Help with engine starting

[250250]

I have a mc16 nsr250 and she wont start much and when it does it backfires a bit then runs sweet apart from lacking a bit of power over 7000rpm im lost any idears

[sugilite]

Checking the spark plugs would prob be a good place to start....

[rphenix]

Also dont forget to check air filter, cheap way is to clean with petrol (make sure to get rid of any excess by ringing it out well before putting back in or even better leave to evaporate overnight).

If that and spark plug check doesnt fix it then usually time to look at the carb :(

[NighthawkNZ]

Spark plugs, and leads... battery (also check the terminal is tight)

[Kittyhawk]

Loose spark plug, maybe wiring problem, have a look to see if theres any corrosion on the terminals where the plug and lead make contact..

If spark plugs etc are fine and you are loosing power over 7k maybe theres dirt in the carbi somewhere (if not fuel injected) or something blocking up part of the fuel line. If that's the case run through some engine/ fuel line cleaner..the one you mix with petrol etc (get it from repco)...might do the trick

[jcupit69]

check the carbs for dirt. the loss of power up top sounds like you could posibly be flooding the cylinder under load. had the same problem when i got my zxr, and one of the fule lines to the cylinder was nackerd and was leading to the cylinder flooding and so no surge of power at the top end.

Check the basics to, plugs, air filter, fuel lines etc etc but defo have a look at the carbs.

[250250]

I have checked battery put in new plugs and filter goes better than ever over3500 but still hardly starts and under 3500 it backfires and needs to nursed up to 3500 because if you floor it under 3500 it just dies. Im lost could it be running too rich if so how do you adjust that??

[0arbreaka]

Have you taken it for a decent ride, the 2 strokes love to be raped.

[rphenix]

Have you taken it for a decent ride, the 2 strokes love to be raped.

They certainly do :) My RG used to oil the plugs unless you ringed it all the time hehe

[awayatc]

:2thumbsupNormaly on the carb are 2 screws, One adjusts the idle speed (lets the slide go higher/lower in carb body) the other one is the fuel air mixture screw, has usualy a spring underneath showing. All the way in is lots of fuel and no air.All the way out is lots of air and less fuel....
Carb could need a good clean, maybe compression is low....that makes em start hard, and loses bottom end power....(easy to push bike when in gear...?)
Good luck

[Racey Rider]

What Octane fuel are you using?

[250250]

91 is that right

[Racey Rider]

Yes it should run fine on 91.

Worth trying 96 as an easy way of a slight timing change which could fix the backfire problem. but thats not really fixing the problem just masking it.

Any leaks in the exhaust gaskets ?

[250250]

yea i have had a bit more of a play 2day and found when it backfires it spits some oil out onto the exhaust from somwhere im gutted no riding for me

[rphenix]

yea i have had a bit more of a play 2day and found when it backfires it spits some oil out onto the exhaust from somwhere im gutted no riding for me

Hmm now thats not good, as stated above what is the compression like on the bike? Time to check the rings etc.. as the compression goes oil in the premix of a 2 stroker doesn't get burnt properly and starts doing that lovely oil drip out the exhaust your talking about :(