95 tz250 AVGAS carb settings

[deano123]

80 not to big for power jets? i have a 4dp-40 box as well as stock 95 one any advantage of running the 40 maybe with more static advance?

[erock768]

If you're too fat in the mid-range you will notice that the bike will begin to rev more easily after the power jet solenoids cut out at 11,500 rpm. That's how you can tell. If the bike revs clean all that way to 12,500+ down the strait away then your probably fine. As I said before, those settings will get you close but you have to adjust to suit the conditions, machine etc.......if there was one magic jetting setting the bike would of come like that!

To answer your question re: using the the 4dp-40 box, I think it depends on what your set up is. I would use it, set it to the specified timing of 1.7mm btdc and do plug chops and advance the timing based on your readings. As with jetting, there is no magic timing setting. Its depends on the track, the machine, conditions, etc....Just throw a box on there with a arbitrary timing is asking for trouble. You need to start at a known safe or good value.....like the recommended static timing and incrementally work from there. Ignition advance is the quickest way to blow a hole in a piston. Remember high compression and too much advance is recipe for disaster.

everybody here needs to read this: http://www.le-suspension.com/tz-250-tuning-secrets/

[vince24x]

isnt the -40 box really for ULP? if possible, and assuming you want to use 100LL, you might be better served w/ an older ecu; or one that is programmable.

the bike will run, but certainly the mapping (timing, PoJ, etc) is not optimal if designed for ULP and you end up running leaded.

w/ 100LL, you can use considerably smaller PoJ... suggest 55-ish. on my ignitech, i dont even open the PoJ in the mid range running 100LL. of course, depends on engine setting, but it is much more relevant for ULP than when running leaded. jmo.

one thing to keep in mind there if referencing eric's settings: his larger carb bore reduces the vacuum ....so he would use bigger jets to compensate - all else being equal.

vince

[erock768]

Agree with all of Vince's points. Regarding the 4DP-40 ignition box and its application to ULP....yes, the 97 was the first of the unleaded bikes, but I have run the following combo back to back:

93 TZ same basic jetting and engine specs as above:

4DP-2 ignition (95) with 1995 pipes

and

4DP-4 ignition (97) with kit 96 pipes

both running 100LL

Could just be the pipes but the 4DP-40 and kit pipes were faster than the all stock 95 set up.

I don't get really worry to much about the whole ULP vs leaded debate....I tune by the looks (i.e. plug burn back, piston color etc) I do however run head volumes appropriate for leaded.

Also, and take this for what its worth....but I have on good authority that the curve of the 4DP-40 box is the same as the -Ao kit boxes that Roland Sands was running in 96 (on leaded)....