Front fairing/headlight

[rusche]

Goodies got here

[Weldangrind]

Looks great! 8)

Is that a Toy center section in the milk crate?

[FastDoc]

That really looks great!

[rusche]

Yeah, old Toyota 8", good eyes.
I've been into those for years, just got bit by the bike bug.
Note the avatar :wink:

Performance CDI and hotter Coil on the way. Will let ya'll know the difference it makes. Probably going to jet before I install it. Running a little lean with the intake and exhaust, so I dont want to advance timing until I know shes running closer to stoich. Any Honda or Yamaha jets fit these I can get locally? Its a Mikuni? 26mm, shown in this picture

[SpudRider]

Nice job, Rusche! I suggest you remove the jets from you carburetor, and take them to a motorcycle shop; they should be able to match the jets for you. Perhaps a Yamaha shop might be more likely to carry Mikuni jets.

Spud

[Weldangrind]

I agree with Spud, except I'd remove the jets and just take those. As soon as they see a China carb, they might play a little hard to get. BTW, that looks like a Keihin clone, due to the three screws holding the bowl. I've found Keihin jets at the local Honda dealer.

BTW, stoich isn't ideal for max power with a carb; it's closer to 12:1. Hot Rod and Car Craft have proved that several times. Do you plan to measure with a wide band?

I saw a recent episode of Trucks! where they upgraded a stock Toy 8" with beefed up internals. As if they weren't already tough as nails.

[rusche]

I've broken my fair share, they are tough, but when you add 40" stickies, locked diffs, geared axles and cases, boom.

What jet would you recommend ballpark? Intake and exhaust, CDI and Coil coming. Little lean, not terrible based on plug readings.
Interesting point on 12:1. I come from the automotive world, of closed loop fuel systems, but I wasnt planning on using a wideband, just going to check cylinder temps, and keep reading the plug

[Weldangrind]

Not sure with a 125. Also not sure what the Keihin sizing system means. For example, a Mikuni 110 main jet means 1.10mm; I don't know if Keihin is the same. The only reson that matters is if you're going to drill them out yourself, rather than buy new ones (I'm monumentally cheap).

You should be able to note sizes on the existing pilot and main. Try two numbers up on each one and see what happens.

BTW, plug reading is a fine way to tune your machine, especially if you do a plug chop.

[rusche]

Had an old Yamaha that ran a little lean, hard to start cold. Took the carb in lookin for jets, mechanic took me in the back, ran small hand bit through the pilot jet, worked like a charm. Tempted to try this route first.

[Weldangrind]

I wonder what he used. For example, my numbered index goes down to #60, which is 0.040", or 1.016mm. If you were starting with a 100 main (in Mikuni language) and drilled it out with a #60 bit, you'd end up with a 102 main jet.

The key here is that those are main jet sizes, not pilot jet. Pilot jets are roughly 1/4 the size of a main jet, and you sure wouldn't want to drill the pilot out to four times its size. I've never seen a numbered bit set that goes beyond #60.

Another option (if you can't find a proper replacement jet) is to run a welding tip cleaner into the jet. Be careful, as the jet is only soft brass.

[rusche]

Used the welding tip cleaner trick. used a 1.10mm tip to open it up a little.
Put on the CDI, Coil and Iridium plug.
Now hard throttle it stumbles and wont rev, but only sometimes.
Half the time it RIPS, half the time it stumbles.
WTF?

Gonna start by puttin the stock ignition and plug back on, I did too many mods at once to narrow it down.

Ideas?

[rusche]

I went from a size 95 jet, to 110. Plug doesnt appear rich, but not many miles on, just around the block. Feels great, minus the misfire, under full throttle, high RPM. Replaced ignition back to stock, so I know its a carb issue.
Could I have gone too big on my main jet?

[2LZ]

Have you adjusted the valves? The Honda clones come notoriously to tight.

I knew of one here locally that had the cut-out and stumble under heavy throttle. He changed the CDI, coil, carb, did the needle clip trick, jetting, everything.
He took it to a Chinese scooter guru and after the scooter guy reset the valves, it ran great.

Just a thought..........

[Weldangrind]

X2 on the valves. If no joy, buy some new jets and try them.

[SpudRider]

Originally Posted by Weldangrind

X2 on the valves. If no joy, buy some new jets and try them.

X3 on the valve adjustment. Other than changing the motor oil regularly, maintaining the valve adjustment is the most important thing you can do keep your engine healthy.

Spud