carb problems (again)

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi all,
im sure your all bored with my ongoing problems trying to set up a 34mm carb on my aprilia rs125,
for which i can only apologise!
but i feel like im getting somewhere!
bike starts first time,
idles ok, if a bit low,
no longer fouling plugs.
only problem is the big one!
bike wont get past 35mph or 5000rpm! (full throttle!)
anyone any ideas on what could be causing this or more importantly - how to cure it!
HELP!
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

What needle / needle position / main jet are you using? With the airbox?

Thought you had given up on the 34 and gone to the 28mm carb.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
still waiting on a bigger jet coming for 28mm carb in meantime....
air box in,
BR9 plug,
K56 needle,
B34 emulsion tube,
60 choke jet,
clip on second from top notch, (moved it up one)
been told to change to K57 needle & B36 emulsion tube 0& get another couple of jets at least 158 &162.??
bikes starting first time without choke.
idling ok,
just no power!
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

From the specs it seems the K56 will give you a generally richer mixture than a K57. So probably well worth starting there.

Diagram of the carb here:-

https://www.smellofdeath.com/lloydy/dellorto_VHSA_VHSB.htm

Attomiser tube on the VHSB in my RS125 is a DP266.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

HI,
was thinking of getting the other needle.
you have just convinced me!
without sounding like a complete noob,
what is the atomiser tube, what does it look like,(still looking at diagram)
& what does it do?
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
gotcha!
took my 28mm carb apart, came across atomiser tube (BN264)
im learning every day!
anyway, now have a bigger jet for 28mm carb, so gonna re-install that for timebeing.
seeing as it ran ok before, im presuming it will run ok now!
this will give me time to strip 34mm carb & see what needs replacing.
so far it looks like : new needle & clip,
new idle jet,
couple of main jets,
& maybe a new atomiser tube.
think it will be worth buying all that or would the expensive be prohibitive?
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Have you any idea what this carb came from? Are you sure it is from an RS125? Have a word with the Dellorto importers and ask about that attomiser tube.

Given that the needle you have is giving a richer mixture than standard I would not be in a hurry to go even richer without a bit of playing first.

To be honest given how common the 28mm carb is compared to the 34 I would be tempted to pick up a cheap decent 28 2nd hand.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi Keith,
not sure if we have a "breakdown in communication here" or what!
but 28mm carb is working ok.
the atomiser tube in the 28mm is BN264.
dunno what atomser tube is in 34mm carb!
will take 34mm carb off bike later,seeing as bike has blown over, god knows what damage has been done!
anyway, the 34mm carb i bought from a guy on aprilia forum who says he had it on his rs,
but i reckon he never got it to work,seeing as it has didfferent parts inside from standard rs set up!
which is probably why he sold it!
im just wondering if its worth replacing all the internals - needle,atomiser(if necessary),idle jet & main jet.
dunno how much all that would cost?
& if i do get it working, will it be a noticeable difference over the 28mm?
cheers,
GAZ

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

The individual bits are not going to be expensive, although it will soon add up buying a load of small items.

I am a bit concerned about what else is different.

There was a fair amount of different on the older 123 engined bikes. As well as a substantially heavier throttle cable.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

Hi Keith,
not sure what else could be different?
i think slide is ok, im sure its the same as everyone else is using.
if i change needle, atomiser tube, idle jet & main jet, is there anything else that may need changed?
im not sure what floats are standard though!
but the body,cap,spring etc is all the same, rite?
cheers,
GAZ
ps- bike blew over during night, so who knows what kind of if damage has been done!
it never rains, only pours!

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

HIi Keith.
took the VHSB LD 34mm carb off bike.
removed atomiser tobe,
its a DP265.
so i should get a DP266 rite?
needle looks rather dodgy as well, middle notch is very worn & its looking like its not true, when i roll it across glass topped table, it seems to have slight bend/curve.
so thats a new needle & a few jets.
hpefully eurocarb will be able to sort me out with correct parts.
cheers,
GAZ