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Honda CG125 project - Page 8 - The Bikeshed Forums

Thread: Honda CG125 project

Results 71 to 80 of 110

  1. #71
    I was just about to make my seat hoop out myself but we couldn't find the pipe bender, and im so glad I bought it instead. The one I bought came with inserts to guide it on and it fit really snug so it was super easy to weld. I really doubt id have had the ability to bend thick pipe to get a diameter to the nearest mm. This is the one I ordered http://www.ebay.co.uk/itm/CAFE-RACER...3D182167249508

    namtip, the electrolysis was loads easier than I thought. I just bought a bag of soda crystals for about a quid from wilcos and dissolved some of that in water, filled the tank right to the top (thats important) and stuck in a bent piece of thin square profile steel they had lying around (anything conductive will work as long as you can put it in the tank and hold it in place so it doesnt make contact with anything). I just found a threaded bar in my garage so im going to use that to give it a final go. Threaded bar is good cos you can put it through a hole in a piece of wood and hold it with a nut on either side (plus i guess larger s.a. for rust to attach to)


    Now to go from giving advice to asking for it. My biggest obstacle to get it running is the carb tuning, I have a megaphone style exhaust and a ramair pod filter (http://www.ebay.co.uk/itm/351222225130?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) im going to use, and im planning on sticking with the stock carb.
    All i know about carb tuning is that ive got a main jet, pilot jet and some mixture screws to mess around with right? Im guessing the first sted is to get new jets, but im not sure what size to buy that would work with my setup, is it just go a couple sizes up and suck it and see? Also, should I put the new filter and stock exhaust on to get it started before I move on, or should I put the new filter and new exhaust on before starting?

  2. #72
    Ok, I'd start by making sure that the ignition and valve timing is spot on and the tappets are set (basically, give it a service). Next, clean the carb out and set everything as per standard.
    There is little point in sorting the jetting and then changing stuff so fit the filter and exhaust.
    As a starting point I would go up 3 sizes on the main jet (make sure you go like for like on the type) and raise the needle by 1 notch (move the clip down the needle, do this inside a freezer bag to avoid loosing the clip ).
    If it bogs and sounds a bit "hollow" right at the bottom, try turning the airscrew out by 1/4 or 1/2 turn to see if it gets better ( past about 3.5 turns out from seated and you need to look at a bigger pilot jet).
    I think this should put you in the ball park and then search online for finer details ( I don't want to fill the forum with page and paragraph).
    If you keep a note of what you've done and what effect it had it will help you to understand how it all interacts.

  3. #73
    thanks a lot bluedog, thats given me much more confidence. Ill have a look in the manual then order a jet, hopefully it comes before I go on holiday.

    Today we finished all the welding that needed doing. All the nuts are now secured on the seat pan, the indicator brackets are in place and I decided to weld the break light bracket to a box I made thats now redundant, which is now bolted to the seat. This was to position the break light properly, but it means I have a little box to use for routing wires, storing little components, tools or keys.

    Ive put the swingarm, shocks and forks on and the wheels in just to position it correctly and to make sure the mudguard wouldnt touch the tyre. But I need to take the swingarm off cos i think ive put a rubber in the wrong place (and im sure it wouldnt come with 3 bush dust caps, but thats all i can find), I need to take the forks out so i can have another go at putting them in as im having trouble getting them through the top yoke, and the wheels are just in temporarily.

    However once ive got those things sorted and the rear inner tube arrives itll be a roller. Then its just wiring the essentials, putting the engine in with new oil, cleaning the tank and tap (and adding a fuel filter), and chopping and mounting the exhaust till its a runner and i can start on the carb tuning.

  4. #74
    Don't think I can add much more than bluedog has regarding carb tuning. I'm still faffing about with mine doing plug chops and using a gunson colour tune, but I found this useful...

    Stick a bit of tape on the throttle grip and another on the handlebars and mark where is closed to 1/4 , 1/2 and 3/4 to fully open. The pilot jet has some influence throughout the throttle range, but is mainly for idling up to 1/4. The needle's probably at its most effective at the 1/2 way point on the throttle. Then the main jet only really gets going when you're past 3/4 up to full throttle. Mucking about with all three jet and needle settings at the same time could be a bit confusing. I dealt with the pilot jet and the idling first, then moved onto the needle and then finally the main jet. You could add the choke or cover the air filter and see if that improves or worsens the situation.

    Plug chops seem to be the most recommended way, but mine hasn't got an engine cut out switch and i've found reaching to turn the key off under the seat, killing all the indicators, while holding the clutch in, braking and pulling into a lay-by a bit sketchy.

    I have a foamy air filter and the stock exhaust and at the moment have gone up one size of pilot jet, raised the needle by dropping the circlip by one notch, and gone up two sizes of the main jet. I'll be very interested to know how you get on.
    Last edited by scott_fury; 4th-08-2016 at 11:07 AM.

  5. #75
    Finally got some time after holidays and results day to get on with the bike. Yesterday I managed to get the forks in and front wheel on, although ill probably have to regrease it before any serious riding as i dont have any high melting point grease.

    As soon as the rear tyre's on the rear wheel can go on, then ill get some help to put the engine back in. Ive got the headlight, brackets and front indicators and the speedo now so theyll be going on soon

    Also managed to take the carb apart to have a look at the jet and thankfully its really clean inside. When I took the main jet out it came out with the jet holder ( the tube with little holes in), how should I get these apart? Also the jet appears to say 82 on it, which is weird cos the manual says it should be 80 but ah well. Im planning on getting a 95 main jet, but im not sure which to order. Is it just thread diameter I have to match up or does it have to be specifically for a cg125 carb?

    I might also get a pilot jet the size up so I have it ready to put in if it needs it.

    Also thanks for your advice scott

  6. #76
    Just get a spanner on the holder and use a screwdriver to remove the jet. When refitting both the holder and jet don't over tighten. The carb body is soft and the brass can really damage the passages if over tightened.

    Any keihin 8mm main jet. Doesn't need to be specifically for the CG.

    If you've got a #82 in and the manual says you should be on a #80, it sounds like you're a size up already. 95 will be several sizes larger. I would get a 85 and 87.5....


    but try the 82 first with a clean plug on wide open throttle. See what happens.

    BTW - hope your results were cool

  7. #77
    Thanks thats a great help! and I got in to my top choice university so I couldnt be happier haha

  8. #78
    Congrats man. Hope you get the bike sorted before you head off. Although if it's not finished there'll be more chance you'll not sell it when you get skint from all the beering and parties you studes get up to!

    Just a point worth mentioning about these aftermarket (non-genuine) jets, they may not be as accurate as a proper Keihin jet. But I made sure I got all my aftermarket jets from the same place.

    Also, they may not fit in the jet holder as easy as your original stock one would. The first one I got, I didn't screw in all the way and it ran mega rich as imagine more fuel got sucked up through the gap in the thread.

  9. #79
    Not sure if it'd help or not but EBC, a british company that makes some pretty decent car brake components (pads, discs etc), they sell carb jets too.

    EBC Jets Hyperlink

    They do mikuni and keihin jets. May be of use if you're looking for highly accurate jets as they're quite a big company so I'd be surprised if they're claims of highly accurate jets were false.

    Also, they sell them individually through ebay, if you go to the EBC ebay store you'll be able to find them. May make the tuning process easier.

  10. #80
    Thanks for your help guys, ill be buying some jets tonight. Ill go a size up on the pilot jet and go for a #85 main jet to start with.

    Since ive last been on me and my dad have put the new tyre and tube on the rear rim, realised we punctured it with the tyre spanners, took it back off, mended it, than put it back on again haha. Lots of wasted time but thats how these things go isnt it :'). If anyones interested the new tyre is a Mitas 3.50x18 I got for £35 from oponeo, and you can fit it on a 1.75 inch rim without too much bother (well it was a lot of work but its not impossible). Ill post some photos soon

    Ive also been doing the wiring. Ive used the original loom and just shortened or lengthened the wires going to components that have moved a bit, like the rear lights at the back and the battery, CDI etc in the middle. The only component ive moved a lot is the ignition switch (from the handlebars to the battery box), so that required some creative thinking. I bought a load of bullet connectors and some shrink wrap that has solder in that you melt with a heat gun (really recommend these http://www.ebay.co.uk/itm/251979562947?_trksid=p2055119.m1438.l2649&var=550846042474&ssPageName=STRK%3AMEBIDX%3AIT).

    Heres what the wiring looks like on the bike all I need to do now is sort the idiot lights and find a horn to hook up.

    Which diodes have people used for their idiot lights? cos i think im going to come across the problem of all 4 indicators coming on because of using LEDs for idiot lights

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