[Jimbonnie]

First the swap: The swaps been done. Thanks M.

Now my first question: The carburetor pilot adjusting screw is, I believe, an air-bleed screw. So wouldn’t turning the pilot screw out admit more air and result in a leaner mixture?

And for my second question: I can completely turn in and seat my pilot screws and there is no change in how the bike idles. In fact no adjustment I make with the screws seems to have any significant impact on the bikes idle. The bike is stock except for a bafflectemy and the previous owner says it wasn’t re-jetted. So does anyone have any suggestions as to what’s going on with my idle circuit?


[ This message was edited by: Jimbonnie on 2006-12-31 16:05 ]

 

[jojje1963]

The pilots are not air-bleed screws, turning them out gives you more fuel.

Never heard off a Bonnie still running with both screws seated, at least not very good, are you sure you are working on the pilot screw? Sounds really really strange if you are

[ This message was edited by: jojje1963 on 2006-12-31 15:41 ]

 

[Jimbonnie]

I'm not disagreeing with your assessment of the pilot screw, but in a pretty good article about the CVK40 for the KLR the author states, "When you adjust the pilot screw that's under the carb, you are varying the amount of air premixing with the gas before it enters the venturi", hence, the confusion. It's really not that uncommon for the pilot screw to be an air-bleed screw.

Yeah; I'm sure I'm working with the pilot screw; it's got that stupid "D" shaped adjusting surface I had to make a tool for. Usually when a motor isn't effected by the pilot circuit it's because the circuit is clogged and the motor is idling off of the needle jet circuit. It wouldn't be that unusual for a set of really old carbs to do that, but I wouldn't expect that from both carbs of a new bike.

 

[jojje1963]

Yeah, it's a mixing screw that controls the air pushing the fuel in. I know it's confusing but an air-bleed screw is much thicker than a mixture screw (not easy to see if you don't take it out of course) and is normally on the side off the carb.

You don't have a high idle, do you? The mixture screws only work up to around 12-1400 rpm. If you turn them out to 6 turns you will almost be able to see the unburnt fuel spray out off the exhaust

 

[Jimbonnie]

No, the idle is easily adjustable and set at 1000 rpms. The bike runs just fine; my only objection is that the idle mixture can't be set.

It's been suggested, and I think it's reasonable, that despite what the owner has said the pilot jet has been changed by the dealer and that it's too big. I'm on my way to the garage to drop a float bowl and have a look-see.

 

[ohiorider]

Jojje - I have a similar problem when adjusting my pilot screws. I installed 42 pilots (along with 125 mains + shims - one under each needle) and also installed the BC knurled pilot screws that can be adjusted without a tool.

Since NB now advertises a set that has needles exactly like the Triumph ones (same profile) I think the ones from BC may have been for a bike other than a T100 .... maybe for an HD with Keihin carb.

I am able to make the engine slow down as I open the screws, somewhere around 3.5 - 3.75 turns open, but cannot make it slow down by closing the screws. I'm guessing these BC needles are too short to cause the engine to slow due to too little fuel.

As I recall, Stu from Florida had a similar issue with the BC needles.

However, my bike runs fine where I now have it adjusted. makes good power, and gets good mileage, so I'll probably leave well enough alone.

Bob

 

[Jimbonnie]

Well, it turns out the pilot jets are the stock size 40.

So the mystery continues.....

 

[jojje1963]

Jim,

Unscrew the mixture screws and look at them, it's possible to seat them to hard and damage either the screw or the seat. Just before they come out it should run very rich, that will tell you if they are working at all.

 

[Jimbonnie]

Jojje:

I removed the jets and examined them with a magnifying glass; they look new, as they should.

When I opened them up almost all the way, as you suggested, the idle did become uneven, so there is some connection between the pilot circuit and the engines idle.

By decreasing the idle rpms to 500 or so I was able to get some response from the idle mixture screws, but not the distinct changes one would expect between fully seated to open several turns.

Unless everyones T100 is the same, there's something going on with my carbs that still needs discovering. Thanks for your interest and please pass on any other thoughts you might have.

 

[Bonnie1000th]

On 2006-12-31 17:38, jojje1963 wrote:
Jim,

Unscrew the mixture screws and look at them, it's possible to seat them to hard and damage either the screw or the seat. Just before they come out it should run very rich, that will tell you if they are working at all.

Jorgen rules!

 

[Jimbonnie]

Jorgen may rule indeed, and thanks Jorgen, but how come my carbs aren't working right?

 

[Olderyoungster]

ALL of the above listed information is exactly what I need to read, study, and read again. It's kinda making sense to me, but it's also creating a mental block, kind of a sensory over-load.

I've been playing with my needles, shims, main jets and pilots. Adjusting my 'D Screw' and what exactly it's doing has been a bit of mystery to me, sort of a series of trial & errors. I for one am VERY grateful for the above posts, but will be returning to read it when this rum & coke wears off.

[ This message was edited by: Olderyoungster on 2006-12-31 22:28 ]

 

[jojje1963]

On 2006-12-31 21:45, Jimbonnie wrote:
Jorgen may rule indeed, and thanks Jorgen, but how come my carbs aren't working right?

You need to hook it up to a CO meter, most garages will have one, and set it to 1.5-2%. A bit more if it backfires but not more than 3.5%.

If that can be done all is good and you don't have to worry about it any more