cg125 carb tuning

[cxjuggs]

I've just bought myself a '99 honda cg125 last week to practice on, ran okay but the carb needed cleaned out and while it was in bits, I figured what's the point of keeping the choke - you never need it (in non-cold london weather), so was wondering if I could just remove the butterfly plate?

For some reason, probably from the butterfly screws being overtightened and poor quality screw material - the threads on the screws got stripped/distorted whilst removing them. One of them went back in ok, but not the other... The one screw holds it ok, but I've not glued it yet, so not taking too much of a chance as it might well work itself loose.

Ideally I'd remove the whole spindle and block the hole off, but wonder if I'll then need to change the jet/needle to suit, or just adjust the mixture screw to make it a little richer ?

It's a HEIKIN PD88E carb - I'd assume that removing the choke plate will improve flow, throttle response and give faster acceleration - or are there better carbs to use on this engine?

Any thoughts appreciated, if this is a definate NO-NO as well, please let me know. Lastly I know it's only a cg125 so not expecting miracles or anything out of it, just want it to run the best it can for the few weeks/months I have it before buying a bigger bike.

cheers

[bladerunner]

if that butterfly gets sucked into the top end then you are in trouble!!! Best make sure it's secure. As for removing the butterfly type choke then yes it will smooth the air flow through the carb by as much as say having a 2mm bigger carb but like you say it's a cg and any performance gains will be so small you wont really notice......And when it gets cold it might be a PITA to start !! Also are you still running a std airbox?
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

[cxjuggs]

thanks bladrunner,

yeah, i know, going to just take the plate out, not worth the risk with only 1 screw holding it there, will probably oscillate, and the screw will fly loose into the fiery pit, causing much nastiness. think the plate would get stuck though, it's too big to fit through the inlet manifold end of the carb.

Would remove the spindle and block the hole but can't be bothered waiting for the aruldite to dry, want to ride today.

will try to find a replacement screw before it gets too cold and i need the choke, or i sell the bike.

yeah still using a standard airbox/filter - are there any documented mods to improve efficiency ?

[bladerunner]

To entertain the idea of any performance gain I'd say the bar HAS to be removed as without the plate in there it will probably make things worse as the air flow will eddy around the bar worse than when it has the plate to help smooth out the flow. As for tuning I had an old pre pump carb type many years ago and I ran no airbox or even filter (I know I know!!) and the exhaust was a little less restrictive than the newer ones but i still put a poker through the baffle plates to erm....Help the gas flow lol. motor was pretty standard apart from skiming the head to raise the compression a little and removed what I could of the valve guides and polished up any rough casting and flowed it as best I could.....end result with a 3 tooth bigger front sprocket was a bike that would pull 85mph on a down hill with my head in the tank and still around 75 on the flat. Also found that running the engine oil lower than half way let it rev better but valve bounce on the old cg pushrod motors kinda stopped any real gains but the motor would be able to valve bounce even in 4th gear.....18,000 miles of total valve bouncing thrashing it everywhere and it never died ....best £40 I think I'll ever spend that was!!
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's