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Hi folks

Is a BE4 mixer tube richer than a BE3 please?

Thanks for any help

Cgt75b
@chandlerman avatar
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Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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Yes, the BE4 is the richest.

This has been discussed in great detail in the past.

What's the problem you're trying to solve?
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chandlerman wrote:
Yes, the BE4 is the richest.

This has been discussed in great detail in the past.

What's the problem you're trying to solve?
Thanks man, a wee flat spot.
@chandlerman avatar
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Lucky
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did you change anything to cause it, i.e. install a different exhaust or top end?

If not, you've probably developed an air leak and will only be able to jet around it for so long before you seize it and kill the piston & rings, if not the whole top end.

(hence why I asked about context)
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chandlerman wrote:
did you change anything to cause it, i.e. install a different exhaust or top end?

If not, you've probably developed an air leak and will only be able to jet around it for so long before you seize it and kill the piston & rings, if not the whole top end.

(hence why I asked about context)
It's a stock motor with an Sip road 2
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If you haven't changed anything, then I'd start by cleaning the jets, but you may have a seal failing causing an air leak.

What's your current jetting? Somewhere in the neighborhood of 160/BE3/112, I'll guess?

If you don't have a leak, but do have a bit of a flat spot, then you probably want to bump up to a BE1 or BE6. You shouldn't need much richer with just a SIP Road on an otherwise stock 150.

And your main may also be too weak, which could also cause a flat spot as it fails to transition from the atomizer to the main.

Can you post a video of it running on the stand, blip the throttle a few times, rev it out a bit more? That will help diagnose things.
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Molto Verboso
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Cgt75b wrote:
It's a stock motor with an Sip road 2
Did you upsize the main jet when you installed the Road 2?
Should be 2 to 4 higher on a stock setup with that box.
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Ray8 wrote:
Did you upsize the main jet when you installed the Road 2?
Should be 2 to 4 higher on a stock setup with that box.
I did Ray8 I'm gonna go up another 2

I'll report back when I get one and get out for a ride.

Thanks 😎
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1980 P200E - "Old Rusty", 1976 ET3 Primavera
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Yeah don't underestimate the main jet needs of the Road 2. Start high and work down. Even a shop underestimated it with mine and I soft seized pretty bad when I was pushing it. Running a bit higher than the usual "sito+" recipe and it's a bulletproof machine now at all speeds
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Bit of an update

ATM I'm on a 122 main but think it could go upto 123/124 but I don't have these to hand just yet, most British dealers are out of stock.

Just recently I've had what was like an over fueling issue bogging down and stalling, anyway spoke to a tuner here, and he suggested checking a few things one of which was the mixture screw.

Checked this and it was 2.5 turns out he recommended 1.5 turns out which I did, and low and behold things are sweet as a nut now, no flat spot no bogging down, just need to make sure the MJ is correct which I'll get too once I've scoured those jets.

Anyway thanks for all advice given

It's much appreciated

Cgt75b
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1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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Something I was told many moons ago (but cannot confirm if it is true, but seems to work & I understand spray nozzle dynamics) is;
The higher the hole (up the mixer as shown in the prior drawing), the higher the revs that it is affecting.
The bigger the hole, the richer at those specific revs (ie. more mix can come out the hole at the same pressure)
THEREFORE
If you have a lean spot low down in the range, then make a pair of holes slightly larger to richen it up in that rev range.
Can also ADD holes at a rev-range if needed

if you suspect one is a bit damaged or has a burr or sharp edge (take closeup pic on phone) by something getting stuck or whatever:

Model shops sell packs of teeny precision drills
OR
Poke a thin bit of wire (single strand is ok, but multiple strands of very thin wire twisted together can be better as they k8nda work like a teensy saw) thru hole & spin the tube to smooth the edge off.
It can make the mix "spray" thru the hole "cleaner" (better spray pattern).
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Hi an update on the update 😀

Gone upto a 125 MJ now seems much happier also changed from a SIP road 2 to a Polini exhaust which was recommended by a tuner.

Anyway just been for a blast and it's real nice to ride now, "no flat spot" just rolling on and off.

Cheers

Cgt75b.
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Molto Verboso
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
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Molto Verboso
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^^ How do you like the Polini? is a Polini Box right? I am trying to sell two of the three expansion chambers that I have and try a Polini Box. I would love to swap an exhaust with someone.
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scooterist wrote:
^^ How do you like the Polini? is a Polini Box right? I am trying to sell two of the three expansion chambers that I have and try a Polini Box. I would love to swap an exhaust with someone.
Tbh I haven't done a lot of miles with it being winter season, but on initial impressions seems like a pipe with great characteristics, I think it would be even better with a tuned 208.

But that maybe further down the line.

I hope that helps

Cgt75b.
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