DT125R ARCHIVE

Sgt-syphilis · Guru

Dt wont start after top end rebuild...

NORFE · DTR Trusted Engine Builder

are you getting a spark?
could of caught one of electrical connections when stripping it

MDK · DTR Legend

even if carb is blocked have you tried the bit of fuel in the head way ? if it starts then it maybe carb ?

if so strip and clean carb run compressed air throu all holes you can find no matter how small and see if any feel blocked . or if you put air or blow down one inlet or hole you should feel it escape somewhere else . another method is a strand of wire out of a old clutch cable ect run it throu jets or holes .

like norfe says use prosses of elimination if no spark its electrics .....if fires with fuel in head its carb .

Sgt-syphilis · Guru

yeah sparks good, poured some petrol into the head...only a tiny amount and it sorta fired...didnt sound good though. have carb out now and stripping it down...

Sgt-syphilis · Guru

Right well now I've taken Carb out and apart. It had a small amount of dried oil but nothing major. Cleaned it all anyway, floats jet etc are all good and correct. All ports, pipes etc free of blockage. Connected it back up... Nothing. Plug is gettin wet, it's sparking and has compression. I'm really at a loss here.

It back/misfired a lot more this time. Only when I had the throttle pinned or on the over run if you will...

Sgt-syphilis · Guru

Also, I'm thinking I may have put too much oil in barrel when putting piston in. Had that before?

eG x LoGiKzZ · Guru

tried bump starting it?

NORFE · DTR Trusted Engine Builder

u only need a dab of oil on the barrel when rebuilding , soon as it gets fuel its getting oil

so u may just be fouling the plug every time u try kicking it mate, ull just have to keep going u only need a drop of juice in the bore if ur poring some in, engines work on vapor not liquid fuel, so if u pore to much juice in that will also wet foul the plug, conditions have to be just right mix in the chamber to run smile

NORFE · DTR Trusted Engine Builder

also just kick it with the choke on dont tutch the throttle keep it shut

ToySoldier · DTR Legend

norfe its a dtx electric only

Sgt-syphilis · Guru

Yeah I just dipped my finger in the lid and rubbed it round piston etc. I put a tiny drop of petrol in...the plug is wet, but seems very dark liquid...

Have tried all choke/ throttle combos possible!

Will just keep trying! It fires every now and then and gives a good blow of pressure out the zaust!

NORFE · DTR Trusted Engine Builder

ToySoldier wrote:
norfe its a dtx electric only

ahhh unlucky. see what u get with all this new fangle dangle electric bling ha ha, get a kicker put on it smile

Sgt-syphilis · Guru

Seriously getting annoyed now. Ok so the bike fires occasionally...it back fired with a savage bang and was spitting flames. That indicates to me that it's getting air/fuel in, it's not firing but then randomly fires and ignights everything in the cylinder and zaust. What could be causing this? Warped head? Crank seals/bearings gone so it's leaking oil into the chamber (the wet plug has very dark liquid on it...like black oil, this isn't the same colour as the trans oil though.?)

And ideas?? Start over and split the cases??

NEV · Guru

Just as a matter of interest, check the flywheel is sitting on the woodruff key properly, or that it hasnt lost the woodruff key, backfire can often mean timing out.

NORFE · DTR Trusted Engine Builder

check timing like nev said

ur getting fuel thru and uv cleaned carb,good compression, head and barrel torqued up on refittin so hed gasket shunt be leaking

as soon as u start the engine turnin over the oil/fuel will be washing the carbon from off and around the bore so it will look mucky on the plug

how much oil did u actually put in it on rebuilding then ??

get one of ur mates to tow u in a car or another bike

get the engine pumping the excess oil out iff posible

iv every fing is ok just the plug getting wet then it must be that

put the blow torch on the spark plug get it red hot then try it

fused420 · DTR Senior Member

Sounds like too muck fuel/not enough air to me. Thats if its not down to the timing as suggested above.

MDK · DTR Legend

yeah fused I kinda thought that a wrong fuel to air mix causeing backfires .. be great if you had some one close with a dt or spares to eliminate items like swap carb over ect ..

have you any mods like derestrictions ect ...

GADGET · Guru

Timing /woodruff key on flywheel Or check the plug gap ,it might seem silly but on some bikes if the gap is out it will try to start but just backfire as the spark is not strong enough Good luck dude Also are your reeds ok ?

-- Edited by GADGET on Monday 4th of June 2012 02:28:56 PM

-- Edited by GADGET on Monday 4th of June 2012 02:30:00 PM

tripr · Guru

not a backwards piston is it that gives the missfire an confusion of it about to start your on about ,, had all the same symptoms on an engine i bought ages ago the guy had fitted the piston in reverse

NORFE · DTR Trusted Engine Builder

you would hear the rings catching on the exhaust port would make some noise surely noticable

tripr · Guru

NORFE wrote:
you would hear the rings catching on the exhaust port would make some noise surely noticable

no it sounded totally normal mate to try starting up, it even rode kinda after being dragged with a mates car to kick it up an keeping the revs high but wasnt nice poppin an backfiring.

bear in mind back then id never seen inside an engine before

bought another dt for its engine to use my already insured non runnin bike.

then pulled its engine apart to find the arrow facing the wrong way an even being clueless i thought the arrow should face the exhaust. turned it round an it fired right up 1am in the mrs kichen too i never expected it to work lol.

NORFE · DTR Trusted Engine Builder

ha ha nice....never had the problem but seen the mess it makes when the rings caught so assumed it would make some nasty noises ha

DTCrazedKid · DTR Senior Member

i had a problem pretty much the same as this, tried all obvious things, and then it turned out i was getting warter in/on top of piston and onto spark plug, sorted that out and then a few bump starts later it sorted itself out

MDK · DTR Legend

tripr wrote:
not a backwards piston is it that gives the missfire an confusion of it about to start your on about ,, had all the same symptoms on an engine i bought ages ago the guy had fitted the piston in reverse

thought I had seen your name lol in the 125 forum I was reading it the other day about the wrong way round piston and pulling bike with a car ect lol ...

Sgt-syphilis · Guru

Right so im going out again to try and fix it...im thinking im going to strip it all right back and start over.

Calum122 · Guru

Have you tried putting a new plug in it mate?

Calum122 · Guru

What's the continuity of the spark?

Is it intermittant?

There should be no reason for it not running if it's been put together properly.

Follow all the cables.

If you can't figure what cables are not working then do what I did. Wire the CDI to the battery to the engine. Forget about everything else. Just try and get it started. Sounds like an electrical fault. Hard to tell.

Is all the balancing shaft all align up properly?

There's things inside the gearbox which need to be perfectly align.