DT125 X 56 plate - Difficulty starting

[JonW]

Hi, looking for some advice.

I have a DT125 X 56 plate, had it for almost 4 years now and never had any trouble with it, but at the moment I'm having difficulty starting it.

I decided to clean my strip down and clean my carbs & check reed valves. After putting it all back together, feeling confident that i'd done a decent job, I still have difficulty starting it. I've checked my spark plug, which was a bit black and coked around the edges, in spite if this it is getting a nice blue spark.

Whenever I turn the engine over it seems to splutter a bit as if it wants to start, but cuts out if i let go of the starter. I can get it running if i persist, but it seems as though something is stopping it from running as it should, it seems really slow to pick up enough revs to idle correctly and seems boggy on the throttle until it gets up to a decent idle speed. It runs fine once its running at idle without any problems and even revs up without any bogging or cutting out.

I have tested the compression on the engine by putting it in first gear and pushing, it's hard to push and drags the back tyre. It had a top end rebuild about 13,000 miles ago and has been run on castrol racing T2 oil. Bike is well looked after, but its been getting ever more difficult to start.

Any help would be greatly appreciated.

[Ariel Badger]

Strip the carb and reed again to find what you did wrong first time. Why did you play with it?
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[JonW]

I stripped the carbs down because of the trouble I'm having getting it started, thought it may have been a fuel related issue, dirty carbs or something, not only that, it was leaking petrol from the carb overflow so i needed to check the float valve. While i had the carbs off i also checked the reeds, they are in good shape & are flush with the reed cage with no gaps and are pinging back correctly.

I checked the main jet which was ok and also the pilot jet which was also ok. I also made a slight adjustment to the float to put a little extra pressure on the float valve, but not too much to restrict fuel entering the carb, the carb has fuel and no longer leaks from the overflow.

I have put the carbs back on the bike and I'm still having the difficulty starting the bike. The bike runs, fine when its running, but its a struggle to get it going. At one point the bike started up straight away, now its reluctant to start.

[m3-paul]

Spark plugs are cheap so I would replace it as a matter of course. Have you checked that the choke is operating okay. Cold starts with with my tzr250 are always a bit interesting for the first 30 seconds until it has cleared its throat.
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[stevo as b4]

New sparkplug gapped right, and see what happens. Its often said that once plugs have been washed in fuel or fouled that they are no good again after.

It's an electric start only on the DTX? Does it spin over quickly on the starter, as if not it could be a battery or starter issue maybe? You should be able to piss easy bump start that bike by walking along side and popping out the clutch at walking speed. If it starts first time easily this way, then I'd be looking at the electrical system, battery voltage etc.

[JonW]

Been working on the bike all morning, decided to strip the carbs down again just to make sure everything is in order, all ok. Then I decided to look on the electrical side of things, checked spark plug again for spark and i noticed it was sparking for a few seconds but if i kept my finger on the start button the spark would stop? Anyway, started checking and cleaning up electrical connections and checking for any improvements each time, then i got to the stator wires, unplugged the connection block and cleaned it up, plugged it back in and tried to start it, still wasn't starting so i decided to unplug the block again and try to start it, it started really easy within a second or two and went straight to a decent idle speed instead of taking about 15 seconds to get there.

Going to take it off and have a look at it and see whats going on.

Thanks for the suggestions also, once i get it sorted I'l go halfords and pick up a new spark plug.

I'l let you know what I find out about the stator.

Ok, so tested the stator with a multimeter and its generating 40 volts, is this right?

[Stalk]

So, it ran OK with the alternator disconnected? If so I would be looking for a short circuit in the stator and/or loom. Its possible that it may be causing your idle to bog a bit without frying the loom.I know that sounds ridiculous, and I would not have belived it myself had it not happened on stepstalk's little 125. It would not run properly until a short on the sidelight was sorted, but bizarrely no fried loom or fire.

Good luck!
Stalk.

And 40 v seems OK, presumably thats AC. Probably best to check the regulated voltage at the battery. Looking for about 13.5 to 14.5 v DC, varies from bike to bike.

[JonW]

Been tinkering with it, guessing the stator will be a three phase, hence the three wires coming off it? Should all three wires read the same voltage, because two are at 40 volts AC and one is at about 20 volts AC at idle. Checked the regulator and its giving out 14 volts DC. Voltage across the battery is also at 14 volts while the bike is running. Have checked the wiring loom for any short circuits, nothing looks suspicious. Still can't get it started while the stator is plugged in, but starts fine without it, then bogs down when its plugged in. Also found a few blue and black wires in the loom had came separated, joined them back together and resolved the problem with the intermittent spark.

While i had the stator cover off to have a look at the wiring, I gave the round magnet thats attached to the crank a few turns, I noticed it was easy to turn and compress the piston, could this be a sign of low compression? Putting the bike in first and pushing it tells a different story, not east to push and drags the back tyre. If the bike was in need of a top end rebuild or new piston rings, would i experience any symptoms similar to this? Unfortunately I don't have a gauge to test the compression. Bikes running great when I get it started.

[Stalk]

Based upon what you have said I would say the mechanical side of things is OK. Your readings on the stator indicates a problem, if its the problem that causes the bad running is unknown until you change it, as a fault has either ruined the stator, or the stator is the problem. I assume you have a known goog battery?

[JonW]

Looked at the stator again, tested the resistance across all 3 wires, lets call them A B and C. A - B = .8, A - C = .8, B - C = .8. There is also no short circuit from either A B or C to earth. Not sure what make the battery is, it does hold its charge.

When i get the bike running, with the stator plugged in, if i remove the ground wire from the battery my idle revs pick up again.

Battery has a good charge and reads 12.98 volts while the bike is running. If i remove the earth wire from the battery with the stator plugged in while the bike is running the idle revs pick up.