Modern Vespa

Put a few more miles on the Chetak with the 45-140 pilot and 120AC BE3 130MJ. Seems pretty good had a few open spaces sustaining speed at 50, 55 and 60. It all feels excellent so much power on tap. Idle seems good a little rough in the mid range.

This is the hot plug at WOT in 2nd gear.

Last edited by Jack221 on Fri May 15, 2020 7:22 am; edited 1 time in total

What does the CHT read when you hold it where it's rough in midrange?

Don’t have a CHT gauge darn it. Plug color is tan on ground strap and slightly more color on opposite side on porcelain. Does it look too lite?

Still a slight gap at crossover.

Turned air fuel to 2 1/2 took another picture.

If this was a 4 stroke motor I would say you're jetted nicely , not starving for and and using it all. Sorry I'm really just learning about these 2 stroke engines so I'll just sit back and see if I can learn something.

Second picture looking better. No CHT. Do a sound recording while riding. Tickover to fast through the years.

Have about 100 miles now on the new plug running without the float spacer.

Things have improved but not perfect yet and wondering if it ever will be but it's getting better so optimistic.

Setting out for some different terrain with Charlieman22 almost immediately going uphill Charlie is leaving me in his dust. I'm opening my throttle but it's not making clean power, sputtering and causing a back up of cars behind me. Concerned I may foul the plug I pull over to let the cars pass and start back up at a pace the engine can handle. Deep now in this tuning business I'm trying to pay attention to what's happening and at what throttle position etc. Charlieman has pulled over and waited for me to catch up at which point we park so I can adjust the carburetor. Reduce the main jet to 128. This seemed to run better the sputtering went away as did most of the incline is now behind us.

Ran pretty good the rest of the day but not worth a seize to see if Chetak is faster than the unicorn. Impressed with how fast unicorn is.

I was going to say , if its sputtering , it may be getting too much gas , down jetting sounds like it helped. I often wonder if anyone can get these old scoots dialed in like the new bikes. On my everyday ride I got a tune done on it with max timing in the right places and correct afr's, makes a world of difference.
I think with these old ones things aren't going to tune in so well , old old technology and the crappy gas is a bad combination.
Just as an after thought is there anyway of getting more air into the mix along with that bigger jet?

A liite embarrassing that the Bajaj doesn't keep up with the sidecar. Means the main jet is too rich or too lean. As you reduced it one size and it got faster, you can go with 130 was too rich. There is more in it. Don't ride it hard but drop to 125 and try 3/4 throttle again. Test it in the same gear on the same road at 3/4 to get it close with no risk. Do like CM does and do the same run to a marker each time to see what is better. 120 is probably too weak but if 130 was not good then 122 is probably correct.

Jack's "colorful" observations...
One thing about those outings - they put us in more demanding situations than local riding likely would have.
That hill was combo of steep and curvy - so lot more load than normal.
Once Hibbert down jetted - it seamed night and day.
Hibbert - we need to sort out a reliable phone holder for your runs.
Also - selfishly I wanna see what the leaner looks like snaking through sweeping turns! 🙂
Would also be interested to see what the piston wash looks like on yours.
This is my fave $30 camera.
Wifi to phone means no cables to connect and film or view directly from iPhone. Great tool really.
https://www.amazon.com/gp/product/B07C9C6P5D/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I like it for the very small size of the camera head as well - tho of course - I cut a bit of the collar off to create more flex at the tip...

Thanks guys will happily accept a 2nd in place of a no finish, been down that road. Unicorn is fast though we'll see.

After carving the Malibu hills came home and dropped the pilot to 38-120. Doing things out of order again but seems like it helped forgot to mention in previous post.

After posting dropped main jet to 125 and took for a ride. Seems fantastic less vibration and better acceleration. Went to check on flywheel for PE still not finished. Scooter Speed let me stick their inspection camera into the spark hole this is what it looks like after a 5 mile ride on the 125MJ.




exhaust port and clutch side transfer

clutch side transfers

fly side transfer

a little brown color by transfer

From what I can make out it looks perfect. Black to the edge with clear spot Infront of the transfers. You could go down to 122 safely enough. How smooth is the lower rpm running now?

Got out with a few for a Sunday ride. Really got to stretch the Chetak out, long stretches of sustained 55 mph and it sings along 90 miles slept well last night.

Everything seems to be perfect but still shy to go WOT in 4th. Scooter is fast enough for me. One nagging issue the crossover point from pilot to main it's a problem.

The problem is at 1/8 throttle where I presume the main jet comes ON line, there is a hiccup. Being less bashful now and wanting to keep up with the group driving it a little more aggressive now. Noticing how the hiccup, throttle position coincide with shift & clutch release, not good. If I'm on it and giving it love it burps at the shift in all gears. If not giving aggressive throttle can drive around issue.

Coming down seems to be the bigger nuisance. When reaching the 1/8 throttle position and just keeping engine speed it's really at it's worse herky-jerky behavior it wants to be on either side of that condition or jet sharing either more throttle which is not desired or completely closed also not desired. Problem is I want to close the throttle and reduce speed but engine wants/needs more or less of something that is not dialed correctly.

Idle speed is great, RPM drop great, acceleration great, reaching high speed great!


Start mileage 4897









Final mileage 4987

cold plug Monday morning
120AC BE3 125MJ
38/120 Pilot
3 Turns air fuel

Since you seem to have the main jets pretty damn close try a larger idle jet. You could be lean in the transition area. Based on your description that's what I'm thinking. Main jet doesn't come in till much later than 1/8 throttle. There is a hole just as the slide opens that draws fuel from the idle jet that supplies fuel at that transition point.

Agreed with BT5.
Think its definitely worth trying a richer idle.
That hesitation you describe accelerating - and the surging I think you are referring to on deceleration - both read lean to me on idle.
No harm in walking the idle up and seeing if it eradicates.

Agreed too. I would like to see how 45/140 works. Main jet might still be a bit big.

Great suggestions guys. Increased pilot to 45-140 some improvement surging on de-cel. Increased pilot to 55-160 and reduced main jet to 122 think I'm in love.

Plug from regular shut down looks to be a dryer black on shell and very dark on insulator. To me it looks dryer and darker it runs very good need to give it some miles. Wiped plug shell clean and installed.

Need to improve the brakes!








'Jack Stack' 120ac BE3 122MJ
55-160 pilot
2 1/2 turns air fuel
T5 air filter


Last edited by hibbert on Tue Jun 02, 2020 12:19 pm; edited 1 time in total

Still looks pretty rich to me. Another main drop or two to go, maybe three.

Looks rich to me too. 55/160 is too rich at the bottom. 48/140 would be the next to try.

48-140 pilot jet on order

Over the weekend met up with a group of riders at a local Lambretta shop for a nice coastal cruise. Before the ride reduced the air fuel mixture 2 turns. Ran great.

Having a problem keeping the Pinasco Air Box seal. The lid is plastic and tends to lose it's shape when torqued down then squeezing the seal out.

Shocked but pleased to see brown again on the cold plug following the ride.


















seal keeps coming off Pinasco box lid

'Jack Stack' 120ac BE3 122MJ
55-160 pilot
2 turns air fuel
T5 air filter

'Jack Stack' 120ac BE3 122MJ
55-160 pilot
2 turns air fuel
T5 air filter

Look like a fantastic ride hibbert. I'm glad it's running nicely and thanks for the pics!

We want video! Need to hear this thing running!

Received the 48-140 pilot and it's not correct. Didn't take long to know. Still took a good 15 mile ride to give it a stretch and it's got to come out.

55-160 back in very happy at 2 turns on the air fuel seems to be where it runs best. Dropped to 120 main jet. Seems OK maybe less vibration will be very cautious for now plug looks good. Don't think have any complaints at this point.

Interested to know what is wrong with the 48/140? The 55 is too big and will be wasting fuel. If it runs ok that's something.

If you have a new plug do a plug picture from a 30 second WOT run, see how good that 120 main jet is.

With the 48-140 pilot there was still a stutter at the transition point on acceleration, didn't notice as much a problem on decel compared to the leaner pilots.

With the 55-160 there is no transition just robust power all the way, a more solid feeling of power.

The 48-140 felt a little more peeky in the mid range, noticeable but the driveablity was not good.

Back on 55-160 reducing the main jet to 120 seems to have smoothed out the engine more will need to be cautious for the moment.

Dang kill switch on handle bar stopped working when I tightend the fork tube the other day must have knocked a wire loose. Have to get this fixed to do the plug chop.

Hibbert - perhaps I missed it - did you try both 50/160 and 48/160?

Jack - when you do one of those clean plug WOT runs - do you have to cut the plug to see the core - or can you tell from the tip?

Plug tips always just look like gray nothingness to me when I perform.

Charlieman22 I haven't tried the 50-160 or 48-160 don't see those on the chart are the 'custom'?

Nope - they are standards.
You should be able to get:
42/160
45/160
48/160
&
50/160

If you wanted to walk your leaness down while holding the air mixture at 160 - that would have been my first option.

If you need to borrow some - you can try mine - and then just return em please.

Maybe I should try the 50-160 didn't know it was available this is the chart I'm working from.

With the 48/140, was the stutter at 1/4 transition like a cough? Where it didn't pull like a weak bog?
If it is you need a 50/140 for the next try.
I do suspect it was weak as that jet is too small to give rich stutter.
Getting this right will really feel great.

Maybe more like a cough, was going to say burp or bubble in my first post definitely a moment of a missed beat then beyond that point onto the main. With 55-160 good no interruption.

Yeah, this is too weak. 50/140 next. Do you have one of those?

Don't have a 50/140.

A little confused on the jet ratio. If a 50/140 pilot provides a 2.8 ratio would that make it richer than the 55/160 @ 2.9?

A 50/160 ratio is 3.2 and 4 jet sizes (Vivo chart 38/120-3.158) leaner than a 55/160-2.9.

When fine tuning that chart doesn't work. It gets it close but won't get it smooth.
50/140 is the next one to try. If it was only just coughing at 1/4, it should be enough.

Do you have any 50 pilots?

Think so

Finally got a 50-160 pilot and went for a 50 mile ride down PCH. A quick ride around the neighborhood seemed fine but on the highway not so good. Had the 1/4 throttle cough again felt in 4th gear where you'd want to cruise. Had to throttle past to keep things happy and go faster than want. Air fuel was at 2-1/2 turns. Everything feels good except 4th gear cough. Going to put the 55-160 back in, it feels better and sounds better but need to run at 2 turns on the air fuel.

Think I'm having another problem when fuel level goes to reserve. Seems the float bowl runs out. The scooter might run a bit and then just die out of gas. Needs choke to start again. If run scooter fast it empties quick. Everything is fine until tank hits reserve level then things act up.

Removed fuel tank and observed decent flow from valve. Could not observe above reserve flow didn't have enough fuel but reserve flow looks ok.

I'm using a SIP XL tank it's a P bottom and Rally top. Wondering if the tank bottom has created a below carb level symptom? I think the standard tank bottom might be much higher giving better pressure?

50/140 is what was said before. Did you get one of those too?

Electric fuel pump under the tank will fix it. Just something small will be enough.

Something like this?


https://www.amazon.com/Solid-State-Fuel-Pump-Posi-Flo/dp/B072HFLQWX/ref=lp_17459765011_1_1?srs=17459765011&ie=UTF8&qid=1597353882&sr=8-1

Wow Christopher_55934 that looks interesting thanks for posting.

These are the details I could find on the pump.


https://www.facet-purolator.com/tech-information/

I'm looking at this regulator also, setting it up as bypass the same as people do with a jet etc to bypass some fuel and not dead head the pump.


https://www.speedwaymotors.com/Holley-12-804-Adjustable-Fuel-Pressure-Regulator-1-4-PSI,383.html

Last edited by Christopher_55934 on Fri Aug 14, 2020 3:51 pm; edited 1 time in total