dt250mx poor starting

[elliottles1]

Good day folks,

question on my dt250mx. recon engine, good compression etc.

starting from cold with or without choke, it will fire ONCE and then appear to flood. if I remove and dry the plug it will repeat the same fire once. I can start it by bumping and it will run very well after that.

I have changed the carb for a brand new one, and messed with jetting/mixtures, same problem.

so my question is this. could a weak spark get flooded out and then fail and appear to be caused by flooding. if so I will start replacing electrical parts one by one.

any advice appreciated.
thanks and stay safe folks.
les.

[m in sc]

ive seen this before.

In my experience, its usually from fuel seeping into the motor after its been turned off., a slight amount. when it fires off the one time, it kicks the raw fuel up the transfer ports and fouls the plug.

the reason pushing it off works is because it pumps the fuel through the motor allowing the frash air to get in and make a combustible mixture. so, check your fuel valve. 

to verify if this indeed the case, disconnect the fuel line after its been run. check for drips overnight if possible. (let drip into an empty can, etc)

try to start again next day see if its ok.

[elliottles1]

m in sc

thanks for that, It makes sense, I hope its that simple! could be a week before I can get to it to try.

any other ideas appreciated, I will try them all.

les

[gargantua350]

Try some prime kicks. 

1.  Ignition off choke on and gas on
2.  Kick a few times
3.  Ignition on
4.  Kick and the it should light up and run.

[elliottles1]

Me again,

definitely not fuel leaking into crank case, drained, stripped, tested everything, filled with fresh fuel. exactly same problem. tried a brand new coil, still the same.
I am now going to replace the points and condenser, and while the flywheel is off, I will have a look at that too.

I am hoping that a weak spark can appear as flooding.

cheers
les

[m in sc]

it can. bummer. well, at least you eliminated one thing.

[Dvsrd]

Assuming the ignition is flywheel magneto, not battery and coils. Is it possible that the magnets have become weakerkver time?  I experienced this with a much older 2 stroke, a Villiers 12D 125 cc single. After having the flywheel re-magnetized it started and ran perfectly.

[elliottles1]

Dvsrd,

I will check the magnets when I pull the flywheel to fit the points/condenser. yes, it is just a one wire ignition. how do they re-magnetise them??

such a simple engine, I cannot believe that I cannot find what the problem is, I will end up changing the whole engine!

cheers
les

[Dvsrd]

Dvsrd,

I will check the magnets when I pull the flywheel to fit the points/condenser. yes, it is just a one wire ignition. how do they re-magnetise them??

such a simple engine, I cannot believe that I cannot find what the problem is, I will end up changing the whole engine!

cheers
les

I believe coils/electro-magnets are used to re-magnetize old flywheels. It is definitely an expert task, as far as I am concerned. I also believe magneto flywheels should be stored "on" a status or paired with another flywheel, to prevent magnetic decay.

[m in sc]

we battled this on a bsa500 a few years ago, was super frustrating. Im leery if this is the issues here, but its possible. 

[elliottles1]

I will persist in solving this problem, and then I will post what it was, as I don't think that happens enough, threads just seem to run dry and leave me wondering what cure was!

cheers for now
les

[Dvsrd]

we battled this on a bsa500 a few years ago, was super frustrating. Im leery if this is the issues here, but its possible.

A spark checker may be useful here? Chainsaw repair shops use them.

[Barrie]

I recon it's the condenser

[1976RD400C]

You say you can push start it and it will run well after that? Very odd. I would try the spark tester and see if it is sparking while kicking it when it is having the problem.

[elliottles1]

hi again,

I have new points and condenser to go in,  but have lost my flywheel puller, so I am waiting for a new one to arrive and will post the result soon enough. I really hope it is one of the two.

cheers folks
les