thanks for the advise, i have already readjust the fuel screw. i added more than 3.5 turns. i think it is 3 and 3/4 turns or more. but not more than 4 turns. throttle response on low RPM seems good. but i need to ride the bike at higher RPM to know the results on higher RPM response.

pijuthanks for the patience.

Brand Duro

Model maybe is DM1198

website: www.duro.com.tw

Cant find the RS

Anyway, ban this tire for me....

This post has been edited by NewGUY: May 16 2014, 10:02 AM

yeah. thanks to you too my brother.
now i readjust the fuel screw again. i set the idle screw until i hear high revving and after the adjustments on fuel screw, i reset the idle screw now back to normal. maybe on 1200-1500 RPM i think, i dont have a takometer to measure the RPM. throttle response quite good on lower and higher RPM. my bike is energetic same as the fuel screw on 5 turns out position. i dont have problems starting my bike either it's in cold or hot temperature. morning starts never had problems. i'm not sure either my setting now is rich or lean. let me bring along a screwdriver with me when i ride the bike tomorrow. if i feel any bog or hesitant either on lower or higher RPM, i will adjust it by opening more or closing back the fuel screw. i will keep you posted about the results later.

thianzthanks for sharing bro. I'll go town and look for this tyre and take pics...

i still using 70/90 on rear, the sisik like maxxis but the center line i straight, maxxis is like snake not straight....

i notice also Michelin Tires are very expensive also, I heard the shop quoted 80/90 for 115, 90/80 for 135...

RM 135 can get R13/70H tire for car for cheap brand...

For my record change 6 pcs of tires already...

1) Duro 100/80
2) Comet 90/90
3) Duro Thailand 80/90
4) Used Battlelax 90/80
5) Duro Taiwan 70/90
6) Duro Taiwan 80/90

Tires 1 to 3, get to use to above 10 000 km which should be over safety limit guide but no feel of shaking or feel like tire puncture

80/90 was change almost 9 000 km bcos of the feeling

now 70/90 put at front at 137 km /h GPS like shake liao, no confident to go more...

now 70/90 put at back at 129 to 134 km/h GPS start vibrate or shake....

Tire still got about 50% to safety limit guide.....

Hope finish it soon....

alexei, your km/l seems to be higher but petrol for full tank+2T full tank would cost more....so km/sen will be higher, mind to share that...

Since naik harga, more reasons not to use Michelin liao.
My RGV fuelly:

2T around 1L per 1000km, RM20 each botol.

alexei

i think i know what is the biggest problem tuning mikuni bs25 carburetor. it is because of the low restriction air filter. i think i solved the problem by reinstall the stock paper air filter and retune the fuel screw until i hear maximum RPM.

if i still want to use the low restriction air filter, i think i need to rejetting the carburetor to compensate the air. as i know, the perfect combustion will need 14.7 air and 1 fuel. means 14.7:1. if we allow more air to enter the combustion chamber, then we need to allow more fuel by rejetting the carburetor. this is critical on higher RPM but not critical on idle and low RPM.

if we allow more air and more fuel, means we are dropping the fuel efficiency. we still dont know either the combustion chamber can handle the burning or not. if it can handle, then we will get more power. if it dont, means no perfect combustion then we will have fuel efficiency drop and the side effect is our piston maybe dirtier than before.

am i right bro alexei ?

This post has been edited by piju: May 17 2014, 06:31 PM

I think someone mentioned BS25 carb needs some restriction at the intake, with the high flow air filter, quite a lot needs to be done.
Basically, without the intake restriction, the carb would lose the required vacuum to open. That means, it will never reach max throttle opening.

To rejet, is critical for all rev range, not just high RPM.

In real case, for the same engine, improved air flow will produce more power and smoothen torque curve.
It is about making it easier to drive, and when that happens, sometimes it actually improves FC.

About the carbon deposit, I think it is inevitable.

ok bro alexei maybe i need to do a lot with mikuni bs25 if i want to use it with high flow air filter. or else, change the mikuni bs25 with the vm22 carburetor. now i know why people change their yamaha lc v2 carb to v1 carb. it should be carb first, then the air filter change.

for EFI systems, or normal type carburetors, i believe that using high flow air filter will improve their torque and HP. maybe not for vacuum operated carburetors like mikuni bs25.

the yamaha v1 carburetor which is mikuni vm22 operates differently from mikuni bs25. for the vm22, throttle controls the needle jet. so if we twist the throttle from close to maximum opening, you will force the engine revving from low to high RPM.

for mikuni bs25, throttle controls the butterfly valve. not needle jet. if we twist the throttle from close to maximum, it only allows more vacuum pressure to the rubber diaphram for liftting the needle jet. we cant force the engine revving to the max, it will do by itself, slowly.

if we install high flow air filters on mikuni bs25, i think it will reduce the vacuum pressure and slowing down movements of the rubber diaphragm and it also will never reach the maximum needle jet opening like you already said.

now i see why yamaha created bottleneck for air to enter the yamaha lc v2 air filter box. to create high pressure for lifting the rubber diaphragm.

what say you alexei ?

This post has been edited by piju: May 17 2014, 07:45 PM

pijuIf use high flow filter on BS25 carb, it actually 'restricts' the throttle. So, it doesn't improve performance. Unless if the engine is modified to demand more air through the carb, then perhaps it can make a difference.
Honestly, I haven't tuned a BS25 carb before, so I can't say a lot about it.

This post has been edited by alexei: May 18 2014, 05:07 PM

So means every tank of fuel is 4.6 liters + about 250ml right?

u getting 250km per tank?

how much per km?

mine around 0.065 sen per km

i just 1 to know the difference....

Bcos a lot of ppl say untune 4T compare to untune 2T, have 50% saving in petrol and 2T....

My fuelly includes highway, so a bit too good for city riding.

Petrol: RM9.6 for 170~180km, 5.5 sen per km.
2T: RM20/1000km, 2 sen per km.

Mine petrol + 2T total is 7.5 sen per km.
Yours at 3.0L/100km, is about 6.3 sen per km.

This post has been edited by alexei: May 18 2014, 05:14 PM

bro alexei,

i have already retune my BS25 and reinstalled the stock paper air filter.

i warned the bike, and then i closed the fuel screw to it's close position. i opened the fuel screw for 1 turn and started the bike.
then i opened fuel screw 1/4 turn more and listen to the RPM. i end up with 2 and half turns. on 2 and half turns, the bike started to rev on higher RPM. when i open more, the RPM stays high. when i open more and more, the RPM went down. so i closed the fuel screw again, and yet end up on 2 and half turns. i assumed that on 2 and half turns position. the bike reach it's first maximum RPM level. i added more turns, maybe about 3~4 minutes more. total turns maybe 2 and 3/4 turns.

is this the correct way to tune ? i'm not sure is my setting now rich or lean. could you clarify me bro alexei ?

thanks

got it blinking quite sometime can get max pump till 3.928 liters

using 150cc block modded only 2.5L/100km...

pijuThat looks correct.
NewGUYGood what?

sorry bro alexei, i didnt mentioned that after i warned to bike, i set the idle screw to higher RPM than before. maybe around 2000 - 3000 RPM.
am i on the right way tuning the carb bro? am i getting the best and optimal setting result ?

pijuHere are the steps, in short:
- warm up
- set idle screw to high, RPM ~1.5k to 2k RPM.
- set pilot screw to reach max RPM, open few more minutes.
- set idle screw to normal, RPM ~1k, or engine is running smoothly.

Check:
- off-throttle performance: from idle, pulas the throttle fast and see if engine can follow or not
- steady acceleration at fixed throttle opening
- acceleration with continuous throttle opening

If there is any engine bog or flat response, continue to replicate the condition, and check the plug to tell if rich or lean. Perform tuning, and check again. Until puas.

In the end, your bike will have very low FC, good power across RPM and throttle opening. No semput-semput or misfire here and there, perfect.

Then, if you upgrade parts, may need to go through the whole process again. If lucky, some minor tuning is enough.

thanks bro. i followed your steps.

1. off throttle performance good.
2. steady acceleration good.
3. acceleration with continuous throttle opening also good.

heard no misfiring or semput.

i think i'm good to go now.

bytheway bro alexei, i asked 2 friends and they told me that stock setting for mikuni bs25 on yamaha lc v2 version is at 1 and half turns. on 1 and half turns, i wont get maximum RPM. is this true that most bike's carburetor factory setting are on lean mixture ? not tuned to it's maximum performance ?


This post has been edited by piju: May 19 2014, 01:39 PM

pijuI know it's 1 5/8 turn for the VM carb, not sure for BS carb. I'll need to look at its service manual to tell if that is true or not, which I don't have. Do you have its service manual, since you own one? IMO, factory setting is usually richer, so that the bikes produced are more likely to run smoothly.

Keep this page for your reference: http://www.zrxoa.org/webpages/techinfo/carb/carbtuning.html