1986 CR250 no start problem

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8/1/2018 2:50 PM

Hello,
I recently "completed" a rebuild/restoration of my Cr250.
The bike was a basket case when I bought it, and over the last year and a half I have completely rebuilt it.
My problem is, it will not run.
I have checked for spark (it's new and.properly gapped) and spark is there, I'm getting fuel, as on the 2nd or 3rd kick it will fire but not run. After that nothing. I checked for fouling on the plug and its wet but not dripping.
Brand new reeds, brand new plug, cleaned carb and ensured that it flows fuel. New cylinder plating , new gaskets etc.
At a loss currently.
Any help would be appreciated.
Thanks

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8/2/2018 12:43 PM

since no one has replied yet I will throw out 2 simple things. any chance any animals took up to nesting in the airbox or exhaust?

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8/2/2018 8:07 PM

Went through this also had to buy a new carb

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8/2/2018 8:24 PM
Edited Date/Time: 8/2/2018 8:27 PM

Is the timing adjustable on the stator plate? If it is maybe the timing is off and it's not firing at the right time.

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8/3/2018 9:48 AM

backinthesaddleagain wrote:

since no one has replied yet I will throw out 2 simple things. any chance any animals took up to nesting in the airbox or ...more

nope. Airbox is clean, as is the pipe.
I went through this thing completely, all new bearings in wheels, steering, swingarm, linkage, new clutch, new reeds, replaced the cylinder and had it re-plated and matched to new piston and rings, all new seals, rebuilt the forks etc.

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8/3/2018 9:49 AM

detour174 wrote:

Went through this also had to buy a new carb

Hope not. I inspected and cleaned the carb before I reinstalled it.

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8/3/2018 9:51 AM

SmokinJoe439 wrote:

Is the timing adjustable on the stator plate? If it is maybe the timing is off and it's not firing at the right time.

I will look into this this weekend, I am also going to check for a bad ground and after that, float height in the carb.

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8/3/2018 10:45 AM

Easy way to tell is if the mounting bolts the holes on the stator plate are oblonged shape. The owners manual would have the setting for BTDC it needs to be set at and you'll need the gauge to set it.

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8/4/2018 12:57 PM

Inspect carefully the Jets in the carburator!
I had the same problem with my 86 cr 125 that sat in storage for 10 years. The pilot jet has small holes that were blocked.
i was kicking, it started for a sec and died !
after i cleaned the pilot jet it starts and runs as should!

or

if you have spark you have to set the timing as said above!

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8/6/2018 3:47 PM

The choke knob is also idle adjuster and try turn it anticlockwise so it dos not choke so much when you pull it up .

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8/7/2018 3:46 AM

New plug may just not spark under compression, specially seeing you state it's wet, did you replace or dry it real good, other wise sounds like the primary coil is charging the capacitor and the SCR is releasing the voltage, coil may be bleeding to ground. Start with the simple checks first.
If your sure the spark plug is not the problem, check from the outside in.

Look for at least 50 ac volts out of the power source coil
Pick up coils usually send 5ac volts to the SCR, this takes a peak reading voltage meter to read
I use a coil tester, however you can do the normal OHM and K ohm coil test, issue here is it's not firing under compression.
Hope this helps

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8/8/2018 10:00 AM

wolfy0067 wrote:

New plug may just not spark under compression, specially seeing you state it's wet, did you replace or dry it real good, other ...more

I did the standard resistance tests on the stator and coil today and everything returned within normal range as per the manual. I can't do a peak test
As my multimeter isn't capable.
Checked timing marks and it is perfectly lined up.
Next I'm going to doublecheck the carb over. As Well, I mayremove my spark plug cap and trim the cable end and reinstall the cap to eliminate any issues there.

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8/8/2018 12:21 PM

How do you know the timing marks are in the correct position. Without using the gauge you can't be certain of that. I went through this a year ago with my yz 250 and ended up chasing my tail everything "looked" right. Had the carb off like 10 times checked all the electronic components and in the end until i borrowed the gauge from my friend and correctly checked and set the timing nothing worked. Once i did that it started in like 3 kicks.

It shouldn't have happened cause all i did was pull the top end have the cylinder replated and put in a new top end but some how it got out of whack.

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8/9/2018 5:38 AM

You can check the timing without the bike running by removing the spark plug, put it in the cap and ground it, hook up your timing light, spin the engine over at the flywheel with a socket attached to a drill and check the timing. I bought a bike that wouldn't run and this is how I found the timing was off 180 degrees. The coils were mounted backwards. This way you know for sure where it is firing.

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8/10/2018 2:45 PM

I would try some starter fluid in the spark plug hole, then put the plug back in and try it quickly. At least then you'll know if it's a fuel problem or an ignition problem.

And this may sound dumb.... but may be worth double checking to see if the piston is in the right direction?

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