|
Post by scooterpimp on Sept 16, 2018 15:04:34 GMT -5
18-20mm with proper jetting is sufficient unless your going extremely crazy.
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 16, 2018 15:27:03 GMT -5
Now it seems to work! See previous post for explanation. EDIT #2: Bad idea to de-restrict airbox! At least i cannot get my 49cc scooter to run good no matter the jets, if i have the airbox de-restricted. So i have restricted it again, as close to original as i could make it. EDIT: Bad idea to remove metal mesh. It protects against possible backfires. Reading forums, it seems more common than i first thought, and air filter can 'easily catch fire' without them.
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 16, 2018 15:38:14 GMT -5
scooterpimp: Yes probably, but why put 20mm carb if hole is 18mm all the way? Even if i change intake manifold to 20mm also, then hole will abrubtly shrink to 18, with a noticable edge, between (new) 20mm gasket and cylinder head. To me, it just feels stupid but maybe the air/fuel mixture will accelerate when forced from 20 into 18mm hole, and it will still work (better) than running 18mm all the way? I dunno. You tell me. Hmm but maybe i can make a smooth "funnel" by modifying the original 18mm gasket so it is 20 on one side, 18 on other side? Then it makes a little more sense... I dont want that abrupt edge.
|
|
|
Post by scooterpimp on Sept 16, 2018 16:25:22 GMT -5
Was mostly suggesting that anything over 20mm is overkill. Most applications will start large & get smaller when entering intake runner etc. Cars etc. You seem to have it under control. For example single plain 4barrel intake on a v8 it starts as a big square hole then funnels into narrower runners entering cyl. Heads. Im not the best explainer , just my 2 cents.
|
|
|
Post by dexameth on Sept 17, 2018 11:08:37 GMT -5
I run a 24mm carb on my 139qmb build. It runs fine, and yes, increased power. I had a standard 50mm build when I did it and it was a noticeable gain instantly. Now, with my setup, it's pretty much port-matched with a funnel like scenario to the valve. 24mm carb, 23mm intake, port goes from 23mm to a 21mm valve. Runs absolutely amazing AND it's all bolt-on stuff.
What I've noticed is the motor will still run and drive just fine even under load with a 20mm or even an 18mm carb that is jetted correctly... but they aren't feeding the motor to it's capacity. Hell, I have a 26mm CVK carb I may try just for laughs.
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 17, 2018 14:06:24 GMT -5
dexameth: Very interesting info! Thanks! I'll take that into consideration.
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 17, 2018 14:25:26 GMT -5
I couldn't resist going up from 82 to 84 main jet today, after derestricting airbox yesterday. It kind of ran a little better. Then i put needle clip in downmost position to give it even more fuel - it ran (!!), and i could go for a test run. Didn't run good though, worst so far compared to other running setups. Very bad top end power, did 45 km/h max and hesitated not only on standstill, but kinda randomly everywhere. While adjusting clip pos, i flipped back diaphragm the original way again, disregarding the wavy patterns (just made an edit #2 in my original post about diaphragm) because it was very hard to mount and get it to seal around the edge in the non-wavy pattern. As i was doing that, flipping diaphragm, i noticed there is a little hole in the throttle. In what direction should it be aligned when installed in carb? The diaphragm sits snug on the throttle, so when installing it, you can accidentally or not get that little hole to point in another direction than it is supposed to, which i don't know which direction that is, if it even matters. I figured, i should maybe put it facing the cylinder head, so that the groove underneath throttle aligns with the hole, on the "fuel" side of carb. Is that correct? Please advice!That could be relatated to the original hesitation problem if i'm lucky. I cannot remember how it was aligned before i started fiddling with diaphragm. Here is a pic for reference: I feel like installing the 86 main jet tomorrow...
|
|
|
Post by GrumpyUnk on Sept 18, 2018 10:44:00 GMT -5
FHOL:"As soon as i hit the throttle, engine just dies. Now it is definitely running lean instead of rich on the same 82 jet! And i wont be riding it before i've fixed that."
"The hesitation problem seems to be a much more complicated issue than just the size of the main jet."
I don't remember, but did you check the accelerator pump operation? If faulty or mal-adjusted, you will get hesitation and stumble when you open the throttle.
The metal mesh is to protect the paper part of the airfilter from catching fire if you have a backfire. Fire cannot penetrate wire mesh.(flash, anyway). The sponge is not to be oiled as I understand it. Unless an owners manual suggests oiling the media, I would not do so. I do not think it causes much restriction.
On the boxes I have seen, there is a small diameter snorkel just inside the airbox, right after the external snorkel with the screen on the inlet. The small diameter snorkel may possibly be removed with no ill effect on some machines. It is a ribbed tube mounted to a slanted flat plate of plastic that appears to slide into slots on the inner surface of the airbox. I would leave the sponge and perforated metal screen, personally. tom
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 18, 2018 12:55:20 GMT -5
@grumpyunk: I can't find what is the accelerator pump in this carb that i have, can you? www.manualslib.com/manual/976572/Peugeot-Kisbee.html?page=64#manualInteresting info about metal mesh in airbox! I didn't think of that, ooops! Wonder how likely it is to catch fire on a 4-stroke. As far as i know, cars don't catch fire too often because of that. Gonna consider putting it back anyways. Cone shaped "hi flow" filters, are they safe in that way? They're not made of paperish material so i guess safe. EDIT: Looking at them, most seem to be draped in a thin metal mesh. Also seems to be more common than i thought that 'paper' air filters catch fire if you remove metal mesh in front, so don't do it! I was beeing stupid / uneducated.About the snorkel.. i'm not 100% sure (despite removing it the other day) but on my airbox i think the external snorkel extends into the airbox so is one piece external + internal. Gonna order 20mm carb, new 20mm manifold, and cone filter NOW. While i wait, put in 80 main jet, metal mesh, sponge filter, and some duct tape in front of airbox air intake to restrict it a little again, to hopefully restore it to initial hesitation state (but running great otherwise). Now it just runs like crap + hesitates.
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 18, 2018 14:23:57 GMT -5
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 20, 2018 12:50:17 GMT -5
I've been reading a bit about diaphragm and slide operation in carbs now. So to answer my own question about that tiny slide hole... which is VERY important: As i understood it, as piston goes down, the volume above piston increases therefore pulling air/fuel into the cylinder head. Piston movement also creates a lower than atmospheric pressure through the carb main passage. This lower pressure is propagated through the small hole in the bottom of the slide (that i called "throttle" before, sorry about that), up to the inside of the lid covering the diaphragm. Since the underside of the diaphragm is connected to atmospheric pressure all the time via an often oval hole at the top air side of the carb, you get a pressure difference. The lower pressure above diaphragm forces the slide upwards, overcoming the spring force in center of slide, lifting needle out of the main jet, causing more fuel to get inside your engine. It is possible to test this functionality after mounting, to make sure diaphragm is air-tight. Will do that soon. For if its not, it will probably run bad or lean. Here is guy drilling a small extra hole in his carb slide, BUT, he seems to have gotten it all wrong about lean vs rich. youtu.be/7Sxu7bqEaPU?t=44Though he says the extra hole "pulls the slide up more quickly" in the end = MORE fuel, not less fuel. I'm still not sure how my slide should be rotated in relation to the diaphragm, that has a fixed position with that little "ear". I know slide hole should be on the fuel side of carb... but the bottom of carb where slide hole "sits" on minimum throttle, is not a flat surface. Right now it is in the middle so it is "open" even when slide is in downmost position. Gonna try altering that alone sometime, to see if there is a difference in how it runs. If offsetting it, so it rests on a more "flat" surface and is more closed than now initially, i suspect it would delay the lifting of slide a little, making it go a little leaner in the beginning. By the way, also found out what the third non-removable ? 35 size jet in my carb is - it is the choke jet! I will not give up until i have mastered this stuff!
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 20, 2018 17:18:01 GMT -5
Ok, so i have UN-derestricted airbox by covering the part of the hole i made larger with duct-tape, put sponge-filter back, installed 80 main jet, put needle clip in middle pos, rotated slide inside diaphragm so it aligns with the flat surface (could be bad, i dunno), se pics, in an effort to get back to 'square one' + a little more fuel added. Scooter hesitates slightly and has less power than when i began troubleshooting. Unfortunately, can't remember original slide hole positioning. Before UN-derestricting, i experimented with various amount of tape in airbox air intake. It seems to be very sensitive and hard to get correct air/fuel mixture if fiddling with airbox. I reckon the factory restriction along with 78 main jet was carefully selected, and that sucks for me now! Can't wait to get my hands on the new 20mm carburettor i ordered yesterday. Gonna inspect it very carefully before installing it.
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 22, 2018 15:45:03 GMT -5
Day of the scooter. Been testing different things from 11 to 21 today. Many miles driven too. First i bought new air filter with metal mesh, hot glued what i filed off from airbox, put sponge filter back so now airbox is as close to original as i can get it. Ran 80 main jet, clip in middle, slide hole over concave surface facing cylinder. Scooter ran ok, except the usual hesitation. Checked spark plug after ~10km running full throttle most of the time. It was slightly darker than my spark plug pic on page one, so ok air/fuel mixture. Now i had a working setup to use for experiments with slide hole. Slide hole experiments: Seems to work best if pointing to cylinder, but rotated a little just so it is above the flat surface in carb and not over concave surface (though that worked too). Tried every direction possible, even pointing at air intake. Did not change anything else on each test. Pointing a air intake = BAD. Engine got starved of fuel, as suspected. I'm still eager to hear from someone who knows for sure how to point slide hole. After deciding on slide hole pos, i tried putting needle clip at top. Engine starved, ran bad. Put it in downmost pos instead (since i've been running in middle pos all day). That made hesitation less but still noticable, and i also felt (highly subjective) a little power boost. So that is where i'm at now. Runs absolutely great again, except small hesitation. Spark plug looked good even in middle pos so... it should not be running lean now. My new "don't touch" setup with original carb: Main jet: 80 (78 was original) Pilot jet: 30 Choke jet: 35 Slide hole: pointing to cylinder, but slightly turned over flat surface Air/fuel mixture screw: 1.5 turns out Clip: downmost (max fuel) Spark plug gap: 0.7mm (following owners manual) Air filter box: close to original resistance Bonus info: Weather: 10-15 degrees (Celcius), light rain, damp air Elevation: 0-200m above sealevel Now i'm not gonna do anything more til i get all the new and shiny chinese parts i ordered. OH i almost forgot! Going to buy parts, i parked close to another Peugeot Kisbee that looked the same year as mine, same color too. The owner left just before i did, and i definitely heard the exact same hesitation from that scooter too!
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Sept 30, 2018 12:36:49 GMT -5
Twelve days later and no parts in sight. Guess i'll be for a while.
|
|
fhol
Scoot Member
Peugeot Kisbee 4T 2016
Posts: 81
|
Post by fhol on Oct 3, 2018 14:45:01 GMT -5
Pilot jets China -> Norway took 15 days. Short-lived happiness tho - i ordered the wrong f**** jets. They're M6 "Keihin", too big thread, and wouldn't fit in my original carb. Beeing an idiot, i forgot to always measure twice. BUT, they will probably fit in the new 20mm carb i ordered that should arrive soon. A little frustrated, i upped the main jet from 80 to 82 again. Figured since i ran needle clip in downmost pos on 80 (worked good), i should be able to run clip in middle pos on 82. Testrun... ran lean and hesitated like a m-f! Then put clip in downmost pos on 82 jet and... it runs better than ever now! Almost hesitation-free and good power. My new "don't touch #2" setup with original carb: Main jet: 82 (78 was original) Pilot jet: 30 Choke jet: 35 Slide hole: pointing to cylinder, but slightly turned over flat surface Air/fuel mixture screw: 1.5 turns out Clip: downmost (max fuel) Spark plug gap: 0.7mm (following owners manual) Air filter box: close to original resistance (probably slightly less restricted) Bonus info: Weather: 5-10 degrees (Celcius), raining Elevation: 0-200m above sealevel So this was interesting. Changing needle clip pos from middle to downmost seems to give a larger fuel boost than upping main jet from 80 to 82. Why? Because it hesitated noticably MORE on 82 middle pos, than on 80 downmost pos.
|
|