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Discussion Starter · #1 ·
As some of you may know, I have been working on this machine for a few weeks now off and on. I had two issues with it. The first one was electrical. The second being overheating. Installed a new water pump impeller and a new thermostat. Tried to start it to purge the system and it will not hit a lick. There is spark at the sparkplug, so I have fire there. I tried starting fluid and I even shot some fuel down into the cylinder. Still it won't hit a lick. This machine was running before so I do not understand what could have happened. With the electrical I installed a new voltage regulator, new battery and a 10 Amp circuit breaker. The machine ran before I started in on the cooling system. I do not understand how or why it will not hit if its getting both fuel and fire? Anyone have an idea what this may be? If it were the valves I don't see how it would have ran okay prior to the cooling system work. I did remove the front rack, and forward body plastic. Along with that was the instrument cluster but it appears to be working okay. Could there be any sort of electrical connection somewhere that may not be hooked up? If so, why would I have spark but it won't hit?

Now here is one thing I have noticed about this machine. Sometimes while trying to start, it will kind of cough through the breather. In fact, when I sprayed starting fluid into boot, it backfired and ignited a little residual that was in the bottom of the breather box. But this is not a constant.

Compression check?

Valve adjustment check?

I am at a stand still once again.
 

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New spark plug first - it may have spark outside the cylinder but not inside due to carbon fouling or a shorted plug elkectrode.
 

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Discussion Starter · #3 ·
New spark plug first - it may have spark outside the cylinder but not inside due to carbon fouling or a shorted plug elkectrode.
That's true. I was going to replace the spark plug but didn't have the right size in my shop inventory. I do have an inline spark tester that tests the plug under a load (in the cylinder). Guess I should try that first. The plug was dry and I cleaned what little carbon was on it. The plug does look old on the outside. I will tackle that in the morning and go from there. I may make a trip to town and get a new plug anyway. At least I have something to go off of now and I thank you for that.

If that doesn't do the trick I'll get back in touch.

Thanks again.
 

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How did you clean the carbon off? Sandblast?

What brand of plug was in it? Champion? A Champion plug can go bad setting on the shelf and not fire when screwed into a cylinder when brand new.
 

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Discussion Starter · #5 · (Edited)
How did you clean the carbon off? Sandblast?

What brand of plug was in it? Champion? A Champion plug can go bad setting on the shelf and not fire when screwed into a cylinder when brand new.
It was an NGK. There wasn't much carbon on the plug overall. I took a the wire wheel to it that's on my bench grinder. I have no sand blaster. But it doesn't matter now because I bought a new NGK to replace it. Hope to be able to get with it this morning.

If the machine still will not start, can you think of any plug or connection that may have been disconnected that would cause this? With spark and fuel one would think it would at least hit. I had the instrument cluster out but put it back on for testing purposes.
 

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Discussion Starter · #6 ·
Okay guys, it still will not hit. I located 4 different connections that is not plugged into anything. According to the wire schematic the one is not to be used on this model. The other three I have not figured out yet.
Motor vehicle Automotive exterior Hood Automotive tire Gas
 

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Okay guys, it still will not hit. I located 4 different connections that is not plugged into anything. According to the wire schematic the one is not to be used on this model. The other three I have not figured out yet.
Those two are accessory power supply and ground.
 

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Do you know if they are supposed to be unhooked?
YES

Im wondering if they should be unhooked or if any of the unhooked connectors would be a factor in the engine all of a sudden not want to hit?
NO - the spark is AC generated - unplug the black wire from the CDI box and if spark is restored,you get to find where the black wire is grounded killing the spark. If unplugging the black wire does not restore spark, get out a peak voltage meter and I'll guide you through the process of determining what part of the ignition system failed.
 

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Discussion Starter · #13 ·
YES


NO - the spark is AC generated - unplug the black wire from the CDI box and if spark is restored,you get to find where the black wire is grounded killing the spark. If unplugging the black wire does not restore spark, get out a peak voltage meter and I'll guide you through the process of determining what part of the ignition system failed.
Okay, I don't understand all of this post, but I'm heading back out to my shop now. I'll get back with you in a couple minutes.
 

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No - if the plug is new, you need to start checking peak voltages. The only thiong that is known good at this point is the pulse coil - it is telling the CDI to fire, so now the problem is in the stator, flywheel magnets, CDI box probably OK which leaves the coil, spark plug cap spark and compression.
 

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Discussion Starter · #16 ·
The
No - if the plug is new, you need to start checking peak voltages. The only thiong that is known good at this point is the pulse coil - it is telling the CDI to fire, so now the problem is in the stator, flywheel magnets, CDI box probably OK which leaves the coil, spark plug cap spark and compression.
Well, the dynamics has just changed. Thought I’d try it again and machine started. I let it run for about one minute and by chance my hand was near the new voltage regulator I installed. It was getting hot enough to almost burn my hand. Something is definitely causing the regulator to over heat.

Any idea?
 

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Two things cause heat - resistance and current flow - If there is a poor connection between the battery and frame or the regulator and the frame, it will cause a high resistance connection and that will result in heat - by the same token, if the battery is at a low charge, it will need higher than normal current to charge the battery for a longer period and the resultant heat may cause an electrical failure. The rec/reg should get hot, but not hot enough to boil water. If the stator has low voltage generation, it will cause the rec/reg to run hot. Lowering the voltage increases the amperage and increased amperage means more heat.
 

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Discussion Starter · #18 · (Edited)
Two things cause heat - resistance and current flow - If there is a poor connection between the battery and frame or the regulator and the frame, it will cause a high resistance connection and that will result in heat - by the same token, if the battery is at a low charge, it will need higher than normal current to charge the battery for a longer period and the resultant heat may cause an electrical failure. The rec/reg should get hot, but not hot enough to boil water. If the stator has low voltage generation, it will cause the rec/reg to run hot. Lowering the voltage increases the amperage and increased amperage means more heat.
It got the machine started a couple of times and finished purging the cooling system, I think. Seems to be okay and is not overheating now. The fan kicked on like it should. I never did get to the bottom of the regulator heating up so badly but last time I checked it, it was not suppling the 14.6 volts to the battery. Brand new $170.00 regulator too. I hope it didn't burn up on me.

However, for whatever reason, the machine just does not want to start very well. When it starts, it starts right away. But most of the time now, for whatever reason, it simply is not interested in starting. Wasn't that way before the best I can tell. The battery is fully charged but it acts as if its possibly slow for some reason when cranking. But the thing that concerns me most is during cranking, it sometimes wants to "poof" out the breather, which I know is not right. When it runs, it runs well. Plenty of power and is smooth. Doesn't smoke. Doesn't idle the greatest but its not bad either. I'm thinking valve clearances and Lord help me, possibly cam shaft?

I think it would behoove me to run a compression test, either static or a leak down test.

I am not finding the valve setting for the intake valve in the manual. I did see exhaust valve clearance of .006" but not sure if it's for this machine or the 500. The manual leaves a lot to be desired.

A couple more things I would like to find out here. The pulse trigger. Would that possibly aid in starting the machine, as in gives it a little more spark?

Also, exactly what is the function of the CDI box? Would either of those possibly be a factor in a finicky starting machine?

Anyone?

Thanks.
 

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I am not finding the valve setting for the intake valve in the manual. I did see exhaust valve clearance of .006" but not sure if it's for this machine or the 500. The manual leaves a lot to be desired.

A couple more things I would like to find out here. The pulse trigger. Would that possibly aid in starting the machine, as in gives it a little more spark?

Also, exactly what is the function of the CDI box? Would either of those possibly be a factor in a finicky starting machine?

Anyone?

Thanks.
Excessive valve clearance is not as bad as not enough clearance - .006 is fine for both intake and exhaust. My CRF calls for .010 on the exhaust and .010 on the intake.

Regardless of the peak voltage of the pulse coil, it does not affect the strength of the spark - too low a peak volts = no spark anything over the minimum voltage = spark. The voltage coming from the CDI box to the coil, the coil (transformer) raises the pulse sent from the CDI box to appx. 30,000 to 40,000 volts, The spark plug cap has a resistor inside which delays the spark a microsecond making the spark stronger. And the spark is like a lighting strike - a blue spark is about 50,000 degrees, a white spark is about 40,000 degrees and an orange spark is about 30,000 degrees - it only requires about 550 degrees to ignite gasoline, but it requires a strong spark to jump the gap of the spark plug electrodes.

What does the CDI box do? In the 400 you are working on, it takes the appx. 45 volt pulse of the CDI charging coil and amplifies it to about 100VDC - the CDI unit uses the 100 volts to charge a capacitior - when the pulse coil signals the CDI that spark is needed, the capacitor discharges through the coil transforming the 100 volts into 30,000 to 40,000 volts and the transformer makes a spark jump the spark gap and completing the path to ground.
 

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Excessive valve clearance is not as bad as not enough clearance - .006 is fine for both intake and exhaust. My CRF calls for .010 on the exhaust and .010 on the intake.

Regardless of the peak voltage of the pulse coil, it does not affect the strength of the spark - too low a peak volts = no spark anything over the minimum voltage = spark. The voltage coming from the CDI box to the coil, the coil (transformer) raises the pulse sent from the CDI box to appx. 30,000 to 40,000 volts, The spark plug cap has a resistor inside which delays the spark a microsecond making the spark stronger. And the spark is like a lighting strike - a blue spark is about 50,000 degrees, a white spark is about 40,000 degrees and an orange spark is about 30,000 degrees - it only requires about 550 degrees to ignite gasoline, but it requires a strong spark to jump the gap of the spark plug electrodes.

What does the CDI box do? In the 400 you are working on, it takes the appx. 45 volt pulse of the CDI charging coil and amplifies it to about 100VDC - the CDI unit uses the 100 volts to charge a capacitior - when the pulse coil signals the CDI that spark is needed, the capacitor discharges through the coil transforming the 100 volts into 30,000 to 40,000 volts and the transformer makes a spark jump the spark gap and completing the path to ground.
Well said latebird.
 
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