DT125r Starting after re-bulid

[Rift.]

Got the DT125r as a 1/2 built project. Block had re-bore, and we put the new piston in. Put everything else together.

We have spark, and fuel in the carb bowl.

Carb is not adjusted fully, we just put it in as it came. It came in a box with the other parts, which needed putting together.

We think compression is good.

All we have is a nice turning over sound, and loads of white smoke coming from the aftermarket (full Dep) exhaust. Sounds like it will start any second... but nothing

Help/suggestions please
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[alains]

adjust the pilot screw (i do not know how much on this bike , but it's 2 1/2 round screwed and unscrew on the NSR) like your book said , and i hope both carb and tank are cleaned
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the worst day fishing is better than the best day working

[Rift.]

Both are clean
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You only live once so get a bike and ride

[alains]

is it a cdi ignition ? does the ignition timming is adjustable ?. sound it's a lack of advance or a poor spark
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the worst day fishing is better than the best day working

[alains]

i forgot , did you put the choke on ? generally a cold 2 strokes engine starts choke one without any throttle .
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the worst day fishing is better than the best day working

[gsxrboy]

Sounds flooded to me.

Empty the carb, take the plug out then open the throttle full bore and kick it over untill there is nothing coming out of the plug hole or exhaust, a good 30 seconds or so should be plenty.
If you can afford it get a new spark plug unless you are sure the one you have will run.

Put the plug on the engine so it earths out and kick it over to see if the spark is good, you need a good strong brite spark, if thats all good re-fit the plug.

Next dont refuel the bike but instead use a half second squirt of easy start directly in to the back of the carb and quickly kick it over, it should fire a couple of times, dont do this many times as you are running unlubricated. If it does not fire you have a electrics problem, if it does fire now then turn the fuel on (make sure the fuel is brand new).

If it still wont run you either need to clean the carb out or you have a much deeper problem and with out seeing the bike it is difficult to say what it could be but if you do as I have explained above it should run in some kind of fashion, albeit a bit rough as it will need setting up.

Concentrate on getting it to fire, thats the key to being close to getting it running!!

[Rift.]

Tried all that: cleaned plug a few times. Emptied carb and refilled.

Petrol is new, btw.

Its a CDI ignition. We have a spare CDI, we'll test that one. . Ignition is non-adjustable.

Spark is ok, but we'll test the other CDI to see if one is better than the other.

Tried choke/no choke etc everything...

Let you know how it goes...

"Easy start"- Do we have to use this, or can we use something else solvent/flamable spray, kinda thing?
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You only live once so get a bike and ride

[gsxrboy]

Easy start is the best but brake cleaner works pretty well. The more flammable the better....

So does it actually fire?

[Rift.]

Well I dont know what you mean like "fire". It sounds like its just about to run by itself.

The best way to explain it is the engine sounds like its "running" when you are kicking it over. So it sounds good, but it doesn't "complete" and run by itself.
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You only live once so get a bike and ride

[Keith]

Daft question, but have you tried bump starting it?

Sometimes a good bump can get it going. (Worked on my friends DT after it wouldnt start by kick.)
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[gsxrboy]

Sorry "fire" is the term used to describe the engine making one successful revolution on its own, ie; it compresses the fuel and ignites it and returns under its own steam. You can feel it on the kick start as it will go loose under kick. The engine will give a different note aswell.

If your engine is doing this continually with out starting over a long period of time I would say it is more likely it is an electrical problem. Getting hold of a bike exactly the same is the best way to find the fault, just keep swapping bits untill you find the offending item. Trying the cdi is a good move but make sure the part numbers are exactly the same and make sure that that part number matches your ignition system, you'll need to speak to Yamaha to make sure.

[Rift.]

[binge]

A similar sort of thing happend on my speedfight... I thaught it had cmpression, but there was 1 score line down the barrel causing lack of compression which stoped it from starting... BUT kicking it over felt like it had compression...

Do you have a compression tester?

<|Binge|>

[Rift.]

Yes, but it won't fit in the space^.

Still not starting. Tried different CDI. Spark and plug are both good.

Tried pilot screw in different positions. Nothing...
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You only live once so get a bike and ride

[palmer]

Seek professional advice.

[Keith]

[Smoto Bob]

whne i arse over mate i will bring one of my old nackerd chains and sprokets with a puch down the road will have her turning over allot faster.

And i can have a gander at what ya have done
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[Kickstart]

Hi

This may seem like a silly idea, but double check that the reed valves are in place (not that I would ever forget them ).

If you can put a chain and sprocket kit on it then do try bump starting it.

You can use something like Easy Start. Some say they are not suitable for 2 strokes, but not sure why. If your DT still has the oil pump connected up then you are getting oil in as well so you do not need to worry too much about that.

Spark wise it sound like you are OK. I have had ignition problems where I have got a spark but at totally the wrong time, but only once (and on that bike the ignition system fried the rev counter).

If you cannot start the bike using cold start / WD40 / etc sprayed into the inlet then I would suspect that either there is a compression problem (maybe you have snapped a ring putting the barrel back on, or possibly something more serious in the bottom end (unlikely really, as it would likely start if you tried enough, just rattle like crazy).

All the best

Keith
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[Rift.]

Rings are ok (checked them again yesterday).

Compression: can’t be 100% because the gauge we have won't fit on the cylinder head.

Thought about the reed valve not being there... Will check it out

Need to get a chain to push start it...

Emptied the crud out of exhaust/crankcase, and now it just spins over. If you open the throttle a bit when kicking it over, white smoke comes out the back, guessing it’s the 2 stroke...

Thanks for the help so far
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You only live once so get a bike and ride

[Keith]

[Rift.]

White/grey smoke. Not 100%, it's been dark when working on the bike...

Powervalve is 100% open will this make any difference? Piston seems to hit the powervalve when its turned 180 degrees forward, (so it's not fully open).
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You only live once so get a bike and ride

[Smoto Bob]

might get a lift of dad and wonder over 2night mate if ya in? as i ant doing anythign lol and i cant be arsed to ride
____________________
F'it DO WHAT EVER MAKES YOU HAPPY!!!!! Even if it screws over everyone else :p
Titz wrote: "..and my 3rd accident was when this police car....."