Nsr 150 Sp

[sapi]

hellop, long time havent post in this forum.

anyway, i need some guidance and advice on setting up carb for nsr 150 sp.

the old carb (original) is starting to acting up....smooth on low rpm, coughing on middle rpm.

let me explained little bit what happen here,

saturday last week, finally able to do service at honda service center, replaced the sprocket, chain, and front bearing.

Went to phanomsarakam (20-30kms) for testing, very nice ride, smooth sound.

i went home and found out that they mess up the gasoline tank (not center) so i put it back to normal. Now, things started going south on me. The bike runs nice on low rpm, but coughing on middle rpm, cant reach high speed.

At first i thought the fuel ratio is too rich (black spark plug head), i reduced the air ratio 1/4 in. Sound and feel better but still cant reach higher rpm like before.

any advice on jet setting?? which one to reduce and increase?? idle, slow, main jet??

and one more thing, which carb is the best, mikuni or keihin??

thx in advance.

[thaicbr]

i went home and found out that they mess up the gasoline tank (not center) so i put it back to normal. Now, things started going south

sapi. as a guess it will be down to the fact that you repositioned the fuel tank. does the SP have a fuel pump or is it VACUUM FEED. if vacuum feed then check the fuel lines for kinks etc. sound to me that its not getting enough fuel.

[Lickey]

sapi, sounds like the normal 2stroke breathing problem, if the spark plug is black then that says to much fuel, but,, if the exhaust gasses dont have a free flow through the exspansion chamber of the exhaust system, the plug will be black,

If you have oil in the end of the silencer, [put your finger in,if it comes out wet and black] then you need to clean the exhaust system,

Remove exhaust, pour in some caustic soda crystals, add some water and leave for an hour, the caustic soda will eat away at the carbon and clean exhaust, you can tap exhaust with a piece of wood or soft mallet to help the process,flush after 1 hour tapping system as water runs through.

On old british 2 strokes, we used neat petrol, remove from bike, pour in about 50ccs petrol and set fire, when the fire is finished, hold up exhaust and tap with wood or soft mallet, the coke would fall out.

After this, your enigine is breathing at its best, assuming air filter is clean, then if its still not right, try differfent settings on the carb.

[sapi]

thx for the advices.

@thaicbr: no problem with the fuel system, no kink in the line, flow normal. took out the fuel filter, no plug.

havent open the carb, i save it for later, its time consuming.

@lickey: And for the breathing problem.... ouch....i just cleaned it 2 months ago and it took me 1 week to dismantle, clean the exhaust, clean my house floor , and assemble it. yup, the exhaust tip is wet with unburn oil. i remember now, at that time when i tested my bike, going 130km/h, went home to see black oil on my fairing close to the exhaust.

thank you for the exhaust cleaning advice, i did the same last time. Cleaned it first with turpentine or kerosine, and then put the coustic soda mixture. And dont forget to pour vinegar or any acidic solution to neutralized it.

thx again, let me test it on friday (labour day) and see if the fix is right.

cheers.