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Discussion Starter #1


I have a friend who lives locally to me, and he rides a Chinese Skyjet 125.
And he is letting me try out some fairly crazy ideas on it :D
Poor fool probably thinks I ACTUALLY know what I am doing >:D

First of all, I removed the baffle from his exhaust, which was welded in.
This made a huge improvement to the sound.
I will upload photos / videos when I get a chance.

The second thing I did, was to re-wire (or make a solder bridge connection between some wires rather) so that he can have his headlights and sidelights on at the same time.
Interestingly, the chinese figured it would be a good idea to have only one OR the other on.
This was rather fiddly, as the cheap chinese wiring was rather... delicate.

Next, I want to open up his airbox and see what I can do in there, to perhaps get more air flowing through.

THEN, I need to learn how to tune a carb, and perhaps get this bike running a bit faster. At the very least, I would like to compensate for the exhaust / airbox mods I have done / have planned.

I will update as and when I think of new things to do to his bike :)
 

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Discussion Starter #3
You like it? Why is that? :p
 

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There's not much of an art to tuning a carb, more playing around with changing the jet sizes, which have to be bought.
You can get full kits of jets for tuppence though, it's fantastic :D
 

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Discussion Starter #5
There's not much of an art to tuning a carb, more playing around with changing the jet sizes, which have to be bought.
You can get full kits of jets for tuppence though, it's fantastic :D
Fuel air mixture?
Would more or less any jet fit any carb?

Edit: I just brushed up on my carb knowledge.
I have decided I probably DO need to re-jet his carb then...

How much are a set of jets, and how would I know which ones will / wont fit?
 

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the nose of it just looks flat!
maybe u could try and get the body work more sleeker lol!

and also u could lower the handle bars and hight the foot pegs? just an idea?
 

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Discussion Starter #8
Your mate bike
What do you like about it?

The seat is comfortable to be fair. Although the whole thing rattles and shakes you to pieces.
 
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On my mates old 50cc dirt bike we drilled out the inlet manifold which increased the top speed to 45mph but it was only a 50cc
 

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Discussion Starter #10
Did you have to adjust the carb or anything?
 

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Discussion Starter #12
Ye
For the jets cam, find the brand of carb that's on there, it's NEVER made by the company themselves.
Then you should be able to buy a set from that company.

Edit- while trying to find out what carbs they use, I did find this:
http:hmm:/www.ebay.co.uk/itm/SkyJet-Sky-Jet-SJ125-SJ-125-cc-6-Sigma-Custom-Carburetor-Carb-Stage-1-7-Jet-Kit-/330647723462?pt=Motorcycles_Parts_Accessories&hash=item4cfc23ddc6

Yeah, I saw that too!
Right. I shall do that :)

And so what... I buy a set of jets, and then trial and error to find the best size? :p
 

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Some trial and error, some science involved.
Generally it's an interative process; you can tell whether it needs to be bigger or smaller from the start, then you go smaller or larger until it runs nicely
 

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is he declaring your fiddling? otherwise you may land your friend's bike through his letterbox as a cube.
 

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Discussion Starter #17
Well for now, I am doing mods that don't cost anything.
And for now, nothing has been done that is worth considering...
We don't declare when we remove our baffles do we?
 

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You want to be looking at letter drills for playing with the jets, but be warned once you have gone bigger you can then not go smaller, so get yourself some spare standard jets to resort back to.

You mention the wiring was fragile, are you sure it is capable of taking the permanent current draw?
 

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Discussion Starter #19
You want to be looking at letter drills for playing with the jets, but be warned once you have gone bigger you can then not go smaller, so get yourself some spare standard jets to resort back to.

You mention the wiring was fragile, are you sure it is capable of taking the permanent current draw?
By fragile, I meant the little tiny circuit board, and the switch complex which consists of very tiny little contacts and springs which are very difficult to position in a way that they don't come out :p

As for the rest of it... Fairly sure :p
 

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Discussion Starter #20
So from what I can tell, this bike has a "Shen Wey PZ26" Carb.
(http://www.ebay.co.uk/itm/Skyjet-SJ...ycle_Parts&hash=item27b4532991#ht_1541wt_1163).

I will confirm, once I see the bike again.

Would I be right in saying, that I COULD increase the airflow as much as possible...
By modding the **** out of the exhaust and airbox...

Then SLOWLY increase the size in the jets, using a Drill, until the bike appears to be running at it's peak?
Failing that... I could perhaps find an alternative Carb, a performance one? That would also fit?

How would I know if it will fit, will all 26mm carbs fit, or what?

Also, isn't there some sort of adjuster you can play with to adjust the fuel / air mix?

Honestly, I do understand how a carb works... Just don't know much about tuning them ><
Would absolutely LOVE to learn though!
 
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