Two Stroke Motocross

Two Stroke Motocross Forum => Technical => Topic started by: eprovenzano on December 16, 2012, 07:57:45 PM

Title: Coil issues (I think)
Post by: eprovenzano on December 16, 2012, 07:57:45 PM: Sorry but this post is for my old (4 stroke) utility quad. I use the quad to help cut / clear trails. I also lend it out to people thinking about getting into off-road riding. Of course I then school them on two stroke motorcycles....

The quad will run great until the engine get warm / hot. It just cuts out and will not restart. If allowed to let sit for a little while, it will start and run fine, until it get warm / hot and it will die. I'm thinking its a coil issue. If there any specific test(s) I can run on the coil to test its effectiveness.
Title: Coil issues (I think)
Post by: cnrcpla on December 16, 2012, 09:38:52 PM: To test the coil, they sell these spark testers that will connect to the coil and the plug itself and you can run the engine while its all hooked up. It will light up if it has spark, so I'm thinking that if you got one and ran it until hot with the tester on it, you could see if it cut out, or what ever its doing.

Personally I don't think it's the coil. I had a kawi prairie come into the shop one day with similar problems and turned out to be the fuel pump.

Here's a link to the tester: http://www.sjmparts.com/inline-spark-tester-st752329-p-13386.html Pretty cheap in my opinion. It's also a very handy tool to have if you hate getting zapped like I do

Oh.. And does it slowly gurgle down, or just sign right off even if your riding it, as in giving it gas?
Title: Coil issues (I think)
Post by: SachsGS on December 17, 2012, 01:01:03 AM: Friend's Honda ATV had the exact same problem, turned out to be the CDI module (black box). Typically when you have a CDI ignition problem, and you've eliminated the obvious - bad plug/ kill button/ resistor spark plug cap etc., you can't test the CDI module but you can test the stator and high tension coil so by a process of elimination you arrive at the black box.
Title: Coil issues (I think)
Post by: Stusmoke on December 17, 2012, 11:57:17 PM: Quote from: SachsGS on December 17, 2012, 09:01:03 AM
Friend's Honda ATV had the exact same problem, turned out to be the CDI module (black box). Typically when you have a CDI ignition problem, and you've eliminated the obvious - bad plug/ kill button/ resistor spark plug cap etc., you can't test the CDI module but you can test the stator and high tension coil so by a process of elimination you arrive at the black box.

This. CDI units are the last thing you do usually. But Crncplas fuel pump observation makes sense too. Damn four strokes... Anyway I would start by getting out the multimetre and checking resistance on the coil and plug and go from there.
Title: Coil issues (I think)
Post by: Jeram on December 18, 2012, 05:33:42 AM: could be one of many things if it happens when the engine is hot..

Simple tests to narrow it down.

ride it again untill it fails, then pull the spark plug spark plugs and place them on the engine (or any good earthing point), turn motor over, do you have spark?

if no spark, its an electrical issue

change plugs and retest,
test coil resistance, or simply replace the coil as they are cheap from wreckers/ebay
if its an injected quad ensure the ambient air temp sensor isnt getting hot (due to bad positioning, our benelli 1130 had this issue!)

many many things it could be, but you need to look at this as a process of eminiation starting with the most likely and easiest things to test for.

if you do have a spark and its still strong and visable it is mostlikely not an electrical problem
check fuel pump
check fuel lines (kinking when the get hot (softening hose)
Title: Coil issues (I think)
Post by: SachsGS on December 18, 2012, 05:42:24 AM: Many of the modern ATV's have such fine sparks that I check them at night in darkness.
Title: Coil issues (I think)
Post by: TMKIWI on December 18, 2012, 06:25:58 AM: Quote from: Jeram on December 18, 2012, 01:33:42 PM
but you need to look at this as a process of eminiation

Are we talking about a process of elimination or a process enamation. ?
I would be a bit nervous about the second one.
Title: Coil issues (I think)
Post by: eprovenzano on December 18, 2012, 03:13:54 PM: Thanks for the updates guys. The quad in question is a 94 Suzuki LT250F. Its slow, antiquated but its been a great tool for cutting trails... it does a great job of carrying tools, saws, trimmers etc.

I know its not the fuel pump as I eliminated it a few years ago and now its gravity feed. I'm pretty sure its electrical, and now after the posts I'm leaning towards the CDI. I need to get off my lazy arse and pull the plastic so I can get to the CDI and coil.
Title: Coil issues (I think)
Post by: SachsGS on December 18, 2012, 03:42:13 PM: I changed a black box recently on a chinese copy of a Yamaha ATV with a chinese copy of the japanese CDI. Yamaha part $450 chinese copy (identical) $70!
Title: Coil issues (I think)
Post by: eprovenzano on December 19, 2012, 06:18:53 PM: SachsGS lets face it the quad is 19 years old, its slow, acquainted, but has been a good tool. So I'm not going to spend big $$$ on it... and I too will be ordering a Chinese version of a Japanese CDI box.

Thanks
Title: Coil issues (I think)
Post by: SachsGS on December 19, 2012, 11:50:23 PM: Problem is the japanese version is probably made in China. I almost found this out the hard ($!) way.