My boys Beta 80 keeps killing spark plugs and I'd like a little help with it please.

Most of the time they only last a few hours then you have to fit a new one. When you take an knackered one out it is black with oil not brown and dry like I think it should be. You can clean it up till it's spotless but it will never start the bike, does spark against the frame though.

It's had a new fuel filter, air filter, carb stripped and cleaned and setup but nothing changes, I must be missing something. I've been using around 70ml of Ipone strawberry 2 stroke to 5 litres of normal unleaded.

We've been lucky so far that it hasn't left us stranded but it has nearly ruined a few days when I've forgot a spare plug.

If anyone has any ideas on what could be causing this I'd love to hear them. Buying a box of b9es plugs hopefully isn't the only option.

Running rich will kill plugs, you need to determine the source. Is it standard carb, and in good condition ?  Check needle position, float level etc. Over oiled air filter will contribute also. Will it start from cold without choke ? Are you using the correct plug ?

If all above are correct, the ignition may be failing.

Edited March 27, 20188 yr by b40rt

You have ‘fouled plugs’ stating the obvious really, but once the plug has become contaminated it will need to be replaced. There will be people telling you to clean them, dip them in bacon fat and hold them up to the moon, but once coated in the dreaded by product of incorrect combustion there dead! You say the carb has been stripped, cleaned and set up, but has it been set correctly to the manufacturers spec. and is the plug grade correct. Are you sure that’s the correct fuel oil mix. To all intents and purposes the engine is running too rich, hence the fouled plugs. The carb float level may be set too high, the needle valve may be leaking allowing the carb to flood, the main jet may be the wrong size and the needle may be worn, again causing rich mixture. The fact that a cleaned up plug will spark faintly when earthed against the frame indicates that the centre electrode insulator is fouled. A new plug should produce a nice big fat blue spark, have you tried doing this? 

What year of Beta 80?

1 hour ago, shazsfan said:

At 70mls that is correct, we have always ran our Beta 80’s on super unleaded fuel.

If the carb is unworn and all jetting is standard, check the reeds, if all is good it has to be the oilseal on the crankcase. Do you get the same amount out as you put in at an oil change?

 

 

In my experience, burning oil will not kill plugs.

Might be being dumb here, but a rich mixture would produce a sooty black plus. OP says 'black with oil not brown and dry'. That suggests to me it's an issue oil burning. Might also be running rich as well, but issue sounds like the issue is burning oil.

I would be thinking about crank seals, especially if the bike is known and has either been standing or it's been slowly getting worse. Maybe filter is over oiled. If new to you could be an issue with the crankcase gasket not sealing right and it's pulling oil through the gearbox. I've had this and the oil level didn't really drop because the gearbox was being refilled with petrol. Does the oil smell of petrol? this could be a clue.

Then the daft stuff like forgot and put a second shot of oil in the petrol, though at modern ratio's would be surprised if this would oil the plug that badly. Does the exhaust smoke when you give it some beans? blue smoke usually means burning oil.

 

try a softer plug, is that the correct plug,B9Es I think is a hard plug I had same problem on a 125 years ago & a softer plug cured it.

 

Edited March 29, 20188 yr by digger144

I would replace the carburetor inlet needle and seat. on two stroke engines the vibration from the engine wears the inlet needle and it starts to not control the inlet fuel perfectly and will cause a rich condition. on my arctic cat snowmobile I used to have to put new inlet needles in every season or the engine would not run right thru the second season with the worn inlet needles. it would be rich and down on power. if u inspect the inlet needle and it has any visible wear at all on the tip it is bad. the wear is actually not the tip but a ring around the tip where the needle sits on the seat.

Edited March 29, 20188 yr by maxwell smart

I would go with Diggers advice try something like  Champion N21(assuming its a long reach plug)  or equivalent. If it runs how you want it to now why start changing the carburation and other things?Often on kids bikes they dont get any real hard work to do so the natural cleaning process never takes place then you end up with a black sooty plug that doesnt work.

Check to see if there is an Iridium Alternative. They can stand the heat and will last longer.

 

its not standing the heat  that is the  problem,its running too cold on a hard plug up & oiling up.with a hard plug the engine the needs to be revving and running hot .ie like a race engine

Thanks guys, excellent input so far.

 

Will start from cold without choke with new plug. Correct plug as far as I know. Carb settings are written on his fuel can, I don't know them off the top off my head, sorry.

Fresh plug gives big fat spark against frame.

2001 model.

Engine oil is good. Levels same before and after, nice and clean. Very black oily exhaust.

It can be worse if I have a go to get it unstuck or clear a trail obstacle he can't. Me revving it higher doesn't clean the plug as expected it just oils up quicker.

I have a b7es spark plug in the garage. Lower the number the higher the heat?

What is meant by a softer plug?

Carb is your problem. It should not, ever,  be possible to start from cold without choke.

 

(Assuming "away with the fairies" is in the uk )

Edited April 1, 20188 yr by b40rt

I just tried it again with fresh spark plug and you're right, no start from cold without choke.

Carb stuff written on the fuel can is 70ml oil, fuel screw 1 1/2 turns out, clip on second from bottom, Jets 100 70 38.

I cleaned the carb again, still spotless. I use carb cleaner and compressed air.

I found the clip was second from the top so moved it down one to second from the bottom, what difference would this make?

I fitted the b7es plug seeing as it was handy.

The wee bike started first kick and didn't rev it's wee head off in a cloud of smoke like it usually does. I'm taking tomorrow off to let him try it out so will report back.

I'm in sunny Scotland but really actually awa wi the faeries.

Edited April 1, 20188 yr by 8690q

Moving the clip down, raises the needle, allowing more fuel. This will make it run richer at higher revs.

Does your carb have an air screw, or a petrol screw ?

 More turns out with a petrol screw = richer. 

More turns out with a air screw = leaner.