Carb heater lines and fittings

Hi - I am new to monster ownership (1996 m900) and in the past week the bike has begun to run rough - particularly when damp and cold. I immediately fear the worst and assume I've bought a complete dog thats about to die - but take some comfort from Utopia's earlier thread and the fact that the bike had been running like a champ up to recent changes in weather. Have also changed serviceable items to rule out any other basics.

I then figured I had it sussed when I noticed the carb warmer tap on the oil cooler line.... but it didn't make any difference. Having had a poke around to see how it all works this morning I noticed that the heater line is just blocked off and doesn't fasten to the carb.

There is the connecting line between the carbs but nothing else. There is also no return line from the carbs or any obvious 'return' point to the oil system (either at the cooler or anywhere else).

This is my long winded way of asking if anyone can point me in the direction of any diagrams/pics of how the setup should look - have looked through Haynes and Google'd but can't find anything.

Any pointers as to where to get suitable lines from also welcome (I'll be searching eBay whilst motogp is on). As an aside will running the bike with no connections to the carbs where heater line should be be harmful? Has clearly been like that since I bought it a couple of months back so am hoping it doesn't matter.

Apologies for rambling on and thanks in advance for any advice

[Mr Gazza]

Found these pictures on ebay.





Hopefully that should explain how they are plumbed.
Here's a link to the listing. https://www.ebay.com/itm/DUCATI-MONS...4AAOSwVJhZRkVK Rather remote and expensive, but there are more pictures there, so might be helpful.

I'm fairly sure that the tap is a bypass valve, so the oil cooler is never left out of the circuit whichever way the tap is orientated. If you have been running it with the tap in both positions it's fairly certain, as it wouldn't run very long with the oil cooler blocked . The oil comes from the pump, round the cooler and then to the mains.

Nice one - many thanks. Having done some more searching I can see how it works (pretty simple I know). Looks like I am just missing the return hose and fittings to connect to carb as I can see now where it feeds back to the cooler. Will put a quick post in wanted section.

Cheers, Steve.

[Nickj]

On the carbed monster and SS I had there were oil jackets on the carbs and .... neither worked. They were connected but the fuel needs to be hot for the water component not to freeze when it blasts out of the jets. Might be the design predates ethanol and the massive water load it can carry.
The fuel injection motors on the other hand were fine.

I used to use additives and half decent fuel, which did work.

Cheers Nickj - have got some silkolene pro fst on order and always use decent fuel (my wrx demands super unleaded so am used to the pain of expensive fuel)

Am hoping getting it set up as it should be will help a little... still have fingers crossed that it is the change in weather that has resulted in the hesitation / splutter I'm experiencing and nothing more serious/technical.

[Mr Gazza]

Running premium grade fuel can only help, I don't regard it as more expensive, as you need much more of the cheap stuff to go as far.
I haven't got any experience of additives so I can't comment.

When you get some oil lines make sure they are flushed through and that all the fittings are surgically clean. Flush the galleries in the carbs through too if you can. Any muck left behind will go straight to the big end shells, un-filtered.

Moto Rapido might be able to supply new lines at an affordable price. You will get 10% discount too, if you mention you are in UKMOC.

You will probably be able to make the system work better by blanking off the air flow to the oil cooler... There's mention of that in the thread you referred to above, and a picture of how I blank mine off.
You can run with the cooler covered pretty much all Winter. I take mine off when it gets into double figures reliably. There's no worry about it getting too hot unless you get really bogged down in standstill traffic.
If that were the case you could quickly rip it off, if you made a Velcro attached item like mine.

[utopia]

First of all, I would bet virtually anything that you definitely are experiencing carb icing.
Typically, this will first manifest itself in one of two ways ...
1) On slower roads, you'll arrive at a junction and find that your tickover has become virtually non existent and you need to constantly blip the throttle (with spluttery response) to stop the engine from dying. After a few moments at standstill though, the engine heat soaks back into the carbs and the tickover smooths out.
2) On faster roads where you might hold a constant throttle for a couple of miles or more, when you try to shut off for the approaching roundabout or whatever, the engine revs initially wont drop at all and then will do so reluctantly .. and ultimately the tickover issues described above will appear. The icing forms and/or accumulates much more severely at constant throttle openings. I sometimes drop the throttle every now and then on faster roads, merely to minimise these prime icing conditions.

Don't let me dissuade you from fitting the missing pipes to restore your oil heating system to working order .. I'm sure it must help a little.
But (and its a big but) don't expect a cure or even a difference large enough for you to notice .. the general opinion is that they do next to nothing.
ProFST is the only reliable remedy that I've found.
Trouble is, with a tank range of 150 miles, you can never go further than 75 miles from home unless you carry a dose of proFST to dose the tank at a refuelling stop.
My solution (partial) to this is to overdose the tank when I set off and then to make sure that I refuel early enough to retain enough overdosed fuel in the tank to dilute to acceptable levels when topping it up.

As a final point to ponder, I believe that the fuelling mixture/s will have some (probably fairly minor) effect on the propensity toward carb icing .. don't quote me but I believe a richer mixture is less likely to promote icing than a leaner one (though it could be vice-versa).
Anyway, getting the carbs/fuelling accurately adjusted (and maybe erring ever so slightly on the less ice-promoting side) might help.
This is a kind of long shot suggestion on my part and not something I have tried myself, nor (probably) would I .. unless I had other reasons to want to get the carbs readjusted, eg due to age/mileage or an exhaust/air-filter modification. Maybe you might have such a reason, in which case its worth mentioning the icing tendency at the time.

My bike sees little cold weather use, but it definitely does see some and that may well be a distance run too.
That's the main reason I bought my flatslide carbs, cos apparently they're not prone to icing.
I mention this because it highlights the possibility (likelyhood, even) that the direct cable-to-slide connection in the FCRs is more effective at breaking an ice formation than the diaphrahm-controlled slides of the std carbs.
Not that you can do much about that without swapping the carbs, but the knowledge may help somewhat in visualising exactly what's happening.

I'm glad my "icing" thread has been helpful.
I was pretty sure there would be someone out there who was experiencing it for the first time, and was baffled.
I was too and, like you say, the first thought is that there is something much more serious amiss within your engine.
That's mostly why I posted it in the first place.

Oh, and its probably worth pointing out that, to the best of my knowledge, it is the moisture in the air, and the air temperature which are the two main variables in the chain of causation.
Water entrained in the fuel is probably also a factor (as Nick describes) and this can be minimised by using premium, low (or zero) ethanol fuels (which I always do anyway, in all seasons) .. but the airbourne moisture will still getcha.

[Dukedesmo]

Originally Posted by utopia

That's the main reason I bought my flatslide carbs, cos apparently they're not prone to icing.
I mention this because it highlights the possibility (likelyhood, even) that the direct cable-to-slide connection in the FCRs is more effective at breaking an ice formation than the diaphrahm-controlled slides of the std carbs.

To add to the above, my bike has Keihin FCR (flatslide) carbs and whilst it doesn't see much cold weather use it does see some, including on one ride with Utopia where his Mikunis were icing and my FCRs weren't.

Now there is another variable that might have an influence; that mine are split-single carbs and as such are on much shorter manifolds and so closer to the cylinder heads, meaning they are (by location) better heated, plus don't have the 5 inches or so of air-cooled alloy tube for the engine heat to dissipate from before reaching the carbs? but I've never experienced any icing problems with them.

Cold starting and running is another kettle of fish; although the starting is OK once you learn what needs to be done but they are rather stall-prone until there's some temperature in the engine, having a '916 style' fast idle twistgrip helps somewhat - although the extra-heavy throttle action from the FCR springs does sometimes overwhelm it...

[utopia]

.. note that the venturi conditions are also different in the two types of carb and this is perhaps the more likely primary reason for the difference in their tendencies to ice .. but the diaphragm operation to the slide seems more than likely to be an additional contributory factor.

[utopia]

Luckily (?), carb icing begins and ends roughly in parallel with road salting, at which point I ride my thumper instead.
For some reason, it never ices its single carb.
I'm inclined to conclude that the monster's long inlet manifolds may have some influence.
As Dukedesmo suggests below.

[Zimbo]

I had FCR41s on a 900 monster, fitted as a pair with airbox, and they were never affected by carb icing. The standard carbs however definitely are, the only reliable solution is to use ProFST in the fuel when the weather gets cool and damp ...

[Darkness]

Originally Posted by Zimbo

?.......the only reliable solution is to use ProFST in the fuel when the weather gets cool and damp ...

Or wrap it up warm in your garage/shed and ride something else on the salted roads.

[Zimbo]

Originally Posted by Darkness

Or wrap it up warm in your garage/shed and ride something else on the salted roads.

I must admit that's what I do these days, SORN the monsters and use the car. Heated seats, aaaahhhhhhh ....

Cheers for the replies and advice... am loving this forum - very helpful!!!

I must admit I relied on the car this morning and bike is tucked up in garage.

With it being relatively new to me I am working through the issues as they arise. I figure the more I do when the weather is pants the more 'trouble free' time when it warms up. I already know the starter motor needs some attention and the clutch feels like it's been slipping when giving it some beans.

Never worked on a duc before so expect more daft questions to come...

Cheers

Steve