Author Topic: Starting  (Read 2536 times)

Offline Schurminater

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Starting
« on: August 06, 2017, 11:30 »
May be a trivial question, but having never run Dellorto's before I thought i would ask.

When starting a bike with Dellorto carbs and accelerator pumps,is it normal practice to twist the throttle a couple of times before hitting the starter button?.........or just use the choke system as you normally would and without throttle.

Thought had occurred to me before and i had seen a couple of Laverda riders 'pumping' the throttle before starting up,does the accelerator pumps function with a non running engine?.

thanks in advance of educating

Steve

 

Offline laverdas

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Re: Starting
« Reply #1 on: August 06, 2017, 12:27 »
no need to twist the throttle before starting just use choke and a little throttle , pumping the throttle will just wet your plugs, but if you have no choke then a couple of pumps will aid starting. hope that makes sence
regards andy

Offline Schurminater

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Re: Starting
« Reply #2 on: August 06, 2017, 18:26 »
Loud and clear Andy  (bigthumb) many thanks.

Offline Dellortoman

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Re: Starting
« Reply #3 on: August 07, 2017, 01:59 »
does the accelerator pumps function with a non running engine?.

Yes.
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Offline Laverdalothar

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Re: Starting
« Reply #4 on: August 07, 2017, 08:09 »
On a new (to me) engine, I always start with the least amount of choke possible and gently engage choke while the engine is cranking. This helps to avoid wet plugs.

Make sure though, all choke plungers open and fully close at the same time, else what is just enough for one cylinder might cause another one to piss on the plug (or not start that cylinder), which causes rough running - if the engine barks into live...
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Offline Paul Marx

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Re: Starting
« Reply #5 on: August 07, 2017, 14:55 »
Both methods, eventually combined are used, depending on engine and tune.
The accelarator pumps are mechanical.

Paul

Offline Schurminater

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Re: Starting
« Reply #6 on: August 07, 2017, 17:09 »
Thanks for all the information guys,very useful info,.......i have just adopted the choke on and fire up method with choke reduced and off as soon as possible to prevent over wetting of the plugs,seems to work okay for me and my set up but always good to ask and learn  (thumbup)


Offline CLEMTOG

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Re: Starting
« Reply #7 on: August 08, 2017, 10:36 »
I have seen a lot of triple and twin owners starting their bikes when hot, and having to use the choke to get (re) started, something is wrong if you need to do that, a hot engine should be able to be started using a stick three feet long and just stab the starter button, no choke, no throttle, no pumping the squirt jets, smooth and regular idle should also be instant on a hot engine.

Do 10 miles and then try yours
CLEM

Offline nick7

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Re: Starting
« Reply #8 on: August 08, 2017, 12:40 »
I am not sure about that Clem..think of the heat from a hot triple being conducted through the metal back to the carb..cannot be good? Maybe you have rubber carb mounts which would presumably make a difference...

Offline Grant

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Re: Starting
« Reply #9 on: August 08, 2017, 13:26 »
Why do you think the factory fitted a heat insulation gasket between the head and the alloy inlet stub then Nick?
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Offline nick7

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Re: Starting
« Reply #10 on: August 08, 2017, 17:21 »
To seal  the air joint? Why do you think they might have changed the whole design later as I seem to recall ..was it the series 2?

Offline Grant

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Re: Starting
« Reply #11 on: August 08, 2017, 17:31 »
Leading up to the 120 engine introduction.
That needed to be rubber mounted to counter the different vibes from the 120 crank, and hence the rubber engine mountings too.
A thick fibre gasket doesn't do the sealing. Why do you think it has a recess for rubber 'o' rings?
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Offline sfcpiet

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Re: Starting
« Reply #12 on: August 08, 2017, 19:59 »
The rubber mounted carbs were introduced quite some time before the introduction of the 120 engine.  1000 from #7517, 1200 from#3308.  By then, rubber-mounted carbs had become the norm, almost universal practice by the japs.  The move was probably initiated by Dellorto, rather than Laverda.  Anyway, large stub-mounted carbs were quickly phased out by Dellorto.

Advantages of the rubber mounts are less vibration influencing the carbs, ie fuel frothing, less heat getting to the carbs, and above all, less distortion from the solidly mounted stubs.  To remove most stub-mounted carbs, I need to resort to using a soft mallet, even after loosening off the stub nuts a bit to allow the stubs to align better.  Simply a grand pita.  The insulation plates can be troublesome, allowing the stubs to distort when tightened too far.  Add decades-old o-rings... :o

Actually, the rubber mounts are not ideal for the carbs on 120 engines.  The float valves suffer prematurely from the fierce vibes, which lowers float heights, leading to leaning out at mid to high revs.  Difficult to say if solid stubs would have been better, don't think anybody has tried that.

piet
« Last Edit: August 08, 2017, 20:04 by sfcpiet »
180s feel quick, 120s are...      If it ain't broke, fix it till it is.

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Offline Grant

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Re: Starting
« Reply #13 on: August 08, 2017, 20:45 »
The rubber mounted carbs were introduced quite some time before the introduction of the 120 engine. 

Which is why I said "Leading up to the 120 engine introduction".
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Offline Gravelroad

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Re: Starting
« Reply #14 on: August 08, 2017, 21:52 »
Advantages of the rubber mounts are less vibration influencing the carbs, ie fuel frothing, less heat getting to the carbs, and above all, less distortion from the solidly mounted stubs.  To remove most stub-mounted carbs, I need to resort to using a soft mallet, even after loosening off the stub nuts a bit to allow the stubs to align better.  Simply a grand pita.  The insulation plates can be troublesome, allowing the stubs to distort when tightened too far.  Add decades-old o-rings... :o

Actually, the rubber mounts are not ideal for the carbs on 120 engines.  The float valves suffer prematurely from the fierce vibes, which lowers float heights, leading to leaning out at mid to high revs.  Difficult to say if solid stubs would have been better, don't think anybody has tried that.

piet

Not to forget the factory aproach on the early triples to keep vibes/heat away of the carbs, by using the infamous "rubber sock" stub design. The only thing I really like on them is, that they are somehow self-aligning under operation, so the carbies can be wiggled off rather easy. Otherwise the tubber socks have a rather limited life. Furthermore, it seems the factory had troubles to keep the casting tolerances low enough to align the stubs correctly to the inlet ports, sitting deep down inside the head casting. At least on my 3C, the stub of the R/H cylinder was reworked to align to the inlet port. Must have been a real PITA, so quite understandeable that they went away from this design.

My recommendation for owners of bikes with those old heads with rubber sock stubs (probably not many left), is to check thoroughly the alignment between the stubs and port bores, and in case you find a reworked stub bore on yours, make sure that the stub is installed to its matching cylinder, and in the proper orientation. Will for sure improve the engine performance. Guess how I know. ;)