I now presume this is the reserve tap?!
You would all be right if you guessed that I didn't have a user's manual, and that I don't know much about them in terms of "specialist" knowledge.
But, I'm learning every day.

It basically cuts out mid-rev range under load, and then returns, as if instantaneously/transiently it simply can not get enough fuel.
Which is why I thought is was a fuel pressure problem., vacuuming problem etc.

I have got one carb stripped down, and it honestly looks very clean inside, no residues, staining, blockages - that I could see. Needle was like new but all the rubber bits are a bit worn, or very worn.
I've just bought a 10L ultrasonic cleaner, so the carb bodies will get a good deep clean, all new seals and so on. (Some good ideas there John, that finally persuaded me to get the cleaner!!)
Apparently, it had been sat in someone's collection for years largely unused. That's what I was told when I bought it anyway. It is showing signs of storage. Classic duff fork seals and poor oil of a bikle that has sat around.
I haven't swapped the plugs yet...you never know I once tried three pairs of iridium plugs in the Norton, which ate them. And ran dreadfully, where other people did not have a problem. Nope, no ideas.

Harry, that's an interesting point. If none of the basic simple stuff works, I'll look at that.

I love the sound of the pancake filters Simon, can you advise size etc? I might still have a pair from an old A65, but I think they'll be to big.
I started the Norton yeasteday, after draining 5 pints of oil from the sump, it has been locked down for 6 months! It then started halfway through the stroke of the first kick! That's what proper K&N's and the right jetting and set up can do.

Still, the 500 goes around bends just as I remember the 350 doing, back in the days of my yoof. Wistful smile, small pause, rose tinted specs...

...and then back to bloody carburettors!

Thanks again lads,
Jack

[AntietamClassicCycle]

Does anyone know what other, if any, manual fuel taps can be used to replace the electric one?

Moto Guzzi V35/V50/V65 petcocks fit and work pefectly.
https://www.gutsibits.co.uk/pr/TheShop/ ... rch=SEARCH

[3potjohn]

I get mid range stuttering and occasionally cutting out when throttling back at speed on my 507 but the chaps following me yesterday all said the could smell petrol so it sounds like I am running too rich. It has certainly felt like another bike I had when the choke seals had failed but these are good. Will have follow this up. I find carbs to either be dead easy and completely reliable or a SOB.
John

[simonnorthroad]

Guzzi dealers usually sell a variety of taps: on/off, on/off/reserve, bottom outlet, rear outlet, side outlet
If you buy ramair filters they are soft foam and will sit under the tank happily. Just measure your carb rubber diameter and order accordingly? either to push over or in. I have drilled and used self-tappers through both filter neck and carb rubber as belt-and-braces to stop them dislodging

[Steve Brown]

You mentioned the rubber parts are in poor condition? Well the rubber seal at the bottom of the cold start plungers/'chokes' are very important. If they don't make a really good seal then you will never have good carburation. So as well as the ultrasonic cleaning (do that a few times) fix those seals as soon as possible. Either separate seals or complete plunger can be had.
If the bike has stood as long as you say then the carb internal passages can take a bit of effort to clean.

[Jack]

Steve Brown: a very delayed reply. Thanks for your help, very useful indeed.
I threw the choke cable away (seals were utterly knackered - good shout), and took the choke lever off it now has the carb chokes on each carb.
I stripped and sonic cleaned the carbs, and due to previous poorly repaired damage to the air-box put new K&N filters on.
Now it fuels and breathes well, I'll just have to keep an eye on the filtration side. The plan is to repair the air box using the 3d printer.

And in conclusion, I did a full service, new fork oil seals, new cam-belt etc., and some tuning, and now there is another Morini back on the road!

I went to the Bell at Aldworth with George on Wednesday evening, and it ran well over the 85 miles or so that we did. The only thing that broke was the speedo cable! But I am expecting to replace all of the cables over the next few weeks anyway.
And I must lower those foot rests, I really, really must...
Thanks to everyone for advice and help, which is much appreciated.
Jack

[Team Buffoon]

I realise this thread is a bit old now but I am struggling with the carburetion on my 501 Camel in NZ. It is an American Import so it is running two
PHBH 30 ES. It is also fitted with K&N Pod filters. If I give it a handful of throttle it bogs down, if I gently increase the throttle it pulls cleanly.

Yesterday a friend and I pulled the carbs apart and checked to make sure everything looked OK. It did but I will be ordering a rebuild kit for them. All the settings were the same on front and rear pot except the needle position. Front was in the 2nd from top slot and the Rear was in the bottom of four (highest needle position).

Question is it normal on a Morini for front and rear cyclinders to have the same settings and sizes? I know some Ducatis have a slightly larger main on the rear.

I have read elsewhere in the Forum that these carbs are hard to set up and people have discarded them in favour of the European Spec ones which I think are a bit smaller and a different model.

Any advice gratefully received.

[3potjohn]

When it bogs can you notice any change with a choke on?
I don’t like the needle position difference. Is that a bodge to work around the air filter?
Can you double check the numbers on jets, atomisers, needles, slides, float action and float height, colour of floats ( white or black) and report findings? Do make careful notes as it is easy to get muddled.

I have had trouble with non standard air filtration leading to an impressive bag of spare jets until I returned my 507 to a standard air box (PHBH28 carbs)

Can you partially cover the airfilters and see what happens?
Useful also to mark the throttle twistgrip to easily show 1/8,1/4, 1/2 positions when testing. Most problems seem to be sub main jet in my limited experience. There is no water in the floatbowls I take it.
Good luck
John

[jb666]

I've got a US Camel 501 and the carbs have a pumper unit in them when you give it some!! I rebuilt my carbs as they were full of gunk and a trip to the ultrasonic bath sorted that out. As for needle positions I can't offer any info without taking the carbs apart.

John.

[norbert]

I´ve done more than 100 000 km with two 501 engines with PHBH 28 (with original 350 airbox, cheap K+N imitations from Luis (imposible with rain!) and Polini airfilters) allways with the same needle position in front and rear carbs. I use 268T atomizer with needle X18 and slides 50 (instead of 40). The position of the needle and main jet changes acording to the airfilters (about 130 with the 350 filterbox wether they are empty or with filters inside, actually 112 with the Polinis).
Consuming about 5,5 l /100km when riding some kind of sportive (no motorways!)