Aprilia Riders

[AEoM]

so are u gonna outrun glenn? haha!!!

 

Already did yesterday night

 

Anyway, my bike gets boggy at 5-6k rpm. Should I increase or decrease my main jet size?

[mesab0ogie]

Hi Mesa.... i might be wrong but from my understanding... its like eating KFC.... too rich the chicken will be oily.... if too lean the chicken will be uncooked.....

 

a lean mixture has a higher ratio of o2 and subsequently the resulting combustion generates more heat up to the point of a misfire or incomplete combustion. thus this heat generation and lack of fuel actually deteriorates the piston top resulting in seizure...... i might be wrong but this is how i understand it.... maybe the gurus around can point my mistake out as well.....

 

In simple terms, from what I understand, fuel/petrol serves 2 purposes in our engines. 1 is for combustion, and the other is for actually cooling the cylinder. A lean mixture results in all the fuel being used for combustion, none left whatso ever for cooling the cyclinder. Therefore, a lean mixture results in a very responsive bike, but it is prone to heating up. You can easily tell when a bike is running abit lean when you close throttle at higher RPMs, 10K onwards, and the bike jerks. This is because the cyclinder is starved of fuel.

 

Lawrence should be able to clarify.

 

Thanks for paying attention during class, Vik. Very good student lah you.... hahahaha

 

Now you can share with the rest of the class about carburetion and tuning also... Save me some time...

 

Yes, for 2-strokes fuel is used as a cooling agent as well as for combustion. I was running too lean before my last rejetting that my spark plug was completely clean! Which is really really bad.

 

Too lean, all fuel used for combustion, none left for cooling, everything expands beyond design engineering parameters, and BAM! Seizure.

Tolerances are tight so too much expansion is bad.

 

No amount of lubrication will save you from a lean seizure.

 

 

Ok guys, buckle up coz ur in for some serious thinking and debating.

 

Firstly, can we safely assume that in ideal and purely theoritcal conditions, a combustion at stoichiometric ratio, ie 14.7:1, would produce the greatest amount of energy, correct? So this would mean that at this ratio, the temperature released by the combustion would be highest.

 

So question 1, assuming this is true, this would mean that if more air(oxygen) is added to the mixture after it has reached stoichiometric ratio, the amount of energy released cannot increase. Which would also mean that temperatures will not rise further. In layman terms using a size 50 main jet(on a 34mm carb) should not cause temperatures to rise higher than say a 140jet(which many would agree to be too lean already based on standard tuning knowledge).

 

Bt that is purely theoretical. So moving on to practical.

 

My research has led me to many things regarding both 2-storke and 4-stroke internal combustion engines. The things i will talk about might be derived from 4-stroke engines, but if u look at the big picture, at the end of the day we are talking about internal combustion so the idea is the same.

 

One of the things i found out is by looking at EGT(exhaust gas temperature), CHT(cylinder head temperature) and lambda sensors and their relationships with one another. I could not find much in regards to 2-stroke engines. But its understandable as these instruments are used mostly in 4-stroke engines. Nonetheless, what i found out is rather baffling. Looking at some charts, it shows that indeed, a richer mixture will produce a cooler running engine. As the mixture is leaned out, the temperature rises till it reaches a peak temperature. Now is the confusing part. If the mixture is leaned further, the temperature actually falls. This peak, from what i found out, occurs at around lambda 1.1. Anything leaner than lambda 1.1 will actually cause a temperature drop. Now if the temperature actually drops after a certain amount of leanness, wouldnt this mean that going "too lean" actually not harm the engine? In fact, the temperature drop as the mixture gets leaner is greater than the temperature drop if the mixture gets richer.

 

take a look at this chart

 

Again i understand that this is not a 2-stroke engine. But again, consider that it IS an internal combustion engine. The concept/principal of the engines are different, but they must follow the same laws.

 

Do note that this is not the only example i found but i wasnt able to retrieve all the sources i found as the days off extensive googling led me to hundreds of web pages and i cant keep track of all of them.

 

Consider a blowtorch. When u turn it on and ignite the flame, the flame is orange. But back down on the gas and the flame turns blue. This as we all know is the hottest flame. Now back down on the torch more and what happens is the flame actually gets smaller, while still being blue. The smaller flame isnt as hot as the bigger flame. Shouldnt the same thing be happening in the combustion chamber?

 

Considering that only a tiny amount of fuel(a fraction of a gram) goes into the combustion chamber, and only a fraction of that is unburnt in a rich mixture, i doubt that it plays a part in absorbing the heat from the combustion, given that the surface area of the cylinder is hundreds of time larger than that of excess fuel, meaning that most of the heat will actually transfer to the engine.

 

Im in doubt that a lean mixture is the cause of engine seizure. Maybe theres something else that happens in a lean running engine that causes it to seize. Has anyone here ever seized their bikes solely because their mixture is too lean and knowing that everything else is ok, such as having enough lubrication?

Edited April 22, 2011 by mesab0ogie

[AEoM]

Chim to the maximum. FOR ME

[AEoM]

Anyway the blank keys should be arriving on Monday if my calculation is correct. For those who have not pay, kindly transfer the amt to 178-20309-6 posb savings.

 

I'll update the list tonight

[rafi92]

Tried push starting my bike today at 11am. The bike gave a weak grunt and died off.. guess i'll be leaving my bike at the carpark today :\

[AEoM]

Tried push starting my bike today at 11am. The bike gave a weak grunt and died off.. guess i'll be leaving my bike at the carpark today :\

 

Engine too cold very hard to push start bro.

[rafi92]

Engine too cold very hard to push start bro.

 

Hmm, does your bike start at the first push of the e-start on a cold engine?

[AEoM]

Hmm, does your bike start at the first push of the e-start on a cold engine?

 

I did try to push start on a cold morning before when my batt got flat last mth. I push from the highest lvl of my mscp and give up. Called tow instead.

[Feelicks]

Ok guys, buckle up coz ur in for some serious thinking and debating.

 

Firstly, can we safely assume that in ideal and purely theoritcal conditions, a combustion at stoichiometric ratio, ie 14.7:1, would produce the greatest amount of energy, correct? So this would mean that at this ratio, the temperature released by the combustion would be highest.

 

So question 1, assuming this is true, this would mean that if more air(oxygen) is added to the mixture after it has reached stoichiometric ratio, the amount of energy released cannot increase. Which would also mean that temperatures will not rise further. In layman terms using a size 50 main jet(on a 34mm carb) should not cause temperatures to rise higher than say a 140jet(which many would agree to be too lean already based on standard tuning knowledge).

 

Bt that is purely theoretical. So moving on to practical.

 

My research has led me to many things regarding both 2-storke and 4-stroke internal combustion engines. The things i will talk about might be derived from 4-stroke engines, but if u look at the big picture, at the end of the day we are talking about internal combustion so the idea is the same.

 

One of the things i found out is by looking at EGT(exhaust gas temperature), CHT(cylinder head temperature) and lambda sensors and their relationships with one another. I could not find much in regards to 2-stroke engines. But its understandable as these instruments are used mostly in 4-stroke engines. Nonetheless, what i found out is rather baffling. Looking at some charts, it shows that indeed, a richer mixture will produce a cooler running engine. As the mixture is leaned out, the temperature rises till it reaches a peak temperature. Now is the confusing part. If the mixture is leaned further, the temperature actually falls. This peak, from what i found out, occurs at around lambda 1.1. Anything leaner than lambda 1.1 will actually cause a temperature drop. Now if the temperature actually drops after a certain amount of leanness, wouldnt this mean that going "too lean" actually not harm the engine? In fact, the temperature drop as the mixture gets leaner is greater than the temperature drop if the mixture gets richer.

 

take a look at this chart

 

Again i understand that this is not a 2-stroke engine. But again, consider that it IS an internal combustion engine. The concept/principal of the engines are different, but they must follow the same laws.

 

Do note that this is not the only example i found but i wasnt able to retrieve all the sources i found as the days off extensive googling led me to hundreds of web pages and i cant keep track of all of them.

 

Consider a blowtorch. When u turn it on and ignite the flame, the flame is orange. But back down on the gas and the flame turns blue. This as we all know is the hottest flame. Now back down on the torch more and what happens is the flame actually gets smaller, while still being blue. The smaller flame isnt as hot as the bigger flame. Shouldnt the same thing be happening in the combustion chamber?

 

Considering that only a tiny amount of fuel(a fraction of a gram) goes into the combustion chamber, and only a fraction of that is unburnt in a rich mixture, i doubt that it plays a part in absorbing the heat from the combustion, given that the surface area of the cylinder is hundreds of time larger than that of excess fuel, meaning that most of the heat will actually transfer to the engine.

 

Im in doubt that a lean mixture is the cause of engine seizure. Maybe theres something else that happens in a lean running engine that causes it to seize. Has anyone here ever seized their bikes solely because their mixture is too lean and knowing that everything else is ok, such as having enough lubrication?

 

wif proper lubrication, i dun think ur engine will seize. im running on a premix setting of 1l fuel to 20ml 2t... had a clogged fuel filter in my carb 4 a time so i was running pretty lean(white spark plug tip) but very responsive.

 

however a drawback was tt everytime i opened my valve, my engine would jolt n die off (lack of fuel, high rpm, increased air flow)... but after letting e rpm settle down back to 7-8k it'll come back to life wif a twist of e throttle. checked out my piston later on wif my mech n he said it was ok, no seizure, no scratches.

 

i think tis is a gd example of how proper lubrication can save pistons n brings me back to my statement abt lesser 2t for a smaller amt of fuel into e system.

 

i agree wif lawrence's statement abt e amount of fuel in e mixture going up as one reduces e 2t amount going in. however i did'nt realise tt despite restricting e amount of charge(fuel/2t premix) going into e system via dropping jet sizes, if e 2t ratio was maintained, it would remain e same no matter how lean u go as e charge was premixed from e start n e worst fate one would suffer would be from a bike tt dies due to a lack of fuel.

 

having said tis, i feel tt its not tt a lean mixture seizes engines, its e lack of lub which kills e fun too much rubbing n things get too hot... pretty soon ur left wif a big headache lol

 

one thing im still curious abt... subzero had an accident once (no offense bro =p) where he seized his piston at track cuz he put too much 2t into his system... anyone wanna try explaining y too much lub kills?

Edited April 22, 2011 by Feelicks

[rafi92]

I did try to push start on a cold morning before when my batt got flat last mth. I push from the highest lvl of my mscp and give up. Called tow instead.

 

I see i see. Do you reckon i should get my battery replaced? Every single morning cannot e start at all.

[Mdsufie]

Wa sian, i just went to Yishun Tune In motor to change spark plug as my 2T overflow probably coz idling too long. After the mechanic change the spark plug, he rev so hard till 12000pm like no one's business sia. My bike mileage only 300km sia and still running in.. I dont think he should do that right?

[vteclee]

Wa sian, i just went to Yishun Tune In motor to change spark plug as my 2T overflow probably coz idling too long. After the mechanic change the spark plug, he rev so hard till 12000pm like no one's business sia. My bike mileage only 300km sia and still running in.. I dont think he should do that right?

 

haha lucky no cold seize.

[vteclee]

I see i see. Do you reckon i should get my battery replaced? Every single morning cannot e start at all.

 

its time to change la bro.. charging a weak battery is useless when i cant hold charge for long. if change liao no diff than u shud look into ur starter motor already.

[rafi92]

its time to change la bro.. charging a weak battery is useless when i cant hold charge for long. if change liao no diff than u shud look into ur starter motor already.

 

Okay... i'll heed your advice. Bro, do you know any workshops which are open today?

[AEoM]

Okay... i'll heed your advice. Bro, do you know any workshops which are open today?

 

Check yr fuse as well. It plays a very big part as well. The fuse is very cheap. 1 or 2 bucks will do the job.

[xxes123]

Ok guys, buckle up coz ur in for some serious thinking and debating.

 

Firstly, can we safely assume that in ideal and purely theoritcal conditions, a combustion at stoichiometric ratio, ie 14.7:1, would produce the greatest amount of energy, correct? So this would mean that at this ratio, the temperature released by the combustion would be highest.

 

So question 1, assuming this is true, this would mean that if more air(oxygen) is added to the mixture after it has reached stoichiometric ratio, the amount of energy released cannot increase. Which would also mean that temperatures will not rise further. In layman terms using a size 50 main jet(on a 34mm carb) should not cause temperatures to rise higher than say a 140jet(which many would agree to be too lean already based on standard tuning knowledge).

 

Bt that is purely theoretical. So moving on to practical.

 

My research has led me to many things regarding both 2-storke and 4-stroke internal combustion engines. The things i will talk about might be derived from 4-stroke engines, but if u look at the big picture, at the end of the day we are talking about internal combustion so the idea is the same.

 

One of the things i found out is by looking at EGT(exhaust gas temperature), CHT(cylinder head temperature) and lambda sensors and their relationships with one another. I could not find much in regards to 2-stroke engines. But its understandable as these instruments are used mostly in 4-stroke engines. Nonetheless, what i found out is rather baffling. Looking at some charts, it shows that indeed, a richer mixture will produce a cooler running engine. As the mixture is leaned out, the temperature rises till it reaches a peak temperature. Now is the confusing part. If the mixture is leaned further, the temperature actually falls. This peak, from what i found out, occurs at around lambda 1.1. Anything leaner than lambda 1.1 will actually cause a temperature drop. Now if the temperature actually drops after a certain amount of leanness, wouldnt this mean that going "too lean" actually not harm the engine? In fact, the temperature drop as the mixture gets leaner is greater than the temperature drop if the mixture gets richer.

 

take a look at this chart

 

 

 

interesting but think harder there are few major flaws in your thinking

 

Consider a blowtorch. When u turn it on and ignite the flame, the flame is orange. But back down on the gas and the flame turns blue. This as we all know is the hottest flame. Now back down on the torch more and what happens is the flame actually gets smaller, while still being blue. The smaller flame isnt as hot as the bigger flame. Shouldnt the same thing be happening in the combustion chamber?

 

If i remember correctly, the term should be Flame front and heat front. they are 2 different things inside the cylinder..

 

Lean burn engines are for 4 stroke with compression ratio usually lower than 9.1:1.. try comparing it to RS125 level..

Edited April 22, 2011 by xxes123

[rafi92]

Did my first DIY with my dad for the replacement of the battery. Unluckily it rained just after fixing the battery in so I would need to wait for awhile before heading down and starting the engine.

 

If all goes well, the bike should start with just 1 push of the e-start right?

[AEoM]

Did my first DIY with my dad for the replacement of the battery. Unluckily it rained just after fixing the battery in so I would need to wait for awhile before heading down and starting the engine.

 

If all goes well, the bike should start with just 1 push of the e-start right?

 

Yes. Check ur volt meter as well. Rev it to see if it's charging

[rafi92]

Yes. Check ur volt meter as well. Rev it to see if it's charging

 

Will do that once the damn rain stops. Thanks guys! Couldn't have done it without the endless supply of suggestions/solutions. Will keep you guys updated on how the battery turns out!

 

Cheers and have a Good Friday!

[Feelicks]

yup, as long as ur display lights up, u noe e fuses r working fine. its a new batt rite? so u shld'nt have probs starting...

[Feelicks]

Check yr fuse as well. It plays a very big part as well. The fuse is very cheap. 1 or 2 bucks will do the job.

 

bro, i think u kanna carrot already la, hardware store sell e fuse 20cents per piece lol

[rafi92]

yup, as long as ur display lights up, u noe e fuses r working fine. its a new batt rite? so u shld'nt have probs starting...

 

Yes, it's a new battery. Well keeping my fingers crossed for later on.

[AEoM]

bro, i think u kanna carrot already la, hardware store sell e fuse 20cents per piece lol

 

I prefer to go bike shop and buy. Haha!

[AEoM]

Hey guys u know the 'tongkat ali' which ah Seng sells rite? How do I fix it to my cdi? The wire looks like it's for the battery.

[mesab0ogie]

interesting but think harder there are few major flaws in your thinking

 

This is the problem. Everyones says that a lean seizure will happen. But no one can say why. All arguments i have come across so far are from experience of friends of friends or grandfather or a simple explanation like "oh the excess fuel cools the engine". Gasoline has a latent heat of vaporisation of approx 298J/g. The combustion of 1g of gasoline at stoich produces 47KJ/g of heat energy. So the logic that excess fuel "absorbs" the energy is flawed as only a small amount of energy will be "absorbed" by the excess fuel. What happens to the rest of the energy? It gets transferred to the cylinder.

 

Im nt saying i am correct or anything. i just wana know why because none of the layman logical explanation of things actually explains why a lean seizure happens.

 

Btw lean burn engines run at AFR ratios of up to 65:1. Im talking of ranges closer to that of stoich. I personally have run on a 142 main jet on a totally open pod carb and have run it at WOT. My engine did not seize up. Any bros out there who have experienced a lean seizure care to share their experiences?