OP
|
UTC
quote
First the back story, I rode across town and lost the actuating lever for the shift cables, therefore I was stuck in 2nd and rode about 8 miles or so home in 2nd gear at a pretty high RPM. I decided to look at the plug right after killing the motor. I am a bit confused at the readings, some say it's rich looking at the outer ring, some say lean looking at the insulator, some say just right looking at the electrode. As for the ground strap, mixed feelings. Any insights?
![]() Vespa Plug after 30 min at high RPM
|
Molto Verboso
![]() '13 LML Star 200, '81 50 Special, '81 P 150 X, '87 PK 50 Nuova, '84 PK 50 S
Joined: UTC
Posts: 1475 Location: Ukraine. Kyiv. |
|
UTC
quote
There is lots of info on " tea coloured being right" but a plug chop test is just that, NOT what you just did. You just looked at an old plug after a random hi rev run.
For a plug chop you need a new or very clean shiny plug of known condition , and a rag and wrench Warm the engine up using an old plug. Fit the clean plug. Select a nice flat road ( no lugging up hills or flying down them) . Set off accelerate hard through the gears and hit wide open throttle and wait till your scoot hits the speed for WOT. Then hit the kill switch and pull in the clutch, NO THROTTLE. Roll to a stop , let the engine cool a little just so you dont get your fingers burnt, remove plug then read the plug colour. Hope this makes sense 👍 |
OP
|
UTC
quote
That really makes sense. Now I have a great reference and a good known procedure.
I thought I might be a bit lean. I'm thinking I might have developed a slight leak. Thanks again |
OP
|
UTC
quote
A few more questions now that I have thought for a while.
1. When I do the plug chop, do I just focus the results on the insulator and ignore the outer ring, electrode and ground strap? 2. Do I do the test for the entire RPM range with reference to the jets. Jets as in idle, part throttle etc.... I'm sure I should ignore the starter jet. |
|
UTC
quote
Two strokes detonate at WOT so thats what a plug chop is for, its not a broadband tuning technique. If you want all that head for a dyno and hand over some cash 👍👍.
The plug chop just ensures your not too lean and not likely to hole a piston. Have a look at a few u tube videos to get a feel for the technique |
OP
|
UTC
quote
Not wanting to tune the thing but now I know I am lean at close to WOT.
I really putt around town about half throttle in mostly 3rd gear 90 % of the time. If it's lean with those operating parameters I should address it. So I'm guessing, warm it up with old plug, install new plug, cruise at half throttle in 2nd or 3rd gear, keep it steady there, kill it, check plug. About how long of a ride would you think? |
![]() UTC
Hooked
Some Vespa, some Yamaha, some Suzuki, some Kawasaki, some Honda...
Joined: UTC
Posts: 250 Location: Hamilton, Ontario |
|
Hooked
![]() Some Vespa, some Yamaha, some Suzuki, some Kawasaki, some Honda...
Joined: UTC
Posts: 250 Location: Hamilton, Ontario |
UTC
quote
It's an old plug, by the looks of it, so kind of an average reading of its life in the motor. It would be helpful if you at least stated what kind of plug you are using.
The strap says it's too hot, the ring says good jetting overall, the electrode suggests timing is a bit too advanced and the porcelain says you use oil without too much dye, or maybe a lean oil mix on a hot plug that is staying clean. Either way, the porcelain is not super important as long as it doesn't show blistering. On four strokes you wouldn't even bother with the porcelain colour, on two strokes it mostly displays oil mixture strength. |
OP
|
|
UTC
quote
Is this on a stock VBB 150 engine or are there any mods that have been done? What carb? Jet stack and idle jet?
|
OP
|
UTC
quote
Bone stock motor
As for the carb, see this previous post: Carb Model? Jet Stack: 185 Air Corrector/Main Air Bleed E1 Mixer/Emulsion Tube/Diffuser (could be BE1, but stamped E1) 100 Main Jet 60 Starter Jet/Choke Jet 40/120 Idle Jet My goal was to run as rich as possible during the first few hundred miles break in period with my box of assorted jets. By the looks of it, I might be pretty lean. |
|
OP
|
UTC
quote
To make sure I go the correct way in the future,
As for the Air Corrector/Main Air Bleed; is 140 leaner than 160 Mixer/Emulsion Tube/Diffuser; is BE1 leaner that BE5? And is BE and E the same? Main Jet; is 96 leaner that 102? (I think you gave me that answer) Choke/Starter Jet; is 60 richer that 50? Idle Jet; is 38-120 leaner than 50-120? Is it true that you divide the larger number by the smaller number to get the ratio and if so; is 3.12:1 leaner than 2.4:1 Also is 140-48 the same as 160-55? |
UTC
Ossessionato
1958 Allstate 177VMC, 1962 Allstate, Yamaha Vino 70cc
Joined: UTC
Posts: 2253 Location: Philadelphia |
|
Ossessionato
1958 Allstate 177VMC, 1962 Allstate, Yamaha Vino 70cc
Joined: UTC
Posts: 2253 Location: Philadelphia |
UTC
quote
chippieboy wrote: To make sure I go the correct way in the future, As for the Air Corrector/Main Air Bleed; is 140 leaner than 160 Mixer/Emulsion Tube/Diffuser; is BE1 leaner that BE5? And is BE and E the same? Main Jet; is 96 leaner that 102? (I think you gave me that answer) Choke/Starter Jet; is 60 richer that 50? Idle Jet; is 38-120 leaner than 50-120? Is it true that you divide the larger number by the smaller number to get the ratio and if so; is 3.12:1 leaner than 2.4:1 Also is 140-48 the same as 160-55? BE and E are not the same. And those numbers are just at which point they were created, they don't go in numerical order by way of richness or leanness. There's a chart in the how to tune an si carb on the main page of NSM that shows their order in richness. Correct on the idle jet thinking. Higher the ratio the leaner it is. Main jet your correct on as well. 96 is leaner than 102. Choke is correct as well. |
Modern Vespa is the premier site for modern Vespa and Piaggio scooters. Vespa GTS300, GTS250, GTV, GT200, LX150, LXS, ET4, ET2, MP3, Fuoco, Elettrica and more.