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Gilera DNA 50, starts sometimes, 90% of the time it doesn't.


DillHD
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I bought this Gilera DNA for practically pennys to rebuild it, pretty much it was a project.

It needed new top end gaskets so I bought and fitted them (bare in mind, the engine didnt start at this time) while the top was off I checked the piston and rings and barrel, all fine.

Put some fresh fuel in it... still didnt start, turns out its "vacuum powered" so I took the vacuum pipe off and gave it a suck ( :oops: ), petrol then started flowing through the pipe & now it flows normally when you kick it, and then it started and sounded alright gave it a little rev and had it going for about 20 seconds then it cut out and when you kicked it the engine didnt even want to start, there was nothing there, so I went inside baffled came out 20 mins later, kicked it, it started but done the same thing, cut out, didnt even sound like it had life in it again. Petrol is going to the carb its clearly visible (see through pipe).


Now, cut to today messed with a few pipes (nothing much just took them all off to check the carb then put them back on) and the bike started and actually stayed on this time although it couldnt idle for long, it would idle but would eventually start to cut out so when i did finally let it cut out i tried kicking the engine again and long behold.... the engine sounds like its got no life in it, not even a little cough.


before this, i took the carb off and one of the jets was blocked so bad it wouldnt clear, so i replaced it with another screw, same size jet, from another DNA carb, and just generally cleaned the carb (just putting this here so it doesnt get said in the replies)

Also compression is good, spark is good, no leaks anywhere.

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Does the battery have the required charge.. and also are you sure you haven't flooded it in the attempt to keep getting it started?

 


Forgot to mention in the main post its got a brand new battery and its full, and flooding might actually be a possibility how would I know for certain?

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Forgot to mention in the main post its got a brand new battery and its full, and flooding might actually be a possibility how would I know for certain?

 

I believe a wet or fouled spark plug indicates a flooded engine of which if it is the spark plug might need replacing in order to allow the bike to start again, so remove the spark plug cap and then the spark plug and see what the condition of it is and take it from there.


If it is fouled allowing the bike to sit and the excess to evaporate is one choice (clean empty area with the spark plug removed so the hole is exposed), alternatively keeping the throttle all the way open when attempting to turn over is another option (sounds like there's a method in the madness to allow a full throttle to clear it).

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Forgot to mention in the main post its got a brand new battery and its full, and flooding might actually be a possibility how would I know for certain?

 

I believe a wet or fouled spark plug indicates a flooded engine of which if it is the spark plug might need replacing in order to allow the bike to start again, so remove the spark plug cap and then the spark plug and see what the condition of it is and take it from there.


If it is fouled allowing the bike to sit and the excess to evaporate is one choice (clean empty area with the spark plug removed so the hole is exposed), alternatively keeping the throttle all the way open when attempting to turn over is another option (sounds like there's a method in the madness to allow a full throttle to clear it).

 

ah! Thanks for the info, will take the sparkplug out now and leave it overnight!

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Sounds like fuel starvation to me. Just because there's fuel in the line doesn't mean it's getting through.


I'd take a punt on the bowl running dry - hence why it'll die out and start again a little while later.


I'd be looking at the float needle valve in the carb, the fuel pipe and tap for grime and debris.

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Forgot to mention in the main post its got a brand new battery and its full, and flooding might actually be a possibility how would I know for certain?

 

I believe a wet or fouled spark plug indicates a flooded engine of which if it is the spark plug might need replacing in order to allow the bike to start again, so remove the spark plug cap and then the spark plug and see what the condition of it is and take it from there.


If it is fouled allowing the bike to sit and the excess to evaporate is one choice (clean empty area with the spark plug removed so the hole is exposed), alternatively keeping the throttle all the way open when attempting to turn over is another option (sounds like there's a method in the madness to allow a full throttle to clear it).

 

I left the sparkplug out over night, and it took awhile but now it starts everytime :cheers: , but it keeps "bogging out" somewhat only when its idleing?

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I left the sparkplug out over night, and it took awhile but now it starts everytime :cheers: , but it keeps "bogging out" somewhat only when its idleing?

 

By "bogging out" I'm going to assume you mean cutting out like a complete loss of power, is this when it idols all the time or only when warming it up for the first time?


I assume you haven't got as far as taking it out on the road yet, of which you'll need to do to solve the issue and work out witch one it is.. get it out on a ride for at least ten minutes and let the engine get up to temp properly, and then when you return and ten minutes leave the bike on and running and adjust the idol speed.. could be the engine idol RPM is set to low causing it to run to cold and not warm up properly therefore cut out.


Don't adjust idol speed unless having used it prior because you'll end up setting it to high when it does get up to temp out on the roads and then will need putting back down.

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I left the sparkplug out over night, and it took awhile but now it starts everytime :cheers: , but it keeps "bogging out" somewhat only when its idleing?

 

By "bogging out" I'm going to assume you mean cutting out like a complete loss of power, is this when it idols all the time or only when warming it up for the first time?


I assume you haven't got as far as taking it out on the road yet, of which you'll need to do to solve the issue and work out witch one it is.. get it out on a ride for at least ten minutes and let the engine get up to temp properly, and then when you return and ten minutes leave the bike on and running and adjust the idol speed.. could be the engine idol RPM is set to low causing it to run to cold and not warm up properly therefore cut out.


Don't adjust idol speed unless having used it prior because you'll end up setting it to high when it does get up to temp out on the roads and then will need putting back down.

 

I warmed the bike up, so well actually the temp started flashing (I assume this was because it was not being ridden and no cold air was getting to the radiator?), but it was warm and the power seems to be all there, but when youre not putting some throttle on it will start to die (starts losing revs if that makes sense). It constantly needs revving for it to "stay on". Also I would say throttle response is not the best at low rpm


some more info: the bike has been sat for 2 years prior, i cleaned the carb when i first got it & again when some fresh petrol had been through it, but my assumption is it might need cleaning again?

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I warmed the bike up, so well actually the temp started flashing (I assume this was because it was not being ridden and no cold air was getting to the radiator?).

 

Sounds like your bike is air cooled, the temp light is not something I have on my Chinese 125.. can only assume it would come on when the bike gets to hot as you say because of not having air pass through it, i'd do some research and find out why that light flashes.. google or a user manual should tell you that.


Again the whole revs dropping and it cuts out is the idol speed, kind of contradicts the temp light though.. again find out what the temp light means and take it from there, although for my bike it's recommended by other owners to set it at 2,000RPM (it's hard to recommend something for you becuase I've never owned a twist and go, and or your manufacture).


My knowledge is limited sadly, never touched a carb as I've only been riding a few months.. so.. do what you think is best after all the rider knows his bike best, advise against messing with something unless getting the basics out the way first.


Out of interest what is the lowest RPM it gets to before cutting out, or what idol speed do you have it set to (just because you may feel warm, the bike is a very different situation).

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I warmed the bike up, so well actually the temp started flashing (I assume this was because it was not being ridden and no cold air was getting to the radiator?).

 

Sounds like your bike is air cooled, the temp light is not something I have on my Chinese 125.. can only assume it would come on when the bike gets to hot as you say because of not having air pass through it, i'd do some research and find out why that light flashes.. google or a user manual should tell you that.


Again the whole revs dropping and it cuts out is the idol speed, kind of contradicts the temp light though.. again find out what the temp light means and take it from there, although for my bike it's recommended by other owners to set it at 2,000RPM (it's hard to recommend something for you becuase I've never owned a twist and go, and or your manufacture).


My knowledge is limited sadly, never touched a carb as I've only been riding a few months.. so.. do what you think is best after all the rider knows his bike best, advise against messing with something unless getting the basics out the way first.


Out of interest what is the lowest RPM it gets to before cutting out, or what idol speed do you have it set to (just because you may feel warm, the bike is a very different situation).

 

It idles around 2000 then within 3-5seconds it will drop until its eventually to low which is around a little below 1500

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It idles around 2000 then within 3-5seconds it will drop until its eventually to low which is around a little below 1500

 

Is this in neutral or in gear?


After a quick google search I found this;

http://www.bikersoracle.com/vfr/forum/a ... 13049.html


Different model but might be worth a read?

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It idles around 2000 then within 3-5seconds it will drop until its eventually to low which is around a little below 1500

 

Is this in neutral or in gear?


After a quick google search I found this;

http://www.bikersoracle.com/vfr/forum/a ... 13049.html


Different model but might be worth a read?

 

It seems the problem in that article is about a manual clutch, this is a simple rev and go ped engine.

Ill clean the carb properly tomorrow and let you know how it gets on. Thanks :cheers:

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It seems the problem in that article is about a manual clutch, this is a simple rev and go ped engine.Ill clean the carb properly tomorrow and let you know how it gets on. Thanks :cheers:

 

Overlooked that, my apologies.


As I say my knowledge is limited.. could be a simple issue someone else will be able to point out when reading.


Good luck :D

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Idle speed sounds OK - If it dies and stops when warm (without throttle), it is more than likely your idle jet setting is askew (either set wrong or even blocked)


You state that you have already swapped out a jet - Did you set it correctly?


Have you adjusted the mixture or idle screws?


Lots of vids on youtube which may help you.


:cheers:

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