Pocketbike jetting.

[Nutter34]

How sensitive are these to jetting?

I have the a115/cag/daytona/trademe special.

What's the best way to determine jetting? Run at max and kill it? Check plug? Biscuit brown colour? I know to start with the main, then sort the needle etc afterwards.

Do you guys change jetting from summer to winter?

I ask since we are curious about the effects of temperature. We currently 'play' at night when it's between zero and 10 degrees C...

[CookMySock]

For general running they are relatively insensitive - they will always "go". If you to boogie, jet them as lean as you dare for maximum performance, or else they run rich and shitty and won't rev right out. Most people won't though. They will get scared and run them rich for "maximum power" and so they don't "blow an engine".


Steve

[White trash]

Engine rebuild's what, 30 bucks?

Lean it out, lean it out, then lean it out some more till it goes bang then pop a new pistone in it and back it off a little. Job done.

[Nutter34]

Lol, WT, fair enough too.

Thanks for the replies lads.

We did a chop on one of the bikes the other night and it was light grey, so getting up there already.

PS: How long do you guys run at full throttle to do a plug chop. I think I've heard someone say 25 seconds.

Thanks.

[White trash]

Mt Wellington isn't long enough to run for 25 seconds full noise so I wouln't know. Maybe 15 max.

[imdying]

Stopwatch and a pile of jets. Find the one that whips down 100 metres from a standing start the fastest, and then balance that against the one you feel gives you the best low down poke. 5 needle clip settings to make it a bit more fun :D

Winter = colder air = denser air = leans you out, so you might want a little richer compared to Summer.

[888mike]

Shit you guys are gettin serious

[Nutter34]

Shit you guys are gettin serious

Not really...

It's a few minutes to swap a jet. Considering we ride at night and it's pretty close to zero degrees C, I'm willing to play a bit to get the jetting right...

Mmm, gonna have to source a pile of jets, lol.

[Junkers]

Be careful with that float arrangement, these things love to leak. I've heard you can drill the throat of the carb out as well.. food for thought.

[CookMySock]

we ride at night and it's pretty close to zero degrees CFark that.. and we shiver through our 11 degree days.. I guess theres no cold wind inside though. :shutup:

Steve

[Nutter34]

Lol, we ride outside. It was 6 last night.

Did one plug chop, bike burning grey on the plug. May just leave it.

Man, it gets up to speed real quick though, lol.

[{.bLanK}G_o_D]

We have an ass load of carbs to jet, so what I did was I brought a high quality "true" pin chuck for $80 from Gorge Henry (chuck to hold tiny drill bits) and a few different sized drill bits. 0.6 and 0.7 for a start.
Solder the hole in the jet and then drill it out using a tight drill press.

[imdying]

Yep, once we're sure of the direction to head, we'll get some genuine ones... well except for the cag ones, drilling will probably have to suffice unless someone knows where to buy them?

[CookMySock]

Lol, we ride outside. It was 6 last night.Is there no politics with noise etc? A few club members here (glares at Mike) are afrraaaaaid to ride at night coz we might kick up a storm. :rolleyes:

Anyway, we might get cold hands at night, and the girls hate that. ;)

Steve

[Nutter34]

We have an ass load of carbs to jet, so what I did was I brought a high quality "true" pin chuck for $80 from Gorge Henry (chuck to hold tiny drill bits) and a few different sized drill bits. 0.6 and 0.7 for a start.
Solder the hole in the jet and then drill it out using a tight drill press.

Yeah, we were wondering what size they'd be. One guy was thinking just that...


Yep, once we're sure of the direction to head, we'll get some genuine ones... well except for the cag ones, drilling will probably have to suffice unless someone knows where to buy them?

I thought Newmanz had a jet set...


Is there no politics with noise etc? A few club members here (glares at Mike) are afrraaaaaid to ride at night coz we might kick up a storm. :rolleyes:

Anyway, we might get cold hands at night, and the girls hate that. ;)

Steve

We aren't riding in the suburbs. Lets just say we're far enough from everything for it not to be an issue (we think) and it is 'private property'...

[imdying]

I was hoping for something other than a Chinese jet... the Chinese must've copied them from somewhere, so maybe the original manufacturer sells them.

[Nutter34]

True. I take it Keihin or Mikuni etc jets don't work...

On the subject, kinda...

Anyone modified an exhaust, similar to the cags one, as seen on pocketbikeplanet?

http://www.pocketbikeplanet.com/f47/how-mod-your-stock-exhaust-24043.html

ok. with this mod you will experience better top end, better low and also better mid.

instructions:

1. take stock pipe off

2. make 3 cuts. one, the start of the expansion chamber(you will notice about 1.5 inches of pipe sticking in there*BAD*. the second cut is right where the expansion chamber goes from its largest part and going back small. the third and final cut is at the part where the first cut was, just back about 2 inches.

3. weld a "belly" in between the cones of the expansion chamber about 1.5 inches long.

4. weld the new expansion chamber to the cut you made in the headpipe.

5. reinstall!!

the pictures do a great job of explaining this. i have to admit, i DID NOT take these pictures, they are from the site and i found them while i was searching. the pics do a better job of explaining than i do.

this mod is great and better than a pipe i bought! it has pretty good power and great top end!

[imdying]

I've seen that mod before, but I don't really pay much heed to what American teenagers have to say, so would be nice to have it confirmed locally. Mine is currently in bits, so maybe it'll be me first!

Haven't been to the carb shop, I put a genuine Dellorto on it instead (SHA14).

[Nutter34]

Do you know what size the standard jet is on these? Even just as a reference...

Yeah, we are supposed to keep the bikes standard and only do what we can without spending heaps of money on performance parts. Suppose the pipe mod fits kinda within those parameters, lol.

Mind you, I'm already tapped out on stock gearing, I'd have to go to a seven tooth front to get any benefit, assuming the pipe works.

[imdying]

Not sure, I might get a chance to pop them over those tiny drill bits tonight that Phil mentioned. Apparently drilling jets is fraught with pitfalls though... the finish that it leaves inside the hole will change the flow rate etc. We're just going to use that as a method to confirm what direction to head before buying a heap of genuine jets to fine tune with.

I know the bikes are supposed to be standard for nzmmrc racing, but we don't do that, and we're more interested in a bit more reliablity so that there's more on bike time and less mucking about... there's plenty of attention that they need anyway! Besides which, leaking carbs are just a fire hazard.

The pipe mods might give you a few more revs.

[Nutter34]

Fully understand the leaking carb. Yes, I'd heard the same about drilling, not to mention you never get two jets the same.

One guy... His bike wouldn't stop leaking fuel. Kept on adjusting the float.

Turns out there was a small bit of plastic stopping the needle from seating properly, so the bowl was over-filling. Took the needle out, opened the fuel tap, let fuel pour through. Re-assembled and all was well. Except for it not running, due to adjusting his leaf spring/fingers to close the needle too early, lol. Took some time but he got it right...

Did you have a similar issue?

Actually, on mine, the two fingers/leaves were different heights too. That caused the float to tilt a bit and get stuck. It would leak fuel every time I turned the bike off. Got them level, problem stopped immediately.

[CookMySock]

Fthere was a small bit of plastic stopping the needle from seating properly, so the bowl was over-filling.This happens a lot on the daytonas with a fuel tap. The rubber gasket part inside the tap shits itself and drops rubber all through your carb. Not nice. Best to turn the fuel tap on and then don't touch it.

Steve

[CookMySock]

We aren't riding in the suburbs. Lets just say we're far enough from everything for it not to be an issue (we think) and it is 'private property'...You have a good spot then. :niceone:

Steve

[imdying]

Turns out there was a small bit of plastic stopping the needle from seating properly, so the bowl was over-filling. Took the needle out, opened the fuel tap, let fuel pour through. Re-assembled and all was well. Except for it not running, due to adjusting his leaf spring/fingers to close the needle too early, lol. Took some time but he got it right...

Did you have a similar issue?Have had at various times. As Steve says, the guts of the tap tends to die and block the seat like you say.

[Nutter34]

Mmm, sounds like leaving the tap is a sound option.

May just do that, to prevent deterioration.

Thanks fellas.

[Spearfish]

I thought there were heaps of upgrade parts on trademe?
I found these a good starter when pissing around with jets, needle heights etc
http://www.iwt.com.au/mikunicarb.htm
http://justkdx.dirtrider.net/printcarbtuning.html
http://scooter.wikia.com/wiki/Tuning_a_carburetor


I wouldn't even know where to start with re-jetting this thing...
http://www.youtube.com/watch?v=YzBY54iKLos&NR=1&feature=fvwp

[{.bLanK}G_o_D]

All Good information there dude. Cheers! Bling well deserved.

[imdying]

Ok I've found you can buy the 1486 Dellorto (5mm) main jets here in Christchurch from Palmside Auto, but they don't have anything under about 120 (so about double what we want). However, it's still a source of jets to be soldered and drilled for experimenting with before buying them out of the UK.

For the Chinese carbs, he might have something to fit too, as he has a huge range of jets, so we'll take a Chinese carb down one day and see if something can't be found, even if it's just something to fill and drill.

[Nutter34]

I thought there were heaps of upgrade parts on trademe?
I found these a good starter when pissing around with jets, needle heights etc
http://www.iwt.com.au/mikunicarb.htm
http://justkdx.dirtrider.net/printcarbtuning.html
http://scooter.wikia.com/wiki/Tuning_a_carburetor


I wouldn't even know where to start with re-jetting this thing...
http://www.youtube.com/watch?v=YzBY54iKLos&NR=1&feature=fvwp

Good info. Thanks.


Ok I've found you can buy the 1486 Dellorto (5mm) main jets here in Christchurch from Palmside Auto, but they don't have anything under about 120 (so about double what we want). However, it's still a source of jets to be soldered and drilled for experimenting with before buying them out of the UK.

For the Chinese carbs, he might have something to fit too, as he has a huge range of jets, so we'll take a Chinese carb down one day and see if something can't be found, even if it's just something to fill and drill.

Maybe it's better having the bigger hole for the solder. That way you aren't compromising the bond between the solder and jet as much. Let us know how it works out.

[imdying]

True bro, hadn't considered that. Might be worth running a 1mm up the jet before soldering it then.

[{.bLanK}G_o_D]

I was thinking more like a 2mm.

[Nutter34]

How do you plan on getting it centre? Or don't you think it's THAT crucial?

Maybe a very small hobbie lathe. Put the jet in the chuck and that way it should be more centre? It should at least be more consistent.

[{.bLanK}G_o_D]

Yip a wee lath would do it. We'll probably try the wee drill press first, as long as it is pretty close to center by eye, I don't think it'd be a huge problem. We'll find out soon enough

[Spearfish]

I was drilling jets out to find the one I needed, but only because I didn't have the ones I wanted.
One problem is you tune with rich jets and work down until WoT pulls the best 1/3- is needle height, 1/4- pilot jet, idle- up air screw.
You run a huge risk of seizing going the other way, considering your pinning it doing plug chops, unless you have two?
But then I was tuning a big-bore cylinder from std, maybe its not so many steps just tweaking.