Rejetting after NARK installed

T

Triumph825

Scooter
Hi all, I had been searching threads about it but I couldn't find the answers, so it would be much helpful if I can get the answers here, it's a torture not to take my baby out!!:wack:so here it goes

After I installed the NARK, I found out there's 2 sets of jets that comes with the kit, so I figure I should put them in:stupid:
After I search thread and find the way to change them, questions arised, I notice some people say should turn 2.5 round and some said 3, which one is my ideal for the bike? I have a 2007 t-100, no mods besides the accesseary muffler from triumph, I asked Brent from NewBonneville and he said the jets that comes with the kit are 150(main) and 42(pilot), some say I don't need to change the pilot just the main, is it true? I don't want to try multiple times to tune, because I don't have a garage and it would be really difficult to take out the carb everytime in a public parking lot. Thanks you in advance for your professional answers:ride:
 
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FoothillRyder

FoothillRyder

Two Stroke
Triumph825 said:
Hi all, I had been searching threads about it but I couldn't find the answers, so it would be much helpful if I can get the answers here, it's a torture not to take my baby out!!:wack:so here it goes

After I installed the NARK, I found out there's 2 sets of jets that comes with the kit, so I figure I should put them in:stupid:
After I search thread and find the way to change them, questions arised, I notice some people say should turn 2.5 round and some said 3, which one is my ideal for the bike? I have a 2007 t-100, no mods besides the accesseary muffler from triumph, I asked Brent from NewBonneville and he said the jets that comes with the kit are 150(main) and 42(pilot), some say I don't need to change the pilot just the main, is it true? I don't want to try multiple times to tune, because I don't have a garage and it would be really difficult to take out the carb everytime in a public parking lot. Thanks you in advance for your professional answers:ride:
Click to expand...

Try this: http://www.triumphrat.net/club-cafe/71457-main-jets-and-pilot-jets-3.html#post873630

Lots of info there about jetting with different mods.
 
coopv2

coopv2

Street Tracker
Hey there 825, Here is a copy of my post on my own air box mods and jetting hope that helps.....
Got down to the dyno room this morning,
After fitting up the stock air box with restrictor plate removed, Uni filter, and dual inlet (right side venturi added does bugga all) as the left side inlet is suppyling more than enough air, to feed the next restriction in line(inlet manifolds, carb bore, cam )
Anyway, removed the stock 40/110 combo. fitted a 42/130 to start with.
the idle mix was at 2.1/4 turns out and was running at 12.2:1 which was a little rich, and even wound all the way in, did not hit 13.5:1 which I would say could go back to the 40 pilot. but left it at 1.1/2 turns out on the rich side.
1 shim on the needle was a little rich in the mid range, but ok as it kept the curve nice.
130 main was too big running about 12.:1 air fuel up the top revs, so I ended up fitting the 125 main that came with the airbox kit. and it picked up the top HP and smoothed the curve out nice.
Final road test showed a noticeable strong pull all the way to 8000rpm, and I am happy with that for now.
 
coopv2

coopv2

Street Tracker
Triumph825 said:
would the 150/42 be the ideal combo? since it comes with the kit
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I doubt it. so if you read my above post, and still had to ask the question, I guess we better start from scratch.
You have upgraded your intake with the NARK and have the free flowing trumpy mufflers right?
40/130 is probably a good starting point.
But no one can answer the jetting question for you as so many people are running a big variation in jetting, depending on altitude, exhaust flow, air cleaner, mileage, etc.
You have no choice but to start at one point and with expertise and skill make the needed tuning adjustments.
But Really. just give the bike to someone that can do it right for you first time..
or you will be stuffing about in the car park 5 times.
I think the 150 main is too big. others will say put it in. good luck
 
S

SCBonneville

Two Stroke
Triumph825 said:
I am using the K&N that comes with the kit
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Ok... here are a couple of things to go on to get you in the right neighborhood on jetting...

The OEM carbs are fine for most folks... but they are NOT a precision "matched set" of racing carbs...

If you want to be spot on on your carb tuning you need to find a good dyno operator to dial them in. And even then, you will only be spot on for that days atmospheric conditions and elevation... But you will be so close for every day use so don't wory... remember, carbs are compromise unlike EFI that can adjust to conditions...

And TOR's are the most restrictive of the "performance" exhaust for the Bonnie...

Also... everyone will swear that THEY have the exact perfect answer to your jetting needs... BULL!... go back and reread the truism about the dyno...

Ok... a couple of truisms that I have found to work out...

40 pilot jets with the screws turned out around 3 turns (maybe a bit more, maybe a bit less) will give you approximately the correct low end A/F ratio... 42 pilots with 1 to 1 1/2 turns out gives you about the same ratio...

Shim your needles with genuine Keihin shims... they are half the thickness of the shims (washers really) that the aftermarket guys sell and give you a much more precise adjustment of needle height.... and they are ground flat rather than being punched out by a stamping machine...

The carbs vary within the set... they are not matched... I had to put a 145 main in the right carb and a 148 in the left to get them matched up A/F wise...

You haven't said what model Bonnie that you have... but there are three different needles that were installed...

the 790 engined bikes all got the "nail"... very little taper... works fine with the air box in place...

The "865 needle" comes installed in Bonnie/America/Speedmaster 865 engines... a better/slimmer needle that flows more gas in the low/midrange of the needle rise/pull... This needle works well with the air box removal...

The Thruxton needle comes installed in the Thruxton and Scrambler and has the most taper and flows the most gas....

Taking a stab here... based on an 865 engine with TOR's, I would say that you can use either the 40 or 42 pilots with the above noted turns out on the screw, put one Keihin shim in and I would think that 135 to 138 mains would be plenty... This should get you pretty much in the neighborhood...

There are two indicators that you can look at to see how you're doing... after re-jetting, are you getting more bluing on the headers? If so, you're lean... Install fresh plugs and run it for a while... pull the plugs and take a look at them. They should be a light cocoa tan.... If they're whitish... you're too lean... Blackish or sooty... you're too rich...

Also... remember... the three "jetting areas" (pilot jets/needles/main jets) all have areas of overlap... a change to one affects the other... If you want to get "spot on" tuning... get a good dyno operator/tuner to work with... Once your close to where you want to be, ideally an A/F ratio of between 13.5 to 1 and 14 to 1.... which is just slightly on the rich side... good for building torque and cooler cylinder temps... he should check the A/F ratio in BOTH tail pipes.... if he leaves it reading in just one side... your not getting an accurate picture... The carbs vary... remember...

Sorry for writing a novel...
 
BlueJ

BlueJ

Blue Haired Freak
Triumph825 said:
would the 150/42 be the ideal combo? since it comes with the kit
Click to expand...

No, you'd be way too rich. That would be fine for fully open pipes like Preds or something. On TORs you'll want 135 mains at most, could probably get by at 130. 40 or 42 on the pilots, depending on whether you like to use the choke to start it (42 if you don't). The number of turns on the idle mixture screw will be different by "about" 3 between those last two choices - the 42s are richer so you'd need fewer turns out. Finally, you might decide you like a shim under the needle - probably 1 will give you the smoothest torque curve.

The jetting is easy enough to do yourself, and you can get it dialled in on a nice afternoon, put in the combo I describe and ride it and then adjust as necessary. And before you start, read this: Jenks's Bolts Tuning Guide.

And definitely replace the crappy stock carb body screws with some nice SS ones from NB or elsewhere, because you will strip the stockers in no time!

Enjoy!!
 
Thrux181

Thrux181

Scooter
As BlueJ posted, Jenk's Bolts Guide is a good start. It will help you understand wants going on. I'm assuming his recommendations are based at sea level. I would do only do one thing at a time. That way if it's not good you know what you did. Good luck.
 
T

Triumph825

Scooter
Thanks a lot guys, that would be plenty of studying after my school's final, but that would fun! lets just hope that this parking security guy not gonna bother me for operation in the parking
 
BlueJ

BlueJ

Blue Haired Freak
Triumph825 said:
would it be easier if i take off the tank or the seat?
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You only need to take off the seat if you're going to take off the tank. And you don't need to do either to rejet.

And you don't *need* to remove the carbs, although it's not really that hard, and does make the job a bit easier for rejetting, at least the first time, until you figure out what goes where. Just be careful to drain the float bowls, and when you extract the main (I think it's the main) be careful if the needle falls out to put it back in correctly.

If you are going to shim, you'll need to take the carb tops off, which is of course easier with the carbs off the bike.
 
H

HepcatBob

Scooter
FWIW, my '08 T100 is NARK'd with D&Ds. It has the 150/42 combo that came with the kit. I also changed to Dynojet needles. They're a lot easier because you just have to move a little clip to adjust them. It's been a while since I set 'em, but I'm pretty sure they're on the 3rd slot from the top. Although I haven't had it on a dyno, it runs great, gets good gas mileage and doesn't pop anymore in deceleration. (And if you change all the screws to hex heads, it's easier to get to the needles to adjust them with the carbs on the bike)

YMMV :)
 
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Bonniebret

Bonniebret

Rocker
+1 On going with the stainless hex heads. Be warned, Triumph figured out a way to torque down those soft screws so that the heads don't strip going in but do coming out.
 
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