Modern Vespa

Couple questions about putting a 24/24 on a stock barrel P125. I've heard from others and read posts in the pasts about folks who have tried it and were not happy with the results. But so far I've been having fun playing with it. Midrange acceleration is ridiculous. It's a stock barrel P125 with a prima pipe, electronic ignition, and spaco 24/24.

1) I modded my 125 airbox to fit the 24/24. To keep my autolube, is there anything else I need to be aware of?

2) Right now my jets are 55/160 (has a tendency to run lean at 1/4 throttle) idle jet and main stack is 140/BE3/125. Had a 160/BE3/125 but plug chops were showing very lean. dropped in the 140 air corrector and it started to show tan. 125 is currently the largest main jet i have and plan on putting in an order for fatter jets and go back to a 160 air corrector. Is it just me or do these jets seem huge for a P125? a stock p200 main is a 116...

3) should i play with a 190/be4 combo?

hit 65 mph (gps tracked) today, so the thing is moving pretty good, but i don't want it to blow up.

125 main jet is very large for your application(in my opinion). I am running a 122 or a 125 on my two malossi 210cc scooters with 24mm and 26mm carbs respectively.

I also have a 166 malossi PX150 and I am running a 115(what came with the cylinder kit). All my scooters have either sito plus or expansion chambers.

I don't know your altitude but just by judging your carb jetting I think you are running a little bit big. my .2c

Still not resolved.

I put a 145 main jet in there and plug chopped. Still very white, almost no change.

I'm starting to think I have an air leak somewhere but it idles fine, doesn't race, and returns to idle as normal.

Gonna pull the head and jug off and make sure they are sealed. Also plan on making sure fly side seal is good, if not replace.

Any other thoughts?

I think you have an air leak as well. After you check the carb base gasket and flywheel seal, check your gear oil for gas.

If the 140 air corrector was getting you tan why not stick with it?

That plug doesn't tell you anything about your main jet. Hard to see the electrode but it looks like your timing might be off.

2 things


1 is scooterist lives somewhere in the fucking alps and shouldnt give jetting advice without mentioning that part



2 you should be able to feel when the main jet is too rich dont look at the end of the plug, feel it when riding



and theres something else going on if your scoot runs fine with 130+ on stock 125 top end

65mph on a stock 125... it'll run great and nice and fast when it's too lean.. all the way until it goes KaBoom!

Check you your timing very carefully and check for air leaks.

just suggestions... I wouldn't push it until you do though.

I think the 24/24 carb is an overkill for the standard 125 cylinder... I think ultimately it will adversely effect performance.

That aside sounds very much like an air leak, check where the card mounts to the case.

I have a buddy that has an Allstate 125 with a 24/24 and a sito + (I think...some kind of upgraded pipe). I don't know the jetting but it is still 6v points. That thing is a great scooter. I wouldn't say 65 mph but it can definitely cruise 50 no problem on 8". That scooter is a blast!

Put new fly side seal in, didn't want to take a chance that the other one was bad.

No gas in gearbox oil.

Pulled the head off and resealed it with some silicone gasket stuff and then retorqued it. It's possible that could have been a culprit, before.

New gaskets under carb and carb box.

Timing is 18 degrees, yes a bit advanced but I'm running a cdi not points.

Still bone white on plug chops at wot, plug is nice and brown on the idle circuit.

CHT reads between 150-200f when riding.

It is correct that I can feel when things are too rich, but I have never felt that since I put the 24/24. Quite the opposite that I could just keep dropping in larger jets and push it even further.

Dumb question, did you lap the head?

This time i did not. But i sealed it well with gasket sealer.

But, i did some serious work on getting things flat last summer. Where my cases meet and join with the bottom of my cylinder was not exactly flat before and was the root of problems for a long time. So i got that flat. Also, i lapped the top of my my jug and head to get both of them very flat and mated well.

I just sealed up my carb gaskets with silicon gasket. When that dries i plan on making some more runs.

Good luck, I hope you get it sorted out.

With fresh and silicone'd carb box and carb base gaskets, still no change on plug chops

i did just put fresh gear oil in yesterday checking for gas in it. When i checked it today there was a little less oil in it after going for a plug chop run. Thinking my clutch seal might be bad. Wish it wasn't so hard to get to.

Here's what i'm thinking and need help if my logic is wrong.

Gonna make a few plug chop runs in the morning, but got a tube hooked up to my breather and it does hold pressure.

If plugs show brown without tube plugged, everything is good.

If plugs show brown with tube plugged then it's my crankside seal.

If plugs show white with tube plugged it's somewhere else, probably somewhere in the top end.

Does that make sense to anyone else?

by plug chop, you mean you are cutting open the plug to check the base smoke ring?

Yes. Both base and tip.

I use this as a reference.

ran plug chops this morning. both with breather tube plugged and unplugged no change in chops, both bone white.

Here's a question. In the SIP classic catalogue, they have a formula for size of a carb based on it's cc size. Theoretically a 24mm carb 'should' be able to fit, but lets say that it's too big. And because of the larger venturi size causing slower air movement through the carb, the fuel is basically unable to move, atomize, or mix with the air. Is it possible this is what could be causing the lean readings at WOT?

You keep saying this.. what exactly are you doing? How far and how fast are you riding? and if you're not chopping or cutting the plug open you're not doing a plug CHOP... you're just visually reading the top of the insulator..

are you riding with brand new plugs, pulling the clutch, killing the motor, then taking the plug out, (not riding home on it) putting another plug in to get you home, then cutting the brand new plugs after a riding at least 1/2 mile at wide open throttle? and looking at the band around the bottom?

... and if you are going to do this, and you're in doubt.. jet RICH and work down until it doesn't bog at wide open.

What I'm doing is putting in a used plug and riding to a flat long country rode. I pull over, swap plugs for a new plug. I run WOT getting through gears as fast as possible and running for 1 mile. Then I kill the engine while grabbing the clutch. I then pull over and pull out the new plug and replace with the old one. I then take home and chop by physically cutting the plug and inspecting.

All WOT chop results have been white, with a 145 main. I haven't ever experienced it bogging with the 24/24 on, never. This means that something else is the matter.

The question is what is the matter.

obviously white chops mean the mix is lean, but how can a 145 main jet on a 125cc stock lump show lean. I know there are normal answers such as air leak at the carb/box, air leak at the seals, air leak cylinder base and head. But not to mention there are no symptoms of an air leak (racing, not returning to idle, engine still pop pop pops when coasting in gear, etc.).

As I go through and tick off all these possible air leak points and still show lean jetting with a 145 main, what then is left?

ok, ok... after running wide open for about a mile you have no ring like this?

Have you done a leak test? Have you had a whif of your gear oil to smell for gas?
IIWY, I'd get it running and spray some starter fluid carefully into the joints of the cylinder and the case and the head and the cylinder too.

If your plug is just white w/ No ring at all, you're sucking air somewhere.. based on a 145 main jet on a stock 125.

and I think you checked your timing with a light?

just wanted to give an update

put in a new clutch side seal, new fly side seal, new cylinder base gasket sealed with silicone gasket, and sealed the head with silicone gasket.

plug chops after mile long runs at WOT still showed white.

Rode down to WKRP (about 185 miles) at WOT all day and didn't have a problem.

On the ride on Sat. i soft seized. it wasn't a jetting issue, my auto lube oil line came detached. I made a roadside repair and premixed and rode WOT all day home. with wind at my back i was cruising at 65mph

After inspections when I returned home, I had some minor scoring on the barrel, so I honed them out. I sanded down my piston and ordered new rings.

Long story short, I think that when I'm up and running again I'm going to do plug chops with longer runs. I think 1 mile isn't long enough. I should maybe try 5 mile or longer runs to see if I can get a better read.

I'm still struggling over the notion of a stock P125 doing 65MPH at WOT all day.

tail wind helps. had a yamaha dirt bike in the group who said she was reading 70mph at times, but know her speedo is more generous than my SIP speedo and it's 2-3 mph fast at that speed.

I get on the pipe at 57mph (just above 6000rpm) and can easily hold it above 60mph without a problem, add the tail wind and it was cruising.

I was wondering this as well...?

As soon as someone says "verified by GPS" I tune out.

I have a p200 engine, with a 24/24, And an sip road,,,, and the mph goes like this:
59,59,59,59,60,59,59,59,59...

But you say a 125 will go 65 all day?
Where have I gone wrong?

So, maybe 65 all day long is inflated, but a good 60 and up to 65.

Anyways... Here's my update and still need help.

I put a malossi 166 kit on, ran it in for 100 miles, now I'm trying to get it dialed in. Plug chops are still showing lean with a 140/be4/145 at wot.

Here's my current set up:
Malossi 166
24/24 carb, with an opened up 125 carb box. Running with autolube.
Stock crank
Prima expansion pipe
Timing set at 17 degrees verified with a gun.
Malossi head, no head gasket. Squish says 1.6mm, but I have a cheap caliper so it could be off slightly.
B9 plug

When I do a plug chop I ride out of town. Pull over. Put in a brand spanking new plug out of the box. Get resuited up. Kick it over then immediately gun it through all gears to 4th, then run at WOT for three miles. I then hit the kill switch and pull in the clutch. I pull over, pull out the plug, then drop in the old one. Then I ride home and chop the plug I used on the 3 mile run.

Someone please tell me what I'm doing wrong here that ALL of my plug chops show lean and I never get a good read?

If you're already at a 145 and you still can't make the bike four stroke then something seems off, and I don't think murdering more spark plugs is the way to fix it. You shouldn't even really have to get so fancy with plug chops if you can just jet rich and then work down, but seems like you'll never get there with your current setup. Going for longer runs isn't gonna solve that.

Do you still have the 20/20? What kind of jetting can you run with that? I think at this point I'd be focusing on everything intake related, swapping out parts one by one (carb box, carb) to rule out some hard to find air leak, obstruction, or other weirdness.

No, a 145 and I can't make it 4 stroke, but I can tell it's richer than the 138 I put in. With the 160/be4/138 I was hitting 77mph, with 140/be4/145 it was down to 73mph. I was running in with 160/be4/130 thinking it was rich. But as the adage goes, it runs good lean until you blow up.

So, what I hear is that 145 main should be too rich (which I believe is true) but that I have to somehow go richer in order for a plug chop to show up properly??

I do still have the 20/20, but why would putting that back on help?

Here's a post from another 2 stroke forum that suggests that I should ride around on a fresh plug for a few miles before doing a chop on it.

http://www.2strokeworld.com/forum/index.php?topic=12215.0

P.s. I did go for a 60 mile ride this evening on the 140/be4/145 jet stack mostly cruising at 55-60 with close to no problems. (Pinking at 1/8 throttle above 6000rpms. Richened my idle jet to a 50/120 to try to solve the issue but it just fouled a plug.)

OK, I'm just recommending you stop obsessing w/the plug chops. The easiest way to jet a bike is to jet big so it four strokes, then you know it is way too rich and you can come down a little from there. Plug chops are influenced by a lot of factors and are fun to talk about but there's a lot of variability; on the other hand, moving down from a fat jet that four strokes to one that doesn't is a pretty positive indicator.

If your bike never ever jets too rich it seems like something is wrong, which is why I suggested swapping back in the 20/20 to see if you can run it with a more common jet range, or if you have the same behavior.

That way at least you start getting to where the problem is and can easily identify or rule out carb, carb box, stuff like that.

Just throwing out an alternate approach... keep chopping up plugs though if it makes you happy. Seems like your bike isn't straight up seizing, so maybe it'll all work out.

I skimmed over the thread above so don't yell at me too much...

swapping carb w/ a known working one is a simple test to make sure your carb body is not blocking fuel flow due to being casted poorly. If this carb worked before you kitted the engine then it has to be fuel flow. There could be a problem within the carb body that luckily was OK for a stock top end but once you upped the performance "it" became the limiting factor....??

fuel tap has been checked...??

this makes sense to me
no matter the main jet used the mixture does not get richer

who knows...??

the combination of the expansion pipe, the malossi top end and stock carb / crank might be a factor...?? The crank should have been cut to increase the intake timing to match the needs of the other go fast parts but you know that.

good luck

I'm agreeing with everyone here so far.... also, I never use a new sparkplug when doing a plugchop... I like em slightly used.

I think the issue I have is that trying to check for a lean condition with a brand new plug isn't working because there's no carbon on the plug to start with, and therefore there's nothing to burn off and nothing show on the plug.

I don't believe I'm running lean, in fact I believe I'm running rich. It feels boggy, but doesn't 4 stroke. But when I do a WOT plug chop with a brand new plug it always is bare. Which is why I think that I should try doing chops with 'slightly used' plugs as dr.ona suggested and see if that changes my results.

hp: I understand that murdering this many plugs isn't all that productive, but what I'm trying to understand is why my chops aren't showing up. I'm trying to follow many a thread's advice on how to properly do a chop and it isn't working. Chopping this many plugs proves that the way in which I've been told to do a proper chop isn't working. This is important because 'start rich and come down a few' on the mains could lead to engine failure if I haven't been able to establish a baseline for my engine yet. It's not that I don't think your way doesn't work, because your way is exactly how I'm running it, and running it decently, right now. It's that I would like to be able to tune it in a bit better and not damage things. Beyond having both a CHT and an EGT, isn't chopping a good indicator despite the variability? I do have a CHT and have been monitoring temps closely throughout the whole process, but I don't have an EGT.

I'll do a couple runs this evening after work on 'slightly used' plugs and report back.

I'm guessing 145 is the biggest jet you have? Otherwise you would have kept going up (even though you know it's too big) until the plug started to go brown. Something you might like to try.

There was another thread here recently where someone was running a minimum 20 jet points above everyone else... didn't seem to be any reason for it and I don't beleive he got to the bottom of it. Ran perfectly like yours.

Thanks for the plug reading image! That's going up on the wall.

145 main is the largest i have, then i have to come down on the air corrector. Which is why i'm running a 140 air corrector instead of a 160 or higher.

I did see the thread where someone was running a huge jet with no problems.

So here's a pic of a chop i did tonight. This plug has moderate use. I put it in new and then went for a 15 mile ride both through town and out in the country. Then did a 1 mile WOT pull on it and chopped it. It's a B8 and i would eventually like to run B9s but i bought out the town already.

I finally got something other than white..... Stack is 140/BE4/145

Thoughts???