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Bill Hoddinott VA (Enthusiast) View all posts in this topic  
Mon Jul 18, 2005 4:02 pm
100,000 Mile Road Test of a 1988 Kawasaki 250 Ninja - Part Eight        

It's about time to wrap this series up, since I think most everything has been covered, but let's go over General Operation a little.

There is, and should be, a presumption that every one of these bikes is set up exactly right for trouble-free running when it leaves the home factory in Japan. In fact, so confident is Uncle Sam in this, that he mandates that the carb adjustment screws be blanked off for emission-control purposes so the owner can't tamper with them.

This is fine, and I assume that the factory personnel test-ride each bike and set them up with instrumentation when they make their final adjustment of the carburetion.

With these BIG carburetors, and these SMALL cylinders, this is an extremely important operation!
I've been lucky with both of my engines, though they did not have identical start-up characteristics.

Both the '88 and the '01 wanted full choke applied for cold-starting, except that if the air temperature was 80 F or more, they didn't want quite full choke. If they got full choke, it was too rich and they wouldn't start.

The '88 always wanted the throttle held open about 1/16" with the twistgrip, for some unknown reason. The '01 starts with the throttle completely shut. With the choke set right according to the air temp, both of them start after cranking for one or two seconds.

The choke and some kind of 'fast-idle' system make the engine 'idle fast' at 2500-3000 rpm on startup, or even start to 'run away' and overspeed, but this can be controlled by letting the choke off a little.

After a minute or so, the choke can be flipped off, and now with my 5w-30 oil the engine will idle just a tick slower than the standard 1300. One pulls in the clutch, blips the throttle a couple of times to 'de-stick' the clutch plates, then engages first gear with a slight clunk(always, no matter what you do, inherent in multi-plate clutches: the drive and driven plates rub against each other and cause this). And away you go. As mentioned, when I used 20W-50 oil in the '88 engine, the thicker oil meant keeping the engine running with the twistgrip, until the oil warmed up, thinned out, and enabled the 1300 rpm idle.

It should not often be necessary to adjust the idle speed with the black knob on the LH side under the carbs, but if so, only when hot I might mention that the throttle cables must always have a little slack in them, so that the plates are sitting on the apparatus controlled by the knob. If the throttle cables are too tight, you may not be able to achieve the 1300 rpm idle. The cable adjustments are obvious and easily accessible.

I mentioned earlier that Roland said, I confirmed, and most people on this Forum seem to agree, that Kaw sends these bikes out geared too low, 14-45 rear sprockets. Most prefer to change the gearing to 14-42 or 15-45(both equal 3 to 1, obviously).

Just why Kaw does it their way, I know not. It gives a tiny percentage more acceleration in the gears and in top gear that way, but it also makes the engine run about(I think, never tried it) 500 rpm more for a given top gear speed, which increases wear a bit, as well as fuel consumption due to higher internal friction.

The changeover is certainly simple enough, and apparently most people do it, or have it done, and like 3 to 1 better. Some have reported going even 'higher' such as 15 to 42 or something, but I believe this is overdoing things, and the result will be that the engine can 'pull' this much gear, especially uphill or into a stiff headwind. So one will end up selecting fifth gear under these conditions to make up the difference.

It has also frequently been reported on the forum that people get oil consumption, apparently when they habitually use very high rpm, and/or attempt to cruise at speeds higher than 75.

It appears that what happens is that when you go beyond using about half(say) engine power, which I think is about what is required for 75 mph cruising, into using more than that, up to full, you get more blowby past the piston rings, gas pressure into the crankcase, which vents itself at increasing speed into the airbox, and the airspeed out of the crankcase carries oil mist with it. Which goes through the carbs and is burned, and out the exhaust. Hence your oil level drops gradually in the sight glass.

It appears that these engines are tough enough to take a lot of this kind of use; but every engine has its natural cruising speed, and if you insist on going beyond that, the inevitable result is going to be increased wear and reduced longevity.

As described above, my experience with the two engines so far in my '88, using 70-75 for a cruising speed around 8000 revs, with 3 to 1 gearing, and using 9-11,000 rpm for passing or whenever I want, is NO oil consumption.

I suppose that is about enough to say.
You can see here why I tell people this 250 Ninja is a splendid piece of engineering work, a great credit to the company that makes it, and a wonderful value for the consumer in today's world. It's quite obvious why the '05 is in the shops unchanged from the '88 model, despite being largely ignored by the enthusiast press. It's because word gets around in the real world, and lotsa sensible types really do think hard about how to get the most of what they want, for the least money.

PHOTOS! I do have those photos I mentioned, for you. We WILL get them up on the Photo album link for you. There has been a spot of delay because I managed to send them to Jeb at his 'old' address and he either has to get them there, or I need to re-send them to him.

In closing, I do want to compliment all those responsible for putting the Ninja250 Riders Club on the Internet. This is a valuable communication medium and undoubtedly has given much benefit to many, many people.

End of Part Eight, and Topic.

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