old dude working on old honda mt250

on my honda mt250 the engine revved up on its own. pulled plug wire and it continued to run. had to stuff a rag in the carb to kill it.not sure what is happening. plug insulator was grey appeared to have been working like a glow plug.

What the ...????

Would you like to change a spark plug or consult with enginner.
Probably it's just not running smoothly ...

__________________
Teamworld is offer well-known branded names (i.e. BANDO, DID, NGK, YUASA) and accessories,Supply OEM motorcycle/scooter manufacturers such as Aprilia, Cagiva, Malaguti, Minarelli, Moto Guzzi, Kawasaki,and have Asiawide sourcing capabilities/production facilities.

We need more guys to pay attention to it. to post your idea ,,,

it's too cold here ....

__________________
Teamworld is offer well-known branded names (i.e. BANDO, DID, NGK, YUASA) and accessories,Supply OEM motorcycle/scooter manufacturers such as Aprilia, Cagiva, Malaguti, Minarelli, Moto Guzzi, Kawasaki,and have Asiawide sourcing capabilities/production facilities.

Once a gas is compressed, it heats up. Once an engine is hot, if compression is high enough and gas octane too low, you get self ignition ! This is the very principle of a Diesel engine which uses glow plugs to heat up the chamber then ignites on its own.

Looks like your gas octane is too low to start with. I would check for fuel mixture being too rich on your carb. Excessive carbon build-up on the combustion chamber wall causing excessive compression. There may be timing issues as well. Self ignition is not uncommon with 2 strokes engines.

There is no ghost causing such behavior, it is plain physics.

__________________
There is nothing like riding a Honda MC !

good explanation !!

Cheers,
Miss Mio

__________________
Teamworld is offer well-known branded names (i.e. BANDO, DID, NGK, YUASA) and accessories,Supply OEM motorcycle/scooter manufacturers such as Aprilia, Cagiva, Malaguti, Minarelli, Moto Guzzi, Kawasaki,and have Asiawide sourcing capabilities/production facilities.

Dats-a-bad! Most likely there was some red-hot carbon on the crown of the piston acting like a glow plug. This is left unchecked will blow a hole right through it, and the MT-250's are known to do this. Uncontrolable speed on any two stroke comes from an air leak at the reed box, transfer (crank) case seals or carb.

Before further use pull the head off the bike and "de-coke" the piston crown and head, it's routine maintenance-I think Honda wanted it done like every 2000 miles or so.

Honda made very few two stroke bikes over the years and 2 stroke engines were not their forte in the 70's, Yamaha and Kawasaki made better ones-and and MT 250's were rather problematic in the day. The CR (motocrosser) and MR (off road enduro) were less of a problem due to the intermittent power demands on the engine - but an extended blast on a regular basis on an MT-250 down the freeway caused BIG problems on these-soft seizures, transfer seal problems, piston/ring problems and overheating were top billers on the hit parade back then.

When you are riding it, just keep the clutch covered like you would the brake!

You mean, be ready for the engine to seize and lock up your back wheel ? Great ! (sarcastic).

That reminds me of Dan's Motorcycle course ... http://www.dansmc.com/seizure.htm He basically said the same thing about 2 stroke engine seizures.

Dan even provides solutions for fixing a jammed engine http://www.dansmc.com/stuck_engine.htm

__________________
There is nothing like riding a Honda MC !

As fas as the MT-250 goes, yes. A couple of things to do; although the MT has oil injection, try adding a small amount of synthetic 2 stroke premix to the tank, about a 70:1 ratio. Although the bike needs a greater ratio than this, if something goes awry with the oil injection system doing this *might* help prevent a soft seizure. Also, when the engine is idling very little/no oil is being injected into the engine with Honda's scheme, the other thing is to make certain the fuel/air mixture isn't overly rich. As far as I know this was Honda's first attempt at oil injection and they didn't get it quite right. The MR/CR didn't have OI.

These bikes are really old now and it's a very good idea to go through all of the oil lines to make certain there is no congealed oil plugging things up and that the injection pump is working at full capacity.

If I understand well, if the mix is overly rich the engine might overheat and something will fail or seize, right ?

__________________
There is nothing like riding a Honda MC !