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mrfixitRick, Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 143
Experience:  My first job was Yamaha mechanic in 1972. Working on motorcycles and ATV's since.
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1988 hnoda 300 fourtrax will not start.Replaced plug then started.Sat

Customer Question

1988 honda 300 fourtrax will not start.Replaced plug then started.Sat few days now wont start has gas no spark.Changed plug again still no spark.Check all elec connections then started but sits for a few days then wont spark again.
Submitted: 8 years ago.
Category: Motorcycle
Expert:  mrfixitRick replied 8 years ago.
HiCustomerand welcome to JustAnswer.

My name is XXXXX XXXXX I would like to help with the Honda starting problem. I've owned several TRX300's and have a lot of respect for them!

Perhaps the voltage gets too low from sitting and prevents a good spark. It should be above 12.4 volts. Also, check the 10 mm bolt at the ground connection at the battery on these machines, as it tends to loosen off easily.

Do you know what the initial battery voltage is after the machine sits?
Are you getting a bright green neutral light?

Also, if fuel leaks into the engine from a leaky carb float valve and an open fuel petcock, it will tend to foul the plug and be hard to start. So, the plug may not fire because of weak spark and/or fouling.

Are you using the stock spark-plug and normal .035 in gap?

Customer: replied 8 years ago.
I know it is getting gas. Even tried ether.Had battery charger on over night cranks great.Has new battery.Pulled the plug wire put in a plug to check for spark no spark.Checked all elect connections all nice and tight.still no spark.
Expert:  mrfixitRick replied 8 years ago.
Ok, thanks for the details. I assume you know to ground the sparkplug to the block to check for spark because you successfully got spark before. I also assume the engine kill switch is in the "on" position! (we've all done that least I have! ;) Move the kill switch on and off a number of times to make sure it feels free and working ok.

Sometimes the spark-plug wire cap can disconnect from the plug wire. Make sure it is tight by screwing the cap onto the wire clockwise to secure it. Check the coil wire connection to the coil in the same manner.

If these connections are good, and no water in the spark-plug cap, then it would be the easiest next step to replace the coil with a known good one.

If you don't have a test coil to try, the ignition coil can be tested...the secondary resistance should measure 6-10 kohms between the cap and the coil. If out of range, remove the cap from the spark-plug wire and measure the wire to coil again at 2.7 -3.5 kohms.
The ignition coil primary can be tested at .1-1.0 ohms resistance between the wire terminals with the wires disconnected.

If the above tests prove ok, and the wiring connectors seem to check out ok, then the problem could be a short in the kill switch, (bypass the switch wires and try again) or a more serious problem with the Ignition Pulse Generator or the Ignition Control Module (ICM). The tests for these items are more complicated as they require a "peak voltage adapter" for the voltmeter. You may have to resort to parts replacement if you cannot diagnose between these two main units. If you need to know more about this, let me know.

Expert:  mrfixitRick replied 8 years ago.
Here's another test for you... this is for the CDI unit. The 300 Hondas had some issues with the CDI boxes. To check for a problem with the CDI box, pull the spark-plug and ground it to engine like in normal spark test. Crank over engine and check carefully for one single spark just as it starts to crank. Keep cranking for a couple of seconds more, and check for one single spark at the plug when you release the starter button. If this is happening, you need to replace the CDI box, or repair an engine ground connection.