Accelerator pump issue - help please!

W

Wheelnut

New member
Location
England
Hello all, I've just acquired a Mirage 1200 in orange that was on eBay recently and it's already causing me grief!

It was bought as a complete bike assembled with many new parts, but it hadn't been properly commissioned or run on the road. I was anticipating a few issues...

First problem was that it thought it was a twin. Two of the ignition leads were transposed and also the ignition modules were wired incorrectly - left to left coil and right to right coil, so completely wrong!

So having got the engine running on three cylinders I took it for a run up the road. That's when I discovered that it didn't like to accelerate. Open the throttle fast and not much would happen, but it would run up through the revs okay on a more gentle throttle. So I reckoned the accelerator pumps needed priming. Did that, but still the same. Took out one of the the throttle slides and found that the operating mechanism for the accelerator pump was entirely missing. Same on all three carbs!

Can anyone give me some hints on which bits I need and where to get them from? I haven't worked on Dellortos before so not sure what the missing parts even look like. Strangely, the carbs have been rebuilt and look like new!

Here's one of the throttle slides with a slot for the missing part.

IMG_9065.jpeg
 
There is a plastic arm held on with a pin and a tiny spring between said arm and the slide to hold it against the slide. A hell of a lot of people do exactly what you have as they recon they don't do much to help other than waste fuel spraying it needlessly. In my experience they help, my reason is they do increase the effort required to twist the throttle and my old Husky came with a Del as std and it had horrible slow speed control so I thought I would try removing it. The action was lighter but it lost its ability to wheely over obstacles. I put those bits back and lightly lubed that groove the plastic arm ran in and got a great result. Just to end the correct adjustment for the squirt is X twists should result in X millilitres of fuel. I forget the numbers though. BTW check the jetting and carb are synchronized, the accelerator pumps have an effect but it's not huge.
 
Quite common for the pumps to be deactivated, as Vince said, to lighten the throttle. Opinions are mixed as to the usefulness of them with our bikes at all, except to burn extra fuel, so I wouldn’t waste time with them in relation to your problem.
How’s your advance?
 
So the flat mid range response might not be the accelerator pumps. Carbs have all been cleaned and rebuilt with many new parts by a company called JRS. Don't really know what else has been done to the engine as the guy who did most of the work is sadly deceased. I realise that I need to check everything over, but fitting the actuating arms for the accelerator pumps has to be worth a try to see if there's any improvement. It goes pretty well once past that flat spot and at 5000rpm plus, so I think it's unlikely to be cam timing, but could be wrong.

Incidentally, this is not my first taste of Laverda ownership. I ran an Alpino 500 for a while, all dressed up like a Montjuic in orange with silver frame, but that was way back in the late 1970s. Had to replace the cams at a low mileage as they weren't properly hardened, if I remember rightly.

Here's the Mirage:

IMG_9045.jpeg
 
Wheelnut said:
Incidentally, this is not my first taste of Laverda ownership. I ran an Alpino 500 for a while, all dressed up like a Montjuic in orange with silver frame, but that was way back in the late 1970s. Had to replace the cams at a low mileage as they weren't properly hardened, if I remember rightly.
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Ah! The infamous "chocolate camshafts"!
 
Nice Laverda, hope it meets your needs. May well save time by inspecting the actual fitted Jets, listing them here, slide type number and needle number and clip position. Float height will need careful attention, as a first "adjustment check". Type of air filter. Also Ignition system information will help the experienced folk here to save you time and efforts. Fuel tank cleanliness another easy check. hope that helps. j
 
You may need more than just the actuating arms to get the pumps working again. As rez suggests, contact ducatipaddy

And as John (iis) states, it's well worth checking all carb component details and float heights. Report back with that info plus ignition info.

Finally, is there an air filter fitted inside the airbox? I'm assuming you've checked valve clearances, ignition timing and balanced the carbs?
 
Not accelerating hard is the symptoms people are getting from E10 petrol. I filled my Triumph with E10 recently and when I cracked the throttle open it would splutter and not accelerate. Running okay now on E5. As for the pumpers, I disconnected them on my SF3. Runs slightly better and more mpg.
 
The flat spot has nothing to do with the accellerator pumps, also if you have a double coil supplying number 1 and three have a wasted to spark so you can swap them with no effect.
You need to get back to a starting point to tune your bike.
Your basic issue maybe needles or needle jets.
 
helicopterjim said:
Interesting to see the thin webs on a TS ....... I thought they were long superseded by then.

I suspect that the advice of Paul and Red would inspire me to go through it from front to back. If the ignition was as you reported ........ then some type of monkey must have been the previous mechanic.

Jim
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At risk of the orange paint syndrome.

Paul
 
Thanks for all the advice.

All I have checked so far are safety items and static ignition timing, so there's still plenty to do. The HT leads from the double coil were actually to the centre and one outer cylinder when I got the bike, so that was obviously wrong and easy to put right.

I'm away for a week so there will no progress for a while, but will report back when I get a chance.
 
Wheelnut said:
Incidentally, this is not my first taste of Laverda ownership. I ran an Alpino 500 for a while, all dressed up like a Montjuic in orange with silver frame, but that was way back in the late 1970s. Had to replace the cams at a low mileage as they weren't properly hardened, if I remember rightly.



View attachment 83003
Click to expand...
The needle bearings eat into the cam end surfaces.
Plain bushes cures that.
Paul
 
Just checked and no air filter present. Airbox is empty, which would cause a weakened mixture.

No point in doing anything else until I've checked the carbs and noted what the jets and settings are. The issue is the lack of response at low to medium revs. Over 5k it pulls well.
 
Well, I have managed to get hold of the missing carb parts from the previous owner and fitted them. He had a box of spares, tools and manuals which he got when he acquired the bike, though he didn't feel any obligation to pass them on to me. Some of this stuff is now listed on ebay...

Anyway, with the accelerator jets now working properly the bike feels much more responsive and accelerates strongly, especially towards the top end of the rev range. A huge difference.

That said, I suspect the carburation still needs a bit of tweaking as it doesn't pull quite as evenly or as cleanly through the lower rev range as I would like. But I have never ridden a Laverda triple before, so I'm not quite sure how it should feel.

My Mirage has been fitted with Jota exhausts and the air filter box is empty with no filter, so this may account for the carburation not feeling quite right. I have no idea if the jetting has been altered to suit, or indeed if it needs to be changed with these alterations, but I suspect it does need to jetted to chuck a bit more fuel in there.

I think the next step is to check what jets and needles are actually fitted.

However, a more pressing issue is to sort out the gearchange, which is terrible. Downchanges are fine but it needs a hefty boot to get into a higher gear, especially top, and it's all too easy to find a false neutral when upchanging.

I get the feeling that this is going to be a long project before everything works as it should.
 
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