Bogging - accelerator pump – spray angle

[UK450R]

I have the common problem with bogging under heavy acceleration with my ‘06’ 450R. I tried the ‘quickshot’ and it did nothing to improve the problem, so after a bit of research on this forum I turned to the accelerator pump timing – however despite many hours of adjustment and testing I can’t get ride of this annoying hesitation under power.

My question is about the ‘angle’ and duration at which the accelerator pump squirts fuel into the chamber of the carb. People talk about adjusting the timing so that it ‘just misses’ the slide – but mine fires way too low to ever hit the slide, no matter how it is adjusted (i.e. it squirts fuel almost horizontally along the bottom of the chamber, rather than upwards towards the slide). Should it be like this?

Also people talk about spray duration of 1-2 seconds, my probably only last about half of this – again could this be a problem?

Any help gratefully received

[Jonas]

I am assuming when you say "bogging under heavy acceleration" you mean when you 'snap' the throttle?? What mods do you have? I have ridden about six or so of the '06's and didn't notice anything while I was ridding hard. When I heard of people having problems with this I went out and tried to duplicate it by snapping my throttle as fast as I could and I did get mine to bog down a little. I guess I just have a certain style of riding and don't turn the throttle significantly faster than the motor will even be able to produce power from. When you smoothly engage the throttle does it bog? I am just trying to get a feel if yours is any different than mine because I have no issues when riding mine with the way I ride.

[UK450R]

Engine Mods:

HRC kit: card settings as HRC instruction, although with a 182 main (to match pipe)
EHS air box lid
Akrapovic pipe (http://www.akrapovic-ai.si European make with you may not have herd of, but basically the same as most aftermarket pipes)

Riding style:

Yes I probably ‘snap’ the throttle – I race XC and with a thumb throttle rather than twist – so the riding style is always likely to be a little more ‘on/off the power’ rather than a ‘smooth maintaince of high revs’ MX style.

But this is not something that you can simply put down to adjusting my riding style – I’m sure that even the smoothest of riders with a twist throttle, on an open/fast MX course would still notice a hesitation at present with this bike.

[duke416ex]

I would look at the main jet. My brother had an 05 with a Rossier Exhaust that took a 185 jet. Now with an 06 and full Rossier they are suggesing a 162 jet I believe. He tried a 180 and it is flooding the bike out. He has the Boyseen Quickshot, and also changed all the other jets in the carb trying to get rid of his hesitation. I thkn he has taken care of most of it, but I am unsure of what jets he is using now. I would try a smalle rmain and see what that does.

[Nick110]

I would put a 162-168 main jet, 48 pilot jet, and a 55 leak jet. The leak jet should get rid of the bog/hesitation.

[eagertorace]

Originally posted by Nick110
I would put a 162-168 main jet, 48 pilot jet, and a 55 leak jet. The leak jet should get rid of the bog/hesitation.

^^^^^^^
DO WHAT HE SAID

[Jonas]

He's got a 55 leak jet if he has the HRC kit. Like they said, you must be too rich on the main with the mods you have. More tuning should help. Do you have access to a dyno?

[UK450R]

Thanks for your replies

I have not tried a smaller main – simply because everyone else I know who running a similar set up is on a 183 and are not having any problems

The plug does not suggest that it is rich – although for the small amount of effort it takes to change the main I will obviously give it a go

No I don’t have access to a dyno (at least not near by) – I’m doing everything by the ‘seat of my pants’

If anyone has had a look at their accelerator pump spray angel/duration etc, please let me know how yours looks

[leadfoot_52]

I have an 06 with the HRC kit and I have a 42 pilot, 4th clip down on the needle, and a 172 main and it runs perfectly with no hesitation. I think you need to mess with your needle, and your main jet is too big.

[Nick110]

Ok sorry if i hijack the thread but when it says 4th clip on the needle does it mean 4th down from the top or 4th up from the botton.

[E.POWERSPORTS]

Down from top.

[QuadRacer041]

Originally posted by leadfoot_52
I have an 06 with the HRC kit and I have a 42 pilot, 4th clip down on the needle, and a 172 main and it runs perfectly with no hesitation. I think you need to mess with your needle, and your main jet is too big.

i agree try making the needle richer and the main smaller

[UK450R]

Well I’m pretty confident I have my bogging licked

It was not one single issue – but a combination of factors

1) yes I’m now on a smaller main (170)
2) yes I also lifted the needle up to clip #4

However ….

3) I think the main issue was still the accelerator pump timing, I have it now screwed in by probably 3-4 turns above the HRC settings (to do this I have had to remove orginal spring which sits behind the screw and replace it with a softer coil spring which allows for more adjustment)

I spent most of Sunday on a test track going through things until I got to the bottom of the problem, and although the main and needle certainly helped, adjustment of the accelerator pump was still needed to total eliminate the problem.

Thanks for all your suggestions

PS - I’m in the UK and our petrol is 97 octanes over here – so any small differences in jetting may be down to this.

[chad502ex]

there are lean bogs and rich bogs.

i had a lean bog once with my fcr when i went WOT and the engine instantly went lean with all the air and little accelerator pump fuel squirt.

When i changed the accelerator leak jet down to #35 all was a bit better and the lean bog disappeared. An accel. pump leak down jet is used to control the amount of fuel that the accel pump pushes, or returns, back to the float bowl. The bigger the accel. leak jet the more the fuel is pushed back to the bowl and the smaller the squirt. If a smaller leak jet is used the accel squirt seems to go on forever,...