Carb Pilot size advice

Basically I fitted a Mikuni 30mm carb over the stock 26mm chinese carb, things do seem to be alot better, but I'm having starting issues, its been cold lately which hasn't helped. Going by the mikuni pilot jet I've read 20, is this correct, it seems too small, whereas my other stock carb has k38 size printed. Any idea's what size pilot would I roughly need so I can order a rough range of pilots to try work things out. I had slight starting issues on stock carb as well, but not this bad. Once warmed up things are smooth except on a cold day it still may stall very early into a journey.

Thanks in advance

Alex

I would say that pilot jet for that carb and 125 cc, must be at least 40 or 45.

You mentioned that you have Colortune? Did you use it to check mixture at idle?

According to http://item.taobao.com/item.htm?id=16060415301 (That city is the capital of clone carb) stock 2? = 35# measured by flowing machine.

With stock carb (26mm) on a 38 it was just lean.

So I think 45 is needed if the mikuni one is a 35?

I'm between a 45 and 50 size at a guess as the carb is 33% bigger in area. Plus the choke butterfly has a drilled hole unlike the stock carb, what's people's advice from.experience?

One detail: is your foam air filter properly oiled? I ask that because I think I saw a photo on your blog. It looked to me, that this foam is dry.

Air filter is dry indeed, didn't think it needs to be oiled as I know on cars the oil plays havoc with the MAF sensors, I've never had to deal with carbs up until now.

Quote:

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Originally Posted by arancara

I'm between a 45 and 50 size at a guess as the carb is 33% bigger in area. Plus the choke butterfly has a drilled hole unlike the stock carb, what's people's advice from.experience?

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North American guys had more experience about Mikuni on Honda clone. http://chinariders.net/modules.php?n...=viewforum&f=1 had many good article . Pan-chinese (TW/ mainland) prefers Keihin .

Had a quick look on the link human, similar issues as me on the pilot, but I'm really confused with one thing, is a mikuni 20 a completely different size unit altogether? most of the lads have put a 25 one in on that forum and I've just placed an order for a 45 size... Are the jet sizes not standardized and is there a conversion chat between manufacturers as this has left me confused.

There is no sensors or something similar on your bike's intake system, so you can try to enrich mixture by increasing the resistance to air flow through the filter element by a simple oiling it. This "choking" is old two-stroker's technique, when you don't have carb that "doctor has prescribed" for your engine - maybe won't work for you, but why not to try? The only consequence can be additional degreasing of filter and greasy hands.

Numbers at the jets can refer to, either the diameter of the hole, or flow through jet under certain conditions (I think this is Mikuni, an maybe Solex method of marking).

Carb on your bike came with pilot jet marked 20, and my 50 cc tiller has Deni PZ-17 (Keihin clone) carb and pilot jet marked 35. So, do you see the logic? :eek2:

In short: if someone does not give proven setup that works, you're sentenced to a frustrating experiments.

Quote:

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Originally Posted by Zorge

...Deni PZ-17 (Keihin clone) carb ...

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It's the legal clone. Keihin had shares in Deni until '11 http://www.dekni.com/company/history4.php ...1994...
http://www.autoinfo.gov.cn/autoinfo_...00081_11_3.pdf ...2011 年 6 月 17 日...

I've played around, I found the magic number for main jet to be 110 for my setup. However the float seal is deteriorating with every change. As for the pilot I've given up. Ordered several jets in a size 50, all of them were smaller than the size 20 :S On all the 50 jets fitted things got worse (as they did look smaller).

So I'm back to the stock 20 size which I have no idea on what really its flow rate is. Instead for the time being I've increased idle revs to deal with the cold as things get warmer I'll have to adjust as I'm only finding it too be stable at 2.5k with choke and 3k without choke in the cold morning starts of around -2c.

Also is there a rule of thumb, i know where the idle screw is, but I've got two other screws, one below the float chamber and one on the opposite side of the idle, any idea what either are likely to do as a guess one would have to be the air/fuel mix at idle? As for the other screw I have no idea...

Give us some photos of that carb of yours.

And don't bother with carb, when the weather is still cold. Wait for warmer days.