Racing set up 250 WR 1983: gearing + jetting

Hi!
I bought a 250 WR 1983 from Finland, did some adjustments (the bike was in an overall good condition).
Did the legalization for Germany and did a first vintage enduro race last weekend. I love the bike, but:
I am not happy with the „performance“.
The bike lacks the power for a special test in gearing/low end gearing.
Of course, having done only 20 miles testing before racing the bike, I ran the rather rich original set-up, with a Main jet 410, needle 6F16, pos 3, needle jet P-8, idle jet 35, slide 2.0. Mikuni VM38, of course. New airfilter.
I ran a Q-0 and idle jet 40 before, low power was even less.

Today I mounted a 2,5 slide, needle still 3rd pos. Low end power has improved.

I am trying to figger out, how to improve the performance for special tests.

Gearing is 12-52.

What I have read so far:
Dirt Bike tested the 84 WR and switched gearing to 12-56, which was a great improvement, as they stated. The tested in the mountains, so jetting can‘t be of any use.

Moto Verte tested the 83 ISDN 250 WR of Marc Morales in 1983 and Marc is stated to run the 12-52 gearing(!), which is proved by the pictures. He is quoted with not wanting to share his jeting setup, but he would have a „very lean“ setup. So he must have changed the low end power by the jetting. The bike was unchanged in exhaust etc.

Is anyone out there racing his 83 WR 250 in woods etc and can share a good working setup?

Cheers
Nic

I have an 82 so this may not be any help but I run an 11 tooth front sprocket. I do a lot of technical riding so I still find it fast enough at top speed but it gives me more grunt though the tricky bits and steep climbs

Does the bike have the original exhaust? Have you checked the spark arrestor? These screen type arrestors are notorious for becoming restricted due to carbon buildup thus killing power slowly.

If the spark arrestor is unobstructed then take a look at this Mikuni tuning guide, the short version. I used this to tune my 73 450. It takes time and an investment in jets but it allowed me to get the most HP out of my 450. The full version of this tuning guide can be found at: http://www.klemmvintage.com/mikuni-tuning.htm

I have been using the Mikuni tuning Book But this seems a bit different. Thanks Crash, interesting reading.

interesting, thanks!!!