View Full Version : kx 80

22nd March 2008, 11:20
My young fellas got a kx80 and every time he arses off we cant seem to start the bloody thing even if we leave it for a time or turn the fuel off etc. But put a new plug in and its away like a dog shot in the arse , the trouble is i dont want ot have to keep buying iridium plugs . Any ideas will be greatly appreciated.

22nd March 2008, 15:12
buy a couple of spares and then bead blast em when he falls off

22nd March 2008, 15:36
Thanks Frosty .

Buddy L
22nd March 2008, 22:06
well first he has to learn not to fall off.
secound you have to find out why the plug is fouling up.
running too much oil in your mixture?
main jet too large?
just two of many things that could be wrong

23rd March 2008, 08:57
Cheers mate , running 50/1 mix Fuschs 2 stroke mix .But dont know jack shit about the carb on them , might have to whip it off and get someone to take a look at it .

24th March 2008, 10:51
My boy has a KX80, old 1990 model I think. He is only just learning gear changing and falls off sometimes when it just gets a bit too loose, sand or mud. It has a standard NGK and starts on about the 2nd-3rd kick if it's been lying down or 1st kick if it's just been in the garage. Initially we used a whole tank of gas rolling round in a paddock and never got on the power but used plenty of throttle getting up little hills at not much above a fast idle. The plug always comes out clean.

I don't think Iridium plugs are the "go" for 2-strokes. They are intended for use in the modern 4-stroke bikes. I wonder if someone at the bike shop wasn't just fitting you up with a pricey plug??

I run either 100 octane or last time we put a few tanks of Mobil 95 through it with Motul 800 at 40:1. It's a smokey little thing but that plug never fouls and the motor doesn't even seem to load up with oil.

24th March 2008, 12:02
Fit the correct spark plug. Buy two of them and tape the spare behind the front number plate with a spanner.

Run it 32:1 with 95-98 octane fuel. If it wont start then turn off fuel and lean bike over to clear carb. If it contunues to be hard to start then take it to a shop to be checked out.

Spark Plug NGK R6254K-105
óGap 0.7-0.8 mm

Nothing worse than a hard to start bike

24th March 2008, 12:35
Thanks Speedpro and TWT very helpfull will definately be taking that advice on board.

24th March 2008, 19:35
Just pulled the plug out. Still looking good after a couple of days slow riding round "The Farm". It's a BR9ES, so nothing special, or pricey.

The other thing is that if the bike is being ridden reasonably slowly then you can lean out the oil ratio. Without the revs or throttle there will not be the revs or gas flow through the engine to blow the oil out. It will tend to hang around. Once you start working it a bit harder then increase the amount of oil. I only ran 50:1 initially - first two times out. I use Motul 800 in my bucket which lives at about 10,000rpm and run it at 40:1. I can't see the point in running any more oil than that though plenty of people do. Just a thought.

25th March 2008, 16:54
It sounds like it's flooding. I assume you've tried the throttle wide open and kick it half a dozen times routine after a crash.
Another couple of points.
1. As Speedpro says normal plugs will be fine, don't bother with the expensive ones.
2. If it is fouling plugs through running too rich then using less oil in the fuel will make things worse not better. The whole rich / lean thing has to do with petrol / air ratios not oil, so less oil = more petrol therefore richer. A lot of people get screwed up on this. With modern engines and oils 50:1 will be fine (lubrication wise) as long as the bike is jetted right, especially if the lad isn't holding it at redline for long periods of time.

26th March 2008, 16:44
The KX80 does not have the modern chrome bore. The owners spec sheet says -
Fuel Required Min 95 Research/90 Avg. Octane, Unleaded OK
Mixed 32:1 Gas:Oil

Running less oil will make the fouling problem worse. They great thing about modern 2 stroke oils is they allow you to run more oil in the fuel.

If you want to change the jetting first drop needle/raise needle clip one position. After this you could go one size down on the main jet.

Keep us posted

26th March 2008, 17:05
Thanks guys for all the wisdom, were on top of the problem now i think , the lads much happier about his weekend rides . another KB in the making maybe when he sees what can be achieved with forums kike this .