jetting issue or no????

[mxracernumber1]

I saw it mostly sitting still right off idle, but it does it when putting around in first also. Go a little faster, shift to second and whack it & it will do it ever so slightly. Whack it just about anywhere putting in first or second gear & it bogs hard. If you're close to idle when you do it it will cut off. I'll try to see if I can get some sort of video of it. My wife's camera is a bout 5 years old & is not digital, so I'm going to have to find a camera. Maybe I can do it this weekend.

 

[Fast1]

Haven't you tried moving the clip on the needle yet? move the clip one slot closer to the pointed end.

It helps during testing if you actually measure and place a tape marker on your various thorttle settings with the twist so you do not have to guess at the position.

Also, as Coffee mentioned, testing the thottle response while in neutral is futile.

 

[mxracernumber1]

I put a mark on the throttle and throttle cam housing with a sharpie. I marked the throttle grip at full closed and full open, then measured the angle of the marks (by eye) with my angle guage. Since I'm a machinist by trade, I can eye-ball any measurement within .015", usually any angle within 3 or 4 deg. My old boss can do it within +/-.005". I'm one of those guys who picks up the right wench every time. I marked the throttle with a black sharpie because it doesn't show up well on black unless you look at it at the right angle. Also as resillient as a sharpie mark is, it easily wipes off of any TPR (thermoplastic rubber) or TPV (termoplastic vynil) or any other elastomeric compounds with a little kerosene or lamp oil. It will stay until deliberately wiped away. No tape needed.

By the way, why is throttle response in neutral futile?

I'm going to ty to make a video tomorrow. I don't think I'm coming across to everyone here.

 

[Coffee]

By the way, why is throttle response in neutral futile?

It needs a load.


The marks can be ballpark, the important part is not to rely on your hand "feel" when worrying about things on the trail/road, I've tried that by pretending the marks are not there then look down to confirm - I'm always wrong.

I'm almost sure that your AP was set up initially on the edge of working properly and things have changed a bit. The Pilot circuit will interact with that (fuel screw & pilot jet) and so will the needle taper & clip setting but the AP should be set up so it does not matter a whole lot.


The most important test to do at this point based on your input is to ride in 3rd gear at 1/8 to 1/4 throttle and:

1. with both choke and hot start in whack throttle - your chest may hit the bars
2. pull out the hot start a bit - whack throttle
3. pull out the choke a bit - whack throttle

No where can I find what you specify your leak jet to be, that is the most important jet at the moment. If you want to just snap a picture of the AP arm to show the AP screw I can figure out the distance even if you don't measure it.

 

[mxracernumber1]

Just did that this weekend. The cap is indeed installed on the screw just like the picture you posted. I rode the bike to confirm that is was still bogging. After warmup, I can wack the throttle in 3rd or 4th and get a pretty good bog before it takes off. I did not try the test wiht the hot start/choke knobs-forgot to do that.

I went back home and removed the cap. I set the gap to 1.5, 2.0, 2.5, 2.75mm, then all the way in. It didn't seem to change anything at all-not a noticable amount anyway. One thing I did notice that was different form the videos of the AP on youtube, was that no matter how fast I whack the throttle, the arm stay rightup against the screw. In those videos, the arm would hesitate and recontact the screw after a second or so. Mine stays right on it no matter how fast I whack it. This leads me to think that just maybe it's shooting too much too fast? As far as I know it has the stock leak jet. I'm searching for info on the carb today. I'm going to figure this out or bust. It just isn't the way it was.

 

[pvduke]

....unless i missed something......

Then at 1/8 WOT whack the throttle wide open - what happened?-bog, cut off (sitting still)

It's your fuel screw.... turn it out 1/8 - 1/4 turn, retry....

If no change or worse....go back to baseline and go the other way...

Do this after verifying you PJ is correct.

P.s- I can get any bike to bog...does it do it during normal riding or racing? I.e.- I don't usually snatch the gas WFO from a super low RPM.

Try an o-ring or two on the AP and a 65-85 LJ.

 

[Coffee]

...no matter how fast I whack the throttle, the arm stay rightup against the screw. In those videos, the arm would hesitate and recontact the screw after a second or so. Mine stays right on it no matter how fast I whack it.

It sounds to me like the Leak Jet is missing. There should be a 'squirt' which takes time. Without knowing what all your jets are it is difficult.

And yes set your fuel screw/pilot jet appropriately.

 

[Louge]

Main Jet-180 (did not change)
Pilot Jet-52 (up from 48)
Needle-4th pos. (up from 3rd.-this is a TC needle)

Larger pilots (45 > 48 > 52) and a TC needle have been used to compensate for your disabled AP.

Removing the silver cap has enabled the AP. The bike will probably still have the blank leak jet (small, solid jet) in the bottom of the float bowl. With a blank leak jet all the fuel goes through the AP. Installing the a 70 leak jet (.7mm) gives a bypass path back to the float bowl, less fuel goes through the AP. In cold weather consider a 60 leak jet (less bypass than the 70, slightly richer AP squirt).

The unrestricted AP circuit and large pilot jet can cause your engine to bog down low.

I installed a JD kit soon after purchase. It comes with severals mains, blue (winter) and red (summer) needles, pilot jets and excellent instructions. A bit of experimentation soon had the bike sorted. The bike ran exceptionally from sea level to 13,000' on the TAT.

http://www.jdjetting.com/xcart/product.php?productid=42&cat=1&page=1

 

[Mercury264]

Main Jet-180 (did not change)
Pilot Jet-52 (up from 48)
Needle-4th pos. (up from 3rd.-this is a TC needle)

Larger pilots (45 > 48 > 52) and a TC needle have been used to compensate for your disabled AP.

Removing the silver cap has enabled the AP. The bike will probably still have the blank leak jet (small, solid jet) in the bottom of the float bowl. With a blank leak jet all the fuel goes through the AP. Installing the a 70 leak jet (.7mm) gives a bypass path back to the float bowl, less fuel goes through the AP. In cold weather consider a 60 leak jet (less bypass than the 70, slightly richer AP squirt).

The unrestricted AP circuit and large pilot jet can cause your engine to bog down low.

I installed a JD kit soon after purchase. It comes with severals mains, blue (winter) and red (summer) needles, pilot jets and excellent instructions. A bit of experimentation soon had the bike sorted. The bike ran exceptionally from sea level to 13,000' on the TAT.

http://www.jdjetting.com/xcart/product.php?productid=42&cat=1&page=1

Could you elaborate a little Louge ? I have just fitted a JD kit (including the leak jet and the smaller of the rubber O rings on the AP) and I am still not super happy with the off-idle response.

 

[Louge]

IIRC when searching for HP I baselined with a cored pipe, 180 main and 45 pilot. Different JD needle clip positions and 60 / 70 leak jets were played with thereafter. The bike was an animal!

When prepping for the TAT range was critical. I installed an uncored pipe (thanks again Neilly!), 175 main, 42 pilot and trimmed the needle one clip. I further trimmed the main to 170 when approaching the Colorado high country. I left the 42 pilot installed to soften the bottom end for off-road after returning home.

I started the bike last week in 38-40F temps with the summer needle still installed. She did a lean induction pop and stalled when I snapped her while still cold. The bike was fine after warming up. Adding a half turn to the fuel screw helped.

When starting in warm temps I do three slow AP squirts with the throttle before hitting the starter, when cold I increase the number to five. She always starts first one over. The iridium NGK CR8EIX probably helps.

 

[pvduke]

You sed:

Could you elaborate a little Louge ? I have just fitted a JD kit (including the leak jet and the smaller of the rubber O rings on the AP) and I am still not super happy with the off-idle response.

Yestreday I sed:

It's your fuel screw.... turn it out 1/8 - 1/4 turn, retry....

If no change or worse....go back to baseline and go the other way...

Do this after verifying you PJ is correct.

P.s- I can get any bike to bog...does it do it during normal riding or racing? I.e.- I don't usually snatch the gas WFO from a super low RPM.

Try an o-ring or two on the AP and a 65-85 LJ.
Yesterday 06:51 AM

Yer 'tip in' circuit is all outta whack. It should respond cleanly with moderate roll-on, off idle to 1/8 throttle.
Not whacking it WFO like guys at the track on the stand....who the fark rides like that?

This (slow speed) circuit is metered by the fuel screw and Pilot Jet:

Before doing anything your Pilot Jet MUST be verified our you will be chasing your tail.
Once your PJ is verified, the Fuel Screw is your best friend.

This is all you'll need for any trimming down the line sans some major change to exhaust or intake. IF, you've got it right.

*

I can go from 3500' to 8500' w/o any adjustments. My bike is 100% stock. No jet kits etc...all Husky parts.

Spark plugs etc make no difff at all and there's no magic to it.

It's simple physics and logic.

 

[Riksha]

I read the first post and experienced something similar. My 07 te450 sat afew days and when I went to restart it I didn't use the choke. Well it acted like it didn't want to rev like it did previously. I had to up the idle or when stopping it would die. Hesitated off idle when accelerating and just sitting in the garage blipping the throttle. Just didn't have the same snap to it when riding and hitting it wot.

I came home tightened the intake flange bolts, carb clamp trying to find something different that might be the cause. Nothing was out of place.

Then I restarted the bike again after afew days. This time with the choke. It idled real high, so I turned it back down. Whalllaaa the choke circuit seemed to have been clogged. Now when I hit wot it revs like it did in the past. I figured that maybe the vp c12 race gas that sat in the tank might have something to do with it so I drained it and put in some fuel from a freshly cracked can of vp. I must of got lucky it cleaned out....

 

[pvduke]

While were slightly off topic....

Esp in Calif: If you let yer scoot sit for more than a few days-

See that lil allen head on the float bowl on the left side of the carb? Crack it open and drain the bowl.

Or else.......

I do it every ride, all my bikes.

 

[Mercury264]

One thing I noticed (after re-reading the thread and watching the Coffee vids on YouTube) is that my AP gap is approx 3.2mm. I currently have the small O-ring from the JD kit on there. Would adjusting it to 2.75 make any differance - if so, good/bad WRT to the off-idle bog ? Would installing the thicker of the O-rings from the JD kit help ? Does the bike come with a blank leak jet ? If so would putting the original back in help - in watching the vids, it seems the blank leak jet gives more fuel so I am confused as to why people change from a blank leak jet - isn't the idea of the AP to get more fuel into the engine when the throttle is whacked open

As for what's in the carb, I installed the main, pilot and leak jets and needle exactly as per the JD instructions - note I never go above 3,500 I would think (hard to say with some of the hills in NH etc. but in general I would say all my riding is below 3,500). I installed an after-market fuel screw and I am currently approx 2 1/2 turns out.

Main: 186
Pilot: 41
Leak: Doesn't say in the JD instructions

The bike starts with the first touch of the button when cold (choke on) and I have found that if it stalls when hot, as long as I don't touch the throttle at all, it will generally start first push of the button (I pull the manual de-comp to get it to to spin up, let go, it starts first time) and I don't need the hot-start.

I look forward to having FI on my next dirt bike

 

[pvduke]

Does the bike come with a blank leak jet ? If so would putting the original back in help - in watching the vids, it seems the blank leak jet gives more fuel so I am confused as to why people change from a blank leak jet - isn't the idea of the AP to get more fuel into the engine when the throttle is whacked open

They plug the AP for emissions reasons, w/ emissions controls/jetting.

Ever heard of too much of a good thing? Adding TOO MUCH fuel is the same as not enough with respect to the fact it won't run right.

Carbs work like this (over simplified for obvious reasons):

Idle to off idle - fuel or air mix screw.

Off idle to 1/4 - screw and PJ.

1/4 to 1/2 - PJ and needle.

1/2 to WFO - needle and main.

Most of these off idle 'stumbling' problems are due to incorrect fuel screw setting in combo with the incorrect PJ.

If you have the correct PJ you can adjust the off-idle stumble out with the fuel screw.

Quit messing with AP's and stick and o-ring or two on there- or safety wire it, then a propper leak jet.

I look forward to having FI on my next dirt bike

Think you got troubles now?

I've done this stuff a million times and can get most carbs super close in 15 mins or less.

Thankfully Husky's are the best ever to work on...I tell my 'buddies' with Asian's to get the checkbook ready. They don't like it much when they hear that. Ever taken one of those apart? Nightmare.

P/s- beware using others jetting combo's- it rarely works. Might get ya close, might get ya spot on- might piss ya off. If ya tune on the stand- use a FAN!
No substitute for trial and error and good old fashioned logic.

 

[Mercury264]

They plug the AP for emissions reasons, w/ emissions controls/jetting.

Ever heard of too much of a good thing? Adding TOO MUCH fuel is the same as not enough with respect to the fact it won't run right.

Carbs work like this (over simplified for obvious reasons):

Idle to off idle - fuel or air mix screw.

Off idle to 1/4 - screw and PJ.

1/4 to 1/2 - PJ and needle.

1/2 to WFO - needle and main.

Most of these off idle 'stumbling' problems are due to incorrect fuel screw setting in combo with the incorrect PJ.

If you have the correct PJ you can adjust the off-idle stumble out with the fuel screw.

Quit messing with AP's and stick and o-ring or two on there- or safety wire it, then a propper leak jet.



Think you got troubles now?

I've done this stuff a million times and can get most carbs super close in 15 mins or less.

Thankfully Husky's are the best ever to work on...I tell my 'buddies' with Asian's to get the checkbook ready. They don't like it much when they hear that. Ever taken one of those apart? Nightmare.

P/s- beware using others jetting combo's- it rarely works. Might get ya close, might get ya spot on- might piss ya off. If ya tune on the stand- use a FAN!
No substitute for trial and error and good old fashioned logic.

Well....not sure that helped me much. It left me as confused as before. You don't mention the AP in your explanation of how a carb works - I thought the whole point of the AP was to give more juice when whacking the throttle open, so the motor doesn't get starved of fuel

I think I am going to put the thicker of the O rings on the AP and adjust it to 2.75mm and see how that goes.

 

[pvduke]

Well....not sure that helped me much. It left me as confused as before. You don't mention the AP in your explanation of how a carb works - I thought the whole point of the AP was to give more juice when whacking the throttle open, so the motor doesn't get starved of fuel

I broke it down in very simple terms...not sure what there is to be confused about.

I also mentioned the function of the AP in as far as that too much fuel does the same thing as not enough.
To elaborate:
It fills (compensates for) the 'hole' you create by 'whacking' (vacum drops) the gas open too fast for the amount fuel the metering circuits can provide.

Eg: Mikuni's BST40 has two butterflys, one mechanical and one before that that opens via the engine vacum through a metered vacum circuit.
You cannot bog this carb, when tuned right, as the second butterfly (with the needle) will only open as far as the engine vacum will allow/give as much fule and air it can use as a result.

The Kehin is a totally mechanical carb- it has no 'buffer' or secondary butterfly to meter the required air...thusly it is equipped with an AP.

Installing an o-ring (or two): It ensures a precise shot w/o delay(use a leak-jet!)
Most just pull the cap and safety wire the AP arms together.
The new Kehin's don't have that lame set up anymore.

Look at what I've typed and what your bike is doing, and, where in the throttle opening area's it is doing it.

My TC runs fine as equiped from the factory from sea level to well over 6500' w/ only a slight tweak of the fuel screw here and there, if that. I aint no genius and used no special parts.

 

[restukey]

I think the thicker diameter needles that force you to run the fatter mains are prone to that kind of bogging. I run an EFN needle and a 165 main in my Husky sm610 and KTM 450 smr. I have the AP mod with the arm safety wired. O-rings are ridiculous. The bikes run crisp off idle with the clip in the 2nd position. If I put it in the third position, the bikes get a little lurchy when rolling on the throttle mid corner. The throttle response is just there.