Starfire GT50 engine fires up but stalls prematurely

[AussieSteve]

The fuel-oil ratio shouldn't make all that much difference, really.
Unless there's not enough oil and it's getting too hot, maybe.
All the same, it didn't sit for long so fuel/oil separation shouldn't really be a worry.
Check your plug colour - it should tell a story.

 

[motorpsycho]

If you had too little oil in it (more like no oil) you would definitly know the difference.
A 2 stroke will run like a wild banshee on straight gasoline, but the engine WILL NOT last more than a few minutes.
it will lock up from lack of lube.

 

[AussieSteve]

If you had too little oil in it (more like no oil) you would definitly know the difference.
A 2 stroke will run like a wild banshee on straight gasoline, but the engine WILL NOT last more than a few minutes.
it will lock up from lack of lube.

As I understand it, it's not 'more like no oil'.
The mixture was OK, but the can sat unshaken for several days to a week, before being poured into the tank.
It won't settle out much in that time, and there certainly won't be 'no oil'
(I was speaking purely in the context of this problem, not a 'forgot the oil' situation.)

Mike, in the back of my mind is - watch those electrics. There's something not quite right, hence the high CDI turnover.
This mis-firing might be related. ie another potential CDI failure.
I don't believe for a moment that you're just getting one bad CDI after another.
Something is causing the failures.

(Off to bed now, been working on my regulator circuit and forgot the time.)

 

[motorpsycho]

no, i was just making a point saying that mixture will affect the way a 2 stroke runs.
if the gas can sat for awhile, there will still be oil mixed in. the oil will not completely separate from the gas, but it is a good idea to give the can a shake before using the gas just to stir things up.

 

[DaveinGR]

Bad gas?

If gas sits for too long (over 2 months) it quite often gets "stale". In fact, the recommended "shelf life" for fuel is 1 month. Here in the states they mix ethenol in to increase octane, ethanol is a form of alcohol and evaporates quickly lowering the octane level in the fuel. Also alcohol and water form a gel in gas cans and fuel systems. Check your fuel! Make sure fuel is fresh and fuel can is clean. I fix small engines for a living and the biggest issue we have at the shop is bad/old fuel.

 

[motorpsycho]

I've never had that problem with stale gas.
I have let gas sit in a can for a few months, and it's still fine.
Of corse, i add sta-bil to all my gas, which will keep it fresher.

 

[Hajuu]

Heh yeah I normally give it a bit of a shake (tip it upside down a few times). It has probably been about 3 weeks to a month since I made it up, I have also left it in direct sun for days at a time inadvertently heh.

However, I think it was an issue with my wheel alignment. - Investigating further.

 

[Hajuu]

Hey guys, still seeming to have some issue with my newly rebuilt wheel which I can't figure out.

Basically at very low speeds, there is a horrible shudder kind of effect, like jerking the bike. This stops once the speed increases, which is what puzzles me.

The alignment of the drive sprocket to the wheel sprocket seem ok to me.

 

[whizzer48]

I am jump in to a long thread.

"The alignment of the drive sprocket to the wheel sprocket seem ok to me."




Can it be your chain and sprocket. Chain will stretch in the middle of it and when go around the sprocket will climb on the teeth of sprocket. Sprocket teeth is miss match to chain too. The chain run in the cups or valley not on the teeth. I seen chain and sprocket look good untill one link start to climp out of the cup and then the chain will snap. You may have to it too tight for chain to run. At low sprocket you will feel it and high speed you will not.


I think they say slack is 1/2 to 3/4 for chain.

 

[AussieSteve]

I tend to agree with whizzer48.

Is your chain possibly too tight? That would cause similar symptoms as the wheel turns and the chain tightens and loosens. (These sprockets are never perfectly dead-centre.) You need to turn it to the point where the chain is at it's tightest, then adjust for about 10-15mm play.

Otherwise, the answer might be 410 chain, instead of 415H, if it will fit on your front sprocket. The pitch is good, they're both 1/2", but in some cases the teeth are too wide and 410 won't seat well. I plan to grind the sides of the teeth to suit 410, when I get around to it.
415 often rides on the collar on the side of the front sprocket, instead of seating properly on the teeth.