Author Topic: Jetting for obscure small block  (Read 227 times)

Offline Bazil

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Jetting for obscure small block
« on: December 01, 2022, 03:41:58 PM »
So, I am the proud owner of an obscure small block, a V40 Targa. Made for the Japanese, Greek and maybe French markets ? It's a 1991 two valve head engine with a short stoke Monza piston I believe 74 x 45 stroke.

It's ready to get on the road but I'm having trouble with a hanging idle. Tried the usual things - cabling routing, choke sealing etc. Carbs are PHBH 28s, which typically are used on V50s and Monzas. Found the carb needle was a bit rough near the top of the shaft, so i polished it up, but it's still a little roughened. OK, maybe I should replace the needle ( and jet). That's where it gets interesting. The needle is an X24. Haven't checked  jets yet. I do not have a manual for this precise model and on This Old Tractor I can only find manuals for V35 / V50 models, two and four valve. None of these use an X24 needle.

So my questions: does anyone have a manual for this thing, or at least has a V40 Targa and can confirm jetting ? I'm thinking maybe the jetting is to suit Japanese emission requirements or maybe the oddball engine just had oddball jetting. If I'm replacing needles & jets etc I'd like to be using the correct ones.

Not expecting to have much success with my query given the obscurity of the model, but it's worth a try.

Thanks in advance !
1986 Lario ( long gone, still missed)
1985 Mark IV Lemans ( Gina)
1991 V40 Targa ( L'il Jeannie)
1962 Royal Enfield Crusader Sports

Offline guzzisteve

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Re: Jetting for obscure small block
« Reply #1 on: December 01, 2022, 04:34:33 PM »
OK X24 is in size
cylinder---2.50
tip--------1.00
taper starts 30 up from tip
For reference the V50 used an X6
cylinder---2.50
tip--------1.20
taper starts 26 up from tip

V35 uses an E needle
E27 is
cylinder--2.42
tip-------1.25
taper starts 18 up from tip w/260 atomizer    V50 & 65 is 268 atomizer

Only one I could find w/ X24 is the V35 Imola II

X24--2nd notch
112--main jet
45---pilot
262 --atomizer

https://guzzitek.org/gb/ma_us_uk/V35I2_V50M2_V65L_Atel(GB).pdf

Hope this helps
« Last Edit: December 01, 2022, 04:48:30 PM by guzzisteve »
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Offline Bazil

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Re: Jetting for obscure small block
« Reply #2 on: December 01, 2022, 05:01:25 PM »
Awesome ! Thanks for the quick reply. Great reference point.

I hadn't thought to look at the four valvers. Stylistically it matches the Imola II, but with 18 " wheels. It didn't occur to me that they might share carbs.

Thanks Steve
1986 Lario ( long gone, still missed)
1985 Mark IV Lemans ( Gina)
1991 V40 Targa ( L'il Jeannie)
1962 Royal Enfield Crusader Sports

Online Antietam Classic Cycle

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Re: Jetting for obscure small block
« Reply #3 on: December 01, 2022, 05:11:40 PM »
I'd be making sure the ignition advance mechanism is moving freely. Could be why the idle is "hanging".
Charlie

Wildgoose Chase Moto Guzzi

Re: Jetting for obscure small block
« Reply #3 on: December 01, 2022, 05:11:40 PM »

Online pehayes

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Re: Jetting for obscure small block
« Reply #4 on: December 01, 2022, 05:19:24 PM »
I'd be making sure the ignition advance mechanism is moving freely. Could be why the idle is "hanging".

+1
Notorious.  Advancer mechanism is up front under a partial plastic cover.  Front wheel throws road debris right at it.  Has to be cleaned and lubricated more than other distributor based Guzzi models.

Patrick Hayes
Fremont CA

Offline Bazil

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Re: Jetting for obscure small block
« Reply #5 on: December 01, 2022, 06:07:26 PM »
Thanks Charlie & Patrick;

no problem with sticky advance - it has the Motosplat ignition. Is that a good thing or a bad thing ?
1986 Lario ( long gone, still missed)
1985 Mark IV Lemans ( Gina)
1991 V40 Targa ( L'il Jeannie)
1962 Royal Enfield Crusader Sports

Offline sign216

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Re: Jetting for obscure small block
« Reply #6 on: December 01, 2022, 06:09:33 PM »
Yahoo formerly had a good Smallblocks group.  When Yahoo groups folded I recreated the group, with limited success.  See  https://groups.io/g/Moto-Guzzi-SmallBlock 
09 Guzzi V7C
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https://groups.io/g/Moto-Guzzi-750

Online Antietam Classic Cycle

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Re: Jetting for obscure small block
« Reply #7 on: December 01, 2022, 06:28:16 PM »
Thanks Charlie & Patrick;

no problem with sticky advance - it has the Motosplat ignition. Is that a good thing or a bad thing ?

After I wrote that, I wondered if it was pertinent. Could be a vacuum leak. Are the rubber sleeves between carbs and manifolds in good condition? Gaskets between the manifolds and heads?
« Last Edit: December 02, 2022, 08:14:30 AM by Antietam Classic Cycle »
Charlie

Online Chuck in Indiana

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Re: Jetting for obscure small block
« Reply #8 on: December 02, 2022, 07:18:35 AM »
Thanks Charlie & Patrick;

no problem with sticky advance - it has the Motosplat ignition. Is that a good thing or a bad thing ?

"I know nothing.."  :smiley: but I haven't read anything good about them.
Chuck in (Elwood) Indiana/sometimes SoCal
 
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Online FarmallA

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Re: Jetting for obscure small block
« Reply #9 on: December 02, 2022, 08:38:39 AM »

Tight valve clearances?

Steve
FarmallA

 

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