PZ30 X31 250cc Stock jetting?

[Azriel_Strife]

Hi there everyone, This is my first post and I hope to be of help to other users as I gain knowledge of this bike. I'm quite helpful in other forums that I am part of, such as hondatwins.net (older honda street bikes).

Anyway, my question is:

What size jets does the PZ30 have stock on the X31?

My main jet appears to be a #88 (which I believe is a keihin jet size).

My slow jet, I am unable to get a number off of, however upon much searching, I did find one thread on another forum saying that a guy removed a #36 slow jet in favour of a larger #42 jet.

my bike is stock from what I can tell, so I should be OK with stock jets, unless they are known to be too lean from the factory.

can anyone reccomend a good jet set up for a stock bike?

[Weldangrind]

Welcome!

Azriel_Strife and I have been communicating by PM, and I have a Keihin from an old XR200 for him to try. The Keihin PZ30 has a 108 main, but we think that the 115 and 120 that he has en route will also fit.

The China Keihin carb jet numbering system makes no sense to me. :roll:

Azriel_Strife, perhaps you can report back to us and let us know how the Keihin works for you, and which jets work the best. Do you plan on any intake / exhaust upgrades?

[Azriel_Strife]

No, I think I'll leave the bike stock. I'm just getting back into off road biking after about 20 years without a bike. I just want to get it running!

I was going to ask if the mikuni and Keihin jet sizes are the same? You have a mikuni running a 25/115.

I'm not sure how those numbers relate to Keihin carb sizes.

[Azriel_Strife]

Upon further research, mikuni vs keihin don't match up exactly.

This is from the Jets R Us website. Numbers correspond to the brand at the top of the list, left to right. Keep in mind that the jets alone don't determine how a bike will run, different carbs have different flow rates, different venturi effects ect, this is a good palce to start.

KEIHIN DYNOJET MIKUNI
----------------------------
92 92 85
95 94 87.5
98 96 90
100 98 92.5
102 100
105 102 95
108 104 97.5
110 106 100
112 108
115 110 102.5
118 112 105
120 114 107.5
122 116
125 118 110
128 120 112.5
130 122 115
132 124
135 126 117.5
138 128 120
140 130 122.5
142 132
145 134 125
148 136 127.5
150 138 130
152 140
155 142 132.5
158 144 135
160 146 137.5
162 148
165 150 140
168 152 142.5
170 154 145
172 156
175 158 147.5
178 160 150
180 162 152.5
182 164
185 166 155
188 168 157.5
190 170 160
192 172
195 174 162.5
198 176 165
200 178 167.5
202 180
205 182 170
208 184 172.5
210 186 175
212 188
215 190 177.5
218 192 180
220 194 182.5
222 196
225 198 185
228 200 187.5

[Weldangrind]

Did you find a similar chart that references slow jets? I'd be interested to see that as well.

[Azriel_Strife]

Unfortunately, they dont have them in the size range for slow jets, but one could probably use the chart to discern what the differences would be, since they likely use the same measuring system for slow jets also.

[Weldangrind]

I thought about that, but the starting point for a Mikuni that's feeding a 200 is around 25, and it seems to be closer to 38 for a Keihin. The spread isn't as wide in the main jet chart.

Oh well, I'll just stick to Mikunis.

[Azriel_Strife]

I almost have it all worked out!

The bike is acting like the stock 36 slow jet is a bit too small, wandering idle and tends to backfire a bit through the carb when cold. I have a 40 slow jet on order, that should do the trick.

The main jet drilled to Mikuni 116 equivalent (130 Keihin) seems to be bogging the engine, It didn't bog before with the stock jet (wich was smaller) so it must be too big!

I have a feeling the bike will be running beautifully once i get the 40 slow jet and the 125 keihin (110 mikuni equivallant) main jet in there.

[dixonbc35]

Where can i buy parts for 250cc all-rad dirt bike

[Weldangrind]

Originally Posted by dixonbc35

Where can i buy parts for 250cc all-rad dirt bike

Welcome! Are you really from Dixon, BC?

I'm not familiar with your bike. Please start a new thread in the Pure Dirt forum and show us a pic; we'd be happy to try and guide you.

[ssrider]

Where can I get jets for my Gio x31 with PZ30 carb?

[Weldangrind]

Originally Posted by ssrider

Where can I get jets for my Gio x31 with PZ30 carb?

I would say don't bother. You can remove the two jets from your carb and compare them with pics from www.jetsrus.com, but I don't think you'll have luck with the slow jet.

For $40 (including shipping), you can have a brand new 30mm Mikuni that you can buy jets for from the local Yamaha dealer. eBay is your friend.