PDA

View Full Version : This bike is driving me crazy!!!



centaurus
15th January 2007, 18:22
First it died while riding on the other side of the city. Apparently I was riding it too soft (it's a 2 stroker) so the plugs got fowled. I change the spark plugs, and the next time I took it out, after allmost two hours of riding, I felt like the power was going away bit by bit; the bike allmost died. With superhuman efforts I managed to keep it alive (barely kicking, even in the first gear) till I arrived home (I was close by). The next day I started diagnosing and I thought I got it: one cylinder is not firing. I thought I noticed that one of the exhausts was expelling only cold fuel mixture instead of real hot smoke. I assumed I have a wiring problem at the faulty plug. Planned to fix it after the holidays.

Left for holiday for 3 weeks. Today, after I came back, I tried to replicate the problem (I forgot which was the "bad" cylinder) and it worked well. I thought I noticed one of the pipes getting a little hotter that the other and smoking more (especially accelerating hard after idle and when cold).

At this moment I'm even scared to ride it. I live up the hill and if it dies somewhere on the way, I will have to find a car with a trailer hook and rent a trailer to bring it home, even if it's two blocks away. EDIT: when it dies, it dies at idle. If it's revved it works (more or less), but as soon as it's at idle, it goes dead, and to start it I have to keep the throttle open.

Does anybody know what/how could I test or what to look for, what could it be? Or my only chance is to take to a professional? Or is any of you knowlegdeable enough and in Wellington area to have at look at it running and tell me if it runs ok or it really has some issue? I'll jump with a beer (or more :D)

Thanx in advance.

SlowHand
15th January 2007, 18:42
Mate had similar prob on his ns250r I thunk. Wanted a new CDI.

Take it to a shop?

imdying
16th January 2007, 08:02
Sounds a lot like a worn out and ready to pop problem. Time for a top end rebuild most likely. Do it before it blows up, if you melt a piston into the barrels, that is heaps heaps more $$$ than new pistons and rings only.

centaurus
16th January 2007, 08:11
I bought it in november, so I can't guarantee on it's history, but according to it's former owner, it has has a top end rebuid somewhere last year (not too many kms ago). Also I don't think it's a top end, because it can work perfectly and pull really hard for one hour or even two, and then suddenly, looses power and does not hold the idle.

Posh Tourer :P
16th January 2007, 08:54
Your charging system is bad? Are the headlights dim? Or flickering at idle?

centaurus
16th January 2007, 09:11
No. The lights are ok even when the problem apears. and it appears to be on only one of the cylinders. I was suspecting a faulty wiring to one of the plugs (a cut/loose wire that comes off sometimes). Is there any way I can check if a plug gets power?

nsrpaul
16th January 2007, 17:46
cylinder fowling?

check they conecters to the coils

Posh Tourer :P
16th January 2007, 17:52
you can take the coil in for analysis - is it twin coil or single twin output coil? Get any car mechanic to read the voltage off it....

And of course, the obvious, change that spark plug. It may be cracked or faulty.

centaurus
16th January 2007, 20:17
Today I started it again. As soon as the engine warmed up and I turned off the choke, it died instead of idling. I left it for 2-3 minutes and started it again (with half throttle) and revved it's neck off for 5-10 seconds and it idled correctly.

I took it for a ride for a little bit over an hour and it worked fine, but the power was not what it used to be - it was a little bit softer. After more than one hour or riding, I felt it losing power again, I pulled on the side of the road and - of course - it wasn't idling anymore; as soon as the throttle was off, it died like when without gas.

CONCLUSION: from time to time, it just loses most of it's power and doesn't idle. Most of the times when this happens (but not always), one of the pipes smokes much, the other one doesn't smoke allmost at all (expels hot air, but I am not sure it is smoke and not unburned fuel mix).

Tomorrow I will try emptying the fuel tank and changing the gas, who knows... At this point I have no ideea what to do. Until I fowled the plugs and had to change them (50-100 k ago), it ran perfectly. Now, all of the sudden it runs like shit.

Ixion
16th January 2007, 20:49
How did you foul the plugs. and what is "smokes much". A two smoker with pump correctly adjusted should produce a thin, just visible haze of smoke when revved hot.

centaurus
16th January 2007, 20:59
Apparently I was running it too soft (revving it under the power band - only 3-5k rpm). As for the smoke, when it happens, it has a visible smoke, almost all the time (revved and at idle), not just a haze (like when it has too much oil for example). But this happens only when it goes a-wall. when it's rideable, both exhausts have the normal "just visible haze" when revving.

A, and by the way - now I'm riding it in the power band: around 7-9k rpm usually.

Ixion
16th January 2007, 21:15
OK. So, we deduce that the problem is caused by overoiling. For some reason at times the cylinders will receive excess amounts of oil. This will cause misfiring (or no firing at all) and loss of power, and foul plugs.

So the question to be addressed, is what is causing overoiling

Possible things to check

Failing crankseals (suspect if the right hand cylinder smokes more than the left, assuming the primary drive is on the normal side)
Defective oil pump
Oil pump cable catching, or jamming, or the oil pump metering arm catching or sticking.
Defective check or non return valves

Possibly others, I'm not familiar with the Honda lube system, but I assume it follows normal two stroke lines.

Or, perhaps the lube system is set up to provide excessive oil and the excess simply builds up.(it might have always been thus, and you did not notice it before, because you were riding so gently. The oil delivery quantity varies with revs)

Anyway, check pump settings, cable (very carefully, and recheck again), metering arm operation.

If that produces no results, consider having a crankcase leak down test done.

EDIT I assume that you have double checked that you have the correct grade of plugs for the type of riding you are doing. I always reckon two strokes need three different grades for different riding occasions. Though who can be bothered changing them al the time.

Posh Tourer :P
17th January 2007, 09:21
Also, the problem didnt exist until the plugs were changed - If you have the old plugs, get fine sandpaper, and sand the surfaces (or get a new plug). Try replacing it, as the plug you just put in may be faulty and the insulations breaking down when it gets properly hot.

FilthyLuka
17th January 2007, 10:25
just in case, check the spark plug spacing (using a feeler gauge). Im not familiar with this particular ninga ninga but if the space is too small, the spark will suck, bad combustion when cold. once it warms up, combustion becomes easier (thermal effeciency blah blah, you've heard it before no doubt) and a suckfull spark will probably be enough to ignight (CRAP!), light the mixture. Its unlikely but better safe then riding an underpowered, tempremental honda (hehe...).

If you have no idea of service history you might wanna replace rings sometime soon and get the barrels honed.

out of curiosity, what fuel are you putting in? (91, 96, 98, 101 ect ect)

centaurus
17th January 2007, 10:34
Aparently I'm using the race plugs, and the guy at the shop told me they are the good model for my bike. Also there isn't a hotter version (I think mine are 10).

I'm putting 95 or above - the highest I can find (usually 95). I know 2 strokes don't get along too well with low end fuel.

FilthyLuka
17th January 2007, 10:35
Also I don't think it's a top end, because it can work perfectly and pull really hard for one hour or even two, and then suddenly, looses power and does not hold the idle.

it sounds like top end :p

seriously now, check the rings... now just maybe (now im just takin the piss), the last fool put oversized rings in when they werent needed... so when it gets uber heated (like after and hour or two of riding :p) the rings expand and create Uber friction between the bore and rings, effectively making piston travel stupid difficult and resulting in arse running...

hehe, but no... probably not.

The pulling hard bit is relative... if you havent ridden a nsr thats in prime engine condition you wouldnt know how hard it can actually pull... for all you know, your bikes running like a sissy. That being said an nsr running like a sissy will still pull like a mofo but thats not the point!. Pick up a manual, take of the top end and check the wear and tear on the bits and pieces. Piston rings, pistion, bore, gudgeon pin, bearing ect. ect. Also, check your loom. You might have a bare wire that after running for a while shakes around a bit and shorts the system, effectively rooting one piston...

Actually, that last idea is kinda plausible... Check your loom! wrap bare peices in insulation tape... while your at it, grab some wee little cable ties and just tidy everything up, makes electrical faults less of a pain to diagnose in the future...

#twitch# coffee time #twitch#

denden

FilthyLuka
17th January 2007, 10:39
Aparently I'm using the race plugs, and the guy at the shop told me they are the good model for my bike. Also there isn't a hotter version (I think mine are 10).

I'm putting 95 or above - the highest I can find (usually 95). I know 2 strokes don't get along too well with low end fuel.

pick up some feeler gauges from repco (its like $3 and a squashed orange for a set) and set the plug spacing. The area between the two plug connections... err... the metalie bit on the top and the round stumpy thing beneath the metalie bit... google for optimal spacing... tap the plug on a metal surface to make the gap smaller and use a strip of metal (side of the feeler guage works good) to pry it open if its too small. Check, double check, reinstall.

FilthyLuka
17th January 2007, 10:43
another thing... check your carbs.

what might be happening (this happened to my brother with one of his bikes), is youll ride it round and when the carb gets hot, the float gets stuck. Effectively flooding you cylinder and making one cylinder not fire and fuel mixture to drip out the exhaust pipe... either way your gonna be getting your hands dirty.

and just because you can... soak your plugs in vinegar to remove any built up crap and gunk you couldnt get to with sand paper....

xxblackbirdxx
17th January 2007, 10:49
No. The lights are ok even when the problem apears. and it appears to be on only one of the cylinders. I was suspecting a faulty wiring to one of the plugs (a cut/loose wire that comes off sometimes). Is there any way I can check if a plug gets power?

Unscrew the plug, put it back in the wiring plug and earth the tip of the plug to the engine or any other metal surface on the bike where it can earth. crank the engine and see if you can see the spark being generated at the tip of the plug. the ignition will need to be on. check both of them(plugs). if you find that the spark on one plug is weak then check the wiring for faults or lose connections.
Still cant solve it.?
Look at your fuel lines and ensure that they are not partially blocked.
Still cant slove it?
Go back to the carb and if you know how give it a thorough service and ensure your floatbowl settings are correct.
Still cant solve it?
Then you probably have a problem with intake, check reeds and your power valves if this bike has any.
Still cant solve it?
you probably have your choke on or maybe the choke cable is stuck.
Still cant solve it?
write back and i'll see if i can get some more checks you could do before sending it to a shop and begging them to slap you with a big bill.
Good Luck..
If there is anyone out there who feels that i have given wrong advice , please send me a line and correct me

xxblackbirdxx
17th January 2007, 10:50
Unscrew the plug, put it back in the wiring plug and earth the tip of the plug to the engine or any other metal surface on the bike where it can earth. crank the engine and see if you can see the spark being generated at the tip of the plug. the ignition will need to be on. check both of them(plugs). if you find that the spark on one plug is weak then check the wiring for faults or lose connections.
Still cant solve it.?
Look at your fuel lines and ensure that they are not partially blocked.
Still cant slove it?
Go back to the carb and if you know how give it a thorough service and ensure your floatbowl settings are correct.
Still cant solve it?
Then you probably have a problem with intake, check reeds and your power valves if this bike has any.
Still cant solve it?
you probably have your choke on or maybe the choke cable is stuck.
Still cant solve it?
write back and i'll see if i can get some more checks you could do before sending it to a shop and begging them to slap you with a big bill.
Good Luck..
If there is anyone out there who feels that i have given wrong advice , please send me a line and correct me

Also check the plug gaps and ensure the gap is set right

FilthyLuka
17th January 2007, 11:14
Also check the plug gaps and ensure the gap is set right

see my previous posts....

centaurus
17th January 2007, 13:18
Does anybody know where I can buy/borrow/copy/steal a Honda NSR repair manual? I found some info on the net but it's far from sufficient if I start taking off the carburetter, checking the wiring or meddling with the cylinders (let's hope this won't be necessarry :shutup: )

Posh Tourer :P
17th January 2007, 13:57
Aparently I'm using the race plugs, and the guy at the shop told me they are the good model for my bike. Also there isn't a hotter version (I think mine are 10).

I'm putting 95 or above - the highest I can find (usually 95). I know 2 strokes don't get along too well with low end fuel.

Try change the plug. All you changed to create the problem was plugs. The plug might be faulty from new. Sometimes the ceramic insulation is problematic. Even if it doesnt solve the problem, you have a spare spark plug, not a bad thing for a 2-stroke

Ixion
17th January 2007, 14:20
Racing plugs will always be problematic unless you are in racing conditions.And if you are overoiling as well, it will be worse.

centaurus
18th January 2007, 19:25
I took it apart today:
- checked the fuel
- checked the wires (as best as I could) - all of them seem ok (insulated, connected, protected form rain).
- Checked the power to the plugs
- checked the plugs - and here it gets interesting: the plug from the bottom cylinder was fowled (the cylinder connected to the right exhaust which was smoking). It was so fowled that didn't make a spark anymore.

I tried the old sparks and... surprise: one of them was working, one not. I thought it was just a coincidence. I installed the good one and the bike started at first kick, like it used to when I bought it.

To make sure that I am not dreaming, while assembling the bike back, I tried to start it again 3 or 4 times and every time it started perfectly.

I put it all together and started it to go riding. However, the right exhaust (lower cylinder) was smoking as yesterday. As soon as it warmed up and started decreasing the revs, I was just about to pull the choke in when it revved slower and slower until it died, just like yesterday.

At this point it's obvious the problem is too much oil in the bottom cylinder. The question is why. It couldn't be the actual fuel/oil mix because it would be in both cylinders,

PLEASE HELP!!! What could it be? (let's hope something not too expensive of difficult to solve :shutup: ). The 2 stroke specialists, please start throwing ideeas at me please.

Ixion
18th January 2007, 22:14
http://www.kiwibiker.co.nz/forums/showpost.php?p=899845&postcount=13

FilthyLuka
19th January 2007, 06:11
http://www.kiwibiker.co.nz/forums/showpost.php?p=900395&postcount=19

Sparky Bills
19th January 2007, 09:35
Dude!
Id stop riding it or even starting it untill you take the barrels off!
Just to be sure your not starting to seize it.
After you are satisfied thats not the problem, move onto electrics.

Two strokes are funny things. When they are going... FARRRK do they go! But when they're not... they really are not!

Check the top end! Its not hard to do, and will eleminate another problem.

Good luck.

Nutter34
19th January 2007, 12:47
Another thing. DON'T use the choke when the bike is warm and don't ride it that way...

I may be wrong but to my understanding, it richens the mixture a lot and rinses the lubrication from the bores? This could in fact enhance the chance of siezing...

On a side note.... I once had an RD350 that would be great in the revs but would not idle for shite. I eventually found one of the reed petals had a chip missing, so at low flow engine speeds, it wouldn't work... I changed the petal and viola, back to happiness...

Nutter34
19th January 2007, 12:59
Hey Luka. I was of the impression, if the floats get stuck, they would overflow through the float bowl drain lines, not richen the mixture in any way? You would still be relying on the main/needle flow wouldn't you?
Also maybe check the emulsion tube, if the holes are blocked, it'll also have an influence, since you may not flow enough gas, then it slowly buils up oil....

Hans
20th January 2007, 09:17
Can't really help with the mechanical issues as I know faaarrrk all about 2 strokes, but if you get stuck, I've got a van in Welly, so 021 126 33 65 or 04/ 970 1335. I know it's the wrong thread for this but no-one seems to read the "offering help" thread that much.

centaurus
21st January 2007, 10:18
Thanks a lot for the offer Hans. I will try to dismantle the bike this week and have a look around. However, me not having almost any experience repairing bikes and the problem looking quite complicated, chances are I will have to give up and take to a bike shop. If that will be the case, I will use your offer.

Thanks again!

Hans
21st January 2007, 10:45
No problem, PM me the day before or something, and we'll take it there.

Speedracer
21st January 2007, 15:15
Agree with post #13.
My experience is this:
I bought a kr250 bike which would turn over with a LOT of effort, but it wouldn't idle. (this thing was so far gone I pushed my mate up the road on it to get it to fire). I only paid $300 so I don't really mind.
So yes it would run, with difficulty. It had borderline compression (but still ok according to the manual).
The plugs weren't even that oiled. But it was thicker black oil, not the less viscous 2 stroke oil.

Problem? blown crank case seal.

At a guess:
The high temp from hard riding (or power band) will burn the standard engine oil, but as soon as you idle, it won't get burnt fast enough and will fill up. The leak is also proportional to how hard you ride it, at idle it won't leak much but at high speed it pours in. So when you engine brake, it builds up and gums that cylinder, stopping it firing.

I took the engine completely apart to fix it. Didn't put it back together though :whistle:

Nutter34
21st January 2007, 18:45
Agree with post #13.
My experience is this:
I bought a kr250 bike which would turn over with a LOT of effort, but it wouldn't idle. (this thing was so far gone I pushed my mate up the road on it to get it to fire). I only paid $300 so I don't really mind.
So yes it would run, with difficulty. It had borderline compression (but still ok according to the manual).
The plugs weren't even that oiled. But it was thicker black oil, not the less viscous 2 stroke oil.

Problem? blown crank case seal.

At a guess:
The high temp from hard riding (or power band) will burn the standard engine oil, but as soon as you idle, it won't get burnt fast enough and will fill up. The leak is also proportional to how hard you ride it, at idle it won't leak much but at high speed it pours in. So when you engine brake, it builds up and gums that cylinder, stopping it firing.

I took the engine completely apart to fix it. Didn't put it back together though :whistle:

Did you notice any gearbox oil usage? That would be a give-away.

centaurus
21st January 2007, 19:50
I'm assuming you're talking about the seal between the crank and the gearbox?

I haven't checked the oil level in the gearbox because I don't know how to yet on this bike.

The only thing that puzzles me is the fact that only one exhaust smokes and only one plug gets fowled every time - the one at the low cylinder. The other one looks perfectly normal (it doesn't smoke at all and the plug is perfectly dry). All the possible causes that the guys told me to check, including the crank seal - which I also feel it is the most probable one, should have effect on both cylinders. Right?

Ixion
21st January 2007, 20:15
Nope. There'll be another seal between the cylinder crankcase chambers. It's not like a Harley with the conrods both on the same pin. More like a parallel twin.Two conrods, two crankpins. (I think - correction welcome)

centaurus
21st January 2007, 21:50
In that case, how would that seal create such an effect? As far as I can tell, having that seal cracked, would make the crank chambers communicate, but both crank chambers should contain fuel mix, right? Having that seal cracked would only produce a lower pressure in the cylinder, but in both cylinders. Correct me if I'm wrong.

Ixion
21st January 2007, 22:10
Two seals. One on right , seals crankcase off from primary gearcase. If that leaks oil can enter the crankcase.

One of left, between cranks, seals crankcases off from each other.That doesn't leak (luckily - thats a BAD thing to happen).

There's another one on the non drive side too, but as theres usually no oil on that side the effect is not so noticeable. Odds are if right outer is stuffed, left outer will be also.

Very common on two strokes. Do a site search been a few other people had similar problems.

Nutter34
22nd January 2007, 17:06
I'm assuming you're talking about the seal between the crank and the gearbox?

I haven't checked the oil level in the gearbox because I don't know how to yet on this bike.

The only thing that puzzles me is the fact that only one exhaust smokes and only one plug gets fowled every time - the one at the low cylinder. The other one looks perfectly normal (it doesn't smoke at all and the plug is perfectly dry). All the possible causes that the guys told me to check, including the crank seal - which I also feel it is the most probable one, should have effect on both cylinders. Right?


Not so, there are two carbs, either one or two coils, if one, then it may be a split one and one half is breaking down...

centaurus
23rd January 2007, 18:58
Well, I checked the gearbox oil today. I don't know which is the correct level, but if the bike is on the kickstand, I reach the gears before the oil, so it's obviously not enough oil. This means it' the gasket between the gearbox and the cranck case.

Now question: can I just unscrew and take off the gearbox cap from the right side of the engine, or I have to take all the engine off the bike and dismantle from the cylinders side? I have some experience with cars, but I haven't worked on a bike before and I don't have anything remotely close to a repair manual, so I'm kinda walking in a dark, feeling my way through.

jade
27th January 2007, 19:23
The plugs you wanna run are br9ES's if I remember correctly... you dont want 10's
I had an mc18 and altho I didnt have problems with idling my lower plug would fowl up almost everyday if I wasnt riding hard enough
I would just take that plug out, dip a brush into the fuel tank and give the plug a quick clean - problem solved and replaced the plug,
Also I think with this bike, everytime you arent riding it - you wanna turn the fuel off - I was told by a mechanic that this model had a problem when its on its stand, mixed fuel and oil would seep down into the lower cylinder some how fowling the pluge..

FilthyLuka
29th January 2007, 17:39
I reach the gears before the oil, so it's obviously not enough oil.

eeep... get a service manual, shit, ill go and hunt one down for you! never put oil in based on what you can see through the "pour oil in here" hole... im sure theres a dude that did that with his fxr and ended up with white smoke pouring out of both sides of the engine...

ill have a scratch around for a mc18 manual...

and definetly not when its on its kick stand! center stand... wait a sec, nsr's dont have those... hunt down a swing arm race lifety the rear wheel thing... or get a mate to hold the bike up...

centaurus
29th January 2007, 17:46
eeep... get a service manual, shit, ill go and hunt one down for you! never put oil in based on what you can see through the "pour oil in here" hole... im sure theres a dude that did that with his fxr and ended up with white smoke pouring out of both sides of the engine...

ill have a scratch around for a mc18 manual...

and definetly not when its on its kick stand! center stand... wait a sec, nsr's dont have those... hunt down a swing arm race lifety the rear wheel thing... or get a mate to hold the bike up...

Bro', if you find me an NSR manual, I'll be eternally grateful. I took off the clutch and the oil seal and now I'm just about to order, by I have a suspicion that the old oil seal was mounted the other way around, but I can't verify my theory with anything.

FilthyLuka
29th January 2007, 17:48
very good... ill try hunt down a manual but if i come up dry, im sure someone on here knows how much oil to put in a cunting nsr250 gearbox! Hmm, oil seal around the wrong way... hehe... grab another one. I highly recomment new rings and getting you barrells honed while your playing about with engine internals... your bike will be gratefull for it!

denden

nsrpaul
29th January 2007, 19:50
go to www.nsrworld.com

they have a rebuild with pics so you can see which eway the seals go round

gearbox oil sould be up to the dipstick with the bike upright and the dipstick NOT screwed in, and yes it is meant to look snapped off

workshop manual, good luck reding japanese and even then its hopeless, but with a pic by pic rebuild for free on the net, why the hell would you want a manual

slowpoke
30th January 2007, 02:32
I don't have anything remotely close to a repair manual, so I'm kinda walking in a dark, feeling my way through.

...sounds just like my sex life.....

Mr. Peanut
9th March 2007, 17:33
I don't have a problem with fouling up, puttering or otherwise. I use motul 710.

jade
11th March 2007, 10:03
mate I had the exact same problem with my mc18.
Get it working and just before you go to go riding, take the lower cylinder sparkplug out and give it a good scrub on the spark end with some petrol and a toothbrush, plug her back in and see if she goes alright,
my bike used to oil up that cylinder only, never had a problem with the one under the tank. you can get to the lower cylinder sparkplug with all the fairings on, plug her back in and give her a go

wtf?
16th March 2007, 12:05
Maybe also worth a look, is check that your the sparkplug caps at the end of the leads have an effective connection with the end of the sparkplug. It is not enough to just slap the cap on the plug. You gotta feel the end of the plug "click"into place as you push it on. Also, check if your plugs have the little screw on ends on them, coz if they havent and youre using the caps that need them, it will cause the intermittant power loss youre talkin about.

wtf?
16th March 2007, 12:15
sorry, was only reading the 1st page of replies, didnt realise you had worked on cars.