I have a 2008 ttr110.. bike has 102 hrs on it..motor is 100% stock. I had some carb issues with the stock carb so I purchased a mikuni vm26. Bike kicks off on first kick without having to use choke. I worked on the Jetting for 8 hours, New Plug ,New Gas (Non-Ethanol) tried a different Carb, Different Needle,Every Jet combination I come think of and it still fricking Bogs…. I just don’t understand. New spark plug is black and it has a lil bit of black smoke then goes away. Any suggestions
Welcome to the forum!
There might not be a lot of input from here 'cause this forum is 250 based.
What sort of issues were you having with the original carb?
Mikunis are often difficult to get sorted, especially if you have no base settings to work from.
Sooty black plug suggests rich running - too much fuel, and cold start without choke suggests the same. Smaller and smaller jets 'till it won't start at all, then work up!
Wet (oily) black plug suggests bigger problems somewhere other than the carb to me...
I recall being told, decades ago, that the stock position for the idle speed screw was 6 turns out. I recently was playing around with some VMs. When the idle speed screw is 6 turns out the down stream side of the slide is roughly closing the venturi.
Using that as a basic principle, I have set the carbs on my RDLC from that starting point & also an XT250L - one of those with the twin carbs.
The XT had sat for years as it progressively became harder and harder for my son to start. Kick only.
I found some motivation and had a squiz - the slide was nearly 1 cm raised with the throttle closed.
I reset the idle speed screw until the slide rested just with the down stream side fully closed. Hold it up to the light, move the screw half a turn either direction until you're happy.
Bung the carbs back on and screw the idle speed screw in by 1/4 turn at a time until it starts and runs and you can get it warm.
Then you can re-set the idle speed with a warm engine.
If there are issues, you can start with the idle jet and air screw.
Are you able to compare the stock jets, from whatever manufacturer, with Mikuni jets? That may get you into the general area.
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In the Riverina.
'73 RD250, '80 XS1100, '81 RD373LC, '96 Tiger 900/sidecar, '02 TTR250, and another XS11 - this time a chain drive Period 5 race bike that may be ready to race eventually.
