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I'm not used to the small frame carb , used to do it in my sleep 40 years ago tearing down but I've had some running issues and suggested I check float needle . Carb is a shbc L 20mm delorto . So I ordered a viton bgm one and it's turned up and the retainer to
float is too small so sending back . However , in the pic you can see old one at top and new one at bottom. The new one has defined point on it like a needle , the old one the tip looks flat . Now is the tip flat cause it's worn or is it supposed to be like that? When I look online at replacement 3 sided float needles, some of them look pointed and others flatter tip, but wondering if some are crappy made and others better. Your help appreciated because if my old needle is ok will stick back in a completely cleaned carb and rule that out as an issue. These needles in pic are both sprung loaded . Thx
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Its not the tip thats the issue, its the shoulder towards the base of the rubber. Definitely replace
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Too cheap and easy not to throw a new one in there.
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Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
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'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
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dsnyder586 wrote:
Its not the tip thats the issue, its the shoulder towards the base of the rubber. Definitely replace
Explain ?
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Moto64 wrote:
Explain ?
When the needle valve wears, you will see a ring worn into the rubber where it seats when closed. The seal is not made at the tip but further up.
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orwell84 wrote:
When the needle valve wears, you will see a ring worn into the rubber where it seats when closed. The seal is not made at the tip but further up.
Well I've ordered one anyhow however you can see new ones online just like mine that have that ridge towards the bottom. Some have needles like a sharpened pencil to base and some have a shoulder at the bottom near metal . My needle is off an ets 20mm shbcl carb. Attached is example of a new float needle online. You can see the ridge at bottom , so are you sure my original is worn as it looks the same?
New needle
New needle
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So having stripped my carb , cleaned , drained fuel and refreshed the float needle was not worn. Contrary to belief that a ridge on the float needle is wear for an shbc carb it is normal for my shbc L carb. If you look on delortos site which I include picture below a ridge is clearly seen. What was the problem with mine is that the spring load on the needle valve was slightly sticky depending on what position you placed it in the float housing. Some carb cleaner and constant plunging of the spring end has freed it up. Valve float needles are not equal on small frames , you might buy a needle which is claimed to fit your shbc carb however the end that attaches to float can very by as much as 0.5 to 0.75mm in height thus changing float height when seated. I guess the ridge delorto put on their valves is necessary for the valve housing hole, in my case a 20mm ets carb . I also stuck in a new plug too to cover both angles of flooding and all is good . Starting when hot and cold very easy. Buying a cdi , although updating an old 1995 one did not sort issue. So my question is , how can you really tell what a worn float needle looks like for an shbc carb, three sided, not four like an SI. ? Maybe just don't analyse and just stick one in but to get an official one from delorto costs money, not for the part but postage and customs whack on top, 13 pounds instead of 5 pounds.
Delorto official shbc needle jet with default ridge!
Delorto official shbc needle jet with default ridge!
⬆️    About 1 year elapsed    ⬇️
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Molto Verboso
'13 LML Star 200, '81 50 Special, '81 P 150 X, '87 PK 50 Nuova, '84 PK 50 S
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ferriswolf wrote:
Sorry for the off-top but I have few questions about SHBC 20 L.
Is it give more noticeable performance than SHB 19.19 ?
What idle jet SHBC 20 L have - long or short?
How rubber air bellow mounts on the SHBC 20 intake manifold?
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It doesn't have a bellows , it's a small frame Carb with plastic air filter . Pdf attached . I don't know what benefit it gives over a 19mm as never had different on my pk75 as standard and also standard on my ETS
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'74 50s x3 '87 PK125XL '92 PK50XLS Plurimatic - & - '58 AllState '68 Sprint '66(?) Super125 and '72 DanMotor Super150
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16 & 19 carbs have bellows, they're just different than largeframes. But the 20 has no aluminum sleeve, it clamps directly to your intake. I dunno about stock, but I just cut up a standard 19 bellow so it's best fit - not dust tight but better than nothing.

I am currently swapping a 20L onto my brown 125cc smallie that I brought back from the island. I'm using a modified Polini reed 19 manifold and a thin bushing to mate them up. I'll let you know how it compares to the old 19 on the same manifold I just removed, and is headed for my 70cc PK.

I think they are a worthwhile improvement, more details here: https://modernvespa.com/forum/post2614405#2614405

BTW, if you have float valve leak problems, you can try burnishing the brass valve seat in the carb body w/ a souvlaki stick in your cordless drill. It's in tips n trix somewhere... Nerd emoticon
Aluminum sleeve for a PK19 and the Polini 19 manifold had the same four tabs , but cast integral when it was made. Sawed them off to make room for 20L clamp.
Aluminum sleeve for a PK19 and the Polini 19 manifold had the same four tabs , but cast integral when it was made. Sawed them off to make room for 20L clamp.
The inside of the Polini manifold is bigger than stock PK 19 manifold, they used thinner tubing and it's same as my 20L carb smallest bore - 9/16 socket snug fits both.. So there should be little or no turbulence if they mate up close enough.
The inside of the Polini manifold is bigger than stock PK 19 manifold, they used thinner tubing and it's same as my 20L carb smallest bore - 9/16 socket snug fits both.. So there should be little or no turbulence if they mate up close enough.
Slots were sawed part way down the thin bushing we made so it would clamp up tight which works well. I filled them w/ goop before installation to avoid any air leaks.
Slots were sawed part way down the thin bushing we made so it would clamp up tight which works well. I filled them w/ goop before installation to avoid any air leaks.
You can see Polini has a LARGE exit to the motor...
You can see Polini has a LARGE exit to the motor...
which encouraged me to do some of this.
which encouraged me to do some of this.
Test install before filter and bodge bellows dust boot.
Test install before filter and bodge bellows dust boot.
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Molto Verboso
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ferriswolf wrote:
V oodoo wrote:
Thanks guys!
I found a SHBC 20 intake manifold in my garage that came out of nowhere and wondered if it was worth trying to find a SHBC 20 carburetor.

V oodoo I will look forward to your comparison results.

And still open question about idle jet type in SHBC 20 L.
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I couldn't get new carb running right in the bike. Will NOT start without a shot of gas in carb throat. Now gonna pull the motor out and deal with it in the stand where it's so much easier to swap jets, track down air leaks and generally see and access the whole motor. 3rd time I've mounted a 20L but first time for this problem.

So first thing is pull the idle jet & take a pic for you.
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roland87 wrote:
Thanks guys!
I found a SHBC 20 intake manifold in my garage that came out of nowhere and wondered if it was worth trying to find a SHBC 20 carburetor.

V oodoo I will look forward to your comparison results.

And still open question about idle jet type in SHBC 20 L.
I'm making progress, suspect an air leak on this motor Livid emoticon. But I can tell you that when I went from 19 to 20 on this bike w/ a very similar motor, it made quite a noticeable difference.

External inline image provided by member with no explanatory text

This one has a Leo Vince expansion chamber, the brown one has a milder Polini kidney pipe.

If you wanna try it and you found a manifold, I found a cheap 20L for you, they usually go for 150 euros & up from Germany. https://www.ebay.com/itm/145072155607
2 more days, listed in England at 15 pounds now.

External inline image provided by member with no explanatory text

PS Mine has a long #50 idle jet.
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Molto Verboso
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V oodoo wrote:
Thanks for keeping me updated V oodoo!
Delivery from UK to UA now is hard and expensive, so even if I won that carb for 15 with all delivery costs it turns near 100.

Long idle jet is not good for me cos I have lot of shorts and no any long.

Please remind me on what engine setup you have 20 carb?
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Mostly both stock used 125 top ends from ppl who installed new kits. Honed & new rings helps, but as you'll see, I only split one. The one that's been giving me trouble was originally a 90 4 speed which I have never split, the other one was a 50s so I had to put in a bigger stock crank(also used) and brand new stock 90/100 primary gears. So now w/ the 20L and except for the pipes the motors are now pretty much twins. But the gray one is mostly old paint has a PK fork which I got cheap bent. I straightened it and I like the improvement in ride and braking over the brown one which is rattle canned. Both frames were pretty rough, a lot of body work on brown and structural help on both.

It's probably mostly just the 90/100 primaries, but both feel plenty quick to me and geared well for any goat trails I must explore. I'm not interested in anything over 50 or so on these. P200 for that.

Here's an old thread when I built them:
Cannot recommend...
You can see how much bigger PK front brakes are. The gray also has 5 bolt rear hub so bigger rear brakes too.
You can see how much bigger PK front brakes are. The gray also has 5 bolt rear hub so bigger rear brakes too.
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Molto Verboso
'13 LML Star 200, '81 50 Special, '81 P 150 X, '87 PK 50 Nuova, '84 PK 50 S
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V oodoo wrote:
But the gray one is mostly old paint has a PK fork which I got cheap bent. I straightened it and I like the improvement in ride and braking over the brown one which is rattle canned.
Thanks for answer mate!
My 50 Special also have PK fork, hubs and rear brake plate. As for me it is one of the best upgrade after engine for sure.
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Molto Verboso
'13 LML Star 200, '81 50 Special, '81 P 150 X, '87 PK 50 Nuova, '84 PK 50 S
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V oodoo wrote:
I already have SHBC 20L on hands. Noticed that mixture screw have more thinner tip than on the 19.19.

Maybe you can tell how to adjust mixture screw on SHBC 20L? Or maybe you have link to good instructions?
I googled for few hours and can't found any clear info.

External inline image provided by member with no explanatory text
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