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Check to see haw strong the spark is coming out the dist cap. If it is weak there, possible bad cap/rotor/coil/ module. Make sure the wire from the coil to the cap is good.
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Hi, I do a lot with these bikes, I think if you are getting a weak spark there is a couple things to check. First, do you understand how it builds the power to create the spark? The magnet in the flywheel has to be very close to the magnito or coil, if the gap is too much it will cause a weak spark, if the magnet is weak, weak spark, if the coil is shorting internally, weak spark. If the plug wire is damaged, weak spark. I hope this helps you.
How do you know its a weak spark? Is this a visual check? Will the bike start with the correct new spark plug?
On some bikes, you can hardly notice the spark when looking at the spark plug laying on the head, Try looking at night in the DARK!
low battery bad spark plugs if using old ones to test spark , how did you? are all spark plugs weak.? use a spark tester , or new spare spark plug to do the tests gapped to factory spec.
1) Check for spark remove one of the plugs, connect the plug wire to it and ground spark plug base to a good ground , such as the cylinder head , position the plug so you can see the electrodes , crank the engine over , a fat blue spark should be evident. 2)If the spark is good , check for one or more of the following possible malfunctions 1) Obstructed fuel line or filter.2) leaking head gasket(s)3) low compression. If the spark is not good, check one or more of the following a) Weak ignition coil(s) b) Weak CDI unit. c)Loose electrical connections. d) Dirty electrical connections. e)Loose or broken ignition coil ground wire. f) Broken or shorted high tension lead to the spark plug. Difficulty in starting. Check for fouled spark plugs, Improperly adjusted choke, contaminated fuel system, improperly adjusted carburetor,weak ignition unit,weak ignition coil (s), poor compression
The spark gets power to spark from coil packs.If the connection between coil pack to spark plug is weak or loose then it will not fire.But if the coil pack as well as the connection between coil pack to spark plugs checked ok then its faulty or dirty spark plugs.Clean the spark plugs with the carb cleaner liquid and let it completely dry.Then check.Also check the voltage between coil pack to spark plugs.If both checked out ok then the other possibility can be weak crank shaft sensor.
Thanks.Helpmech.
A weak spark can be attributed to a number of issue: 1. Wire from the magnetto to the spark plug is saturated with oil (clean well with degreaser) 2. Spark plug cap deteriorated. (most are not easily replaceable) 3. Spark plug fouled (insure you are using new) 4. Significant build up of rust on the flywheel (lightly sand rust off) 5. Bad Magnetto or CDI (especially if it has gotten wet or is cracked.) Note: (Cost typically prohibitive for replacement). 6. Spark plug gap significantly out of specs. (Regap to specs, retry)
If you are certain you have a weak spark, these are typical causes. Often, more likely problem is carburation, fuel filter and/or fuel lines - which are much easier and less expensive fixes! Hope for the fuel lines being cracked...Good luck :)
You don't say what make or model. try new spark plug and new spark plug caps. the spark plug caps on most machines are 5000 ohm caps and can be purchased for about $ 5 ( NGK brand) try this first. Always start with the cheap stuff first.
How do you know that the spark is weak?
Replace spark plug.
Check spark plug wire for leaks.
Replace fuel.
Clean points and reset.
If there is a battery check that it is at 12.5 during starting.
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