Poor Spark, Or Rich Mix?

[welshoneder]

I was out on bike yesterday, was running great then I ran out of petrol!! (yes I know idiot!!) Anyway, one of the lads I was with drained some from his, then put it in mine and wounldnt start, bumped it but it felt like it was running rich, everytime I opened throttle it would cut out and not re kick. So took plug out cleaned it, quite black and a bit wet, as expected. Then kicked up first kick, then died again. Then pushed bike for 2miles then tried to re start it. It started and I rode the rest of way home. Went to kick bike up again today and started then cut out after 30yards. Took plug out filthy again, black carbon and maybe a little oily?? Cleaned plug and stripped carb and cleaned then started fine and sure enough opened throttle and it cut out again!! Its a 1999 techno 250. Is this common fault? Going to change plug tomorrow and see how I get on. Been ridig the bike for 5weeks with no problems then this happened yesterday!!

Oh and prior to me running out of petrol it was cutting out on idle after 1.30hr of riding but would re start 1st kick

Any help would be appriciated, thanks

[dan williams]

First thing have a few new plugs ready. Unless you've got a bead blaster you can never really clean a plug. It sounds like you have the wrong heat range plug to start with. Even a perfectly carbureted and timed engine will foul the wrong plug. N7YCC Champion for your bike if I remember correctly or AC Delco #4 or whatever the equivalent. Also hard starting can be from a bunch of issues from sticky kill switches (common on Betas) to cracks in the high voltage wire out of the ignition coil to bad spark plug cap. If it isn't smoking up a storm as you'd get with a bad crank seal then there isn't much more that will gum up a plug. On a bike that old it could be time for a set of rings.

But start out with the simple (cheap) stuff first and get a new plug. Let us know how it works out.

Edited May 3, 2010 by Dan Williams

[welshoneder]

Well the plot thickens, I've just realised my bike isn't a 1999 but 1995!!! and the wrong spark plug is fitted the N7YCC is currently fit where is should be the Champion RN3C or NGK BR8ES. This will be my first port of call then it will be rings change.

Thanks

[stork955]

Gday -it wont be rings. That will give you no compression. Oily black looking plug means too much oil, a dry lookinh black plug is fuel. Plug fouling in a 2 stroke is -

1. Wrong Plug

2. Too much oil - 70 to 1 in the Techno.

3. Too rich fuel mixture - Air Cleaner blocked, float level wrong, worn needle and needle jet (the ones under the slide) or someone "fixing" it in the past -wrong jetting. Go with standard settings.

4. Leaking Crank seal on the gearbox side - your trans. oil level will drop over a period of time as the engine sucks oil through.

Check it in that order. Clean the exhaust anyway, front to back.

Cheers,

Stork

[welshoneder]

how do I gain access to crank seal, wot has to come off??

[scotty97]

Sounds like you've been busy since we went out on them???? i'l keep an eye on this thread to see how your getting on.

[liviob]

Gday -it wont be rings. That will give you no compression. Oily black looking plug means too much oil, a dry lookinh black plug is fuel. Plug fouling in a 2 stroke is -

1. Wrong Plug

2. Too much oil - 70 to 1 in the Techno.

3. Too rich fuel mixture - Air Cleaner blocked, float level wrong, worn needle and needle jet (the ones under the slide) or someone "fixing" it in the past -wrong jetting. Go with standard settings.

4. Leaking Crank seal on the gearbox side - your trans. oil level will drop over a period of time as the engine sucks oil through.

Check it in that order. Clean the exhaust anyway, front to back.

Cheers,

Stork

While it's true that a worn set of rings will lower the compression they will also cause the motor to run rich because of the blowby occuring.

[dan williams]

If it is a '95 it's got that awful DelOrto with the two piece pilot jet. Best mod I did on mine was to swap it out with a mikuni. Worn rings will make the bike start harder. A new set really restores the spunk to the engine.

[welshoneder]

Changed the plug today, started up and runs fine, although I'm a little dubious that I could put the poor bike performance down to a spark plug, but it seems to work fine, I've just stripped the exhaust of and is currently soaking in a bag of oven cleaner to try and de-coke it, the header pipe only had about 30mm internal diameter where it should have been closer to 45mm, need to re pack the back box, just wondering what to do with the intermediate one as theres no way of repacking that, I'll see how oven cleaner gets on!!

Think i'll prepare myself a little tool kit for future rides!! (inclusive of spark plug and bottle of fluid!!) Anyone know where to get one of those front mounted fuel cells???

Thanks

[welshoneder]

FOA Dan Williams where did you buy the mikuni carb from? will the 96> fit same OD's on pipe work? Also do you know off had what the model number is? and last but not least did the standard settings suit the engine?

Thanks

[dan williams]

Ugh I wrote a nice long reply and Iexploder froze. I bought the carb from the US Beta importer. Beta used the same Mikuni VM26-208 from the '89 TR35 (I think) to the '94 Techno, changed to the DelOrto in '95 then back to the Mikuni from '96 until '07.

I might be being too harsh on the DelOrto carb. The problem wasn't the DelOrto but the fact that you couldn't get jets for it. The carb used on the '95 was a new DelOrto with a two piece pilot jet and finding jets to tune it was near impossible. The jetting from the factory was just plain wrong. Too rich on the pilot circuit, too lean on the needle and again too rich on the main. The practical upshot being that as you approched an obstacle and rolled on the throttle it would bog until you started to get into the needle jet. All of a sudden the bike would get very interested in the proceedings. This made timing a hit a somewhat random process. Forget correcting on an off camber or climb. My buddy managed to get his hands on a "factory" bike that was going to be for a sponsored rider. The sponsored rider liked his '94 so much he just changed plastic and graphics and kept his old bike. Anyway the factory bike was an animal with the DelOrto. Man I seen some ugly crashes...UGLY!! After swapping out the carb on my bike it became smooth, controlled and wonderfully powerful. I talked my buddy into getting one too and his bike went from an unpredictable beast to the most amazing bike I've ever ridden. It would grunt like a hog in high gear but you could just roll on the throttle and the power would just build to a terrifying scream.

I suppose I should get to the point. Jets for that DelOrto should be pretty easy to get at this point so it's worth trying to tune the carb you've got before you run out and spend big crinkies for a Mikuni. Still if you find one cheap it's a good mod.

I think you're off to a good start opening up that carbon plugged exhaust.

As an aside, from a purely aesthetic standpoint I think my '95 was the most pleasing bike to look at. Seriously, look at a, er, well proportioned woman lying on her side then look at the '95 and tell me what inspired the frame and rear fender of that bike. Pure Angelina Jolie.