Help!!!, cannot start my rebuilt engine!

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gertie6car
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Help!!!, cannot start my rebuilt engine!

Post by gertie6car »

Hi All,

I am really disappointed having rebuilt my KDX200E2 engine completely try as I may I cannot start it!

The bike I bought as a non runner, the previous owner had come off, flooded the engine and believe it or not had cracked the crank cases around the kick starter gear. I sourced a second hand set of cases and set about a rebuild.

All bearings were replaced, new seals throughout, new big end & small end, piston and barrel were in limit/new so I used those. I have only partially stripped the carb but have blown all the jets out with compressed air. The fuel is what was in the tank when I bought it back in april so it is a bit sus I guess. The bike came with an after market SPES exhaust but runs the standard silencer.

I have tried all combinations of fuel tap on/off, choke on/off, throttle closed/partially open and all I have managed after very considerable effort is what sounds like two loud back fires! The spark plug is sparking strong but the plug is very wet after prolonged kicking.

Dont know what to do next other than change the fuel, completely strip the carb, clean and check float height. Any other suggestions would be welcome!

This is the first engine I have rebuilt in many years that has not fired up after 2 or 3 kicks, to say I am utterly disappointed is an understatement!

I am hoping you can give me some checks to run as I have tried most of what I know. Help please!!!

Gert
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Indawoods
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Post by Indawoods »

Check your timing?
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Post by gertie6car »

Hi thanks for the response, ok the stator is set so the middle mark on the unit alligns with the mark on the crank case. The fly wheel is keyed to the crank. Have I missed something?
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Indawoods
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Post by Indawoods »

Sounds like carb then....
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Post by gertie6car »

air screw is set ok, not checked the needle but surely it should try and run? even badly are kdx's that sensitive on carb settings ? think the previous owner changed the jets when the pipe was changed. Surely it should be close enough to start!
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Post by gertie6car »

Hi guys, any other suggestions would be most welcome!! I need help!
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Indawoods
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Post by Indawoods »

Spark, fuel, compression and timing. Has to be one of them.....
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gertie6car
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Post by gertie6car »

Hi Indawoods,

ok so the spark is good,

the timing is as per the manual,

compression feels ok but have not pressure tested it yet, have a compression tester but need to acquire an adaptor for a bike plug, piston and rings new, cylinder looks good but will test.

fuel and fuel delivery might well be the culprit. Fuel is old, will change in the morning. Will strip the carb and clean again, will also substitute the spare carb I have, old and visually not as good as the one fitted but it is probably running stock jetting.

Just cannot understand why it will not even try to run!

thanks for your help though, will keep you posted! this is my first kdx so really want it to work!!
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Post by GS »

"Fuel is old...." That is a most likely culprit!!

Amazing how fresh gas can make all the difference.

Hope that's all it is.

Old Truism....if there is an adequate spark, occurring at the right time, fresh gas and compression...IT HAS NO CHOICE BUT TO RUN. Simple as that!!

I hope.......

Let us know?
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Post by gertie6car »

Hi GS,

thanks for your comments!

Thats exactly why I am so frustrated it wont run, never had this problem before!

The crank is from the replacement engine I sourced for the crank cases, it happened it had a better crank where the seals run, but as I said it was completely rebuilt. The piston looked good, the gearbox internals were swapped over. Cylinder is the original and looks ok. stator is original, flywheel is from replacement engine, I used it as it was in better condition than the orignal.

Carb is the original item with suspected new jets for the spes pipe. Looked no better or worse than I have used before.

Can fresh gas really make the difference between running and being completely dead? I hope so!!

Any ideas what it could be if not the fueling side??????
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Post by kawagumby »

Just squirt some fresh fuel down the sparkplug hole, about a teaspoon, quickly place a NEW plug back in and see if it fires (spark plugs can fire at atmospheric pressure but not always under compression)....it should start if you have enough compression and the spark timing is right. If it quickly runs out of fuel following, it's probably a plugged up pilot jet (or even a tank fuel filter gooped up if you haven't checked flow from the tank yet).
1994 KDX200, Beta 200rr, yz125, yz250, kx100 modded for adult, gasgas contact 250.
gertie6car
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Post by gertie6car »

Hi Kawagumby,

thanks for the response, the fuel runs freely from the tank, will check as you suggest and get back to you. Thanks for taking the time to email me! gert
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Post by GS »

How old is the gas you are working with and how was it stored? Was it mixed with oil when it was still fresh?

I always find fresh re-builds take a few really good kicks.....or even push starts down a hill to get 'em going the first time.....which doesn't say much for me, I guess.....

But I've had 6 month old gas completely fail to fire an engine and taking out the plug(gas petcock OFF) and kicking it over a few times.....replacing with fresh gas and a dry pug.....and a good push down a hill and she spluts....snorts...huffffs...wheeezes(like me) and then gathers her skirts and steps onto the dance floor with a roar.

There-after.....no problemo!!
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Post by Colorado Mike »

By all means try fresh gas, but I had an '82 KDX that started on the 2nd kick with 10 year old gas in the tank.

Are you absolutely sure you put the piston in facing the right direction? Arrow or dot points to the exhaust port.

Assuming that is correct, also check that your reeds are not sticking open. The "very wet" spark plug might indicate they are. also try it with the air filter removed.
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GS
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Post by GS »

Hey, C Mike,
Was that gas premixed for the 10 years??

Just curious , cause I know some of those premixes sure help retain some 'flavor' to the fuel.

Or, maybe that was 1982-vintage gas.....you know...the GOOD stuff?
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Post by gertie6car »

Hi Guys,

latest update. Got the bike started today - ran beautifully :grin: for a couple of minutes and died while I was trying to adjust the idle screw. :cry:

Sounded really nice and was very responsive to the throttle I was not worried it had died as it sounded so good I thought it would just restart after a couple of kicks - sadly not the case! :evil:

Ok what I did to get it running was

used fresh fuel

changed the flywheel for the original one (both are visually identical with same part numbers on them)

used a new plug.

Initially I used the replacement flywheel, new fuel, new plug and easy start squirted into the cylinder. That achieved exactly nothing other than a couple of big back fires!

Then reverted to old flywheel and hey presto! it ran - at least for a bit!

Can anyone offer me some advice on starting one of these engines?

Technique/choke/throttle setting etc - I am thinking I may not be doing something right! Also are these engines generally easy to start or are they always difficult.

As ever thanks for your comments,

Gert
gertie6car
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Post by gertie6car »

Would the engine run if I had somehow put the piston in back to front? I really dont think I did and the engine did run really well when it did fire!
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Post by fuzzy »

SOmething isn't right....You can almost start one of these engines with your hand. Seal leak or air leak somewhere could be problem. Carb could be a problem. Make sure exhaust is sealed well. Make sure tank is venting.
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Colorado Mike
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Post by Colorado Mike »

GS, it was premix, and I'm sure was very nasty. This fuel is just what had been sitting in the tank when I stopped riding for a very long time, no winterizing was done. Certainly not what a smart person would do to a machine. I just mention it to show how forgiving these machines are.
Mike

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Post by kawagumby »

My starting drill for a cold engine is this:

Lean the bike over until the carb overflow drains.

Choke on

VERY slowly kick the engine through about 4 or 5 revolutions, throttle closed. (If you have a plugged pilot none of this will work btw)

Get the kickstart up against compression then kick it quickly. All my 2smokes fire first kick doing this.

If your bike ran well above 1/4 throttle but dies and won't start, it is likely a misadjusted idle mixture screw or plugged-up pilot jet or both. Also make sure your throttle is opening some at idle, by that I mean check the idle screw to make sure it isn't backed out all the way. Turn your idle mixture screw until it bottoms and count the number of turns. It should run at about 2.5 to two turns out from bottom (as a start) assuming the pilot jet isn't plugged.
A plugged pilot jet is fairly common on bikes that have been stored for a while, btw.
1994 KDX200, Beta 200rr, yz125, yz250, kx100 modded for adult, gasgas contact 250.
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