Greetings Morini aficionados, it’s been three years since I last posted here, and that is for unfortunate reasons. You see, in my last thread I gave the impression that my 350 Sport was cured and we lived happily ever after, but in truth the bike still ran badly and was banished to the edge of the garage. After hours of exhaustive experimenting and adjustment, I was stuck, and gave up.
My previous thread: http://www.morini-riders-club.com/forum ... f=4&t=4819
I’ll try and keep it to the point. Over time I had some new ideas which I have just recently tried out, but am still not quite there. The bike starts, runs and rides quite well but the engine idle keeps changing speed, and often will slow to a stop. It’s tricky to restart the Morinis in traffic; find neutral, swing the left-hand kicker and hope it catches first time. I need a steady reliable idle to enjoy this bike.
In addition to what I’ve documented already I have recently:
• Sealed the cylinder head gaskets with Wellseal
• Replaced the rubber carb manifolds with brand-new – old ones had cracked internally
• Retightened and threadlocked inlet stub/carb mount on rear cylinder – was loose
• Set the float height to standard 10mm, refitted 50 pilot jet
• Rebalanced carbs, adjusted mixture screws
The bike is now the best it has ever been, but the idle is still inconsistent, moving between roughly 1900 and 1200rpm, and often slowing to a stop quite suddenly. Blipping the throttle seems to cause the changes. I suspected air leaks (and still do) but haven’t had consistent results.
First I sprayed around the carb seals with GT85, and when applied to the cylinder/manifold seal the engine stopped. This occurred on both sides. ‘Bingo’, or so I thought. This is the point I inspected the rubber manifolds and replaced them. However, subsequently the same thing happens with the new manifolds fitted.
What I find strange is the engine didn’t stop when I tried WD40, or water. Was the GT85 stopping the engine for a different reason beyond my understanding? Is it a false lead? Are my carbs simply worn out?
The idle issue feels like an air leak to me, but I can’t prove it. Moving forward, I'm going to buy some brake cleaner and try that, and also try removing the plastic collars that the jubilee clips sit on.
Any thoughts from your experienced minds would be hugely appreciated – thank you.
Three years later, still having problems with idle
Re: Three years later, still having problems with idle
In an ideal world borrowing a set of carbs would be useful.On my Sport I have never had carb problems.Any changes I have made e.g. to idle jet size have adjusted exactly as you would expect.
On another Morini With PHBH carbs it has been very troublesome. This used to idle then cut out.I still think there is something amiss with one carb, in spite of much cleaning, replacing jets and needles and adjusting floats etc.I even blocked off the enricher circuit with a small bolt in place of the jet to eliminate that cause but to no avail.I cannot see any light through the slide when closed either.
In my case air leaks at the exhaust/ silencer joints definitely did not help.
If you close the mixture screws on each side does that cylinder cut out or at least nearly so.
Of course your problem may be ignition related. Not had this luckily.
Keep at it.
John
On another Morini With PHBH carbs it has been very troublesome. This used to idle then cut out.I still think there is something amiss with one carb, in spite of much cleaning, replacing jets and needles and adjusting floats etc.I even blocked off the enricher circuit with a small bolt in place of the jet to eliminate that cause but to no avail.I cannot see any light through the slide when closed either.
In my case air leaks at the exhaust/ silencer joints definitely did not help.
If you close the mixture screws on each side does that cylinder cut out or at least nearly so.
Of course your problem may be ignition related. Not had this luckily.
Keep at it.
John
Re: Three years later, still having problems with idle
Thanks for your thoughts John.
-
harrymuffin
- Posts: 292
- Joined: 07 Apr 2014 16:06
- Location: west midlands
Re: Three years later, still having problems with idle
Inspect the suction side of the carburettor slides. They should be flat but owing to the crap material they are made from, wear and you can see the inprint of the choke. If this is really bad then the slide does not seal against the body of the carb, so you get a varying vacuum and hence varying engine speeds till there is no vacuum left to suck any fuel through the idle jets. That maybe why you get the engine slowing ans stopping if ypu blip the throttle as you upset how the slide came to rest and then not enough vcuum to keep the slide to close off the main choke.
-
mad muller
- Posts: 182
- Joined: 19 Aug 2011 11:29
- Location: liverpool, england
Re: Three years later, still having problems with idle
It sounds like it's hunting for fuel have you tried another set of carbs or maybe loan a pair I have put manual fuel taps on mine it's on or off to eliminate doubt , as the electric one was buggerd check the slides are in the right way obvious but check as you say there is no air leaks like us all the bikes are getting on a bit and parts ware out there might be a mikuni or other carb that will go on I don't have any carbs spare otherwise I would let you have them , try setting it up one cylinder at a time eg running on one then running on two if balance pipe is fitted between carbs remove and blank it off to see if it runs any better it's worth returning to standard jet sizes if you can , stick at it you will get there.
Re: Three years later, still having problems with idle
Thanks Harry, something else which is new to me which I will inspect.
And thanks Mr Muller - I've considered different carbs like the PHBL but for now want to keep the spending down until I am convinced something needs changing (the rubber manifolds cost me £90 all in!). They'd also need jetting and tuning etc, another headache. However I'm willing to do it if I have to.
I've got a manual fuel tap fitted, and tested the float needles today - strong flow. There's no balance pipe. Jetting is standard. Trying one cylinder at a time is another good idea.
I do remember now that I have a pair of VHBZ 25 HS (Kanguro?) knocking around. I tried them years ago but didn't realise that the copper takeoffs were potential air leaks. I will consider retrying them with everything blanked off.
And thanks Mr Muller - I've considered different carbs like the PHBL but for now want to keep the spending down until I am convinced something needs changing (the rubber manifolds cost me £90 all in!). They'd also need jetting and tuning etc, another headache. However I'm willing to do it if I have to.
I've got a manual fuel tap fitted, and tested the float needles today - strong flow. There's no balance pipe. Jetting is standard. Trying one cylinder at a time is another good idea.
I do remember now that I have a pair of VHBZ 25 HS (Kanguro?) knocking around. I tried them years ago but didn't realise that the copper takeoffs were potential air leaks. I will consider retrying them with everything blanked off.
Re: Three years later, still having problems with idle
Hi,
Since many have already covered possible carburettor issues.
I will chuck some alternatives I have seen on a few occasions.
Erratic idle found to be due to a disintegrated or loose aluminium core of the pick up rotor,
when on the road it runs fine as the slack is taken up, but when idling it chatters.
It is worse than the erratic idle seen with a very loose belt.
I have a couple of broken rotors and one with a magnetic core that has gone soft,
the usual cause of the failure is the lack of the special cup shaped washer.
Weak ignitions systems can also fail to spark when the vacuum is suddenly increased
due to the higher spark voltage needed. If the revs can be increased gently and smoothly,
but stutter on quick throttle openings then do check out the ignition
as well as the condition of the slides as advised by Harry
Similar issue of erratic idle on a strada was simply a corroded HT lead.
Just some other things to check and rule out.
Mark
Since many have already covered possible carburettor issues.
I will chuck some alternatives I have seen on a few occasions.
Erratic idle found to be due to a disintegrated or loose aluminium core of the pick up rotor,
when on the road it runs fine as the slack is taken up, but when idling it chatters.
It is worse than the erratic idle seen with a very loose belt.
I have a couple of broken rotors and one with a magnetic core that has gone soft,
the usual cause of the failure is the lack of the special cup shaped washer.
Weak ignitions systems can also fail to spark when the vacuum is suddenly increased
due to the higher spark voltage needed. If the revs can be increased gently and smoothly,
but stutter on quick throttle openings then do check out the ignition
as well as the condition of the slides as advised by Harry
Similar issue of erratic idle on a strada was simply a corroded HT lead.
Just some other things to check and rule out.
Mark
Re: Three years later, still having problems with idle
I agree to what Harry and Mark said.
I don´t know what GT85 is, but too seek false air you should use brake cleaner and not WD40.
I would try the VHBZ from that Kanguro after getting them setup with the jets required for the Strada air filter. But you need a VHBZ 25 HS!
I´ve examinated lately the VHBZ 25 and VHBH 28 a bit more serious and found out astonishing things (mainly with the VHBH 28, I´ve got for examle three diferent housungs all named VHBH 28
) There is an article about that in the last La Strega 
Just a little resume of the VHBZ 25, if you like:
There are two, the BS and the HS. One of the two main differences is that the BS is for the old metal intake manifolds and therefore slotet on the side towards these manifolds carburater/head. You can use them with the rubber manifolds but then need the black plastic reducing tubes on this side fitted in the HS version (right hand BS of the foto). Meanwhile you cannot use the HS with the metal maifolds. The second main difference ist that the HS have the brass coloured vacuum tubes (for using balance clocks, depression fuel taps, scott oiliers etc.) This ports mut be connected with a tube or closed carefully. And the HS have two little brass tubes for ventilacion of the float chamber. They are useful on enduro and cross bikes because these ones are more often lying on the side and will not loose petrol that easy if there are tubes on them reaching up under the tank. Forget about the ventilacion tube on the outer side (with the screws for mixture and slide height) This ones are fake drillings, not reaching to the chamber.
The BS ventilacion drillings are semiclosed with a metal seal that allows breathing (like the older VHB 25 and the older VHBH 28). With the VHBZ BS it is the other way arround: Here the inner ventilacion drillings are not reaching to the float chamber, so ventilacion works on the outside. And there a very little drillings as well in the ventilacion chimneys close to that metal seals. This drillings are open as well, meanwhile they are closed on the HS version.
Since I´ve discovered that, Im quite sure that the famous carburator problems with strong side wind is happening probably only with the BS edition. Can anybody confirm this?
The fotos show the two sides of the VHBZ BS above and the VHBZ HS below:
(the metal seal of the left hand BS was taken off to replace it by a little corner tube that some of the enduro riders will know, the forerunner of the later brass tubes with the HS)
BS with the metal manifold
last not least: the BS dont´t show a production year, the HS do. But you have to remove the floats to see the year. My VHBZ 25 HS housings with dismantled floats are from 1985.
norbert
I don´t know what GT85 is, but too seek false air you should use brake cleaner and not WD40.
I would try the VHBZ from that Kanguro after getting them setup with the jets required for the Strada air filter. But you need a VHBZ 25 HS!
I´ve examinated lately the VHBZ 25 and VHBH 28 a bit more serious and found out astonishing things (mainly with the VHBH 28, I´ve got for examle three diferent housungs all named VHBH 28
) There is an article about that in the last La Strega Just a little resume of the VHBZ 25, if you like:
There are two, the BS and the HS. One of the two main differences is that the BS is for the old metal intake manifolds and therefore slotet on the side towards these manifolds carburater/head. You can use them with the rubber manifolds but then need the black plastic reducing tubes on this side fitted in the HS version (right hand BS of the foto). Meanwhile you cannot use the HS with the metal maifolds. The second main difference ist that the HS have the brass coloured vacuum tubes (for using balance clocks, depression fuel taps, scott oiliers etc.) This ports mut be connected with a tube or closed carefully. And the HS have two little brass tubes for ventilacion of the float chamber. They are useful on enduro and cross bikes because these ones are more often lying on the side and will not loose petrol that easy if there are tubes on them reaching up under the tank. Forget about the ventilacion tube on the outer side (with the screws for mixture and slide height) This ones are fake drillings, not reaching to the chamber.
The BS ventilacion drillings are semiclosed with a metal seal that allows breathing (like the older VHB 25 and the older VHBH 28). With the VHBZ BS it is the other way arround: Here the inner ventilacion drillings are not reaching to the float chamber, so ventilacion works on the outside. And there a very little drillings as well in the ventilacion chimneys close to that metal seals. This drillings are open as well, meanwhile they are closed on the HS version.
Since I´ve discovered that, Im quite sure that the famous carburator problems with strong side wind is happening probably only with the BS edition. Can anybody confirm this?
The fotos show the two sides of the VHBZ BS above and the VHBZ HS below:
- k-VHBZ 25 (BS oben, HS unten).JPG (50.07 KiB) Viewed 6801 times
BS with the metal manifold
- k-VHBZ25 BS mit Metallansaugstutzen.JPG (35.67 KiB) Viewed 6801 times
norbert
Re: Three years later, still having problems with idle
When I replaced my choke plungers it made a huge difference to idling. Have you thought of doing that?
DD
DD
MRC 3082½
Re: Three years later, still having problems with idle
Thank you everybody for your informative and interesting answers. I have to go to work now but will write again later.
Lots still to consider and check. Will try to pick up some brake cleaner today.
P.S. GT85 is similar to WD40, except it's a penetrating lubricant rather than a water dispersal. Smells strange too!
Lots still to consider and check. Will try to pick up some brake cleaner today.
P.S. GT85 is similar to WD40, except it's a penetrating lubricant rather than a water dispersal. Smells strange too!
-
harrymuffin
- Posts: 292
- Joined: 07 Apr 2014 16:06
- Location: west midlands
Re: Three years later, still having problems with idle
A bit of useless information for you. WD40 was developed by an Australian company trying to produce a liquid product that would displace water and leave a film on the surfaces that would deter further deposits of water/condensation. They kept failing with all the combinations and amounts of various liquids and labelled each formula, Water Displacer 1, 2, 3,---40 which was the eureka moment. Rather than call it something stupid they simply labelled it as WD40 and the rest is history and even NASA use it on their rockets.
Re: Three years later, still having problems with idle
To add to the fund of knowledge, it is also used in Nuclear Reactors as it is free of silicones (IIRC).harrymuffin wrote:A bit of useless information for you... and even NASA use it on their rockets.
Re: Three years later, still having problems with idle
So when did the can change from white, blue and yellow, with the Rocket on it?
I am now wondering about those slides on my PHBH carbs especially in view of a lack of response with one mixture screw and a blanked off choke.They looked OK or so I thought..Not a cheap item.However on close inspection I believe that the good carb has a perfectly round hole visible with the pilot screw removed but the bad carb has a very slightly oval hole, so I may never have a responsive mixture screw.Bit more testing .....
John
I am now wondering about those slides on my PHBH carbs especially in view of a lack of response with one mixture screw and a blanked off choke.They looked OK or so I thought..Not a cheap item.However on close inspection I believe that the good carb has a perfectly round hole visible with the pilot screw removed but the bad carb has a very slightly oval hole, so I may never have a responsive mixture screw.Bit more testing .....
John
Re: Three years later, still having problems with idle
Hi John that with the oval hole dosn´t sound very good. I guess you are talking about the little mixture screw. Are you sure that you dismantled and put back the tiny washer and O-ring on both carbs?
I think you are talking about the PHBH 28 BS originally for the 501 motors. Which model do you have? I´ve got three diferent housings, all named BHBH 28 BS (1-4 from the left side, 4 is only a variation of 3 with a corner tube to ventilate the choke system)
The most interesting diference is between 1 and all the others (newer ones): The idle mixture sistem is totaly diferent. You can see from the outside that the chanel (where the modern ones have written PHBH 28 BS. The older ones have written this on the otherside )is going a very diferent way, ending up at the head-side like this: the old one on the left . The idle sitem end in two rabbets, meanwhile the newer ones are ending like we know that from the VHB carbs on the right hand at about 5 o clock
I discovered this a few month ago when trying to adjust my carbs. And noticed that I have an old and a newer one each on Dulcinea and Rocinante. They work both more or less fine, but maybe this is an explicacion for strange and diferent behavier using chokes to start them (one of the old ones is on the front and on the other bike on the rear cilinder and it´s a bit dificult to reach the rear choke at Dulcinea because of the big aluminium tank). There are still some miracles appearing with that old fantastic bikes 
I wonder wether this change of the idle sistem was an imrovement or just dued to lower production costs
ciao
norbert
I think you are talking about the PHBH 28 BS originally for the 501 motors. Which model do you have? I´ve got three diferent housings, all named BHBH 28 BS (1-4 from the left side, 4 is only a variation of 3 with a corner tube to ventilate the choke system)
- k-PHBH 28 BS (1-4 von links).JPG (55.9 KiB) Viewed 6741 times
the old one on the left . The idle sitem end in two rabbets, meanwhile the newer ones are ending like we know that from the VHB carbs on the right hand at about 5 o clock
- k-PHBH 28 BS (1 links, 2+3 rechts).JPG (42.05 KiB) Viewed 6741 times
I wonder wether this change of the idle sistem was an imrovement or just dued to lower production costs
ciao
norbert
-
Stubaker58
- Posts: 72
- Joined: 28 Apr 2019 21:02
- Location: Felixstowe, Suffolk
Re: Three years later, still having problems with idle
Hi Norbert,
Great photo information, thanks.
BTW the toothbrush I understand but the plastic bull?!
Regards
Great photo information, thanks.
BTW the toothbrush I understand but the plastic bull?!
Regards