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DT250a fuel/carby issues - maybe


DTGordo
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Hey all,

Please help:

Replaced the points and condenser and set the timing (ta for previous advice on that) and was running pretty sweet.

I also got hold of a bigger plastic tank and had to repair a couple of holes.

Was running great up to the servo to fill up then crapped itself 50m after that. Just stopped. Would start but then stop with any throttle. Then nothing. Luckily that's not far from home.

It has spark.

I pulled off the carby as I was thinking that some water maybe got in there (I was checking for leaks in the tank before I put it on but thought I dried it out ok) and also thinking that maybe the inlet valve might not be stopping the fuel coming into the carb b/c of the extra 5 litres worth of pressure in the tank (which happened to another bike I had ages ago).

In the carby the O-ring looked pretty stuffed but have to wait until Monday for a replacement but apart from that everything looked about the same as before.

I had a quick look at the reed valves and they looked ok as well.

Plenty of fuel in the cylinder through to the exhaust so I'm thinking back to the carby sending too much in?

Any advice/thoughts mucho appreciated.

Almost there.....

01062009.jpg

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  • Moderator

Hey all,

Please help:

Replaced the points and condenser and set the timing (ta for previous advice on that) and was running pretty sweet.

I also got hold of a bigger plastic tank and had to repair a couple of holes.

Was running great up to the servo to fill up then crapped itself 50m after that. Just stopped. Would start but then stop with any throttle. Then nothing. Luckily that's not far from home.

It has spark.

I pulled off the carby as I was thinking that some water maybe got in there (I was checking for leaks in the tank before I put it on but thought I dried it out ok) and also thinking that maybe the inlet valve might not be stopping the fuel coming into the carb b/c of the extra 5 litres worth of pressure in the tank (which happened to another bike I had ages ago).

In the carby the O-ring looked pretty stuffed but have to wait until Monday for a replacement but apart from that everything looked about the same as before.

I had a quick look at the reed valves and they looked ok as well.

Plenty of fuel in the cylinder through to the exhaust so I'm thinking back to the carby sending too much in?

Any advice/thoughts mucho appreciated.

Almost there.....

01062009.jpg

Hi mate, so long as you have good compression thats the main thing, you say it has spark double check your ig timing hasnt slipped since you worked on it recently. That only leaves fuel, reading between the lines it looks like you tested the tank with water, maybe there was a bit left in there, just drop off the drain plug at the bottom of the carb, also disconnect the fuel pipe from the carb and run a bit through on reserve, water is heavier then fuel and if you leave the bike leaning on the side stand any water will congregate around the fuel tap area run it into a glass jar, let it settle and you will see if theres water in there so you can deal with it.

...Paul

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I would also put the old tank back on and see if it stops the problem. The gravity pressure of an additional 5 lts may be pushing too much fuel through the carb, as you said. If you cant change the tank try restricting the fuel flow by clamping the fuel hose. If it is too much fuel and the plugs get fouled then it will be a pig to start so clean the plug or get several to swap them around whilst testing.

Oh yes and make sure that there is a breather hole in the cap and it is clear.

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Hey thanks guys,

I squirted some fuel into the 2nd sparkplug hole (so it does have use after all!), blocked it up again and it started fine for a second so I'm sure it's isolated to the carby. I'll be pulling that off again and cleaning and checking. Nice thing is there's not much to them so it doesn't take long. I'm waiting for a new o-ring to arrive which I'm hoping is also some of the story.

Anyways thanks again and have good weekend. Hopefully good news next week.

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