Rejetting the Steamer

[nightrunner]

There's been some talk on Advrider about jetting the steamers, especially the '98 since it has the Keihin carbs and no Dynojet kit was made for it.  I'm putting together a write-up on how to re-jet the '98 (or at least my recipe for it).  I wanted to post this link to a good tutorial on how motorcycle carbs work, and some guidelines for tuning and altitude corrections.   Its been posted on a number of sites in both HTML and PDF format but thought I'd link it here for ref.

http://hondanighthawks.net/carb14.htm

More to come
Cheers

[tigerrider]

dog gone it...there was once a guy who had a site that detailed just this thing..the rejetting of a '98. I was a green bike also. He had all the details, including what had to be drilled out and what needles to use...last I saw that was 4-5 years ago...

I had Atlanta Triumph/Ducati rejet mine several years ago...

[nightrunner]

Yeah, I think that site is still up.  Have to do some digging to find it again.  He drilled the main jets and butchered the needles to do it.  Lots of work.  He reported increased performance but also that he could smell gas at idle.  I prefer to change jets and shim the needles so its all reversible.  Details coming soon.  I'm at work now and the nerve of them, they actually expect me to work. :lol:

Interesting.  I was talking with IIRC the head mechanic at Atl TR Ducati a few years ago.  He new nothing of DAR and he told me that bikes run better lean and it should not be rejetted.  He also ripped on chat groups for spreading such misinformation.  I guess he missed the tech service bulletin on DAR.

[Stretch]

Interesting.  I was talking with IIRC the head mechanic at Atl TR Ducati a few years ago.  He new nothing of DAR and he told me that bikes run better lean and it should not be rejetted.  He also ripped on chat groups for spreading such misinformation.  I guess he missed the tech service bulletin on DAR.

Geez.  Another great reason to do all our own work.

[Mudhen]

Was it 'Blake's' page?

http://pages.cthome.net/bmantel/index.htm

[abruzzi]

Was it 'Blake's' page?

http://pages.cthome.net/bmantel/index.htm

Interesting page, though my favorite part was:

Coming Soon:  Rides & Stuff

and:

Last Update-> 06/09/00

New definition of "soon" I guess.  :-)

[nightrunner]

OK, I had hoped to get this out a bit sooner.  This is a first draft of a write up on rejetting the steamer.  I would appreciate comments before making a PDF that we can hopefully post here somewhere.  One issue is whether to include the Mikuni carbed Tigers.  I have no experience with those and don't know the jet sizes, so I would need some input from someone who has done it.  Or I could just target it for the 98 Keihin models.


DRAFT
Rejetting the Steamer (carbureted Tiger)
by Nightrunner of TigerTriple.com

This how-to is mainly written for the 1998 U.S. model with Keihin carbs, but the procedure is the same for the 93-97 models with Mikuniís.  First note that Dynojet makes a carb jetting kit for the Mikuni models, and a seemingly well kept secret is that Factory Pro makes a kit for the Keihin equipped models.  Also note that most of the Triumph line of that era used the same 3-cylinder 885cc engine so the same procedure applies.

Triumph jetted the Tiger to run very lean, presumably to keep emissions low.  The trade off is hard starting, slow warm-up, and less than optimal performance and gas mileage.  Mine was even leaner than factory specs and I suspect it was not the only one.  If you change to the K&N air filter and/or install aftermarket cans, the bike gets even leaner.  The procedure outlined here presumes you have some experience working on your bike, and already know how to remove the tank, carbs and airbox.  Either the factory Triumph, or Haynes manual is recommended to have.  It further assumes stock air filter and exhaust but it is easy to adapt to even richer jets if you plan those mods as well.  Lastly, it is recommended that you find and read the article ìMotorcycle Carburetor Theory 101î.  It is posted on several web sites and Google should get you to one.  This will give you a very good idea of what you are trying to achieve.

Balancing
Its not crucial but still not a bad idea to verify that your carbs are in balance before you go rejetting them.  If its had regular tune-ups, the shop may have checked and done this.   Balancing accounts for slight variations in the linkage between the carbs.  You want all three butterfly valves opening simultaneously; balancing achieves this.  Youíll need either the classic mercury carb sticks, or one of the new electronic differential vacuum devices ($100-175ish), or you can build a differential manometer that uses water or oil as the fluid.   Do not use a vacuum gauge, or gauges in parallel, as they are not accurate enough.  Whatever method you choose, youíll be comparing vacuum readings between ports on each carb located near the boots leading to the engine.   One carb is the reference and has no screw.  The other two carbs have an adjusting screw located on the connecting linkage.   These screws are adjusted to give the same vacuum between each carb and the reference carb.  Details can be found in the manuals.

Rejetting
If you are pulling your Tiger carbs for the first time, they are likely well seated in the rubber boots.  And the designers did not leave much room between the carb and airbox to work with.  Still they can be persuaded loose.  The choke cable is easily removed.  Keeping the carbs level, hold a gas can spout or small container under each fuel drain hole and open the screw valve to drain each float bowl.  You have the option of disconnecting the throttle cable and working them on the bench, or suspending the carbs and doing the work next to the bike.  The throttle cables (yup two) are a pain to remove and reattach.  

First youíll need to drill the brass plugs covering the pilot adjusting screws.  These are on the bottom of each carb, on a raised boss, near the engine-side of the carb.  Drill a small hole suitable for a sheet metal screw.  Be very careful as the drill penetrates the brass, as the pilot mixture screw is underneath and you donít want it damaged.  They can be pried out fairly easy with a sheet metal screw.  Once they are out itís a good time to record the stock settings so this entire process can be reversed or aborted at any time.  Counting the turns, use a small screwdriver to turn the mixture screws clockwise until they lightly seat.   Record the number for each carb.  It will likely be close to 2.5 turns but may vary from one carb to the next.  Note that the effective range is 0-3 turns.  Beyond about 2.5 to 3 turns the screws do no more good.

Now remove one of the float bowls.  This not a bad time to verify that your floats are set to the proper specified height.  Again refer to the manual for this procedure.  Locate the pilot jet and main jet and remove them.  The main jet and needle jet may come out together but note that they are two separate pieces.  The stock Tiger jets are as follows:

(this will be a table in the final doc but didn't paste over too well here)
..........................................Main/   Pilot/   Mixture screws
1998 stock (Keihin)                98/   38/   Approx 2.5
1998 recommended for stock filter and cans   102/   40/   1.5
1998 for K&N and race cans   ?/   40/   ?
>1997 stock (Mikuni)                   ?/   ?/   ?
>1997 recommended for stock filter and cans   ?/   ?/   ?
>1997 for K&N and race cans                   ?/   ?/   ?


Any well-equiped dealer should stock a wide range of Keihin and Mikuni jets.  If not, they are easily ordered.  Take a pair of old jets in to make sure you get the right type as there are a few different styles.

Shimming Needles
Next youíll need to raise the needles.  A #4 brass washer works perfectly(0.120îID X 0.281îOD).  I used 0.025î thickness but I see a 0.018î is available perhaps if a milder mod is desired; or use two for 0.036î.  If your local hardware store does not have them, McMaster Carr will sell you a bx of 100 of a couple of bucks.  Remove the top cap on the vacuum diaphragm.  Watch for the long spring underneath.  Carefully remove the slide being careful not to tear the rubber diaphragm in case itís stuck to the carb body.  The needle can be raised out from the top of the piston.  Slide the needle through the washer first and then back into the piston.  This will raise the needle by 0.025î.   Reassemble the spring/top cap assemblies being careful to get the diaphragm seated in the grove in the cab body.

Mixture screws
For the 1998 Tiger using stock air filter and cans, I recommend setting the screws at 1.5 turns out from seated.    This produced about 1.5% carbon monoxide at idle.  The factory manual lists target CO levels at 1% for the U.S. models and 2.4% for the European models.  For other years and setups, we need input from owners who have rejetted.
There are a couple of ways to fine-tune these settings. One way is to read the spark plugs.  Black means too rich and turn the screw in a bit.  White is too lean and the screws should be backed out a bit.  Quarter turn intervals are reasonable increments.  The better way to fine tune the idle mixture is use a dyno, or measure the CO levels at each header pipe (Triumph has graciously provided sampling ports on each header pipe).  However this requires some pretty expensive equipment and is best left to the shops.

Impressions
This jetting recipe on my 1998 Tiger produced a number of improvements:
1)   Much easier cold starts.  
2)   Better low end throttle response.  Before there was a slight hesitation when I snap the throttle.  Now it is smooth acceleration.
3)   Better fuel economy.  Was getting high 30ís; now low to mid 40ís.
4)   I can remove the right side air intake cap to lean the mixture out a bit.  The idea is that I can remove it if needed at higher altitudes if the mixture gets too rich.
5)   I still plan to add the 4 degree timing advance adapter and see how it all works together.
END

So its a work in prgress.  Let me know what ya think and we'll get a final draft together.
Cheers

[ned37]

95 tiger with mikuni is a 105 main jet, 40 pilot and the pilot fuel screw at the bottom front of the bowl is 2 turns out.

[tigerrider]

Was it 'Blake's' page?

http://pages.cthome.net/bmantel/index.htm

Sorry I missed it..Yeah! That was it..good find!
For the longest time...that was the only thing I could find on my bike, carb wise.

[tigerrider]

Wow, that's a great write up nightrunner...THANKS!

Looking forward to cooler weather... 8)

[nightrunner]

Wow, that's a great write up nightrunner...THANKS!

Looking forward to cooler weather... 8)

Thanks.  And thanks Ned for the Mikuni data.  

Need to get started on a DAR write up now.

[nightrunner]

Hey, I just noticed where a fellow has a poll going at the TriumphTiger Yahoo group about jetting the 98.  So far two very different recipes.  Interesting.

[JetdocX]

Hey guys,

Sorry but I've done some looking and can't locate a picture of where to drill the anti-tamper plugs off my Kehin carb to adjust the low speed circuit.

Help for the helpless, please?

[BR]

JD,
Carbs have to be off of the bike.
Flip the carbs over and on the bottom of each they're just down-stream of the float bowl under each butterfly valve.  It's basically just a cylindrical protrusion coming up from the carb body just in front (engine side) of each float bowl.  On each you'll find a brass "plug" that should be flush with the surrounding material.  There might even be an existing tiny hole or dimple right in the middle of each.  This is a good place to start your drilling.  Use a 1/8" drill and slowly and carefully drill through each, being carefull not to break thru hard as you'll hit the actual mixture screw and damage it and likely turn it (no big deal unless you're interested in seeing what your original turns-out are).  Each plug is about 3/16" thick if I recall.  Once you're hole is thru, take an appropriately sized wood screw and start it in the drilled hole... you won't get too far before your plug simply comes out.  Some gentle rocking will help too.  Underneath you'll find a nice shiny mixture screw that hasn't seen the light of day since it left the factory.  You'll need a narrow flat bladed screwdrive to turn it.  If you remove it, you should find it to be a very fine pitched brass screw with a pointed tip and a small spring, washer and O-ring on the end of it (in that order).  Make you have all them!  Once removed, you can blow out the passages with some air or carb cleaner etc.... the corresponding "outlet" holes for the idle circuit are in the carb throat near the bottom of the butterfly valve (6 o'clock spot).

Brendan

[JetdocX]

Thanks BR,

Mine came to me pre-drilled!  I have complete unfettered access to said mixture screws on my carbs.  I'm so happy.  

Now trying to avoid the temptation to "fook" with them. :lol:

I just wanted to make sure they were drilled before I re-install the carbs should I feel the need (and we all know I will feel that need) to screw with them.

Allow me to add the following to BR's previous post:
As you search for said brass plug, the wetness you now feel in your shoes and lower pant legs is fuel from the float bowls. :P