seriously not a new thread.

[hect75]

I know this is not a new thread but need your expertise advice. A couple of months ago, I posted some pics of the spark plug (white color) and received some comments about increasing the mainjet size. I replaced the stock muffler for an unrestricted one. I noticed that after shifting the muffler my ride lost power beyond 80 km/h (kind of stalling). I used a drill bit a little bigger than the stock mainje size (130 teikei) and opened the air box with the same results (notch was at the middle of the needle). Then, I only leave a hole of about 2cm2 in the airbox and moved up the notch to the top. This really increased response the first days reaching up to 90 km/h (beyond that, bike stalls). I did the plug but the spark plug had the same white color. After a couple of days riding this way, the bike start to spend more time warming up by morning and slowly respond the acceleration. I thought this was a warming problem. Three days ago, the bike warmed during 5 minutes but after that turned off when trying to accelerate. Know the bike is sitting until I get the right mainjets but not sure if I should buy these sizes: mikuni n102-221(brand and model recommended here) 125, 127.5, 130, 132.5, 135. I will be in Cruces last week of October and need to buy them online to pick them up in Cruces. I got to play with these guys but need you expertise.

NOTE: I used a drill bit because down her in Mexico mainjets cost about $22 each.

[Weldangrind]

I wouldn't drill a main jet unless I had a numbered drill bit set. For example, if a main jet is a 100, that typically means the orifice is 1.00mm, or 0.0394". If you wanted to increase the size, the next step would be a #60 bit, which is 0.04". The steps need to be very small.

What size did you drill the jet out to?

Also, try to make only one change at a time, so you can narrow in to the actual problem. You indicated that you drilled out the jet (which increases fuel) and you opened up the air box (which increases air flow) and saw the same results. That is to be expected.

You then said you decreased the airbox hole to about 2 square cm and moved the clip to the top notch, which would affect the mid-range power.

I suspect that your main jet is still too small, but I don't know what size to recommend until you tell us what drill size you used.

[hect75]

Originally Posted by Weldangrind

I wouldn't drill a main jet unless I had a numbered drill bit set. For example, if a main jet is a 100, that typically means the orifice is 1.00mm, or 0.0394". If you wanted to increase the size, the next step would be a #60 bit, which is 0.04". The steps need to be very small.

What size did you drill the jet out to?

Also, try to make only one change at a time, so you can narrow in to the actual problem. You indicated that you drilled out the jet (which increases fuel) and you opened up the air box (which increases air flow) and saw the same results. That is to be expected.

You then said you decreased the airbox hole to about 2 square cm and moved the clip to the top notch, which would affect the mid-range power.

I suspect that your main jet is still too small, but I don't know what size to recommend until you tell us what drill size you used.

I can´t find it. let me double check and will answer to your question.

[hect75]

Originally Posted by Weldangrind

I wouldn't drill a main jet unless I had a numbered drill bit set. For example, if a main jet is a 100, that typically means the orifice is 1.00mm, or 0.0394". If you wanted to increase the size, the next step would be a #60 bit, which is 0.04". The steps need to be very small.

What size did you drill the jet out to?

Also, try to make only one change at a time, so you can narrow in to the actual problem. You indicated that you drilled out the jet (which increases fuel) and you opened up the air box (which increases air flow) and saw the same results. That is to be expected.

You then said you decreased the airbox hole to about 2 square cm and moved the clip to the top notch, which would affect the mid-range power.

I suspect that your main jet is still too small, but I don't know what size to recommend until you tell us what drill size you used.

Weld, the drill bit size used is 1.54 mm. I used another size 1.58 mm and move the noth down to the middle. When shifting to 4 the bike turned off. I assume the carb was flooded with gas due to the size of the main jet. I drained the excess gas and turned on again. I could not go beyond 4 cause I was riding around the neighborhood but did the chop at 4. I found the plug is black. I will ride it this monday and see what happens.

[SpudRider]

Instead of drilling the jets, I recommend you follow the advice posted in the following threads.

http://www.chinariders.net/showthread.php?t=6501
http://www.chinariders.net/showthread.php?t=6528

Mikuni jets shouldn't be very expensive. You can buy several jets, both larger, and smaller, than the jet recommended in the threads listed above. In this manner you can experiment with several sizes of jets to determine which works best for you.

[MotoJ]

http://www.jetsrus.com/

This place rocks for jets, in case you didn't know about it already...

[SpudRider]

If they will ship to Mexico, you can buy the Mikuni N102/221 jets at Rocky Mountain ATV/MC for a very low price.

https://www.rockymountainatvmc.com/p...s%20main%20jet