@runes Sounds to me that the mixer screw is the problem, as the mixture is wrong. It's either rusted or been abused and consequently the engines fuel/air mixture is wrong. If the plug is getting wet, surely that's from over fueling and the engine running too rich? Which would cause the starting problem you are experiencing.
I would get a new mixer screw fitted before doing anything else, so that you can adjust the mixture correctly and hopefully that should solve your problem. Then that way you will know for-sure if the engine's mix is correct and eliminate that from your suspected fault list before throwing a ton of cash on it. What RPM does the bike idle at???
@Jens-Eskildsen Absolutely, unless you have a DTRE CDI where it closes the port at 10K RPM. But earth the green and black wire behind the clocks and BOOM! Full power. Easiest bike to derestrict. It's like the Japs knew
have bought a second hand normal dt inlet that im going to trim out.i have the original 4dl 32mm joiner and will try to join that to the original.i have ho idea of the needle size thats currently in it but she is fairly thin and pointy.ive went the opposite way to you and bought a u1 needle to try.the jet size is a 148.
@Louis-James I used the wr200 cables as was a direct swap and I plan to put all new on the wr anyway, It seemed to take far too much air in, maybe try again at some point I'll just have to order a handful of jets and have done with it
I managed to find a company that makes precision jets for mikuni carbs (KMT Products) haven't fitted the 250 yet (240 standard I think) but have now reset then tweaked my mix screw and idle slightly and it is running much better in the lower rev range, no bogging when dropping gears etc. Feels slightly 'held back' in the midrange though and the same at the top end of the revs, with a slight 'cough' at full throttle. Hopefully will have time to fit the 250 main and raise the needle slightly this weekend and see how that does. It also feels as though it's revving extremely high in 1st & 2nd (pinned pv) then taking longer for the revs to reach 6.5K (hit the power band) in 3rd and upwards. Bit of a strange one, definitely a fuelling issue I reckon though...
@vtrn_raptor You have just answered your own question there dude. Just like fire, combustion engine's require three elements to produce combustion or energy; Air + Fuel + Spark = Energy. If the mix is wrong then the combustion will be imbalanced. As long as your spark plug is fine you should be producing a good spark to ignite the fuel and air mixture. Did you fit a new spark plug after the rebuild? If not then I would recommend that you get a new one ASAP.
Too much fuel will cause the engine to run rich, with un-burnt fuel getting pumped out of the combustion chamber by the piston. Basically the mixture will be too wet. Too much air will cause the mixture to run lean aka dry. In effect too much air will dry out the mixture. Have you looked at the spark plug since the rebuild? Refer to a Haynes manual to check the colour of your spark plug? This will tell you if the mixture is correct or not? Adjust accordingly if required? If the mixture is fine then I would look at the timing next, perhaps the engine is miss-timed, which would give you a rough idle and poor running at RPM.
If your bike runs good with the choke ON, that's because you are adding fuel to the mixture, aka over-fueling, which tells us that your mixture is wrong. Perhaps it was poorly set-up by the previous owner, or there was an air leak due to the top-end or a gasket being worn. Now that you have an air tight barrel, your engine requires a different set-up, one which is as it should be.
If you don't have a Haynes manual for your bike then I would suggest that you get one ASAP. They are a wealth of info for home maintenance and have a great section's on diagnosing problems too. There well worth their weight in gold, plus there's always some for sale on ebay.