NZ250 problem

[nudemetalz]

Greetings,

Just joined this forum, really great place to listen and learn.

I've got an NZ250S (the fairing model) which I bought for commuting. Great bike, very economical, handles well and has a fair turn of speed for a 250 single.
Anyway I have this problem where it dies in the rain.
Not long after I get going in the rain, it just starts faltering and then dies. Takes ages to start again, normally backfires when it's turning over on the starter-motor and then repeats this annoying habit.

I thought it may have been getting water into the plug and plug hole so I purchased a new cambox plug-cap cover and sealed it in with silicon so it's completely water-tight.
Could water leaking in from the petrol cap perhaps cause this, or maybe water getting on the coil.
There doesn't appear to be anyway exposed ignition wires.

Can anyone here offer any advice as to where to look?


Cheers,
A frustrated Chris !!

[Dadpole]

Checked the ignition pickup? Not sure where they are on your bike - end of crankcase? Water could be getting in there.
Marine CRC is good stuff

[oldfart]

Chek the whole ignition setup - cdi pickup/points - wiring to coil - coil to spark plugs. Quick fix try spraying around a bit od crc or wd40

[nudemetalz]

Thanks, never throught of that.

I'm taking the engine out shortly to replace the head-gasket (slight oil-leak) so shall check there. Pretty sure it's on them left side crankcase (motor is damn near identical to a DOHC DR-250 apparently).

What I considered doing was idling it on the front lawn one fine day and putting the hose in different places to see what reacts first.

Cheers
Chris

[F5 Dave]

Try running it at night & seeing if you can see any tracking on the HT lead/ plug cap.

Neat bikes, so much better than GNs etc. Only problems were the tendancy of the disc to warp & a teensy issue with the heads being prone to cracking. Hope that's not your oil leak issue.

[nudemetalz]

Thanks, F5 Dave, I'll do that.

Yes had heard of those issues.
The disc is fine (not really that powerful though) and I'm going to get the head checked thoroughly before reassembling it.

It is a great bike, bit slow after some of the other bikes I've owned (RZ500 namely) but getting older now and enjoy RIDING on the road rather RACING.
Plus my missus has just got her restricted and loves riding it so now may have to be myself another bike, now that the NZ is getting more and more prised from my hands....

Cheers
Chris

[vifferman]

Just a "way out there" comment: I used to have a VTR1000, and one of the 'funny' things that could happen to it was getting water and/or crud on/in the end of the fuel tank breather hose. As it relied on gravity feed (no fuel pump), a minor blockage was enough to stop fuel flow...

It also misbehaved badly in the wet, misfiring on the front cylinder. I *knew* it was water getting in the electrics, and it turned out to be a small crack in the plug boot, seemingly made by the plug cap puncturing/tearing the rubber. I still don't understand how water could get in there - it was buried in the plug well, was closed up, and had lots of water-dispersant sprayed all over it. But I replaced the boot, and the problem disappeared.

[F5 Dave]

Try get hold of some Vesrah Redback pads (NRQ or something). They work real well on the RG50 which has same calliper. Much better than the std type.

Also clean the calliper out, pump the piston out, clean, new fluid etc.

[nudemetalz]

Okay, I'll do that. The pads aren't that worn but I think they're OEM type ones. Got to replace the brake lever and mirror after herladyship dropped it in the garage and then didn't tell me cause she thought I wouldn't let her ride it anymore....so much better to find out accidentally ay....

I thought I had eliminated it being the plug cap by siliconing the complete hole, but I'll replace the plug cap like you said and see what happens.
The breather for the tank is only in the fuelcap so could be letting water in there as well.

Cheers
Chris

[F5 Dave]

If it was water getting into the fuel then the problem would last till the water was out of the tank. Meths helps here as it absorbs the water & it burns off.
Make sure you get the right lever, the wrong one will limit travel of the lever. Braided line would help too. Alert in Auckers (on web) will do Hel lines with correct approval numbers on them.

A mate has a RZ500, quite liked it, bit bulky compared to my 350 of the time but turbine power. He's yet to finish it with the FZR upside downers, flatslides, Nikon pipes etc. Sigh.

[nudemetalz]

Yeah the problem goes away after the rain stops even with the same fuel load so pretty much eliminate that then.

The RZ was a great bike but had a few issues, namely, around town a real b1tch as high first gear (115km/h) and not a lot down low meant lots of clutch-slipping to get going.
Quite thirsty and hard on oil.
Used to foul the odd plug if not used hard very often and flighty in the front end under power (needed a steering damper)

BUT WHAT A SOUND AT 10,000rpm FROM THE V4............!!!!!!!
(Yes and very turbine-like)
Plus I reckon they look nicer than the RG500's

Anyway, sorry getting off track with all this nostalgia..

Cheers
Chris

[F5 Dave]

Well it's better to chat than work.

115? pah, my 750SP did 140 on stock gearing & that's not into the redline.

still does about 120 now I've geared it down.

[nudemetalz]

A mate had an RG500 and I had my RZ500. We regularily used to ride together.
Differences between them were these..

RG had much less ground clearance (belly pan used to scrape)
RG used to loft it's wheel waaaaay easier (too easy!!)
RZ was a lot heavier and you sat on it rather than in it like the RG
Bugg'rall difference in top speed (240-250 RZ-RG)
RG vibrated a heck of a lot more.
RZ had real issues in the front end
RG had(has) better potential for power increase because of better engine design.
Acceleration (drags) were fairly even as the RZ could get off the line easier without wheelstanding to kingdom come so negated the slightly less speed.

But when we both went to the Brass Monkey, we could start our bikes the next morning, while all the elecy start bikes were all frozen solid and batteries flattened in no time !!!!

Just my 2c worth..

CC

[F5 Dave]

From what I’ve seen of his bike he has lost a stupid amount of weight off it. Yamaha really tried to tone the bike down by adding weight. Did you ever take the pipes off? They weighed a ton & a ½. Much heavier than the RZ350 pipes for no real reason. The airbox etc had way more stuff in it than required & those wheels were silly.

[nudemetalz]

Yes, we experimented with chambers at one stage. Sounded great but needed severe jetting to make them work properly.
The pipes (in particular the rear cross-over ones) are extremely heavy.

Another thing was in winter, your butt was kept toast warm from the heat off the back-pipes

Then Yamaha did the crankcase front/full-reed back induction system which is not exactly awesome for getting more power.

The RZV500 (jap spec) ones have an alloy-frame and fully adjustable forks which took off about 5kgs, but they were severely restricted (70hp opposed to 89hp).

I reckon if they had cleaned it up and released Mk2 version to counter the RG then that could have been a beast.
Sad really that 500 2-strokes went south.

CC