Trying to get beloved Sport back on the road- poor idling

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Long_Road
Posts: 46
Joined: 19 Sep 2017 20:03
Location: Southampton, UK
Location: Southampton, UK

Trying to get beloved Sport back on the road- poor idling

Post by Long_Road »

I have just rebuilt the top ends of my beloved 1977 3 ½ Sport and got her running again after a long seven-year hiatus (and it’s wonderful to hear that bellowing engine note again), but before I go any further and start randomly spending out, I would very much like to hear your thoughts.

She just won’t idle. I’ve made many adjustments and replaced parts, and things have improved but there is always the inevitable slowing and then stop. In the real-world environment, with heavy traffic and accelerate-brake, the cutting out is more pronounced and common. It’s kick-start only so it takes a little while to get running again – too long for impatient car drivers.

I have read the 3 1/2 forum extensively and so far have made the following changes/adjustments:
Fit new spark plugs
Balanced carbs – idle screws and cables (with gauges)
Adjust fuel mixture screws
Fit new pilot jets - first 50s, then 45s, then 42s
Check and replace all seals in carbs, including choke seals
Adjust carb float height to spec
Check and adjust ignition timing with timing light

It’s at the stage now where it will idle for a good 2 mins, in a controlled environment; well, the garage. However it is prone to changing speed, and always eventually slows and stops. I wonder if the Morinis are vulnerable to the slowing because of the light flywheel and ignition which retards itself to prevent kickback? Just an idea.

The ignition timing session was interesting. Essentially the more I advanced the pickup, the faster and more stable the idle got. It’s currently set at the ANT mark at idle. I know this is massively wrong (and haven’t ridden it) but setting it to spec means it will hardly idle at all, and is also difficult to start. Otherwise, it would appear to be advancing and retarding as normal.

I would like to use the original ignition setup but I’m wondering if it is getting tired. I like the idea of the bike running independently of the battery but am considering NLM’s setup if it gives me a reliable idle.

Any thoughts or advice would be appreciated. Sorry for the long post – I wanted to give the best idea of my current situation.
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MickeyMoto
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by MickeyMoto »

Do you have any leaks in the inlets or exhaust?
Long_Road
Posts: 46
Joined: 19 Sep 2017 20:03
Location: Southampton, UK
Location: Southampton, UK

Re: Trying to get beloved Sport back on the road- poor idlin

Post by Long_Road »

Thanks for the reply. I haven't any leaks in the exhaust, but need some kind of water sprayer to test the manifolds. The rubber is still good.

This is what I need, other angles to get me thinking.
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72degrees
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by 72degrees »

The NLM setup does not require a battery. The Sachse and SWF digital systems do.

You don't have to use the NLM pickup if yours is OK. Their module will work with an OEM pickup.

They currently recommend fairly large HT coils as fitted to XV250s etc. but my road machine runs OK using small 2 pin scooter coils.

Having said that, the 'racer' actually idles even more reliably and at lower rpm than the road version. That does use an NLM pickup where you can set the timing on each cylinder independently, but it needs a faster kick to get it started.

What idle speed are you aiming for? On the road machine I tend to tolerate a fairly high tickover once hot to avoid any embarrassing moments. If I adjust it down a little it tends to then conk out sometimes when only warm.
Long_Road
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Joined: 19 Sep 2017 20:03
Location: Southampton, UK
Location: Southampton, UK

Re: Trying to get beloved Sport back on the road- poor idlin

Post by Long_Road »

Oh, the NLM unit doesn't require a battery either? Now I'm more tempted. Also like the idea of getting both cylinders timed spot on.

It's currently set at approx. 1700rpm, it sounds happy at this speed. These Morinis seem to like a fast idle.

Thanks for your input.
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72degrees
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by 72degrees »

1700 rpm should be achievable reliably but I will confess to letting it settle to nearer 1800 on my road bike since my arthritic hips made it even trickier to start while sitting on it at traffic lights.

Does it have a 'balance pipe' between the carbs? That would be the first place to start looking for an intake air leak. Some people (including Evguru) remove it and blank off the stubs. Might be worth a try to see if it has any effect.

If you go for the NLM pickup be prepared to spend a fair amount of time setting it up. It requires a tiny air gap between the rotor and the pickup coils. I couldn't achieve it as supplied and had to do some elongation of the adjustment plate slots.

I suppose you shouldn't rule out a stator ignition winding that is below par, but if it starts again easily it shouldn't be the issue. Reading your description of the reaction to changing the static advance, however, does make me wonder. Presumably it has correctly 'matching' transducers and pickup as they seem to be the original ones.
mgelder
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by mgelder »

The tickover and starting on my 350k were improved by getting the ignition / alternator stator rewound. I didn't think there was much wrong with them before, but it made a noticeable difference to the steadiness of the tickover.
Morini stuff on RealClassic.co.uk: http://www.realclassic.co.uk/profiles.html#morini
simonnorthroad
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by simonnorthroad »

My thoughts are with MickeyMoto - spray around the manifolds with carb-cleaner/WD40 to see if the revs rise and youve got a slight air-leak
norbert
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by norbert »

simonnorthroad wrote:My thoughts are with MickeyMoto - spray around the manifolds with carb-cleaner/WD40 to see if the revs rise and youve got a slight air-leak
+1
Long_Road
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by Long_Road »

Ok guys thanks very much, I don't have any WD40 or carb cleaner at the moment (and I call myself a biker!).

I tried squirting water over the manifolds (engine running) with my little boy's water pistol, but it doesn't shoot very well!

A bit inconclusive. It didn't have any effect, but I'll pick up some WD40 and have another go. I do remember in the murky past needing to exchange the flywheel because mine had lost it's magnetism - there was also some related heat damage to the wiring loom at the 'exchange' (fuses), but as it was North Leicester who discovered it and carried out the repair work I think everything is ok in that area. Sorry about being vague! My point is perhaps a stator rewind is also needed as it is related.

It does start from cold, and hot restarting well - usually 2nd kick. There is no carb balance pipe.

I've read about the NLM pickup in these forum posts - I don't mind spending the time to set it up. This bike has taught me to be very patient.

Many thanks again for your ideas.
norbert
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by norbert »

Water won´t help much. Probably you´ve got some brake cleaner spray. That´s what you have to spray around the rubber intake between cilinderhead and carb when the motor is idling. If the motor rises you have some leak over there.
Long_Road
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Joined: 19 Sep 2017 20:03
Location: Southampton, UK
Location: Southampton, UK

Re: Trying to get beloved Sport back on the road- poor idlin

Post by Long_Road »

Just sprayed the manifold joints with WD40 with no effect. Also tried spraying the adjustment screws and metal plugs in the manifolds just in case.

Still reading this forum and discovered that the idle and mixture screws are maybe meant to have o-rings fitted? Well I recently used a couple of Dellorto seal kits and found a couple of o-rings that do fit the respective screws, fitted them in and idle seems a little better, but I didn't run it long enough to draw any conclusions - It's the little boy's bedtime and didn't want to disturb him.

Just to add, I did the spray test after fitting the o-rings. Maybe I should remove them and try again...

More tomorrow!
Long_Road
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Joined: 19 Sep 2017 20:03
Location: Southampton, UK
Location: Southampton, UK

Re: Trying to get beloved Sport back on the road- poor idlin

Post by Long_Road »

Tested the spark for both plugs and they seem quite weak and blue. The rear spark jumps around the electrode a bit too, which I believe manifests as a slight loping at idle.

Could somebody please advise how to test the stator output?

HT leads appear good and supple, but I will test those. I also have plug caps with 5k ohm resistance, perhaps these aren't helping?

To continue from my last post, I read the forum a bit more and it seems that some of the Dellorto VHBZs had o-rings on the adjustment screws, some didn't. I don't believe their presence is making any difference in this case.
simonnorthroad
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by simonnorthroad »

A weak spark is orange surely. Seeing a blue spark on a Morini spark-plug is a bonus, Id have thought.

Also try and eliminate any resistors in the ignition. Having said that, Ive got NGK plug-caps which I believe ALL have a resistor in, red or black. Use BP not BPR plugs (NGK prefix)

Are your spark-plugs DEFINITELY the genuine item?. Ive had loads of duff/fake(?) NGK plugs in recent years, but mainly causing non-starting not poor-running problems. Ive always found Palladium BP EVX racing NGK plugs improved starting and running
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72degrees
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Re: Trying to get beloved Sport back on the road- poor idlin

Post by 72degrees »

The stator winding on my 'racer' gives 80v AC at idle rpm (resistance is 250 ohms). Connect a multimeter between the green wire and earth. It was ticking over remarkably reliably yesterday in the rain - despite me finding this morning that the front plug cap wasn't clipped on firmly! That has an NLM ignition setup.
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