In search of snap… Is this stuff useful?

Ok think I found “snap” 5000 rpms in 1st & 2nd gear – whack the throttle and good response. This is what I found. Could not find this information anywhere so made the measurements myself and it took a whole bunch of time – and everything was repeated a few times.

Basically by adjusting the AP screw, adding and not adding o-rings the squirt can be altered (somewhat) without changing the leak jet, which was a big help to me on my bike - 2006 TE250 with a Keihin 37mm FCR-MX carb.

Here is a short video showing the AP in action most of you have already seen it but here it is again:

Here is the AP as it comes from the factory - with cap over AP screw:

Here is the AP without the cap:

Here is the AP without cap over AP screw and with “O-Ring” that is referred to often:

Here is how to measure the “distance” of the “AP screw”:

Here is a graph of at what throttle position the AP squirt starts at:

Keihin recommends the distance set to 2.75mm, which results in the AP starting to squirt ¼ WOT. The AP cap disables the squirt by setting the distance very high – 5mm?

Here are the numbers:

2 mm - 6%

2.25mm – 12%

2.5mm – 18%

2.75mm – 25% <- Keihin recommended setting

3mm – 33%

Here is a graph of amount of squirt vs AP screw setting, the “mLs for 50 WOTs” means the throttle was whacked open and collected into a jar 50 times then measured…with 1 O-ring and 3 different leak jets:

The amount of squirt is determined by leak jet and the AP screw setting when going from fully closed to WOT.

Here is the same graph with just the 65 and 70 leak jets:

Here is a graph of a 65 leak jet with no O-Ring, 1 O-Ring, and 2 O-Rings:

That is just plain weird, but the experiments were repeated many – far too many – times and it is real. Where maximum squirt occurs changes depending on if there is an O-Ring on the AP arm……

Here is squirt duration time vs. AP screw setting with a 70 leak jet:

The squirt duration is mainly determined by strength of O-Ring – if there is an O-Ring installed especially, between 2mm and 3mm. Video camera captured the squirt then single stepped through frame by frame to determine time.

Here is the same information but with a 35 leak jet – Series 1 is no O-Ring, Series 2 is 1 O-Ring, Series 3 is 2 O-Rings:

What does this mean? Squirt duration, amount of squirt, where the squirt starts to occur can all be set (sort of) independently by adjusting the AP screw, O-Ring, and leak jet. It also means changing the AP screw and O-Ring can have a similar effect as changing the leak jet to some extent.

If AP screw = 2.25mm, then squirt starts at 12% of WOT and:

Adding an O-Ring = shorter duration and more squirt

Larger leak jet = longer duration and more squirt

If AP screw = 2.75mm, then squirt starts at 25% of WOT and:

Adding an O-Ring = shorter duration and same amount of squirt

Larger leak jet = longer duration and more squirt

Everything else stays the same and AP screw changes then:

Where the AP starts changes (see graph), duration stays (roughly) the same, and the amount of squirt changes – see graphs.

Useful? Could use a little feedback on this... seriously could use some feed back...

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Info added as of Feb 21 2007:

Here is a summary of all the AP videos:

70 vs 35 vs blank leak jets (new as of Feb 21 2007) - 1:44 in length:

AP cap vs 35 leak vs 70 leak - 50 seconds in length:

slow motion 35 vs 70 leak jet both with no O-Ring 2.75mm - 1:20 in length:

Squirt vs screw setting no ORing 70 leak - 1:33 in length:

blank leak jet data:

This graph (below) continues to show the shift in peak squirt from (about) 2.75mm to 2.25mm when an O-Ring is added. This phenomenon continues to be useful when experimenting. Set the screw for 2.25mm with O-Ring then to make a smaller squirt flip the O-Ring off for instance. Or flip the O-Ring off, and turn the screw to take it up to 3mm and it will squirt later in the rotation of the throttle, be less fuel, but a slower squirt. Then put the O-Ring on and have the same quantity but a faster squirt - that was very handy.

Of course the simplest way to experiment is to double blip the throttle very fast and get a double squirt to make it rich that way...

Results:

Put the blank leak jet in and it worked surprisingly well - thought it would stumble & bog - it didn't - it did act jerky & on/off... as if unstable. If a small amount of throttle were being applied at least for a few seconds and the throttle was whacked open it had good power and lifted the front way easy. For any normal on / off / on / off throttle operation normally used off road it would load up a bit. It seems it all comes down to riding style - at least that is my take - and have seen that posted by excellent TTrs before. Seems the faster the rider (and the more on/off/on/off throttle they use) the higher number leak jets works better.

At this point 35 or 45 is in the bike - they both work well for my riding style - like it a bunch. ?

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PhD is in the mail,give me a couple of days to digest it.I was happy drilling the leak jet and setting the gap,after that my bog off idle was ok,so I take it

you have found the ability to pop the front at speed with throttle only,is this the snap referred to.

I'm flabbergasted. And intrigued. Strong work Coffee.

Coffee, I wish you would take the time to write up some complete and useful information, I know your just spit-balling but some detail would be nice. ?

Nice work Coffee!

I'll wager the fuel gauge hits half full by Christmas!.?

I know that's not why you did all the hard work..just our way of saying thanks!

Had no, and I mean no idea how people would react to this post / thread since I had not seen this information before on TT. Lots of different "smilies" to choose from.

Just did not understand the AP or the terminology, read for countless hours and still didn't get it so I experimented a bit. Took a while to figure out that adding an O-Ring would make the maximum squirt go from 2.75 to 2.25mm.

Yes - snap is opening the throttle quickly at 4000 - 5000 rpms in 2nd gear and lifting the wheel which is a new experience for me so am not confident at doing that. For my type of riding the changes made to my bike seem like improvements to me but keep trying to get other more experienced people to ride it to see if they really are. The search for those people continues.

Try to be a bit more complete next time Kelly! ?

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The point of the O ring is the same as Desmodromics,reducing the valve float,

Ducati uses this to maximise ability to follow the cam,I did not expect such a

radical change with just an O ring,so what is the hot setup you are using and what does it go like,I would like to try it on my 05,TE 250,smaller valves and

differant cams,I think.

The weather here has been weird and am not sure if I have a hot set up. But going to Carnegie (a place to ride) tomorrow and hope the weather has stabilized. So far it has only been road testing.

Larger leak size. Almost midnight here and I am tired, don't remember. More after that.

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As usual very informative and useful...at 1st glance i didnt't get it, but i was just woke up...after 5 minutes everything seems clear ? :smirk:

This thing needs to be sticky....hmmmm....or maybe not , i have another idea, all these kind of articles should /could be integraded/copied in a specific order in one single sticky thread...

Not only about carb, but also DIY electric fan kits, rerouting head cover vent tube (w/filter), rerouting and applying filters and valves to carb vent lines,etc,etc....and a video about valve adjustments...guess i will have some extra work to do very soon ?

Just waiting for a valve adjustment video (hint, hint)

By hot setup I was meaning good setup,not weather related,its summer here in Sydney and we have had temps this week ranging from 19c to 40c,unless your a pro its not worth the drama allowing for this,unless your temp is close to freezing.This is great data but applying it to improve

your particular bike is the key.

Now I'm intrigued. I've read a few threads about this issue already, but I'd like to better understand why particular adjustments have such different results from one another. I've had my older deloris carburetor apart a few times and cannot find a squirt pump mechanism. It might be too old to have one, but the engine is very snappy, so I think there must be something to give the engine a squirt of fuel.

Regardless of whether or not my bike has this feature, I'm interested in learning more about tuning. I, too like low-mid range snap, but agree that it can be a little nerve-wracking until one gets used to it:eek:

I'll try to get access to high speed internet so I can watch the video clip of the mechanism working. I'm more of a visual type of guy.

It's great that you gathered all this information:worthy:

By hot setup I was meaning good setup,not weather related,its summer here in Sydney and we have had temps this week ranging from 19c to 40c,unless your a pro its not worth the drama allowing for this,unless your temp is close to freezing.This is great data but applying it to improve

your particular bike is the key.

I think he knows what you meant by hot setup, but isn't sure if it is yet, since the weather may have had an influence on the performance... ? I don't know~

Its easy to miss a point with local vernacular,better to be precise with the language,oz English and yank do Veriee a bit.

That's true. I didn't mean any disrespect, (I'm sure you knew that), I just thought I'd take a crack at figuring-out what he meant for you:thumbsup:

Yes - I have trouble with non-USA English translations sometimes.

On a cold 40F evening high humidity, and again today 45 - 55F low humidity, 500' - 3000', I liked what the bike had. Lifts up the front 1st or 2nd gear, 4000 - 5000 rpms. Either wheel lifts or tire spins, can't blame the engine if the tire spins... In addition to the added low end snap, the bike may have lost some midrange snap it is hard to tell.

As most of you know - put a smaller CS on the bike and trials tires in May, with that combination the bike lifted the front wheel way up, went right, and foot peg hit just above the ankle breaking both the tib and fib in a bunch of places - So am a little 'gun shy'. It will take a better, or at least more confident rider than I to really evaluate how well it is running.

Another TTr and I went out and rode - and he took a long ride on the TE250 and really really liked it - lots and lots of power. Unfortunately it was the first 4 stroke he rode so while his input was welcome, not sure how important it is.

38 pilot

2.5 turns out

180 main

Blue needle 4 clip position

35 leak, 1 O-Ring, AP screw = 2.25mm

10mm float height, Keihin spec is 9mm (smaller the #, higher the gas in bowl).

With that float height the bike needs to lean over to where the tip of the handle bar is over the word Shiver (kick stand side). The float height seemed to make a big difference, it was drooling before when on kickstand and less than level ground. When I leaned the bike over it was drooling when end of handle bar was above bottom of front tire or farther - at that time the float level was about 7 or 8mm.

Setting the float height, or at least measuring it seems a pain to me. Took overflow / drain tube held it up, opened the drain screw and took a picture, it was on a lift stand and bike was vertical. That just seems easier to me. That or just lean the bike over till it Drools.

This pic shows 10mm float level

Don't really think everyone should run out and re-jet to what I did since every bike seems different, ordered and received a 45 and a 55 leak jet and have yet to try those. Might be interesting if anyone has another TE250 that might need dialing in, or maybe a TE450/510 that I could make some carb measurement - squirt vs screw setting to see if those larger carbs have a similar characteristics.

If nothing else it might be nice to have someone that knows Huskys take a ride on my bike just to get a sanity check.

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At 98 years, I'm not surprised you're a little gun-shy!

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Setting the float height, or at least measuring it seems a pain to me.

You're not the only one^

You're nowhere near up-tite husky, eh? as you know, having George ride the bike might provide some answers...

You're nowhere near up-tite husky, eh? as you know, having George ride the bike might provide some answers...

He is about 5 hours away, thought about a so cal trip. Maybe After Feb when things warm up here.

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There is more ways than 1 to skin a cat,my settings are the same except a 40 idle jet,1/34 turns on the mix,the AP screw set,and the leak jet drilled to

0.75mm which is supose to be equal to a 75 leak jet,no jets avalable at the time,have to try the O ring.

coffee,

First off, impressive work. Really.

Now.... I have ask. I've seen a lot of threads on Husky carb tweaking. Does Husky have unique problem in this area? More so then other bikes? Or is this age old search for that last few HP?

stringer

coffee,

First off, impressive work. Really.

Now.... I have ask. I've seen a lot of threads on Husky carb tweaking. Does Husky have unique problem in this area? More so then other bikes? Or is this age old search for that last few HP?

stringer

Same carb as the Honda, Yamaha, and other bikes - Keihin - Search for the last bit of HP. My TE250 always ran well, started easy, never a hiccup, no bog - but under some weather conditions it just acted like a much bigger motor. Going to do a bit more work on it today.

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Coffee,

I admit I don't know this carb, but watching the video, it looks like the the cam is on the AP side of things. It's mounted on a shaft, and I'll wager the shaft is connected to something behind the wall. My question is: Is there much play in the cam to shaft, shaft to wall interfaces? if so, this could be expected to cause inconsistent behavior. And since the O-ring pre-loads the whole thing to one side, it would tend to stabilize things giving more consistent behavior.

I had a similar issue with a Holy economizer I put on my '71 Datson PU way back when. My solution was to drill and put in a brass bushing for a better fit.

I'm not suggesting you tear things down to check, but if you go back in, give it a feel and see what you think.

stringer