Mikuni VM26 Carburetor Jetting - Need help asap!!!

alfedaud@hotmail.com · Joined: 19 Aug 2008 Posts: 11

Just installed the Takegawa 138cc kit
It comes with the above carb, pilot jet 22.5 & main jet 190
My bike also has an after market pipe installed

After installation we had the plugs foul due to a rich mixture
We slowly decreased the main jet down fm 190 to 150 to 130 but the plugs were still fouling.
Even with a 130 main jet the pipes were still spitting flames.
It was only when we installed a 100 did the plug showed improvement.

I now fear that the mixture maybe too lean.
The plugs look fine but will I have to change the jet when the engine is broken in?

_________________
KSR110
Takegawa 178 Hyper SCUT, VM26mm Mikuni Carb, Air Filter, K10 Racing Cam, Cable Clutch Kit, Kitaco Cdi, Rear Sprocket
Evo Big Bore Exhaust System
Uma Racing Ignition Coil
Asian Concept Handlebar, Fuel Cap, Engine Sliders, Acerbis Headlight.

ferret · Joined: 18 Nov 2007 Posts: 430 Location: Teesside

Plug will foul on tickover, you'll need a plug chop after long straight run aafter warm up. I run a 15 pilot and 160 main but this is with KITACO version VM26 which has different size needle so hard to say with your carb Confused

I'm sure main will not be as low as 100 though, somewhere between 150 and 200, check pilot jet if only rich/ running rough at low revs Very Happy

Safer to be running rich, for sure Razz

Richie

_________________
All the gear and no idea!

sirgagalot · Joined: 28 Sep 2007 Posts: 1352 Location: sunny south

i agree with what ferret says,better to run rich than lean and end up melting ya piston,i run a 150 main and a 17.5 pilot on a 140cc no problems here Wink

that is a kitaco vm26..

_________________
no one here but me! sirgagonmeown!

alfedaud@hotmail.com · Joined: 19 Aug 2008 Posts: 11

Have gone up to a 115 main jet but have remained 22.5 pilot jet
The engine runs well & the plugs looks healthy

However there seems to be fuel overflow from the carb overflow hose from time to time
The overflow seems more obvious when the bike idles for long periods & occasionally during starting when I don't get it firing the 1st time around.
This is followed by rough running which I think is from overflooding the carb.
My mechanic seems convinced that its normal since the carb is Race Use only.

Can someone please comment!
Thanx

_________________
KSR110
Takegawa 178 Hyper SCUT, VM26mm Mikuni Carb, Air Filter, K10 Racing Cam, Cable Clutch Kit, Kitaco Cdi, Rear Sprocket
Evo Big Bore Exhaust System
Uma Racing Ignition Coil
Asian Concept Handlebar, Fuel Cap, Engine Sliders, Acerbis Headlight.

ferret · Joined: 18 Nov 2007 Posts: 430 Location: Teesside

Check float height, might be sticking not shutting off flow of fuel! 115 sounds way to small in a genuine VM, but if it seems ok Confused

_________________
All the gear and no idea!

alfedaud@hotmail.com · Joined: 19 Aug 2008 Posts: 11

No you got me wondering the authenticity of my Takegawa kit...

I guess the reason for the smaller jet is mainly due to the different conditions here.
It is more humid, cooler etc compared to where the kit was intentionally meant for (Thailand).

_________________
KSR110
Takegawa 178 Hyper SCUT, VM26mm Mikuni Carb, Air Filter, K10 Racing Cam, Cable Clutch Kit, Kitaco Cdi, Rear Sprocket
Evo Big Bore Exhaust System
Uma Racing Ignition Coil
Asian Concept Handlebar, Fuel Cap, Engine Sliders, Acerbis Headlight.

sirgagalot · Joined: 28 Sep 2007 Posts: 1352 Location: sunny south

not sure about the humidity theory,where's gaz when ya need him..and as far as the fuel overflow,well join the club,could be sticky float ,mine does it sometimes for no reason Rolling Eyes

_________________
no one here but me! sirgagonmeown!

	GAG BIKE.CO.UK Forum Index » Technical Section	All times are GMT + 3 Hours
Page 1 of 1