Bonneville America Forums Forums Technical Forums Performance Mods another jetting question...

hi~

I'm putting together an order for my preSpring mods for my '03 speedmaster - just picked up a pair of long TORs (killer 50% sale at motorcycle gear shops!), and am planning on pulling the snorkels and putting in a UNI filter. I may drill the bottom of my airbox as well if I can get the gumption up to dig into my stock airbox. I'm also going to pick up the newspeedmaster idle mixture screws and carb screw kit, to install while I have the carbs off...

according to Pat's jetting calculator - I should put in 127 main jets (w/out drilling bottom of airbox) and 132 mains (w/drilling bottom of airbox). The problem that I'm having putting together my order is that it doesn't appear that I can get the 127 main jets from either newspeedmaster or bellacorse. newspeedmaster only has 125s or 130s. bellacorse has 128s. If I get the 128s, is it going to make a huge difference? Are there other resources that would carry 127s? I could just solve the issue and drill out the bottom of my airbox (and purchase the 132s)

Also, should I just leave the pilot jets, needles, etc. alone?

thx for any responses.
pratt

This was almost exactly my setup prior to the Ghetto Freak Mod. At the time I was using TOR longs, a drilled airbox with K&N drop-in filter (bottom of filter cut open), no snorkels, two shims on needles (Home Depot small brass washers), stock pilots (42), and stock-HD-stock Idle Mixture screws. I was using 132 mains and it ran very well.

Drilling the airbox is very simple and easily reversible with god's gift to garage mechanics (duct tape).

Regards,

Tom

could probably get away with 130's

Frank

You will be able to get away with the 130....
Angelis

thx guys. think I'll start with the 130s (and no drilling), and then swap in 132s if I drill out the box...though I'm tempted to just get it over with while I'm in there...
decisions, decisions

Open up the box and get all the air you can....Angelis

My understanding of jets is that the hole in a 127 jet is 1.27mm. The hole in a 128 jet is 1.28mm. That's a diameter difference of 1/100 millimeter. That ain't nothin'. Don't stress over it. If you bought both sizes and tried them out, you probably wouldn't be able to tell the difference by the seat of your pants. (But a dyno probably could)

Pat's Jetting Calculator is a great tool to get you in the ballpark, but don't take it as absolute gospel. It's not based on extensive lab tests. It's based on what guys and gals say works good for them. Your results may vary.

Cody

Sounds like the question I have so maybe someone can give me knowledge from the past. I have an 05 stock speedmaster that I recently bought. I put BUB slash end pipes (End at the center of the real wheel. I wondered what the OEM jets were and what size should be put in as a result of the new pipes...(Which sound fantastic by the way)...I am not sure if the previous owner did anything so the more I know about what the stock sizes are and what should be in there I can discover whether or not they are orig or changed to something close. I will also be taking the AI off if it is still there. What am I looking for to see if it is still connected. thanks Keith

should be 120 mains and 42 pilots

Thanks....I have parked my Honda Goldwing to ride this triumph and so far I really like it now that it sounds like a motorcycle. I assume the slight popping I hear when it is running is due to the smaller jets and the AI system on. I will take care of this next. This forum and web site is a really nice idea. Keith

Welcome Keith! A typical mod for our bikes when putting on pipes is remove the snorkel from the airbox(it's under the seat), along with AI removal, and then re-jet the carbs. Pat/Dinqua, who is one of the moderators around here, has a great website with instructions on how to re-jet the carbs. Download the jetting calculator mentioned earlier in this thread first to get an idea what size jets you'll need. You can order them from either BellaCorse or newspeedmaster.com . If you run into any problems, don't hesitate to ask for help. That's what these forums are here for.

For anybody who might read this thread, earlier there was mention of jet sizes. I always thought the intermediate sizes were .005mm. What I mean is the size graduation was like this....130, 132.5, 135, 137.5, 140, etc. So it seems to me some vendors might round up while others round down. That's why you get 137 or 138, but really they're the same size.

I'm not sure whether this helps but here goes anyway. 2-3 months ago I went from a stock 05 sm with long tors which had the stock jets (120/42's etc). I removed the snorkel and A1 and then replaced air filter with a UNI that I drilled the bottom out of to go with the drilled bottom of airbox configuration. Then Installed 125 main jets with TBS needles and 2 shims and after checking the plugs after a month they appeared really white and lean looking, so I replaced the 125 mains with a 130's but only 1 shim. I also installed Brent's pilot jet thumb screws which are now set at 2.5 turns. I then did a full service and synchronised the carbs and whilst I haven't had a dyno, the bike is running very nicely and pulls a great deal harder than before. My fuel economy around town is about 18 kilometres per litre or 42 mpg in US terms which I believe should indicate I'm not too lean or rich. At this stage I might for interest change to 2 shims just to see if the mid range improves. I guess my biggest query has been the tors which it has been said restricts the breathing compared to the other after market pipes and whether this equates to this set up being a bit rich. Unless I do a dyno it's hard to say but anyway, the bike is running really well with no problems but definitely more getup.

A lot of people have drilled the baffles on the TORs as I am sure you have read. That might help. If you have a mid-range slump in the throttle, you might consider Thunderbird Sport (TBS) needles. Start with no shims.

TBS needles are code N3RF and the Triumph part # is T1241024

Phil, do you think that no shim is best with the TBS needles? Have you tried different combinations? I installed mine with one shim as I had it before with the stock needle. I haven't tried any other combos.

I haven't but from others, even one shim on the TBS might be too rich. Mine's perfect without any.