2-Stroke jetting for Taupo in Winter

[Hoon]

I'm planning to head out to Taupo on Aug 10th.  I was just wondering how much of a difference the altitude would make to my jetting.  Also how much the extreme cold we are experiencing lately will affect this too.

I know I may need to go leaner but I'm not sure how much leaner.  I want to take down a series of jets but not sure how many sizes leaner to take.  I'm running 32mm mikunis with #170 mains which is great for an Auckland summer at sea level.  But for Taupo will a set of #165s do or will I need #160s as well?

Can anyone else give me examples of their jetting changes for the various tracks around the Nth Island?.

[Dave]

Bearing in mind we run 180,182,185 mainly at puke, we normally run 168,170 or175 at taupo. on your practice laps do a plug chop down the straight and coast back to the pits. check to see if its too lean/rich.
Also if you are too lean on the needles you'll get a distinctive surging on part throttle around the sweeper.

[Hoon]

Cool, thanks for that Dave!

Guess I better go shopping for yet more jets!  I'll give the plug chop a try next track day at Pukekohe too.

[750Y]

I'll give the plug chop a try next track day at Pukekohe too.

that's a ways to push it back to the pits. try & organise with someone beforehand to tow You back on the last lap of the session.
there's bound to be someone who'll oblige. or Gary will probably do the honors if You ask him nicely.

hows it running now? better than last time i hope.
what was wrong in the end?

[Hoon]

Originally posted by 750Y
that's a ways to push it back to the pits.

Yeah I was wondering about that.  Didn't fancy taking the hairpin at 200kph just so I could coast it all the way back so I was gonna park the van right at the Pit entry so I don't have to push as far.  But the tow thing might be the plan!

hows it running now? better than last time i hope.
what was wrong in the end?

Yep all sorted now.  See this thread for the rundown.

[Dave]

On the 125 we take the hairpin at about 80k/hr so I can coast to the pit road and then just need to push to the pits from there.

[750Y]

glad it turned out sweet ho-hoon. You don't need a torque wrench for those jets y'know

I'm always overtightening shit, yknow the ol "one more turn and it'll be nice and tight"...CRACK!!! doh!

[Dave]

Thats a really common practice-tighten it up until it strips,then back it off one turn!

[Racey Rider]

So Hoon,
Did you learn anything about your jetting having been to taupo?
What size jets did you run?
Did you do any changing of jets?
Or did you just "Give it Death" as is?

Do you use premix fuel, or oil injection?
If premix, what was the mix rate?

Do you just buy different size jets from the local bike shop, or is there some better place to order them? (Dave?)

[Hoon]

I went from #170's which work for Pukekohe down to #160's for Taupo (#200 is standard for RGV250K's with the 32mm mikunis)

I pulled a plug after my practice and it looked fine (didn't do a plug chop tho).  Kept a close eye on the temp throughout the day too but it stayed OK. 

Changing jets is only a 10 min job - just gotta be careful not to overtighten anything or butcher the screw heads trying to get the carb open.  I buy my jets from Colemans, the local Suzuki dealer.  They cost $10 ea (need 1 for each carb).  I've got about 8 different sizes now.

I use racing fuel, premix 33:1 Castrol TTS oil.

My settings mightn't apply to you though so don't jump in and put leaner jets in or you might sieze your motor.  I'm gonna start chopping up my airbox in an attempt to improve my high speed performance (and hopefully reel in those pesky 4-strokes on the straights) so will probably need to go richer again.