TRX200SX weak spark - Honda TRX Forum
 
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post #1 of 10 Old 06-09-2019, 02:03 AM Thread Starter
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TRX200SX weak spark

I recently bought a TRX200SX not running. I brought it home and got it off the trailer and sprayed some starting fluid in the carb and gave it a few pulls, to my surprise it fired right it up. The throttle was slightly messed up so it ran at a higher rpm than idle so I killed it and ordered some parts for it. While I was waiting I actually fixed the throttle on the carb and when to start it again and nothing. Pulled the plug and it was a very weak and some what inconsistent spark. Changed the coil with no change. Ordered a new cdi and when I plug the new cdi in, the reverse and neutral like come on, where as the with the old one only the neutral light. I unplugged the grey sensor wire with no change.


Any ideas?
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post #2 of 10 Old 06-09-2019, 05:16 PM
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What is the part number on the CDI? Original part was 30410-HB3-005 (which was discontinued)

All these CDI's will replace the original:
30410-HB3-008
30410-HB3-015
30410-HB3-018
All these part numbers are discontinued and units from models and years other than 86, 87 and 88 TRX200SX are not compatible. You can't use a CDI from an XR200 motorcycle or a 200 3-wheeler. It has to be the right part. I found a new 30410-HB3-018 unit on Ebay for $131 here: https://www.ebay.com/itm/Honda-Modul...8AAOSwDclc6h6g, but if it has spark and it's just weak; it's probably not the CDI box and it's not the pulse generator - it's usually a bad alternator stator, spark plug cap or spark plug.

Here's the problem - the reverse light is turned on by the gear position switch - the gray wire provides a ground for the reverse light via the CDI unit - the additional ground limits the engine speed in reverse by working with the alternator to cut spark above a certain RPM. If the reverse light comes on when you plug in the CDI, you either have a DC CDI unit or a faulty CDI unit. Weak spark should always be initially addressed by checking wiring connections first (unplug and plug back together all connectors and clean and tighten ground connections), trying a new spark plug second, a new spark plug cap third, a new coil fourth and a new stator if all else fails.

Now, the battery is not used for spark - the ignition is an AC CDI (it does need a battery to run, just to run the starter motor and lights) - the spark is killed by connecting the black wire with the white stripe to ground (ground is the green wire). When the key switch is turned on, the red wire from the battery connects to the black wire and the blk/wht wire is disconnected from green. The black wire splits into a black and a black/brown - the black goes to the rec/reg and the bk/br goes to the lights and the starter button. There is no power to anything else. The neutral light is turned on when the light green wire with the red stripe is grounded and the reverse light comes on when the gray wire is grounded. Everything else works off the alternator.

Let me know if this helps you.
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post #3 of 10 Old 06-10-2019, 04:15 AM Thread Starter
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The CDI I bought was a cheap Chinese one, so probably a DC one. I cleaned all the connections tonight and the more I look at the spark, the more I think it's fine. Regardless it still will not start, wont even cough with starting fluid. In between me having it fire up and putting the new carb in, I installed all the tappet cover bolts that the PO had removed and installed the starter. When I installed the starter I had to remove the chain tensioner and the ground wire. I reinstalled both before turning the engine over again. Is it possible something got messed up there?
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post #4 of 10 Old 06-10-2019, 03:38 PM
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The tensioner - not important how you removed it, but did you turn the engine over with the tensioner out and what procedure did you use when you installed it?
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post #5 of 10 Old 06-10-2019, 04:00 PM Thread Starter
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All I did was bolt it back in. I pulled the cover off and it looks like it could be off a few teeth. Would that keep it from starting?
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post #6 of 10 Old 06-10-2019, 04:12 PM
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If the engine was turned with the tensioner out, then the cam will jump time and cause bent valves

If the tensioner was not retracted and installed properly, the cam chain (if in good condition) will be so tight the engine will be in a bind and will not start

If you checks the valve clearance and have more than 15 thousandths clearance on any valve, then the valve is probably bent and the engine has no compression - either a compression test or a cylinder leak down test will determine the situation.

Good luck
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post #7 of 10 Old 06-10-2019, 04:13 PM Thread Starter
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It has 100 psi of compression. And then engine turns over fine with the pull start.
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post #8 of 10 Old 06-10-2019, 10:20 PM
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If the cam is even 1 tooth out of time, it needs to be put back in time

!00 psi is low - normal is about 120 to 150 in a minimum of 5 compression strokes and the throttle held wide open - if the throttle is not held open it pulls high vacuum on the intake and lowers the compression reading
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post #9 of 10 Old 06-10-2019, 10:22 PM Thread Starter
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Okay so I want the crank on the compression stroke with the line right next to the T and then both lines on the cam gear level with the head. What's the best way to move the chain?
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post #10 of 10 Old 06-11-2019, 02:23 PM
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Best and only way to move the chain is to remove the tensioner, remove the tappet cover, remove the head cover, remove the cam holder, move the cam so as to get extra slack in the chain and move it to the correct position - reinstall the cam holder and torque as specified in the service manual - stick your finger, a screwdriver, a wooden dowel, drill bit, extended cam chain tensioner or whatever into the cam chain tensioner hole to press against the tensioner blade and take slack out of the chain - turn the crankshaft two full rotations stopping on the T mark and recheck that the cam is in the correct position - if not repeat the timing procedure until it is right. When satisfied the timing is correct, retract the tensioner plunger, install the tensioner, release the tensioner plunger - again, rotate the crankshaft two full turns and recheck the cam timing - when it's right, install the head cover w/rocker arms using a new o-ring gasket (they are discontinued, but there is one on Ebay) here https://www.ebay.com/itm/HONDA-ATC20...4AAOSwuJpc8in7

Readjust the valve clearance and install the tappet cover.
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