Aprilia Riders

[priller07]

Nice one der, Bro Vik.. I wonder y u Aprilians can oso hav conflicts wif 1 another. I tot dat the whole lot of u all r so called united? But sometimes certain ppl nid to fine tune their speech b4 hurting other ppl. Right bro.... Well Long Live Aprilias.............

 

Actually it all depends on individual. If everyone was friendly and treats people nice, the world would be a wonderful place to live in. People treat u good, of course u'll return the same kindness. But if people treat u bad, not all people have the patience to still keep a smiling face and hold back their frustrations.

 

Just my perception. No offence anyone.

[shadantou]

Nice one der, Bro Vik.. I wonder y u Aprilians can oso hav conflicts wif 1 another. I tot dat the whole lot of u all r so called united? But sometimes certain ppl nid to fine tune their speech b4 hurting other ppl. Right bro.... Well Long Live Aprilias.............

 

 

lol. jenggoz. come for outing next time. we are united la. and we are friendly chaps. hehehe. u not in the same wavelength thats why i think u misunderstand me.

 

but in response to ur post, i wun fine tune my speech to ppl who try to hurt us aprilians. and mess around with my dear aprilians. they deserve this kind of "bashings" from me. and there is this need to lower down their big ego, stupid pride, and also senseless thinking about supporting a shop that shouldnt have existed in the first place.

 

i know everyone has their own thinking and everything, but i can dare to say, if we were to cast a vote, everyone would support the crazy chung of what he said. hehehe.

[jenggoz11]

Me still observing u guyz b4 I cum down 4 yor kopi sessions. In fact ders nobody trying to hurt yor Aprilians but its juz dat certain things dat oredy exists b4 you came in the picture dat u cant do anything abt it. 4 eg. abt dat shop u r refering to. Juz let it be. Be cool... As long as Ah Seng is still alive, yor bikes will be taken cared. But still it depends on the owner how dey take care of their bike.

Niwei no offence yeah.. Me juz stating facts to you. Datz all.. I heard dat you guyz r active in yor nite outings. Can I join in n hopefully to get to know all of the Aprilians...

[tomdick12]

happened to me too. Just need to let it warm up longer and it will be okay

 

Hey guys, ive bought my bike =) thanks for the viewings Vik. Anyway i just wanted to ask, how come when i kick down to first gear from stationary, my engine will cut off? i warmed it up properly in neutral also. so everytime i change to first gear i got to restart the engine. this only happens in the mornings when i first start the bike

[jenggoz11]

Hey guys, ive bought my bike =) thanks for the viewings Vik. Anyway i just wanted to ask, how come when i kick down to first gear from stationary, my engine will cut off? i warmed it up properly in neutral also. so everytime i change to first gear i got to restart the engine. this only happens in the mornings when i first start the bike

 

Congratz... 1st of all check out for the side stand is oredy up n not in parking condition. It has a safety relay to cut off de engine if the side stand is still on.2ndly from wat I know frm sum riders, dey hav the same poblem to their bike. Wat de do n teach me is wen u 1st start yor engine, throttle to 4000rpm n stay put for abt a few seconds n let it idle for awhile. U try n c k....

[Ahjin]

Hey guys, ive bought my bike =) thanks for the viewings Vik. Anyway i just wanted to ask, how come when i kick down to first gear from stationary, my engine will cut off? i warmed it up properly in neutral also. so everytime i change to first gear i got to restart the engine. this only happens in the mornings when i first start the bike

 

i hav that problem. seng told me it could be gear oil.

[arsenal2006]

is it true tt 1st hand bikes the shop is suppose to give the bike cover(the grey colour cover to close the bike), helmet, headgear, raincoat and stuffs??

koz my fren said so..sorry if he was wrong.

just curious to noe..wad r the things im suppose to ask b4 i take the bike out.??

 

and the motorworld is at where ah?

ps not sure yet..

[priller07]

i hav that problem. seng told me it could be gear oil.

 

Someone told me could also be worn clutch plates.

[quikslvr]

is it true tt 1st hand bikes the shop is suppose to give the bike cover(the grey colour cover to close the bike), helmet, headgear, raincoat and stuffs??

koz my fren said so..sorry if he was wrong.

just curious to noe..wad r the things im suppose to ask b4 i take the bike out.??

 

and the motorworld is at where ah?

ps not sure yet..

 

 

bullshit la your friend.not all will get that much.i only got FF helmet when i took out my bike last time.

 

motoworld is at kaki bukit.

[lacrimosae]

Explanation of the Dellorto Carburetor VHSB34.

 

The basic operating systems of the VHSB34 are:

1. Venturi & airflow control

2. Idle circuit & progression

3. Main circuit

 

The Venturi and Airflow Control

 

The venturi is a key feature in the design of the carburetor. (36 to 40 mm is preferred for 125cc high performance engines). Since the venturi diameter (in relation to the air intake diameter) determines the resistance to the aspirated flow the larger diameter is preferred because the high performance engine operates at wide open throttle (WOT) much of the time. For this reason inserts are used inside the venturi section to eliminate steps and shape variations while maintaining the diameter value. The power loss introduced by the carburetor then depends on the diameter and shape of its venturi in the direction of the airflow. A ‘full house’ bike racing carb has a round venturi section for minimum resistance to airflow.

 

The VHSB model used in most kart applications has a extended round or oval section to provide better throttle response. Because a smaller diameter venturi improves engine responsiveness the oval section ( by keeping velocity high ) has a reduced diameter when the throttle is lifted slightly creating a higher vacuum for better throttle response from partial to WOT but yet the over all intake area is large.

 

The air flow control or throttle valve system on the VHSB model is referred to as a plane or guillotine ‘flat slide’. A design feature of the flat slide is the ‘driving flyers’ referring to the flat, smooth, plated surface of the downstream side of the valve to reduce air leakage. The flat slide (as opposed to a round slide) also reduces air turbulence under the slide to a minimum.

 

The Idle Circuit and the Progression

 

The primary components:

1. needle - fuel metering component

2. atomizer or needle jet - fuel metering component

3. float chamber - chamber or bowl for adequate fuel supply for the operating range of engine

4. floats - operate the needle & seat to keep incoming fuel at the proper level

5. needle valve - needle & seat component for controlling fuel supply to carburetor

6. main jet - meter full power & WOT fuel mixture

7. idle jet - meter emulsified fuel/air mixture for idle & assist in the transition

 

The principle of operation of the idle circuit is: the fuel in the float chamber responds to the vacuum signal generated by the induction action from the engine.

 

The Idle Circuit is active when the throttle valve is closed. The inducted air flow which draws on the main spray nozzle is very low and not sufficient enough to draw fuel from the float chamber. Because of this the idle circuit is designed into the carburetor which allows the engine to continue running at closed throttle. The circuit also aids in the transition from idle to open throttle.

 

The port in the idle circuit is positioned downstream of the throttle valve at a location that when the valve is closed a strong vacuum condition can supply fuel from the float chamber to the engine. The duct from the idle port leads to the idle jet which can be calibrated for fuel flow. The air required to be mixed with the fuel for idle operation (closed throttle) is provided through a passage (in the carb body) upstream of the throttle valve, bypassing the main air induction system and exiting downstream of the throttle above the idle jet.

The idle air channel supplies the air to be mixed with the fuel for idle operation (closed throttle). It is located in the carburetor body upstream of the throttle valve, bypassing the main air induction system and exiting downstream of the throttle above the idle jet. The idle jet selection is important not only for idle operation but also for engine response during the transition to open throttle operation.

 

Tuning the Idle System

 

Idle jet selection - if the idle jet selected is too large, the engine tends to stall and responds slowly to the accelerator. If the jet is too small the engine RPM does not decrease immediately when the throttle is closed. Changes to the mixture can also be made by turning the idle air screw in or out (in - less air, out more air).

Note that an idle jet that is too small on a two stoke engine can risk piston seizure during throttle closing especially after long periods of WOT.

As stated above, in the emulsion air circuit the fuel supplied by the idle circuit is mixed with a small amount of air by means of a diffuser that flows into the fuel passage from the idle air channel. From that point the passage leads to the progression port located directly upstream of the rear edge of the throttle valve but before the idle port located downstream of the closed throttle.

 

At idle a small amount of air is inducted by the idle port and bypasses the closed throttle valve and mixes with fuel supplied by the jet. As the throttle valve lifts the idle circuit air/fuel mixture decreases and the progression port begins to supply emulsified fuel. The air now comes from the main air intake. The progression port (circuit) is important to the system because of the increased amount of mixture required by the engine as the throttle leaves the closed position.

The transition circuit is activated when the driver begins to open the throttle and the vacuum decreases in the idle circuit. The mixture from the idle circuit decreases and it is necessary to introduce another circuit which can supply the fuel required for the transition from idle to the main circuit. This is called the progression.

At about ¼ throttle the vacuum begins to become constant and stops drawing the mixture from the idle port. At this point the vacuum is sufficient to draw fuel from the progression port fed by the idle jet in the float chamber.

 

The sequence for the progression is:

1. air at closed throttle travels toward the idle circuit jet

2. as the throttle valve begins to come off the idle position the emulsified air/fuel mixture reverses direction (upstream) to the progression port but coming from the idle circuit within the float chamber

 

This describes the importance of the idle jet even in the first stages of throttle valve opening and also the position of the progression port between the main and idle nozzles.

 

The Main Circuit

 

The primary components are:

1. atomizer - a tube that connects the main jet to the venturi

2. needle - the tapered metering rod that moves inside the atomizer attached to the throttle valve

3. main jet - the basic element of the carburetor’s adjustment controlling the calibration of mixture from the main system

 

The carburetor is described as a needle type because of the mechanical configuration of the main mixture delivery system. The tapered needle assures the correct mixture ratio for all operating conditions from ¼ to WOT.

 

The Tapered metering rod or needle is designed specifically to meter fuel in the correct amount for the continuously changing vacuum signal as the throttle valve moves from ¼ to WOT. Vacuum at closed throttle is generally greater than at partial or full openings. The mixture delivery from the nozzle of the main circuit must change proportionately.

By responding to vacuum only, the mixture supply would be excessive at small throttle openings and inadequate at large openings. The tapered needle solves this inadequacy. At low vacuum openings the mixture flow is increased and conversely at high vacuum openings the flow is reduced as the needle controlled by the throttle (driver) moves from closed to open positions through the metering section of the atomizer.

 

The atomizer is described as a tube connecting the main jet to the venturi and is screwed in to a delivery nozzle mounted in the venturi. The important feature of the atomizer is the calibrated inside diameter. This passage works with the tapered needle as described above to provide the correct mixture at all throttle openings from ¼ to WOT.

The main jet is the basic element of the carburetor’s full power and WOT throttle adjustment. It is mounted in the lowest part of the float chamber to ensure constant fuel supply. The main jet is normally chosen experimentally and the procedure is to start with a large jet working down to the proper size by testing an checking spark plug color.

At this point it should be mentioned that Dell’Orto recommends doing simple calculations to ensure that the passage area of the main jet doesn’t become smaller than the annulus created by the tip of the conical needle inside the atomizer. The main jet is always in control of the fuel supply - for instance when the driver suddenly opens the throttle the main circuit must start working quickly. The fuel that feeds the system is calibrated by the main jet. At this moment ‘lean peak’ occurs or in other words the system goes lean for a moment and then returns to the optimal value required for engine operation.

 

Tuning the Main Circuit

 

Main jet - select the correct main jet by testing, using spark plug color as a guide. Remember that the jet number is in hundredths of a mm. I.E. - 168 = 1.68mm. Select the needle based

on testing to work with the atomizer. Or select the atomizer to work with needle for maximum performance only changing one component at a time. Note: charts are available listing the various needles with all the required dimensions & profiles.

 

In summary the evaluation of the Dell’Orto carburetor is a very worthwhile effort for those who seek to understand the design features and operating principles of the carburetor as it relates to maximum performance for the shifter kart power plant. The original market for the VHSB and other models is for competition motorcycles. The units for kart application are modified by Dell’Orto by substituting the correct needle valve to control the fuel supplied by a fuel pump rather than a gravity system.

 

The target for all carburetor designers is a unit that provides the correct air/fuel ratio for combustion - shown as A/F = Mair / Mfuel. If this ratio is considered from a chemical point of view the value of the stoichiometric (chemical reaction) A/F ratio is the one that allows complete combustion without leaving excess air (lean) or unburned fuel (rich).

Computer controlled injection systems no doubt can hit closer to the target but an in depth look at the Dell"Orto carburetor can give the serious tuner a new tool for getting the max out of their shifter engine.

 

In summary, the key to performance is understanding the basic design concepts of the carburetor as:

* Controlling the power delivered by the engine - the flat slide throttle valve reduces turbulence in the venturi during acceleration and wide open throttle operation. It’s design provides the seal to prevent air leakage

* Metering the fuel flow into the air stream and providing the optimum air / fuel ratio over the entire operating range - the idle circuit that also assists in the smooth transition from idle to full power and the needle calibrating system for metering the optimum air / fuel ratio from ¼ to wide open throttle openings.

* The homogenization of the air and fuel mixture to make the ignition and combustion proceed properly - The emulsion action of the idle circuit for correct idle and transition and the specially designed venturi to create the finely atomized spray required for complete combustion.

Edited November 20, 2009 by lacrimosae

[Sub Zero]

Nice one der, Bro Vik.. I wonder y u Aprilians can oso hav conflicts wif 1 another. I tot dat the whole lot of u all r so called united? But sometimes certain ppl nid to fine tune their speech b4 hurting other ppl. Right bro.... Well Long Live Aprilias.............

 

You must really been reading this forum or you must know me to know me by name.

 

I have no issues with anyone. Unless they have an issue with me. Or my friends. Then I am sorry to say I am ruthless as hell.

 

You have to come with us, then you'll know about our inside jokes. They are probably meaningless to someone who has yet to meet us.

 

Please join us soon. I dont bite.

[lacrimosae]

For those of you interested to tune your carb, here is a sample of my tuning chart.

 

Keep experimenting until you get the perfect burn! There are 10 variables in the Dellorto VHSB. Good luck!

 

Glossary of Terms Used:

 

Idle A - Idle Adjuster Screw

Air S - Air Screw

Chk - Choke Jet

Idle - Idle Jet

Idle E - Idle Emulsion

Atom - Atomizer

Ndl C - Needle Clip Position

Ndl T - Needle Type

Thr Sl - Throttle Slide

Main - Main Jet

WOT - Wide Open Thorttle

Tuning Chart.pdf

[IZECUBEZ]

Bleah! I better remove the idle jet 75. Spark Plug wet all the while (when installed). Gonna go for a haircut then settle the carb.. :|

[arsenal2006]

bullshit la your friend.not all will get that much.i only got FF helmet when i took out my bike last time.

 

motoworld is at kaki bukit.

 

ohh..opssii.

ps abang..hmmm

so i should ask for it or wad?ps ah..i too curious to noe..

[quikslvr]

ohh..opssii.

ps abang..hmmm

so i should ask for it or wad?ps ah..i too curious to noe..

 

u arsenal fan?? wont help u unless u change ur allegiance to Manchester United

[Ahjin]

Bleah! I better remove the idle jet 75. Spark Plug wet all the while (when installed). Gonna go for a haircut then settle the carb.. :|

 

hey bro, can u get back with me when u see this post! urgent, tyvm!

[shinya]

Wah....seems lots drama went on the last few days.....

 

Maybe i shouldn't miss this week's jalan kayu outing?

 

Dun have chance to know the 1:47 master arrrrr......T____T

 

Anyway, any outing plan tonight?

 

So boring this week lah

[Sorrie4u]

yea man utd rocks!

[shinya]

Why so quite ar tonight? Everyone go outing?

 

Sigh~ i am so boring at home T__T

 

Btw, this sunday anyone wanna participate PG trackday?

 

Or anyone know the 1:47 whoknowwherehecomefrom ghost rider will hit the track?

 

Think if i can find some aprilian company there or learn something from the master? Hehehe~~

[Ricky Diablo]

guys nid ur advice...juz nw i changed my gearoil n to my horror during the draining the colour of the used gearoil is milky like teh tarik...juz changed last 2 mths...wat could be the cause of it? the mech told me due to rain maybe the rain water go in or maybe there;s leakage at my coolant..if ders any info regarding ths pls get back to me..thx...

[lacrimosae]

guys nid ur advice...juz nw i changed my gearoil n to my horror during the draining the colour of the used gearoil is milky like teh tarik...juz changed last 2 mths...wat could be the cause of it? the mech told me due to rain maybe the rain water go in or maybe there;s leakage at my coolant..if ders any info regarding ths pls get back to me..thx...

 

Milky gear oil could be caused by coolant leaking into clutch case.

[Ricky Diablo]

Milky gear oil could be caused by coolant leaking into clutch case.

 

thx bro for the useful info...

[abbey.smith]

my friend is looking for an rs250 anyone got lobang?

[stevoo]

Why so quite ar tonight? Everyone go outing?

 

Sigh~ i am so boring at home T__T

 

Btw, this sunday anyone wanna participate PG trackday?

 

Or anyone know the 1:47 whoknowwherehecomefrom ghost rider will hit the track?

 

Think if i can find some aprilian company there or learn something from the master? Hehehe~~

 

 

 

You really 'ON' man...

two track days in a month !!

 

Seriously...1.47?

rs125 can do 1.47?

[shinya]

You really 'ON' man...

two track days in a month !!

 

Seriously...1.47?

rs125 can do 1.47?

 

Hahahaz....just change a new rear spoket, wanna try if it helps at T2, T4 and T5:angel:

 

1:47....not sure. But from the history lessions, 2T125/250 can do below 1:50 seems not a big deal. I really want to know what we are lacking now, track grip? (maybe drop, but i still can not reach the limit of tyre/track surface) racing line got some short cuts? or just our skill sucks and dun have big balls:dozed:

 

Anyway, hopes the good weather taking care of us at the weekend then i don't mind the strange raining pattern at weekdays.