One of my cylinders (right exhaust) doesn't seem to fire while idling. Once I give it a bit of throttle it will fire. I've just changed the plugs and that hasn't fixed it. I've checked the battery and that seems to be fine too.
What else should I check? _________________ Jerry Lai
NSR250 [MC21SP]
I go with Andy on the carb one. Make sure that your float height and air screw is to the specifications. That was the problem on mine.
As Andy said look at your jets and give your carbs a good clean. If you need a photo to know from where to where you must take the measurement on your float level, just ask me and Ill mail it to you.
Had some time this afternoon so I had a squiz at the problem.
Andy wrote:As always, do a compression check. If the rings are not seating correctly (i.e. they're worn), then poor compression will not be helping.
I got 105psi, but the bike temp was about 30ºC when I did the test.
Andy wrote:Check the slow (pilot) jet/circuit in the right carb. Could be a blocked or partially blocked jet.
Tried taking the airbox lid off, but there is a rusted screw that just wont come out of the lid. So I went out to the hardware store and bought a drill & screw extraction kit (which wasn't cheap! ).
So, I drill a hole into this screw, I then slowly wind in the screw extractor with a tap wrench - SNAP! - the new screw extractor snaps inside the drilled hole - sh*t!!
So I try to drill it out again - SNAP! - now the new drill bit has snapped off into the hole... FFFAAAAARRRRRKKKKK!!!!!!!!
I think I will just use the biggest drill bit in that kit and drill right through it! _________________ Jerry Lai
NSR250 [MC21SP]
my nut things holding the chambers to the exhaust port were rounded bad on my bike so i couldnt get it off for weeks...ended up getting one of those gripping pliers..worked well...pissed me off bad tho
anyway...hope the bike is up soon...
weather is gettin better here in melbourne and stuff...we gotta get a ride goin soon man...
cheers.. _________________ Philip Ahn
MC21 NSR250R
I got my mate who has NSR/RS experience to give me a hand... as I am a numb nuts when it comes to engines.
I finally got the airbox lid off (ok I didn't do it, my firend did) but the bolt would still not come out... lucky my mate had a spare which he didn't need and saw pity on me to kindly donate it Thanks Karl!
We got the carbs off and removed the float bowl from the right carb and cleaned it out. There was some gunk, so we thought that we had found the problem and preceeded to put the carbs back and connect the fuel to test it, but it was still not right.
We weren't sure what size the jets were, but the bike was running fine before our winter break (Jun, Jul, Aug), so we decided not to mess with them yet.
We then swapped the reed cages around. Found out I have dual stage reeds in there ... but they weren't the cause either.
We then tested the compression difference between both cylinders. Top: 120 - Lower: 115-118
K was fearing the worst as he had once experienced these symptoms before on his NSR and it turned out to be a collapsed crank bearing ... I also told him that Andy had said it might be the rings, so we proceeded to remove the lower barrell to check the rings and crank bearing.
He noticed some signs of detonation on the head of the piston and some light scoring down the sides (I tried taking some photos but the fuckin camera wouldn't focus properly ). The crank was ok though... Thank God for that
The walls of the barrell seemed ok, but we noticed some pitting on the cylinder head due to the detonation. I guess there's no excuse not to do the centre plug head conversion now
We haven't taken the top barrell off yet, but is it worthwhile rebuilding the top cylinder if I am doing the lower? Or can I get away with just doing the lower?
This is oh so much fun... NOT
Thanks again guys for the advice. _________________ Jerry Lai
NSR250 [MC21SP]
You still don't seem to have found the cause of the misfire though.
If it picked up once off idle, I say it's still most likely carburetion or compression somewhere. The compression test sounds OK, and if the carbs are spotless, then maybe a crank seal.
It definitely fired off of idle? And it definitely WASN'T firing on idle?! Please confirm. _________________ Andy.
NSR-WORLD.COM
Please keep all responses to Forum posts on the Forum so that others may benefit.
Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.
For the price of a base gasket take the top barrel off as well,its seems pointless rebuilding the lower and not knowing what condition the top is in. .As Andy says you need to find what caused the missfire,I rebuilt my top end as it had badly scored pistons and cracks around the exhaust ports but it ran fine,it was'nt any quicker after the rebuild.
Andy wrote:It definitely fired off of idle? And it definitely WASN'T firing on idle?! Please confirm.
Yep, not firing on idling RPMs, give it a bit of throttle and it would start to fire.
Karl wasn't familiar very with the stock NSR carbs and had mainly worked on PJ38 carbs, but he said the principal was still the same. One thing he did notice was some fuel was being spat back out from the air intake after shutting the throttle.
I'll mention the crank seal to him. Thanks Andy.
nsr.wayne wrote:For the price of a base gasket take the top barrel off as well,its seems pointless rebuilding the lower and not knowing what condition the top is in.
Yeah we will be taking the top barrell off, we just didn't have enough time to do it. It was just a premptive question just in case the top was still in good condition. I wanted to know if it would still operate ok with just the rebuild on the dud cylinder or do I have to do both no matter what condition the top was in?
Thanks again for the tips. _________________ Jerry Lai
NSR250 [MC21SP]
It'll be OK to rebuild just the lower cylinder, but measure the top up while it's apart. Do you know when it was last rebuilt? It may be due a set of rings at least anyway, and while it's apart it makes sense to do it, especially if you are ordering rings from abroad, as it will only add a few cents to the shipping! _________________ Andy.
NSR-WORLD.COM
Please keep all responses to Forum posts on the Forum so that others may benefit.
Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.
Jezza, I still have the same problem as you do,I have not had time to take the cyclinders apart but I have low compression and think that is what is causing the problem.I have checked and cleaned the carbs and still no luck. Hope you get it fixed and be shure to keep us informed.Thanks
I'll post an update when I complete the rebuild. I will also be installing the TYGA pipes and Dyno tuning it too. _________________ Jerry Lai
NSR250 [MC21SP]
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum You cannot attach files in this forum You cannot download files in this forum
).
Will I have long term issues if I keep riding it in this current state of condition?
I'm a slack bastard!
Thanks Karl!
... but they weren't the cause either.
