Had a prang at weekend ,bike was upside down in bush with throttle pinned. It stopped suddenly before I could kill the engine.

Retrieved from bush and kicked over but it would not fire. At home checked for spark etc. all o.k but won't start.

the plug remains bone dry after kicking over with choke on and throttle open. Striped and cleaned carb in case float needle was stuck. Plug still remains dry.

Removed air box and sprayed easy-start in carb inlet - not a splutter.

Then removed head and all seems o.k.

Before I dismantle further is there anything obvious I'm missing?

Could failed crank case seals leak fuel /ether from before it reaches the chamber via transfer ports?

I'm no 2 stroke expert .

Any suggestions welcome

when it went upside down it was starved of fuel and i would guess muck in the float bowl is blocking jets (dry plug) id re strip carb and blow everything through if it has compression and spark it can only be fuel

mccarro

when you say the bike suddenly stopped, was it instantaneous like it locked up, or like it was starved of fuel due to being upside down?

Like you guessed the float can stick open if it gets a real bang upside down, but this appears to be the opposite of your symptoms.

My next steps would be:-

• Check youve got the same level of kickstart resistance you had before (compression)
  
• Check the throttle is returning properly with a "clack" when you let go of the throttle.
  
• Check there's fuel flowing to the carb by taking the fuel line off.
  
• Check theres fuel in the float bowl when you remove it (fuel on??).
  
• Clean the jets, especially the pilot jet.
  
• Check the float height is OK, in case you bent the float tang.
  
• Check the choke plunger is pulling up.
  
• Check you havent broken a reed by looking down the intake rubber with the carb off.
  

this'll take an hour or so......but these are the obvious research steps.

Dom

Edited May 21, 201313 yr by dombush

Thanks for replies

I have blown out jets and there is fuel getting into bowl as it p****s out the bottom if I loosen the bolt on bottom of bowl. Haven't checked float height yet.

The engine stopped quite suddenly - didn't splutter and die. There is no evidence it seized though.

What's confusing is if I remove plug and spray ether direct into chamber it still won't even splutter - nothing.

I will check the reeds shortly. Also I can get hold of spare carb to try to rule that out.

Could the timing have slipped ?

Thanks

woodruf key sheared ?

bike will still spark but in the wrong place in terms of tdc.

that doesnt explain the lack of fuel though, did you inspect reeds ?

sounds like what happened to mine, take front pipe off and look at piston as mine was scored badly and the rings melted into it, had to have barrel recoated and new piston and rings, sorry mate .

Just checked reeds and their o.k.

A compression test would confirm the knackered piston and rings theory? There's no obvious damage to the barrel

Do u need to remove the rad to get the barrel off

Cheers

Agree with Betabonkers , you will find rings stuck in melted piston .

You might be lucky with bore , acid might clean it up .

New piston kit definitely .

Had exactly the same thing with my 2013 300. Remove the front pipe & check for damage to piston and rings. Any scoring will mean not enough vacuum to draw fuel into cylinder.if it's damaged it'll need new piston kit and rebore and plating.

Don't despair yet.

Peek into the exhaust port, though...look for scoring and seized rings.

If you could get your hands on a compression tester, that would tell you a lot.

I think a strong 2 stroke should be at least 140psi.

But, not even a pop with starting fluid?

Could definitely be timing (sheared key).

Make sure you try a new plug.

Took the barrel off tonight and the piston and rings are knackered.

The barrel is Marked in places but is not scored as far as I can tell.

Is a rebore and oversize piston an option if the bore can't be cleaned up?

Thanks for all replies

m

The barrel is Marked in places but is not scored as far as I can tell.

One mans mark is another mans score. Sorry mate can't help you. You'll need to get an expert to have a look.

Mccarro

ok, so at least you know..

The bore of the barrel is electrofusion (Nikasil plating) plated straight onto the aluminium barrel.

Although very hard the Nikasil plating is only microns thick, so a score, scratch can easily render the barrel in need of a replate.

1. Check if the barrel is beyond repair by checking if the damage is more than cosmetic. Although one would use a bore gauge for measuring general wear, a scratch or gouge is so "localised" that this isn't possible. The rule of thumb I use is that after cleaning off any residual piston aluminium if I can still feel a definite "step" with my fingernail its probably in need of repair.
   
2. There are two types of repair. A diamond hone will deal with the scratch if its a micon or two deep, any more than this and your into a re-plate which costs around a 1/3rd of a new barrel.
   

I cant tell where you live but I can say that the UK and US both have a couple of replating companies and these have a number of "agents" that can organise getting a new piston, sending off the barrel etc. I always buy a piston first and sent it with the barrel. This way i get the bore plated and honed exactly to suit my specific piston using the manufacturers specification for piston to bore clearance.

Generally the replate companies offer a 1 or 2 week turnaround, then a small running in period will see you up and running again.

Dom