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95 Thunderbird Choke Issues

7K views 49 replies 7 participants last post by  Thunderbird 95 
#1 ·
Hello all, this is my first post besides my introductory post. I have a 1995 Triumph Thunderbird with 18,000 miles on it. Bought it from a dealer about 2 months ago. I couldn't ride it for about 3 weeks due to not having my permit. Got my permit and went on a ride and the bike was fine (that was on a Friday.)
Sunday comes and I go to take my bike out. Well I fire it up and it sounds rough at idle, starts dying and finally dies. I pull it into the garage and notice my lights are dim. Charge the battery. Bike won't fire. Check spark plugs. Fouled out. Black on the tips. Replaced those.
Now here's where my current dilemma is.
I re attached everything (battery, fuel tank and side panels) turned on fuel, starter switch, key, pull choke all the way in. Bike starts. About 20 seconds later I push the choke back, bike starts dropping in RPMs I continue pushing and the bike dies. Pull the choke back in, start again same thing starts dying right after I push the choke back. I have a video of it happening if it helps.
I'm assuming a pilot jet is clogged but the bike didn't sit for maybe a couple weeks while all this is happened. I added fuel treatment and it allowed me to push the choke a little further back.
Before I go taking it back to the shop/tearing into the carbs I wanted to check and see if I could check any other things first.

All input is appreciated! Thank you!
 
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#2 ·
When mine did that it was because of clogged jets from fuel which had gone off. But you rode it not so long ago? Is your fuel cap locking or not? Just wondered if someone had chucked something in the tank.

Think I would drain the tank, replenish with super unleaded, maybe richen up the slow running jets then see what happens. For th erecord, my needle jets were mostly blocked with green gunk. :-(
 
#5 ·
What does that indicate to you then? Perhaps a too rich fuel mixture? Plugs were pretty black when I pulled them. I'm not totally convinced it is a plugged jet consider it didn't sit for long and it's summer here (Vermont.) I'm just trying to think of all possible things it could be/I can try
 
#6 · (Edited)
Either too rich or an ignition problem. For grins, put a volt meter on the (+) terminal on one of the coils and see what you get. Measure 3 conditions: key on engine off, starting (cranking) and running. If it won't idle, get a reading at higher RPMs and monitor what happens as the RPMs drop toward idle.

Vermont, huh? Is that anything like New Hampshire? Looking like another week or two in the riding season...
 
#10 ·
11 - key not running
.9 while cranking
13.3-13.5 steady while idling choke all the way in.

As choke was pushed out may a .1-.3 drop as bike started dying
OK, I'm assuming when you say "choke in" you mean the cold start position, and "choke pushed out" you mean the warm running position, right? (If you look at the choke valves on the carbs you'll see this is backwards; they're out for cold and in for warm.)

".9 while cranking" makes me thing you're reading the (-) terminal on the coil. The one you want to read is the one that has the same color wire on all three coils.

That said, I don't think this is your problem, unless you're using the choke backwards..
 
#13 ·
I re-read your original post. What you are experiencing could be explained by reverse operation of the choke circuit. The bike will not idle when warm with the choke on, and will run very rich otherwise. Choke off is the lever fully forward.
 
#14 ·
Went out after work and tried to fire it up. Wouldn't spark. Battery level was low and stayed low. Put it on the charger for the night. Going to try it again in the morning when charged.

Maybe the fact the battery was drained shows something is drawing power and or failing? Just got the Haynes manual today (Triples and Fours carb engines, '91-'99). Super interesting!
 
#16 ·
Those plugs are one heat range too cold, I tried that heat range of plugs for about 100 miles and removed them due to running issues. Also charge the battery and have it load tested. Obviously if it fails you need a new battery for sure.
 
#18 ·
I have a ’96.
The tick over of the triple sounds like a bag of spanners, which is normal.
Have you tried leaving the choke on for a few minutes?
My bike takes a while to warm up. As the revs rise I let the choke off a little and so on until the choke is off snd the bike ticking over.I hope this doesn’t sound as though I’m talking down to you, it’s not meant to. I just like to try simple solutions first.
 
#20 ·
Yeah I had left the choke on for about 2-3 minutes as it would warm up. I started to turn choke off it dies. How long does it usually take you. Once my choke is about 3/4 off the revs never rise it always starts to die down unless I give it throttle or reapply choke.
 
#21 ·
I *think* your issue is twofold: you have a plugged pilot circuit somewhere that by using the choke it is overcoming the plugged circuit and overusing the choke is over fueling creating the black sooty plugs.
 
#22 ·
I would bet you're right. Now when you say circuit is that my physical pilot jet? Also to do all of this do I need a rebuild kit or just clean it and re assemble? Do I need to re synchronize my carbs after? Our season is almost over so now is a good time to do something such as this
 
#23 ·
You never really responded about the direction you're pushing the lever to get the choke to be "on". The markings can be confusing.

The pilot jets have very tiny air bleed holes in the side of the tube. If they are blocked the mixture will be too rich, especially at moderate throttle settings, however, the most common pilot jet complaint is too lean. If you aren't experienced at cleaning them it's probably more cost effective to replace them.

Are you running the stock airbox? Is the filter clean? Is there a family of rodents living in the secondary air box?
 
#25 ·
A great carb cleaner is Sierra Carbon Free and will clean your brass jets perfectly if you can source it then you wouldn’t have to replace the jets. Yes I believe it would be one or more of the pilot jets that is partially blocked. Probably
 
#26 ·
Amazon? If I do look into replacing one (or just for general knowledge.) What size jet is recommended. The one I'm looking at online (Hermys Triumph) is a 40? Is that what came stock? Should I use a different size?

Thank you again everyone for all the timely answers all has been helpful
 
#29 ·
The floats have small o rings sealing them, it wouldn’t hurt to source the proper Viton or Buna o rings to make sure they aren’t going to leak. Balance the carbs as well using the drill bit method, a google search will yield the info you need.

Also the carb cleaner will need some time to work, usually overnight and make sure you remove the emulsion tubes as well to make sure they are clean. Drop all the related brass into their float bowls and fill the bowls with enough cleaner to fully cover the jets and such. While you have the emulsion tubes out check the orifice the needle goes into, it they are egg shaped the plastic slide guides are worn as well as your emulsion tubes and could explain the sooty plugs. A proper rebuild will be needed of this is the case or you could drop the needle down a notch but this only kicks the cam down the road.

Report back please
 
#31 ·
The floats have small o rings sealing them, it wouldn’t hurt to source the proper Viton or Buna o rings to make sure they aren’t going to leak. Balance the carbs as well using the drill bit method, a google search will yield the info you need.
How do I know I have the proper Viton or Buna o rings? Is there a common assorted set of O rings I can buy on their website?
 
#32 ·
A few sources:

https://www.ebay.com/itm/TRIUMPH-CA...323847583241?_trksid=p2385738.m4383.l4275.c10

Ask the seller what type the orings are,

https://www.ricambicarburatori.com/...Service_Kit_for_Mikuni_BST36_carburetors.html

https://www.gixxer.com/threads/bst36ss-carb-o-ring-sizes.246264/

Myself I would replace the bowl gaskets as well as long as you have the carbs out, the inlet needles really should be replaced as well.

For instance I’m helping my brother repair the carburetors on a 2002 Honda Shadow and the bowl gaskets looked quite hard and we are replacing them just to be sure along with the inlet needles.
 
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