Pocketbike jetting.

**imdying** · 28th May 2010, 13:49

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** · 28th May 2010, 13:54

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/...ust-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** · 28th May 2010, 14:23

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** · 28th May 2010, 14:47

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** · 28th May 2010, 15:01

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** · 28th May 2010, 15:20

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** · 28th May 2010, 15:25

Originally Posted by Nutter34

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** · 28th May 2010, 15:26

Originally Posted by Nutter34

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.

Steve

**imdying** · 28th May 2010, 15:45

Originally Posted by Nutter34

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** · 28th May 2010, 16:59

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

May just do that, to prevent deterioration.

Thanks fellas.

**Spearfish** · 28th May 2010, 23:16

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=YzBY5...1&feature=fvwp

**{.bLanK}G_o_D** · 29th May 2010, 03:22

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

**imdying** · 29th May 2010, 11:25

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** · 29th May 2010, 14:03

Originally Posted by 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=YzBY5...1&feature=fvwp

Good info. Thanks.

Originally Posted by 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.

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.