Triumphrat

jstark47 · 03-04-2006, 09:50 AM

Hello all. I have TORs on order at my dealer. In the midst of this, the long-time service manager quit, and his replacement is not knowledgeable about Triumph. I've been trying to educate myself on engine intake set-up (carb, airbox, AI, etc.) in general, and specifically applied to new pipes. I've spent extensive time searching through this site.

There is too much information here, and it's too scattered.

Is there some place where the information is comprehensively gathered and summarized? Someplace I can learn the basics of carb setup (main jet, pilot jet, mixture screw, shims, needle type) and other parts of the intake system (air box, AI system, etc.)??

My bike is a 2005 790cc, but I'm wouldn't mind learning this stuff for the whole Bonnie line - so I can recognize e.g. when someone is trying to give me Thruxton advice, etc. I have a sinking feeling I may be educating the new service manager. There have a Triumph-trained mechanic there, but I don't know whether this new guy will be trying to "direct" the mechanic....

Thanks,
Jonathan

Dinqua · 03-04-2006, 10:16 AM

Dinqua Website

jstark47 · 03-04-2006, 10:18 AM

Pat,

Thanks for the link!

Is there a difference between the factory stock carb on a 790 TBA and a 790 Bonneville?

Thanks,
Jonathan

Panthermark · 03-04-2006, 10:35 AM

I used Pat's guide to do my first re-jet. Good stuff.

(edited)I just re-read it, and it looks like there is even more stuff out there from a year ago. I just got my carb tuner in the mail from NB, so the balencer portion was just what I needed!

But this will help you "learn about" carbs in a hurry...Read this!

Jenks Bolts Carb Guide

Also, the carbs are the same on the BA, SM, Bonnie, T-100, Thrux, and Scrambler. But they do have different jets...

[ This message was edited by: Panthermark on 2006-03-04 08:56 ]

jstark47 · 03-04-2006, 11:40 AM

Quote:

On 2006-03-04 08:35, Panthermark wrote:Also, the carbs are the same on the BA, SM, Bonnie, T-100, Thrux, and Scrambler. But they do have different jets...

I also got the impression that the Thruxton uses a different needle, which has to be matched with different jetting. Are there any differences in carb set-up between the 790 and 865 bikes?

Thanks,
Jonathan

guzzi · 03-04-2006, 08:41 PM

What is under the metal plugs on the side of the carbs? Mine has a metal plug over one hole, and some kinda gritty paste covering another hole. Are these adjustment screws, or blanked out holes that allow the carbs to be used in another application? (maybe another brand of bike)

The idle mixture screw is where? Is it what you are calling the pilot jet screw? Thanks.

Anyone tried to hook a small hose to the bowl drain, loosen the allen screw and drain the carbs w/o removal from the bike?

I'm trying very hard to clean my carbs without removing everything in my path. Once I start pulling parts, the bike will end up with dellorto carbs or some other abortion(that I actually understand) and get painted flat black. That's just my MO :razz:

RedBird · 03-04-2006, 09:41 PM

Guys,

Believe it or not, the Triumph service manual is actually pretty good on carb directions. Pilot screw=air mixture screw=Air/Fuel screw. 2001--2003--the pilot screws are covered with a small aluminum colored plug (about half the size of a dime). The plug and screw are on the bottom front of the carb--you can find it by looking at a mirror held under the carb. The plug has a very tiny hole in the center of the plug. I used that hole to start a small drill bit by hand to enlarge the hole and screw a "grabber" screw into the hole and pull the plug out. Once the plug is removed, you can adjust the pilot screw with a regular (very short) screwdriver. On 2004 and later models, there is no plug over the pilot screw which is located in the same location; however, you will need a "D" tool to adjust the screw. Some have made a "make-shift" "D" tool out of copper tubing and used it to remove the pilot screw and then filed or cut a slot in the pilot screw so they could use a regular screwdriver.

Yes, the needles are different on many of the carbs. The 865cc engines have different needles than the 790cc engines. The Thrux and Speedy have different needles--that is both are 865cc but their needles are not the same. All use the same main jets and pilot jets; however, the stock jet for one model may be/is different from other models. The 790cc comes with 110 main jets and 40 pilot jets. Some of the 865cc come with larger (115), I believe, main jets.

I very much recommend the purchase of the Triumph service manual. You should be able to do about anything needed to these carbs without removing them. It is highly recommended by many, myself included, that you purchase stainless steel allen screws for the carbs prior to beginning work on them. Carefully remove the stock phillips screws holding the float bowls on and replace them with the allen screws. Also do that for the top cover that holds the slide, spring, needle in the carb. Removal of the stock screws are not easily done in many cases. I used a small 1/4" ratchet with a NEW #2 phillips bit in the ratchet adapter. I pushed up on the ratchet with one hand until I saw the carb move a little and turned the ratchet with the other hand. I was able to remove all screws without stripping any that way. Some have not been so lucky, and have had to use vise grips, etc to remove stripped screws.

Jets are purchased from the dealer or from aftermarket vendors--Newbonneville.com and Bellacorse are a couple of the aftermarket vendors who advertise on this site.

Always use a towel under the carbs to catch the little pieces you may drop! Yes, you drain the fuel from the float bowls by connecting a small hose to the spicket and opening the allen drain screw on the bottom of the carb. I have used a small plastic bowl set under the carb to catch the fuel when I opened the allen drain screw without using a hose.

These carbs are very simple and pretty forgiving; however, it's best to know what your are doing--reason for purchase of the service manual, IMHO. The main jet is screwed into the bottom of the "needle jet holder". If you remove the small hex "plug" that the main jet screws into, the needle jet will fall out--it only goes in one way so you CAN get it in the WRONG way. It is best to remove the main jet alone--hold a small (don't remember the size) wrench on the hex "plug" while you unscrew the main jet with a screwdriver. Jets should be tightened snuggly; however, don't overtighten them--same with the stainless steel screws. If you buy a screw kit from an aftermarket vendor such as Newbonneville.com, lock washers will come with the screws. Use the lock washers on all screws except two--the two holding the idle adjust bracket. If you use lock washers on these two screws, you will risk stripping the threads because the screws are too short with the lock washers + the bracket.

Time to ride!

Larry

ssjones · 03-05-2006, 08:40 AM

Quote:

On 2006-03-04 19:41, RedBird wrote:
Guys,
...... Use the lock washers on all screws except two--the two holding the idle adjust bracket. If you use lock washers on these two screws, you will risk stripping the threads because the screws are too short with the lock washers + the bracket.

Time to ride!

Larry

Good advice Larry. I just removed my washers, no wonder they were hard to start! I also use a little Blue Locktite on all my screws.

ssjones · 03-05-2006, 08:41 AM

Quote:

On 2006-03-04 18:41, guzzi wrote:
Anyone tried to hook a small hose to the bowl drain, loosen the allen screw and drain the carbs w/o removal from the bike?

I just take a small Dixie cup, tear it down to about 1" high and stick it under the carb drain. Works like a charm.

FattRat · 03-05-2006, 10:04 AM

What am I risking by not draining the gas prior to removing the bowls? I just threw the remaining gas (that which didn't drip on the towel I placed under the carbs) out onto my drive-way. (Some gas drained onto my Black engine prior to putting a towel in place)

But more importantly:
Is there a standard 'rule-of-thumb' for determining main jet size when replacing the standard Bonnie needle with a Thruxton needle? For instance, if when using 135 mains & standard needle, one should drop (one full main jet size?) when replacing the standard needle with a Thruxton needle(???)

Which begs yet another question to be answered:
I don't understand "steps" in jet sizes, nor do I know what a "full size" is??? I see that jets are available in 130, 132.5, 135, 138, 140, etc (or some'n like that). Are those "steps", and is a full size something like going from a 130 to a 140???

I went into this whole affair blind, and between encouragement & help from the guys here, some light has been shed on this (once) mystical affair of carb's. I've actually gone into the carbs (top & bottom) at least a half dozen times now. Kinda fun, once over the initial intimidation factor.......