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Conquiztador
20th May 2007, 12:30
I have a Suzuki NZ250 that is driving me crazy. (it's my sons) It shoots out the exhaust. Starts and idles perfectly. But when reving she starts to shoot. After about 5 minutes she starts running OK and no problem before stopped and left for a short while. Then it starts all over again.

I diagnosed carbi problems so I replaced carbi with same type. Did not help. I recond carbi. No change. I replaced with other type that I know is workng well. No change.

So I came to conclusion that I am obviously having a problem with valves not closing properly and therefore petrol going out in exhaust. I replaced head with one I know was good. No change.

I then came to conlusion, that if it was not head or carbi, then it must be electrics. So I placed motor in another complete frame I had that had all electrics intact (and that had been running sweet until motor died) Yep U guessed it: same problem.

So what left? exchanged spark plug. Twice. But no change. Ahaa I thought, the only electrical bit I have not replaced is the pickup and magneto coils. So I replaced them on the motor. But still same problem.

So now, the only thing that is left is the bottom end incl. piston and barrel. All electrics, carbi, head, spark plug, muffler has been replaced.

I have the bits to put together another motor, and it is what I will do next. But I hate to be beaten. And if it all works when I replace the motor, then I have the bike back up and running OK.

But I just want to know what is causing this??? Any ideas??

xwhatsit
20th May 2007, 15:25
What is to `shoot'?

Jantar
20th May 2007, 15:41
What is to `shoot'?
To take aim, then squeeze the trigger. :yes:

JimO
20th May 2007, 16:08
i bought one of those beasts last weekend for my boys to learn on and havnt had any probs but yours sounds like its stuffed so i suggest you GIVE it to me for spares:yes: :yes:

Conquiztador
20th May 2007, 18:38
The manual is being sent on Tuesday. I have 3 of these NZ250's. Two are complete and working brilliantly. But this one is a mystery. She is the one that I am setting up as a retro bike. But the motor is driving me crazy. Spending too many hours working on her. But hate to be beaten... Was just hoping that someone out there had some ideas that I have not considered.

JimO
20th May 2007, 19:01
if you ask me flames coming out of the exuast would be the coolist thing to impress the chicks at the school car park

imdying
22nd May 2007, 13:39
I know you said you changed the head, but have you checked the valve clearances?

Conquiztador
22nd May 2007, 17:21
I know you said you changed the head, but have you checked the valve clearances?

Yep. They have been checked. Cheers.

riffer
22nd May 2007, 18:45
Could there be a buildup of carbon in the zorst which builds up pressure?

Once you get enough pressure built up it goes bang...

Does it do this with the zorst off?

Damn. Just reread your post - you've replaced the zorst.

Maybe you've got a cracked piston...

Conquiztador
22nd May 2007, 21:10
Maybe you've got a cracked piston...

Did not even consider that. But it would make sense. As the only thing that has not been swapped is the bottom end of the motor, piston and barrell. I have had the piston out and I did not notice any damage to it. But maybe there is a hairline crack somewhere that I have not noticed? I will inspect and get back. Thanks for that!

Big Dog
23rd May 2007, 00:00
Essentially to get this symptom you must have unburnt fuel making it to the exhaust or there is no resistance to the combustion exhiting the exhaust.

If you know your head is good and your clearances correct, you need to look at why there is too much unburnt fuel hitting the exhaust.

If it is only during the choke or warm up stage then you probably have insufficient spark or insufficient air when warming up.
Insufficient spark can be caused during warm up by any number of expensive parts and I don't know where you want to start but cleaning and gapping the plugs would probably be it.

More likely is insufficient air to burn the available fuel.
Try starting the bike with no air cleaner and an open air box.
You may need to lean out the mix on choke.
Or your air cleaner may be filthy, or otherwise obstructed.

Also may 70-80's bikes had air flow meters on the air cleaner. These are only any use in sub zero conditions if you are going to choke it anyway and often seize in the closed position causing engines to "gasp" often resulting in flames during start up.

Living in the the north island? Not planning on visiting the south island in winter? Bypass it.

Conquiztador
23rd May 2007, 00:32
Your comments are appreciated and I will investigate. The spark plug is fine. have replaced with new and gapped as per specs. The valve clearances are also fine. Triple checked them. And both heads doing the same. The filter on the aircleaner has been cleaned and I have also swapped it. But it is a big box under the seat. And I shall look in to what else hides in there. Said that, I put the motor in a nother frame that had earlier held a motor that did not have this problem (but blew up...), and the problem was still there even if I used all the bits apart from the blown up motor. (Carbi, air cleaner, electrics, tank, muffler etc.). Thats why this thread, I had run out of ideas. But thanks to U guys I am getting some new things that I can look at. Will keep U posted re progress. Cheers.

Kickaha
23rd May 2007, 08:20
I then came to conlusion, that if it was not head or carbi, then it must be electrics. So I placed motor in another complete frame I had that had all electrics intact (and that had been running sweet until motor died) Yep U guessed it: same problem.

So what left? exchanged spark plug. Twice. But no change. Ahaa I thought, the only electrical bit I have not replaced is the pickup and magneto coils. So I replaced them on the motor. But still same problem.


I take it you have checked the timing ? (both valve and ignition) it might pay to do it with a degree wheel and dial guage to make sure it is accurate

Conquiztador
23rd May 2007, 08:53
I take it you have checked the timing ? (both valve and ignition) it might pay to do it with a degree wheel and dial guage to make sure it is accurate

Yep, been there done that. Even adjusted valve timing differently to what is recommended just to see if any diff. But same problem. Tining on these are set and there is no adjustment. But with the problem going away after a few minutes and she then runs sweet I would not think it could be the timing anyhow.

riffer
23rd May 2007, 21:56
Okay, I'm hooked now.

You HAVE to post what the problem is once you find it.

nudemetalz
23rd May 2007, 22:19
Have you had the CDI and or regulator tested ?
Suzuki's of that era had some issues there.
Saying that, my old NZ250 was very reliable.

Conquiztador
23rd May 2007, 22:30
Have replaced CDI. And as stated, placed motor in a frame with all electrics that worked perfectly before old motor blew up.

Spent some more hours on her today. The "not enuf air" got me searching. But after taking off aircleaner and fiddling with carbi (carbies) no change. She starts, she idles, but when going up in revs she shoots out the xhaust. Then suddenly she snaps outta it and there is like no problems ever existed. Almost like the xhaust cam jumps a tooth or two. But it cant be. I am sure it is a mechanical problem. Just have to suss out what.

riffer
27th May 2007, 13:20
still waiting for the answer ...:wait:

MSTRS
27th May 2007, 13:36
You haven't mentioned fuel. Or whether your second bike had it's own fuel and tank....

riffer
6th June 2007, 21:27
still waiting for the answer ...:wait:

nudemetalz
6th June 2007, 21:29
Maybe the NZ fixed itself and no more problems exist !!

Conquiztador
7th June 2007, 01:55
Sadly none of my bikes have ever fixed them self.

I took time out from the NZ. Only so much hair pulling one can stand before one goes bold.

Now spent the evening working on her again. Need valve shims for the second motor to be completed. And there is not many around for the NZ in our country. So will have the old ones machined down.

So spent the evening triple checking (and quad checking some bits) But no matter what I do, she still acts the same.

Once the other motor is completed and in the frame and I have taken the faulty one out and apart I will inform re what I have found.

FROSTY
13th June 2007, 18:08
just one thought here--fire her up and squirt crc all round/over the rubber inlet manifold. See if there is a sudden change.

cowpoos
13th June 2007, 18:17
Sadly none of my bikes have ever fixed them self.

I took time out from the NZ. Only so much hair pulling one can stand before one goes bold.

Now spent the evening working on her again. Need valve shims for the second motor to be completed. And there is not many around for the NZ in our country. So will have the old ones machined down.

So spent the evening triple checking (and quad checking some bits) But no matter what I do, she still acts the same.

Once the other motor is completed and in the frame and I have taken the faulty one out and apart I will inform re what I have found.
the valve shims in the NZ250 motors are pretty generic suzuki items...check the tolerence's and then go see your suz dealer...they should have some to you pretty quick...if needed that is.

the root of your problem is air,fuel or ignition/timing...nothing that hasn't been mooted here yet...I would check the cam chain ain't poked or too slack..and camshaft timing...and ingnition timing...then move to air leaks after the carburator...and since you have check the carb to death it shouldn't be that I would imagine...ya need know though...

onearmedbandit
13th June 2007, 18:23
The most interesting piece of information is that the bike comes fine after a short period.

cowpoos
13th June 2007, 19:15
The most interesting piece of information is that the bike comes fine after a short period.
hmm...good point bro...maybe a valve not seating and after the engine heats up metal expand causing the valve to seal better or something along these lines??

onearmedbandit
13th June 2007, 19:40
I was thinking similar but surely the valve clearances etc were checked when the engine was both hot and cold.

cowpoos
13th June 2007, 19:48
I was thinking similar but surely the valve clearances etc were checked when the engine was both hot and cold.
wheres motu when ya need him!!

Conquiztador
15th June 2007, 21:58
The shims for the NZ250 is a size that the NZ Suzuki dealers do not carry. When comparing to all they have in stock they are bigger then most. They are about a old 5 cent size. Also went to the other jap shops and nothing. So have now had the old ones machined down. (When I give the local Suzuki shop the frame and motor number when trying to get shims, the NZ agent comes back saying that they do not stock parts for her...)

That is for the spare motor that will go in the frame this w/e.

The one with the problem has precise valve clearances. This has been double and quad checked. Hot and cold.

The carbi has been swapped against two other working carbies. Same problem.

The inlet manifold and aircleaner rubber has been swapped. Have also run the carbies without aircleaner. Same problem.

The cam chain is inside tolerances and the tensioner is working well. I was thinking that it was a problem with the chain. But after spending time checking it I came to the conclusion that it is OK. I did run the motor for a very short while without rocker cover as it was the only way I was able to really see what was happening. And could not fault it. (But there was a bloody mess left after from all the squirting oil...)

So will update after I have fitted other motor this w/e.

Thanks for all help!!!

JimO
16th June 2007, 07:27
would another suzi engine fit??

FROSTY
16th June 2007, 12:43
Ya know given the extent you have gone to to sort this Im seriouslly wondering if theres a fault in the lectrics somewheres.
Maybee try swappin the CDI over then at a gifferent time swappin the coil over.

pzkpfw
17th June 2007, 10:36
would another suzi engine fit??

Jim2 has told me a Goose engine will/might (350cc).

The NZ250 motor is based on the DR of the time, so I figured there might be some DR engine that would go in without much hassle.

[I'm keen on doing something like this, as my NZ would not sell (for what I wanted, anyway) so plan to "fix it up" one day as a "project".]

mark247
17th June 2007, 19:27
Couldn't you get the bottom end off the motor that needs new valve shims and the head off the motor thats shooting flames and see what happens?

Wouldnt that mean you have tried a different frame with different electrics, different carbs, different head, different piston and barrel etc, err basically different everything??

Conquiztador
2nd July 2007, 19:37
The motor I have been building up was completed yesterday and fitted to the bike. We started her today and runs like a dream. No strange noises or "shooting". So that solved it.

Now I just have to figure out what in the motor is causing it. As head with valves and all electrics were swapped on the old one with no change the problem must lie down in crank, conrod or something I have not even considered. So one day when I have nothing on I strip the thing and have a look. Maybe...

Thanks for all the advise guys.

Deviant Esq
3rd July 2007, 00:49
Good stuff mate. I bought nudemetalz' old NZ250S and have had it over 18 months, totally reliable so far, and pushing on towards 100,000kms. Great little bikes :)

Pic of mine in my profile.

Let us know what happens with that problem, would be interested to know. Any common issues you know of with NZs - apart from parts being next to impossible to source?

Conquiztador
3rd July 2007, 20:52
Good stuff mate. I bought nudemetalz' old NZ250S and have had it over 18 months, totally reliable so far, and pushing on towards 100,000kms. Great little bikes :)

Pic of mine in my profile.

Let us know what happens with that problem, would be interested to know. Any common issues you know of with NZs - apart from parts being next to impossible to source?

Trying to think...As you say, parts hard to find. Best bet is to have spare bikes/engines. I have a couple of the NZ's, but apart from this problem and not being able to find shims for the valves (had to have mine machined down) there has only been "normal" bike issues like side cover connectors breaking off, leaking tank etc. Had one motor that seized (son did not check oil...) and another one that someone had put together wrong that smashed piston in to valves with serious damage as result. Touchy with the carbi float level setting. But apart from that I recon brilliant little bike. Any idea why she was discontinued when the GN is still made?? Would have thought that the NZ was a bike ppl would have preferred.

gammaguy
3rd July 2007, 21:35
But apart from that I recon brilliant little bike. Any idea why she was discontinued when the GN is still made?? Would have thought that the NZ was a bike ppl would have preferred.
__________________


So one day when I have nothing on I strip the thing and have a look. Maybe...


it obvious-it was discontinued because mechanics hated working on it in the nude....especially in winter:dodge:

JimO
3rd July 2007, 21:35
Trying to think...As you say, parts hard to find. Best bet is to have spare bikes/engines. I have a couple of the NZ's, but apart from this problem and not being able to find shims for the valves (had to have mine machined down) there has only been "normal" bike issues like side cover connectors breaking off, leaking tank etc. Had one motor that seized (son did not check oil...) and another one that someone had put together wrong that smashed piston in to valves with serious damage as result. Touchy with the carbi float level setting. But apart from that I recon brilliant little bike. Any idea why she was discontinued when the GN is still made?? Would have thought that the NZ was a bike ppl would have preferred.

i prefer the NZ to the Gn

xwhatsit
3rd July 2007, 22:08
i prefer the NZ to the Gn

<hints id="hah_hints"></hints>I think because aesthetically it wouldn't/hasn't aged well. It was designed to look sporty in its day, whereas the GN was designed to be a `classic cruiser' style bike, which tend to look the same in any era.

That said, the most important thing is how it rides, and those people with NZs seem to have a lot of fun.

Conquiztador
3rd July 2007, 22:17
__________________



it obvious-it was discontinued because mechanics hated working on it in the nude....especially in winter:dodge:

And I agree. I hate trying to get grease and oil of the nuts and balls. ;-)

Conquiztador
3rd July 2007, 22:22
<hints id="hah_hints"></hints>I think because aesthetically it wouldn't/hasn't aged well. It was designed to look sporty in its day, whereas the GN was designed to be a `classic cruiser' style bike, which tend to look the same in any era.

That said, the most important thing is how it rides, and those people with NZs seem to have a lot of fun.

Maybe the design of the plastics could have a little work done to them. But if U leave motor, frame and wheels and change the rest U still have a very decent bike with a fast and well running one cylinder motor. 40 something Hp as is and can easily be taken higher. 140K/h is normal as is. And she leaves most other 250's in the dust.

So go figure.

Deviant Esq
4th July 2007, 09:40
<hints id="hah_hints"></hints>I think because aesthetically it wouldn't/hasn't aged well. It was designed to look sporty in its day, whereas the GN was designed to be a 'classic cruiser' style bike, which tend to look the same in any era.

That said, the most important thing is how it rides, and those people with NZs seem to have a lot of fun.
Yep, they're a little under rated IMO, but that's because not too many people know about them in the first place. I believe the bike was only produced between 1986 and 1989 and not many made it to New Zealand (this short lifespan and low availability means parts are near impossible to source), so I don't really think that the bike had a chance to actually age cosmetically! Maybe today the S (my one) has aged somewhat, but the naked version doesn't look too dated IMO... but that could be something to do with the current style trends, I don't know. Maybe it didn't sell well due to a high cost? Purely speculation, information is difficult to come by.

I'd choose an NZ over a GN or SR anytime, but the NZ is a different machine, it shares no parts with the GN. People think the motor is a tuned GN mill, but it isn't. It's a modified version of a DRZ engine according to nudemetalz, but others have said it was unique to the NZ. At any rate it produces nearly double the power of the GN, and is a higher & faster revving mill. There's no point even going into the handling and maneuverability compared to a GN or SR... there is no comparison, the NZ leaves them for dead. Over the twisty Dyers Pass Road, I've pulled away from SVs, both 650s and 1000s, on my NZ. Granted if you popped a brisk rider on an SV it'd be a different story... but these guys said once we stopped that they couldn't stay with me. I was just having fun, wasn't exceeding about 90km/h, but the NZ's just so chuckable for a little bike it's excellent in the tight stuff.

The brakes could do with more stopping power, they're a bit weak, but that's one of the few grizzles I have about it. If you're mean to it you can get it over 150km/h... I don't like doing that to mine. Let's face it, it's an old bike with high kms, and doing that sort of speed places heavy stress on the engine. It has excellent fuel economy, nearly 30km per litre if you use 91 octane (I find it gives more power and economy than 95 or 98), and is easy to maintain. It's great to commute on, the 4 stroke single has good torque for around town, and it's narrow and light - good for filtering and parking... though the side stand could use a bigger foot.

Conquiztador
4th July 2007, 15:49
Yep, they're a little under rated IMO, but that's because not too many people know about them in the first place. I believe the bike ... ... ... to commute on, the 4 stroke single has good torque for around town, and it's narrow and light - good for filtering and parking... though the side stand could use a bigger foot.

Well said, totally agree with the whole posting!

xwhatsit
4th July 2007, 16:55
It makes me wonder why not more sporty 250 singles aren't produced currently. They have so many benefits, Deviant listed quite a few, and you only have to see how loved still these bikes are today. CB250RSs are being picked up by older bikers in the UK and fixed up for the commute on weekdays and country lanes in the weekends; SRX250s are still being thrashed around, and customised into flat trackers in Japan; and the few NZ250s around seem to have very happy owners.

A good, solid, high-revving single can make for a very balanced, very light, and very useable bike. It's a shame there's just commuters like the Scorpio being produced (and myriad chook-chasers).

Deviant Esq
4th July 2007, 17:11
People seem to want more comfort it seems. There are more higher capacity scooters around now than there used to be... and no more sports 250s like the CBR250RR and ZXR250. Anyone know why they stopped making those? They were quite possibly one of the NZ's problems too... bikes like those were water cooled and multi cylinder and faster than the NZ, though I can keep up with them up to about 110km/h before they start pulling away. Still, I'm told NZs sold in pretty large numbers in Japan... but yeah, not popular here. Pity really, they're justabout the perfect learner bike. I'd like more power now but yeah. Had the NZ for 18 months already... can cope with another four! I hope.. :confused:

Conquiztador
4th July 2007, 17:32
The NZ is easily stroked. Have a crank pin made with a offset, fit a spacer under the barrel and get a longer cam chain and you will suddenly have more cc's and more HP. Add to that some HP coating of the piston, valves and inside of head. I have yet to play with the cam, but I am sure I can get a few Hp out of that one too...

Oh and open up the inlet in the head and fit a bigger carbi. Same with the outlet. I have not played with the exhaust, but I recon a Super Trapp on a Dyno after all the other stuff is done should help.

Doing all this I be surprised if there is not 50 - 60 Hp that can be whipped out of her.

My intention is to take one of them (have a couple) to 200K/h

I will keep U posted.

JimO
4th July 2007, 17:44
It makes me wonder why not more sporty 250 singles aren't produced currently. They have so many benefits, Deviant listed quite a few, and you only have to see how loved still these bikes are today. CB250RSs are being picked up by older bikers in the UK and fixed up for the commute on weekdays and country lanes in the weekends; SRX250s are still being thrashed around, and customised into flat trackers in Japan; and the few NZ250s around seem to have very happy owners.

A good, solid, high-revving single can make for a very balanced, very light, and very useable bike. It's a shame there's just commuters like the Scorpio being produced (and myriad chook-chasers).

its a laugh really i paid a grand for the one i bought my boys but if it was a cbr 250 itwould have been 4 grand total waste of good $$$ if you arx me, its a step to a bigger bike and its probably going to get a hammering but for a grand who gives a shit

cowpoos
5th July 2007, 19:21
one cylinder motor. 40 something Hp as is and can easily be taken higher. 140K/h is normal as is. And she leaves most other 250's in the dust.

So go figure.

not 40 hp dude...33 acctually...I had my 89 model up to 165 regularly back in the day...




Doing all this I be surprised if there is not 50 - 60 Hp that can be whipped out of her.

My intention is to take one of them (have a couple) to 200K/h

I will keep U posted.

and I wouldn't be surpride if it goes BANG!!! 50-60 hp is very very highly tuned for a motor of this type...a modern dirtbike 250cc single with a really high rev ceiling might achieve this...might!!...I doubt it though on pump gas.


It's a modified version of a DRZ engine according to nudemetalz, but others have said it was unique to the NZ.


not so much the DRZ engine...but the slimilar and much older 80's dr250's but with oil cooling and twin over head cams added and Kehin slide draught carb [correct me if I'm wrong...but I'm sure its a slide...as aposed to the DR's CV carb]

and was definatly not a New Zealand only model...

Conquiztador
5th July 2007, 20:46
"not 40 hp dude...33 acctually...I had my 89 model up to 165 regularly back in the day..."

It looks like U are right. Sorry re that.


"and I wouldn't be surpride if it goes BANG!!! 50-60 hp is very very highly tuned for a motor of this type...a modern dirtbike 250cc single with a really high rev ceiling might achieve this...might!!...I doubt it though on pump gas."


Well, we see. Keep U posted. :-)


Thanks for that info thou cowpoos.

Kickaha
5th July 2007, 21:52
Doing all this I be surprised if there is not 50 - 60 Hp that can be whipped out of her.

I'd be even more surprised if there is 50-60 hp that can be whipped out of one of her

I know the Kart guys were getting this HP out of Moto X 250 bikes, out of a 250 four stroke I doubt you'll get close

Conquiztador
5th July 2007, 22:14
I'd be even more surprised if there is 50-60 hp that can be whipped out of one of her

I know the Kart guys were getting this HP out of Moto X 250 bikes, out of a 250 four stroke I doubt you'll get close

U just want me to prove U all wrong and do it. OK, no promises, but I see what I can do...:shifty: