TT250 carburetor?

[Slopeflyer]

Originally Posted by rojo_grande

The stock main jet is a 108. I'm currently running a 102 Keihin jet and the needle on the top notch, leaner for my 5800+feet. Planning to ride more at 8,500 to 11,000+ ft so I'm trying to lean it out a good bit for even my current elevation. I bought a few different sizes to tweak as needed.

Rojo

Do you have to use a choke when starting? I have yet needed to apply choke. Wondering if the pilot jet (size 38 stock) is too large.

[rojo_grande]

Originally Posted by Slopeflyer

Do you have to use a choke when starting? I have yet needed to apply choke. Wondering if the pilot jet (size 38 stock) is too large.

Typically no choke needed. I have had a few occasions where the bike is hard to start when hot, after riding for 20 to 30 minutes. Not sure what that may indicate.

I did talk to Gerry a couple weeks ago about jetting. He recommended just changing the main jet and adjusting the clip on the needle. As I understand it the slow/pilot jet is only needed up to 1/4 throttle. Don't know about you but I spend nearly 0 time at 1/4 throttle .

Rojo

[2LZ]

At 3000', I've not needed the choke yet. Starts right up. Just a tad lean for a minute but clears up quickly.
Rojo, did Gerry mention the bore size of the stock carb? I didn't see it in any specs. It looks small, according to the slide chimney and the casting on the head side...like a 32 or 34 maybe. Just guessing.

['16 TT250]

Originally Posted by rojo_grande

Typically no choke needed. I have had a few occasions where the bike is hard to start when hot, after riding for 20 to 30 minutes. Not sure what that may indicate.

I did talk to Gerry a couple weeks ago about jetting. He recommended just changing the main jet and adjusting the clip on the needle. As I understand it the slow/pilot jet is only needed up to 1/4 throttle. Don't know about you but I spend nearly 0 time at 1/4 throttle .

Rojo

Mine doesn't need choke either, just a little bit of throttle. Restarting warm is the same. Without any throttle it takes a couple seconds of cranking, open the throttle a little and it fires right up on the button or kicker whether hot or cold. It doesn't take much, 1/8 throttle at most, and it'll fire on the first kick. I mostly use the button, but sometimes just wanna do it the old fashioned way.

I'm guessing the slow hot restarts are a rich condition, fuel in the carb evaporating and "flooding" the motor with vapors. Some bikes are more prone to this than others, but it seems fairly common on this style bike. I assume because the entire intake tract is level that it fills with vapors whereas sport bikes and many others have the carb and airbox above the motor so the vapors would settle right at the intake and clear out more quickly-just theory based on the fact that fuel vapor is heavier than air.

The fact that a motor that should be jetted fairly lean will idle cold with no choke is a little odd, but not unheard of and especially with this style layout.

If the exhaust outlet weren't so small I'd take it over to my smog test buddy and get some numbers.

[rojo_grande]

Originally Posted by 2LZ

Rojo, did Gerry mention the bore size of the stock carb? I didn't see it in any specs. It looks small, according to the slide chimney and the casting on the head side...like a 32 or 34 maybe. Just guessing.

Gerry didn't mention it and I didn't ask on the bore size.

I'm still getting a little hesitation at 3/4 to WOT at the moment with the 102 main. Seems better than the 108. But I'll still tweak some more. Got 650km/400 miles on the bike now and just installed a new iridium spark plug last night. Hope that will smooth it out some.

Rojo

[2LZ]

Originally Posted by rojo_grande

Gerry didn't mention it and I didn't ask on the bore size.

I'm still getting a little hesitation at 3/4 to WOT at the moment with the 102 main. Seems better than the 108. But I'll still tweak some more. Got 650km/400 miles on the bike now and just installed a new iridium spark plug last night. Hope that will smooth it out some.

Rojo

Thanks rojo...
Sounds like a stumble between circuits. What's your pilot screw set at? I had this problem with my Rhino and just a quarter turn more rich helped a lot.
Also, are these the iridium plugs you run? I have these in Q and the Rhino (CG motor). Just want to make sure I'm running the right plug.

https://www.amazon.com/dp/B006B253K8...I1XJPTCSABNEVG

[rojo_grande]

Originally Posted by 2LZ

Thanks rojo...
Sounds like a stumble between circuits. What's your pilot screw set at? I had this problem with my Rhino and just a quarter turn more rich helped a lot.
Also, are these the iridium plugs you run? I have these in Q and the Rhino (CG motor). Just want to make sure I'm running the right plug.

I haven't adjusted the pilot/idle screw yet but will have a look at it this weekend and see if that helps. Thank for the tip. Tweaking the bike is just part of the fun.

I'm running the DENSO 5376 {#IX24B} Iridium Power Sparkplug. Ordered from RockAuto. I believe these are the cross reference to the NGK plug. Haven't ridden with this plug in there yet so we'll see how it goes.

Rojo

[Ariel Red Hunter]

Originally Posted by rojo_grande

Typically no choke needed. I have had a few occasions where the bike is hard to start when hot, after riding for 20 to 30 minutes. Not sure what that may indicate.

I did talk to Gerry a couple weeks ago about jetting. He recommended just changing the main jet and adjusting the clip on the needle. As I understand it the slow/pilot jet is only needed up to 1/4 throttle. Don't know about you but I spend nearly 0 time at 1/4 throttle .

Rojo

This idea of not caring about carb action below 1/4 throttle is OK in the pretty dry southwest. But east of the Mississippi, it is real important to have control at and below 1/4 throttle. Climbing over logs, fording streams, going up or down rock filled streams. And on and on.

[rojo_grande]

I noticed this a couple weeks ago when swapping out the main jet. Not unusual to have the idle/pilot jet covered after being set at the factory for EPA purposes.

My KLR was like this. I drilled out the thin aluminum cover to get access to the idle jet.

On the TT however, it looks as if the jet was set at the factory then the head was ground off not allowing for adjustments or even removal for cleaning as shown in the owners manual.

So out comes the dremel to cut a slot to remove.

BTW. The jet was set at 1.25 turns out from the bottom. Also measured the throat of the carb (on the engine side) while i have it out, measures 29mm ID . 38 mm ID on the air airbox side.

Rojo

[Jayman77]

Originally Posted by rojo_grande

I noticed this a couple weeks ago when swapping out the main jet. Not unusual to have the idle/pilot jet covered after being set at the factory for EPA purposes.

My KLR was like this. I drilled out the thin aluminum cover to get access to the idle jet.

On the TT however, it looks as if the jet was set at the factory then the head was ground off not allowing for adjustments or even removal for cleaning as shown in the owners manual.

So out comes the dremel to cut a slot to remove.

BTW. The jet was set at 1.25 turns out from the bottom. Also measured the throat of the carb (on the engine side) while i have it out, measures 29mm ID . 38 mm ID on the air airbox side.

Rojo

So it looks like the tt community will have to find a replacement carb the Hawks have there's figured out we will have to find ours

[pcspecialist]

that's a cover, not the idle screw. The idle screw is recessed.

[rojo_grande]

Originally Posted by pcspecialist

that's a cover, not the idle screw. The idle screw is recessed.

Nope. Not a cover. It's the idle screw/jet. I cut slot and removed it this afternoon after I took the pic.

Rojo

[Jayman77]

Originally Posted by rojo_grande

Nope. Not a cover. It's the idle screw/jet. I cut slot and removed it this afternoon after I took the pic.

Rojo

I seen a video on you tube where a guy had to do the same thing he said that the manufacturer did it for whatever reason

[pcspecialist]

Originally Posted by rojo_grande

Nope. Not a cover. It's the idle screw/jet. I cut slot and removed it this afternoon after I took the pic.

Rojo

Do you have a picture of it removed? Really surprised it isn't recessed.

[2LZ]

A Mikuni is on the Amazon Wish List. Thanks for the recon Rojo!