Gilera DNA 50cc wont start - video of it turning over

[Guest]

Hi guys.

Please have a look at the video, as my Gilera DNA 50cc wont start.

I have cleaned the carb, air filter, checked the drive belt and fitted a new spark plug, but to no joy.

I was driving home when it lost most of its power and ran about 20mhp whilst shuddering along.

It eventually cut out and after pushing it for 1/2 a mile, it came back to life for a few minutes, this carried on till I got home.

I have then done the above and it just wont fire up?

The bike is usually really good, had it for 2 years and always started.

The day of the power loss, I left it in the rain and wind for 8 hours at work, but I have done this before and it was fine.

Video link:

http://www.youtube.com/watch?v=3nUNaGxUrF8

Thanks in advance,

Will.

[Tango]

After spinning it over like that remove the plug and see if it is wet.....if it is, then you have fuel getting into the combustion chamber....so that would point to spark or compression as the problem.... But if the plug is dry it would point to fuelling. Does the bike have a fuel tap? Is this working correctly? Is there an inline filter in the fuel line? Is this clear? Try starting the bike with the Filler cap removed in case the tank breather is blocked......a few things for you to be getting on with.....

[Guest]

Hi Tango,

Thanks for your help.

OK, the plug is a bit wet, not soaked, not dry, about right I think!

There is no fuel tap and no filter on the fuel line.

Will.

[eastanglianbiker]

check condition of the air filter and replace plug see how it is then

[Tango]

Hi Tango,

Thanks for your help.

OK, the plug is a bit wet, not soaked, not dry, about right I think!

There is no fuel tap and no filter on the fuel line.

Will.

OK Will, if the plug is wet then you can assume that you are getting fuel into the combustion chamber......so, if it won't fire it is likely to be no or a weak spark.....or no compression. Take the plug out and put your finger over the hole and spin the engine.....there should be enough pressure to push past your finger.....if not, then you may have a problem with piston/rings. The other thing to check is to take the plug out......put the old plug in its place and with the new plug in the plug cap put the body of the plug to suitable metal surface on the bike and spin the motor and look for a spark across the gap......just be careful when doing this to hold the plug to the metalwork with something that is suitably insulated so's not to get a shock...... If you don't get a decent spark then you could have a problem with the plug cap/HT lead/coil etc......

[Guest]

Thanks, I will have a look tonight and let you know.

Will.

[Guest]

Hi,

Sorry for the late reply and I have removed the video.

Compression is fine buy I get a weak spark and the plug is dry.

Weak spark: Do I just need a new plug or is there something more adequate I can do?

Fuel: It goes from tank to carb with no stops, I have adjusted the 2 carb screws in case I was cutting the fuel off, any suggestions please?

Thanks

Will.

[Tango]

Weak spark could be the plug.....but could also be the coil or HT lead/plug cap......Are you sure the plug isn't whiskered?......ie, doesn't have a piece of carbon bridging the spark gap? If you have compression and fuel getting into the combustion chamber then it must be the spark that's not strong enough......so maybe check the coil out.......

I posted this for someone having trouble with a Fazer 600.....but I think the reading on most bikes would be very similar.....

[Guest]

Hi guys,

OK, same video, new link:

http://www.youtube.com/watch?v=uwanpQe-rfE

I have replaced the fuel pump, and it looks good, fuel is getting to the carb. There is no filter after the pump.

Compression is good, it blows my finger away.

New plug, and tested it with the plug on the metal, spark looks good.

Now, I have ran out of ideas as I thought it was petrol related.

New carb?

New top end?

Thanks in advance,

Will.

[acting_strange]

Hi guys,

OK, same video, new link:

http://www.youtube.com/watch?v=uwanpQe-rfE

I have replaced the fuel pump, and it looks good, fuel is getting to the carb. There is no filter after the pump.

Compression is good, it blows my finger away.

New plug, and tested it with the plug on the metal, spark looks good.

Now, I have ran out of ideas as I thought it was petrol related.

New carb?

New top end?

Thanks in advance,

Will.

 

It takes 4 things for an engine to run...Induction, Compression, Ignition, Exhaust.. You say you have compression so that one....you say that fuel is getting to the carb, but is it getting to the cylinder?...you say that you have a spark, but is it appearing at the right time?...finally there is the exhaust, if that is blocked somewhere then it also wont fire...especially if its a 2 stroke which needs back pressure to enable the exchange in the crankcase...

[Guest]

Hi. Am having the same problem. The bike over heated and cut out on me. Got a new 70cc head. Put it all together n it wont start for no love nor money. There is compression and fuel is getting to the carb. But from the carb to the cylinder is a no go. Anyone got a clue?

[eastanglianbiker]

for both ops is the fuel tap a vacuum type and have any of the hoses in the vacuum system split or perished ?

[Grumpy Old Git]

looking through the thread you have said:

The plug is wet then later that it is dry?

You have adjusted the two carb screws - why? Are they both back in their original positions?

You have a weak spark then later a strong spark?

Simple tests you can do:-

1. squirt about a 1/2 teaspoon of fuel into the cylinder and replace plug - Turn over and if it fires or tries to then nothing, you have a fuel issue - Skip to 4.

2. With the plug out, ignition on, check for spark as you gently push the bike forward in 2nd gear. Stop as soon as you see the spark and (using a plastic drinking straw, check that the piston is at Top Dead Centre (TDC) or just about there. {Rough Timing Check}.

3. With plug in, turn over with your hand over the exhaust - You should feel the pressure pulse from the engine.

4. Ensure plug is dry and re-fit. Turn over and check plug. If not wet, then no fuel getting into cylinder - check all lines, filters, etc.

5. If plug wet, then either contaminated fuel or incorrect mixture or timing out.

Good luck!