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February 24th, 2008, 10:03 AM   #1
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R and D racing ajustable leak jet AP cover

Greetings all,

I had considered attaching this onto Buzzards leak jet thread http://www.husaberg.org/index.php?name= ... pic&t=6754 , but, thought it would be better for clarities' sake to make it it's own separate thread.

Brief history, I had modified my float bowl to accept leak jets, like all the japanese bikes come with. Only the KTM and Husaberg's come with that casting not drilled and tapped for leak jets. I had already switched over to Buzzards Honda jetting set up http://www.husaberg.org/index.php?name= ... pic&t=5326 , before I had modified my float bowl for the leak jets. I posted the results of this in Buzzards leak jet thread. Even with the #35 leak jet, the smallest, I was still getting a bog. So I ended up wrapping an O ring around the ap arms to get the pressure up on the ap, and that worked out good.

However, recently I was out riding and out of no where I started getting a bog when I opened the throttle quickly, like you do in a bit of a panic to get the front end back up in the sand whoops. I thought for sure the O ring had broken. But to my surprise the O ring was still in tact. The short version of this story is that I think one of two things happened, I either got a piece of debris on top of the ball check valve that is the one valve in our float bowls that let's fuel into the ap, thus letting fuel flow back into the float bowl when the ap diaphragm was compressed. Or, a piece of debris got into the ap circuit and clogged the ap nozzle in the venturi. Of these two scenario's I think the first is more likely.

In any event, I was thinking of just putting a 4mm plug into the leak jet hole and getting rid of the whole O ring business as I didn't like the idea of the rubber band breaking at a really bad time.

However, I came across this web site and product: http://www.r1dean.com/cart/index.php?ma ... ducts_id=4
What intrigued me first was the spring that he sold, that took the place of the O ring, and initially was only interested in that part. I gave the place a call and spoke with the owner, a very nice man, and he was very forth coming with information and intelligent questions about my situation. After sleeping on it I decided to buy the power pump with the adjustable leak jet, the spring I was looking at before comes as part of the kit.

It was pretty easy to install http://www.r1dean.com/support.html, click on the power pump tab at the top of the page, and, this kit coverts the ap to the newer FCR style ball check valve that is located in the ap cover itself. This is supposed to keep air from getting into the ap chamber.

One thing that is nice about the power pump is that A-it's less than half the price of the power bowl, and B-it goes down to full cut off of the leak jet circuit, where as the power bowl, at least as advertised only goes down to a #35 leak jet.

So far I have only been able to check out it's operation on the stand, and it does work, you can dial in a bog, and dial it back out again. I will post later on real world testing as I go.
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February 24th, 2008, 03:01 PM   #2
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Great post Dale, I'm looking forward to your ride report!

Joe
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February 24th, 2008, 08:04 PM   #3
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DaleEO
what I have found out RE. Buzzards mod, if your accel rod pump start squirting before
5-6mm throttle opening and it don't matter what needle you are running a bog will happen
and it just get worse with altitude and it was the same on my 04 450 as my 07 450
just adjust accel pump rod to start squirting at 5-6 mm throttle opening
the honda accel pump diafram defiantly increases fuel economy by 10 miles per tank
in the tight woods
165MJ
40PLJ
Lineaweaver needle
emulsifying needle jet

happy trails VIKING
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February 24th, 2008, 08:57 PM   #4
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Originally Posted by VIKING
DaleEO
what I have found out RE. Buzzards mod, if your accel rod pump start squirting before
5-6mm throttle opening and it don't matter what needle you are running a bog will happen
and it just get worse with altitude and it was the same on my 04 450 as my 07 450
just adjust accel pump rod to start squirting at 5-6 mm throttle opening
the honda accel pump diafram defiantly increases fuel economy by 10 miles per tank
in the tight woods
165MJ
40PLJ
Lineaweaver needle
emulsifying needle jet

happy trails VIKING
So Viking,

You are saying that the slide should be open 5-6mm before the ap starts adding fuel or a bog will occur?

Does that mean that the ap squirt will then not hit the back of the slide and go straight into the venturi?

Just for your info and not contradicting you, Eric's mechanic Brett, had suggested to me to set the slide opening at 1.25mm for the ap start timing for the bigger motors, and 1.0mm slide opening for the smaller motors, 250XF.

I have set my ap gap @ .115", (that's 1/2 turn clockwise from stock setting which is .100"), don't know how that relates to the distance the slide is open and when the squirt starts. However, I did this to lessen the rich stutter, and it did delay the onset. The problem is that if you delay the start of squirt much further than this, you will get a lean bog when the engine temps are down, or elevations are lower. The only way to compensate would be to raise the needle, and I fear that would make it rich in the mid range.

I am hopeful that with the adjustable leak jet, and the stronger ap spring (stronger squirt when throttle opened quickly), I might be able to delay the ap timing a bit more, and then be able to tune the bleed off as necessary, and maintain a good mix in regards to the needle postion. I did not have these options in play the last time I was testing ap gap settings, so we'll have to wait and see.

Thanks a lot for your input, I'll keep this in mind when I'm doing my testing and will let you all know of my results.

Dale
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February 25th, 2008, 09:25 AM   #5
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DaleEO
well it was a few tests to concluded this, to prove to my self that bog was caused by the
AP I disconnected AP, now I had a bog different from previous bog it was consistant at the same throttle opening (8-8,5mm) and altitude had no influence where as with the AP connected the severity of the bog got worse as you gained altitude
and no needle,ABJ or PJ could cure this bog with or without AP
so I was confident that AP was culprit so now it matter of adjusting AP to where it starts
to squirt before the bog (without AP) so the best adjustment was 5-6mm
if you adjusted AP 7-7,5 mm bog would return at low elevation and on cold days and it
improve with elevation
if you adjusted AP 3-4mm bog would return on a hot day and get worse with elevation
how this would work on a ktm 250 sxf I don't know but I can says this that my friends
honda 250x liked similar adjustments
I simply open up the slide and insert a drill bit then close the slide then adjust AP to zero
play
the stock needle root dia. is too large making the eng. run lean it have a nervous feel
to it at small throttle openings going with Buzzards mod cures that

VIKING
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February 25th, 2008, 02:58 PM   #6
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Originally Posted by VIKING
DaleEO
well it was a few tests to concluded this, to prove to my self that bog was caused by the
AP I disconnected AP, now I had a bog different from previous bog it was consistant at the same throttle opening (8-8,5mm) and altitude had no influence where as with the AP connected the severity of the bog got worse as you gained altitude
and no needle,ABJ or PJ could cure this bog with or without AP
so I was confident that AP was culprit so now it matter of adjusting AP to where it starts
to squirt before the bog (without AP) so the best adjustment was 5-6mm
if you adjusted AP 7-7,5 mm bog would return at low elevation and on cold days and it
improve with elevation
if you adjusted AP 3-4mm bog would return on a hot day and get worse with elevation
how this would work on a ktm 250 sxf I don't know but I can says this that my friends
honda 250x liked similar adjustments
I simply open up the slide and insert a drill bit then close the slide then adjust AP to zero
play
the stock needle root dia. is too large making the eng. run lean it have a nervous feel
to it at small throttle openings going with Buzzards mod cures that

VIKING


I have a question.

What is the gap on the ap linkage that you are running with this ap timing based on the slide opening of 5-6mm? Knowing this would give a good ball park figure, and negate having to remove the carb.
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February 25th, 2008, 06:08 PM   #7
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DaleEO
no need to remove carb, remove tank, loosen clamps so that you can rotate carb remove cover for throttle wheel , remove air filter open throttle with a pair of pliers insert drill bit betwen carb body and slide release throttle gently so that slide rest on drill bit now adjust AP adjusting screw, screw the clockwise untill there is play AP linkage then counter clockwise until play in linkage is gone 15 min job let me know how it works

Per
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February 25th, 2008, 06:12 PM   #8
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On my 06 KTM 450 with a 39 FCR, it runs crisp with a JD RED needle in the 5th groove. Measuring the needle with a micrometer at 10MM increments, this needle is a bit richer than stock under half throttle and a bit leaner at 3/4. Fuel screw at 1.5 turns. Main reduced from 178 to 170. Surging and overheating at part throttle eliminated. Stutter bumps caused a rich bog. I installed a Honda accerator pump which has shorter movement for a shorter spray. Eliminated the rich stutter/bog through whoops. AP gap .100. KTM carbs aren't drilled for a leak jet. Slight lean hesitation remained during snap tests. Finally, added the little trick JD suggests to wrap an oring around the AP linkage to strengthen the initial squirt by increasing spring pressure. Snap bog gone. 6 months later, and jetting still spot on and starts instantly. 60 miles is the norm from a bit over 2 gallons. Took the better part of a day to dial it in but worth the effort. A bit different than some other suggestions, but hopefully helpful.
Dan
edited to add that stock needle was an OCDVR. Stock pilot still in use which is a 42.
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February 25th, 2008, 08:09 PM   #9
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Thanks Per and Dan,

I appreciate your contributions, and Per, that sounds easy enough. Unfortunately I won't be able to do much testing other than fiddling with the adjustable leak jet for a few weeks at least. I have my work weekend next weekend for our race, and the following weekend is our race weekend. So not too much time to mess about.

I will post on what adjustments I can make, and persue the other suggestions as soon as possible.

Dan, I tried the JD kit. And just about as you have yours set up, including the O ring. It makes good clean power. I had also installed the 65 leak jet with the kit he sent me. Like I said, good clean power. However, I found that with testing the Honda style jetting, including the HDJ emulsion tube back to back with the JD kit, the Honda stuff is quite a bit different, the Honda jetting set up is a lot more responsive. Don't get me wrong, I'm not knocking the JD set up at all it works great. Thanks again for your suggestions, all are welcome. Never can have too much information!!

Dale
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February 26th, 2008, 08:24 AM   #10
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I'd have to agree that my setup is very crisp yet smooth. Not as responsive as some people would like. Am always riding in hard pack with loose rocks on top and the smoothness is a blessing. Runs similar to my 03 501. Plus, I'm an old guy.
dan
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