Thu Jun 02, 2022 6:42 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Thu Jun 02, 2022 6:42 pm linkquote
Kowalski wrote:
The information to set this kit up is out there. I would start with Malossi's installation manual attached. Your kit is the 31-4093. As I interpret the manual, your baseline is:

Timing-18 degrees BTDC
Idle Jet-52-140
Main Jet-122 (with cut crank)
Air Corrector-140
Mixer Tube-BE4
Sparkplug-B8HS (B9HS for extreme conditions).

It is not necessarily where you will end up, but it is a safe place to start.

The more interesting question is whether you really want a Malossi 166. In its day (note the 2003 date on the manual) it was known for cheap, high rpm horsepower at the expense of low rpm grunt. If you see yourself as a boy-racer out to win the stoplight grand prix, this is your kit. If you see yourself loping along the country roads, not so much. Personally, I would make the effort to dial this in, but a lot of people would not.
Thanks for the manual, I never thought of looking into that for some reason.
As I have it now I believe I'm close but yet still lean.
If I were to go with the suggested setup I would definitely be seizing!
Thats what started this whole topic was me trying to understand why it needs a 135 or 138 main to give me a decent plug when the starting point should be 122 as you pointed out.
Now in my opinion my scooter runs well , holds idle , starts on first or second kick. And is a pure joy to play old man racer on!!
I'm thinking of saying who cares what size main is in there and getting a CHT installed and continue practicing wheelies,,,
I just hate not being in control of it if that makes sense. Fine, it runs and doesn't burn up but I can't tweak it or tune it past this
Thu Jun 02, 2022 6:43 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Fri Jun 03, 2022 12:40 am

Hooked
125 GTR 1977, 50S 1975, GTS 125 Supertech 2021
Joined: 04 Aug 2014
Posts: 194
Location: Madeira Island
 
Hooked
125 GTR 1977, 50S 1975, GTS 125 Supertech 2021
Joined: 04 Aug 2014
Posts: 194
Location: Madeira Island
Fri Jun 03, 2022 12:40 am linkquote
swiss1939 wrote:
The malossi 166 mk2 head uses a long reach. Specifically this is what is mentioned for the same part number in my manual which is the MK2 kit: denso w24es-zu which is a long reach plug.

https://www.densoproducts.com/denso-4032-w24es-zu-platinum-u-groove-spark-plug

So if you don't know which kit you have, the best way to tell is to take your head off and check to see if the short plug sits inside the hole and doesn't come out to the edge of the plug hole.. or if the long reach plug sticks out too far from the hole.

I've confirmed on my mk2 head that the long reach plug is correct.
Before my last post I made a search on Malossi166 and found this one too - the spec sheet said it used a Denso W24 ES-ZU, which is 19mm reach
But looking at the spark I would say its the short one (HS), no much doubt about it.

Peeteboy2, you're halfway to solving your problem now that the big sharks dived into the thread ... respectfully
Fri Jun 03, 2022 3:54 am

Hooked
2005 Stellalossi 177 Fe
Joined: 14 Jun 2020
Posts: 269
Location: MA
 
Hooked
2005 Stellalossi 177 Fe
Joined: 14 Jun 2020
Posts: 269
Location: MA
Fri Jun 03, 2022 3:54 am linkquote
Peeteboy2 wrote:
Thanks for the manual, I never thought of looking into that for some reason.
As I have it now I believe I'm close but yet still lean.
If I were to go with the suggested setup I would definitely be seizing!
Thats what started this whole topic was me trying to understand why it needs a 135 or 138 main to give me a decent plug when the starting point should be 122 as you pointed out.
Now in my opinion my scooter runs well , holds idle , starts on first or second kick. And is a pure joy to play old man racer on!!
I'm thinking of saying who cares what size main is in there and getting a CHT installed and continue practicing wheelies,,,
I just hate not being in control of it if that makes sense. Fine, it runs and doesn't burn up but I can't tweak it or tune it past this
Before you finish dialing in the main jet, I think you should try to get closer on the mixer tube. Yes, the BE3 is leaner than the BE4 (three steps leaner). Put a BE4 in there and, unless you have an air leak, it should become apparent that your AC120/MJ135 combo is too rich.
Fri Jun 03, 2022 5:32 am

Hooked
125 GTR 1977, 50S 1975, GTS 125 Supertech 2021
Joined: 04 Aug 2014
Posts: 194
Location: Madeira Island
 
Hooked
125 GTR 1977, 50S 1975, GTS 125 Supertech 2021
Joined: 04 Aug 2014
Posts: 194
Location: Madeira Island
Fri Jun 03, 2022 5:32 am linkquote
PSMA wrote:
Just one more thing concerning the carb float chamber bore to main jet stack, as it is referred again (above) that needs to be drilled larger. SI24/24E standard bore is 1.5mm, Scooter Center has a BGM SI24/24E all tuned up carb with a set of features for highly tuned engines ... the bore is 1.8mm, not 2.5mm! So I sent them my setup asking if I needed to drill the 1.5mm bore to make use of my main jet on my setup:
BGM 177, ported engine, filter drilled SI24/24E, Polini extended intake crankshaft and variable ignition, SIP Road 3, 55/160 and AC160/BE3/140

Their short and straight answer:
"you can expand them, but you don't have to."

Why do I always insist on opening cans of worms?
Now I'm quoting myself, you know when sometimes you develop a discussion without knowing the facts? I visited the mechanic a couple of hours ago and "touched" the subject ... "- some people drill the bore on the carb on tuned engines...", his straight answer "- Sure, I drilled yours to 3mm"

Enough talk, here's a video I uploaded one hour ago of my yellow:

Fri Jun 03, 2022 12:36 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Fri Jun 03, 2022 12:36 pm linkquote
Kowalski wrote:
Before you finish dialing in the main jet, I think you should try to get closer on the mixer tube. Yes, the BE3 is leaner than the BE4 (three steps leaner). Put a BE4 in there and, unless you have an air leak, it should become apparent that your AC120/MJ135 combo is too rich.
I need to make a correction, when I put the BE4 in yesterday I realized I was running the 150 air not the 120!!
Sorry about that.

So today I will do a proper plug chop and see where I stand!
Thanks
Fri Jun 03, 2022 12:40 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Fri Jun 03, 2022 12:40 pm linkquote
PSMA wrote:
Now I'm quoting myself, you know when sometimes you develop a discussion without knowing the facts? I visited the mechanic a couple of hours ago and "touched" the subject ... "- some people drill the bore on the carb on tuned engines...", his straight answer "- Sure, I drilled yours to 3mm"


Thats funny but most discussions are developed without one or both parties knowing the facts. I find a discussion is just a long question and answer, right?
I hear what you saying.
Nice scooter by the way!
Fri Jun 03, 2022 12:46 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Fri Jun 03, 2022 12:46 pm linkquote
Kowalski wrote:
Before you finish dialing in the main jet, I think you should try to get closer on the mixer tube. Yes, the BE3 is leaner than the BE4 (three steps leaner). Put a BE4 in there and, unless you have an air leak, it should become apparent that your AC120/MJ135 combo is too rich.
I just found the thread and copied this part of it. Its very lengthy!!!!

Atomiser/Mixer Tube

This is where air from the air corrector and fuel from the main jet mix before going to the venturi. Moving from a BE3 to a BE4 mixer tube reduces the amount of mixture from the main jet stack to be introduced into the venturi to mix with straight air from the inlet. This reduction is caused by the BE4 simply having fewer holes for the mixture to pass through. So a smaller amount of mixture goes to the venturi where it is mixed with the normal amount of air coming through the carb throat, thus producing a leaner running condition. *** Therefore, the BE4 is 'leaner' than a BE3.***
Fri Jun 03, 2022 12:47 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Fri Jun 03, 2022 12:47 pm linkquote
swiss1939 wrote:
The malossi 166 mk2 head uses a long reach. Specifically this is what is mentioned for the same part number in my manual which is the MK2 kit: denso w24es-zu which is a long reach plug.

https://www.densoproducts.com/denso-4032-w24es-zu-platinum-u-groove-spark-plug

So if you don't know which kit you have, the best way to tell is to take your head off and check to see if the short plug sits inside the hole and doesn't come out to the edge of the plug hole.. or if the long reach plug sticks out too far from the hole.

I've confirmed on my mk2 head that the long reach plug is correct.
Hey thank you for all that information sorry if I didn't think you already I've gotten lost within my own thread LOL. It's very much appreciated
Fri Jun 03, 2022 1:19 pm

Moderibbit
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: 12 Jun 2008
Posts: 8848
Location: Atlanta, GA
 
Moderibbit
1980 P200E - "Old Rusty", 1976 ET3 Primavera
Joined: 12 Jun 2008
Posts: 8848
Location: Atlanta, GA
Fri Jun 03, 2022 1:19 pm linkquote
So, there have been so many threads on what mixer is leaner - I think it's a rabbits nest and possibly give people wrong info depending on which post is read. I always get confused trying to read those old threads

Scooter center explains the anatomy (in funny English) and why the numbers don't map on simply to "bigger = leaner": https://www.scooter-center.com/en/atomiser-dellorto-type-5353-si-be1-2560001

The takeaway I got from this link is that the mixer is NOT too be used as a primary tuning device. You should set main jet and idle (IMO) and then use mixer changes to tweak the mysterious in-betweens.

For example, excerpt from SC:
"""The mixing tubes have an effect over a very wide speed range. For example, a BE4 mixing tube greases strongly just above the idling slide valve position. A BE2, on the other hand, is relatively lean in the lower speed range, but greases strongly at the top.

The most common mixing tube BE3 covers 90% of all applications of the SI carburettor."""

If you are lean at WOT I think MJ changes must be the focus to cure it, whereas the mixer tube is more for fixing that pesky flat spot earlier or later in the throttle position - adding nuance the MJ alone can't.

As Rob hodge put it: "more actg as a modifier that act on the other jets in the carb, similar to the taper of the needle in a more conventional carb."

As an example, say you've got good WOT jetting but seem to have a slight leanness low the mix screw can't quite nail, you might bump to a BE4 from a BE5 (relatively flat)
Fri Jun 03, 2022 2:30 pm

Hooked
2005 Stellalossi 177 Fe
Joined: 14 Jun 2020
Posts: 269
Location: MA
 
Hooked
2005 Stellalossi 177 Fe
Joined: 14 Jun 2020
Posts: 269
Location: MA
Fri Jun 03, 2022 2:30 pm linkquote
Peeteboy2 wrote:
I just found the thread and copied this part of it. Its very lengthy!!!!

Atomiser/Mixer Tube

This is where air from the air corrector and fuel from the main jet mix before going to the venturi. Moving from a BE3 to a BE4 mixer tube reduces the amount of mixture from the main jet stack to be introduced into the venturi to mix with straight air from the inlet. This reduction is caused by the BE4 simply having fewer holes for the mixture to pass through. So a smaller amount of mixture goes to the venturi where it is mixed with the normal amount of air coming through the carb throat, thus producing a leaner running condition. *** Therefore, the BE4 is 'leaner' than a BE3.***
I don't know where that came from, but it could not be more completely wrong. I regret that I do not have the motivation right now to unlock for you the enigma that is the SI carb mixer tube. Maybe tomorrow.
Fri Jun 03, 2022 2:31 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Fri Jun 03, 2022 2:31 pm linkquote
xantufrog wrote:
So, there have been so many threads on what mixer is leaner - I think it's a rabbits nest and possibly give people wrong info depending on which post is read. I always get confused trying to read those old threads

Scooter center explains the anatomy (in funny English) and why the numbers don't map on simply to "bigger = leaner": https://www.scooter-center.com/en/atomiser-dellorto-type-5353-si-be1-2560001

The takeaway I got from this link is that the mixer is NOT too be used as a primary tuning device. You should set main jet and idle (IMO) and then use mixer changes to tweak the mysterious in-betweens.

For example, excerpt from SC:
"""The mixing tubes have an effect over a very wide speed range. For example, a BE4 mixing tube greases strongly just above the idling slide valve position. A BE2, on the other hand, is relatively lean in the lower speed range, but greases strongly at the top.

The most common mixing tube BE3 covers 90% of all applications of the SI carburettor."""

If you are lean at WOT I think MJ changes must be the focus to cure it, whereas the mixer tube is more for fixing that pesky flat spot earlier or later in the throttle position - adding nuance the MJ alone can't.

As Rob hodge put it: "more actg as a modifier that act on the other jets in the carb, similar to the taper of the needle in a more conventional carb."

As an example, say you've got good WOT jetting but seem to have a slight leanness low the mix screw can't quite nail, you might bump to a BE4 from a BE5 (relatively flat)
No I understand and im not trying to fixate just pointing out that what I read and what I'm told on here don't always jive! Hence some of the confusion.

Thanks man
Fri Jun 03, 2022 2:34 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Fri Jun 03, 2022 2:34 pm linkquote
Kowalski wrote:
I don't know where that came from, but it could not be more completely wrong. I regret that I do not have the motivation right now to unlock for you the enigma that is the SI carb mixer tube. Maybe tomorrow.
Not asking you two im just pointing out that once I've thought I've learned something on here I then find out im wrong, more often then not.
Thanks for your input!!!!
Fri Jun 03, 2022 3:29 pm

Jet Eye Master
PX221 MHR, O tuned PX200, PX172 Quattrini and some motorbikes
Joined: 14 Jun 2017
Posts: 3287
Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX172 Quattrini and some motorbikes
Joined: 14 Jun 2017
Posts: 3287
Location: London UK
Fri Jun 03, 2022 3:29 pm linkquote
Peeteboy2 wrote:
I need to make a correction, when I put the BE4 in yesterday I realized I was running the 150 air not the 120!!
Sorry about that.

So today I will do a proper plug chop and see where I stand!
Thanks
Well, doesn't that just change everything. There is a world of difference between an AC150 and an AC120.
Put in a 120 before you blow it up
Fri Jun 03, 2022 4:20 pm

Hooked
Tuk Tuk.
Joined: 14 Nov 2014
Posts: 448
Location: Hawaii
 
Hooked
Tuk Tuk.
Joined: 14 Nov 2014
Posts: 448
Location: Hawaii
Fri Jun 03, 2022 4:20 pm linkquote
Too much labor, bend the ground wire away and use a loupe to see down there with good lighting.
Mon Jun 20, 2022 1:51 pm

Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
 
Hooked
1980 P125x 2002 Bajaj Chetak
Joined: 20 Jul 2021
Posts: 117
Location: 92024
Mon Jun 20, 2022 1:51 pm linkquote
Well I'm back to square one. If I were to go off of tip color reading I would tend to believe I was running just rich enough.
I got a fast flow tap, drilled my carb from bowl to MJ the recommended 2.5mm, rechecked my timing at 3000 rpm and visually nothing changed with the plug. I would have thought it would have richened it up.

One mile WOT with a softsieze putting an end to my fun this is my chop!



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