I'm using premium pump gas as recommended by US Montesa. That's 93 octane in this part of the US (Atlanta, Georgia). I forget the exact octane equation, but it's something like (R + M)/2, which is different from RON.

Sometimes all a bike needs is a good old thrash down the road to clean them up,if bikes spend a lot of time pottering around they are going to run rich, two stroke or four.

Thanks, ferretflasher. I think I'm on board with your suggestions except for the coil HT earthing. I'll check that soon. I hope to put the bike in its first trial this weekend, so I'll have an opportunity to run it more at higher speeds than in my backyard. As for pressure washing, I don't do that to motor vehicles, but the previous owner may have done so. I have found some rust and corrosion in odd places for such a new machine.

As an old thumper rider I can offer a few suggestions.

1. Most thumpers don't like much, if any, throttle when starting. If cold, the choke/enricher on and no throttle. This point is so sensitive in some bikes you cannot trust your feel about "little" throttle. It best to up the idle screw a tad.

2. If you think it's flooded then try about 3 kicks with full throttle. This lets in some big gulps of air to balance the mixture, and helps dry out the chamber. To become familiar with this condition, check the plug, and if it looks wet then you're probably flooded. If you're taking the plug out often you may want to put a little antiseize on the threads and be careful to not over torque.

3. The sharp point on iridium tipped plugs is supposed to create a better arc.

4. The trick is to learn a starting technique that will not flood the chamber, so begin the learning process with no throttle and no enricher (if you've got one).

Thanks, Don, I went to the school of hard knocks on thumpers. Your tips are all right on the money. My right leg is an inch shorter after 30 years of owning a Triumph TR5MX Avenger. That bike exacted much vengeance when I was so audacious as to expect it to start up and run, especially when hot. I used gold-tipped Champion plugs in it.

As for the 4RT, I took it to the Trials Training Center on Sunday and it ran like a scalded cat on the formerly dead plug. The new plugs didn't arrive on time. Viva!