Gilera DNA 125 cuts out when revved...

[Heterochromic_bikergal]

Hello everyone,

I'm a biking newbie, and I've recently got my first bike (the Gilera DNA 125cc) but frustratingly, I haven't been able to ride it yet as I've run into a problem. When I start the bike everything seems okay until I use the throttle and rev it, then it just cuts out and switches off.

Does anyone have any ideas as to what the problem might be? Any help would be much appreciated, thank you!

[Rogerborg]

The root cause is that those, uh, "bikes" got passed around a succession of 17 year olds who thought maintenance meant splashing some fuel in, or drilling holes in the exhaust.

Help us to help you. What's the history of the "bike"; are there any obvious modifications to it; what (if anything) have you done to diagnose it.

Can you push it freely by hand?

Does the behaviour change if you let it warm up for a while?
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Heterochromic_bikergal]

[P.]

Probably could do with checking the carb is actually clean and its getting the right fuel/oil mix, unless am monkey has removed the auto lube.

[chris-red]

To me this indicates one of two issues, a gummed up carb or a clutch/transmission problem.

Does it do the same if the bike is on a stand with the rear wheel off the ground?

Cleaning the carb as paddy said is a good idea. Take all the jets out and mark sure they are clear.
____________________
Well, you know what they say. If you want to save the world, you have to push a few old ladies down the stairs.
Skudd:- Perhaps she just thinks you are a window licker and is being nice just in case she becomes another Jill Dando.
WANTED:- Fujinon (Fuji) M42 (Screw on) lenses, let me know if you have anything.

[Heterochromic_bikergal]

[P.]

[Heterochromic_bikergal]

[Teflon-Mike]

DON'T dive straight in and start tearing the carburetor apart!

BUY THE BOOK!

There are lots of possible problems that could account for the suggested, and rather vague 'symptom' you describe... starting with 13 previous owners!

That, and fact that OTMH the thing wet out of production a decade ago, suggests the thing aint no spring chicken, and has probably had a rather hard life, in a world where little bikes are only really expected to have a service life of about seven years,bfore being ought by folk without licences or much experience how to either rid'em or look after'em, who tend to thrash, trash and crash them, with something akin to wild abandon, until they do abandon them.

NOW; first up, I believe that most of these has 2-stroke scooter engines. However, some of the later ones got 4-stroke scooter engines. So which do you have? I will take a guess its a two-stroke, BUT, I would be guessing, and a lot of possble problems would hinge on that assumption.

Then: straight off the top; as an old and likely sore used Learner-Legal, refusal to take load, could be a symptom of low compression, caused by gross bore/ring wear in the engine....

Folk tend t be scared of looking inside engines, and are very prone to diving in and taking bits off the outside that 'seen' less scary..... like carburetors.... but whle they aren't as oily and are more accessble, carbs ARE rather delicate and intrcate devices, and a lot of folk completely effup engines repeatedly removing and cleaning them, rather than grasping the nettle and sorting the 'real' problem, which is likely in the exhaust or engine..... and often MAKE more problems than they solve in the attempt

So DON'T be in a rush to make that same mistake... leave the carburettor ALONE until you have GOOD rason to beleve that is where the problem lies.

First curse should ALWAYS be to run the engine up until fault occurs, and KILL the ignition, then remove the spark-plug and compare what it looks like to the photo's.... yeah... in-the-book.

That will tell you more about where possible problems may lie than anything we can, by weeja telepathic mechanics!

While plug out, you do a compression test, either wth a proper compresson tester, or just the old rule of thumb (over the spark plug hole!)

Two simple easy checks that require just one spanner and DONT effup any delicate 'settings', or disturb any critical seals or gaskets.


Worst case; the engine could need, and on balence of probabilty probably isn't far off, needing thorough overhaul, with a rebore and new rings, if four-stroke reground valves and valve seats; if a two-stroke, rebore and rngs or if nikasil chrome bore, new barrel and piston, ad the bottom end stripping to ft new crak case seals and replace r re-set reed valves.

Best case:- the choke is stuck on!

In between lies any amount of frustration..... and given propensity for folk to dve straight nto 'carbrettor cleaning' there is a very high liklihood you have second hand, or no gaskets not sealing the carb to the engine, so it's just sucking air when put under load... which would require carb reoval to sort, and you might as well strp and clean and look for any other faults in there whilst you are about it...... following the instructions IN THE BOOK! But, that is NOT where you should start, and mention of the 'loud' exhaust on MOT advisories, begs suggestion that either the old exhaust is rotted out and holes, which will never let a engine run well, and or, some twit previous owner has tried to 'de-restrict' the exhaust and again, wither omitted the exhaust gasket thinking ts the 'magic restriction washer', or because they did't have a new one, and or, they have caused all anner of carnage, drillng holes to make it louder, or naively convinced they are removing restriction'
, or have fitted some sort of after-market 'performance' exhaust, which, usually at best beg the carburettor be re-jetted to suit, and at wort increase noise and fuel consumption and make the motor run like a bag of crap, and cause problems for no reason....

But STILL there is no reason to dive in and start pullng carburettors to bits, until you know there IS a problem in there!

So start at the top... plug chop... inspect exhaust; look for simple stupid, like cables that aren't clamped up, or have been fitted ase about; bts that are missing or extra bits that shouldn't be, etc... all of whch you wll get best clue from... you... looking in the book! NOT on the net, which tends to just add more 'random' to the already 'random' panic mechancs making more problems chasing dead leads and NOT grasping the nettle to fix the damn thing!

That' my advice... start at the top, with the book, and be prepared for the worse, like said, its no spring chicken!
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[P.]

^ignore him. Sperganator 5000 in full 1975 mode.

Remove carb, take photos before doing so and check everything is clean and clear.

[Heterochromic_bikergal]

Firstly, apologies for not replying to this thread sooner! I wasn't able to do anything with the bike until Saturday.

Good news, leaving it running for 5 minutes prior to revving did the trick, it's run okay after that so far. So I guess it was a case of impatience and lack of knowledge on my part...

Thanks to everyone for your replies.

[andyscooter]

Haynes manual 4163 according to the list in mine

also does the runner
____________________
gilera runner vxr200 (chavped)
if its spelt wrong its my fat fingers and daft auto correct on my tablet