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Old 03-15-2007, 12:33 PM
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Unhappy No spark with compression tester

     

Hi everyone,
firstly I appologise for asking the question on this forum, as the bike that I have is a 94, rm250, but I don't seem to be getting much response from other Suzuki owners.
Quite simply my bike will not start, I've gone through everything from satator/HT coil, CDI, new plug, cap and HT lead, I've even replaced the reeds as one had a huge hole in it, compression is around the 150 psi mark.
When I take the plug out and check for a spark, theres a nice blue spark, however, when I screw a compression tester in and ground the spark plug out, I have no spark, so under compression my bike refuses to spark, has any body got any idea, as I'm really starting to scratch my head big time.
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Old 03-15-2007, 12:49 PM
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Default Re: No spark with compression tester

Am I reading this right? You have the plug out of the head, and grounded well. You have a compression tester in the sparkplug hole, and you kick it over. No spark, but if you remove the compression tester and keep the plug grounded in the same place it was, it will then "spark". Is that what you are saying?
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Old 03-15-2007, 04:11 PM
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Default Re: No spark with compression tester

Hi,
yes thats exactly what I'm saying, plug is in exactly the same position when I perform both tests but as soon as the compression tester goes in, no spark, I'm truely baffled and just don't understand why this should be happening ?.
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Old 03-15-2007, 06:19 PM
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Default Re: No spark with compression tester

I must have read your post 20 times...I don't get it. The only thing I can think of is the kill switch...I'm at a loss right now. Keep chiseling away at that bike bro I'm sure its something simple..it has to be.

-Kevin-
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Old 03-15-2007, 06:40 PM
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Usflag Re: No spark with compression tester

I have not a clue but I'll leave the post in this sub-forum since it is getting some notice. Let me know if you want it in the 2-stroke General Forum, maybe it will get more notice, but if Andy can't figure it out I am too stumped to even guess. Best of Luck.

Bill
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Old 03-15-2007, 07:13 PM
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Default Re: No spark with compression tester

i am unfamiliar with this but i will help with what i can... maybe this will pop up other ideas... What rotates the stator? IS it a key way or is it bolted to the crank ??? My thinking is under a load the stator stays in place and while not under any load it moves with the crank... just a thought.
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Old 03-15-2007, 08:31 PM
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Default Re: No spark with compression tester

ya thats what i was thinking that maybe the key holding the magneto to the crankshaft has broken and it only spins with the crank when there is no load but when there is the magneto doesnt.
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Old 03-15-2007, 09:40 PM
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Usflag Re: No spark with compression tester

Stator is stationary and the rotor is on the crank spinning its magnets.

Bill
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Old 03-16-2007, 03:16 AM
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Unhappy Re: No spark with compression tester

Thanks for all your replys, but like I said I've checked every component, the key way is in place, infact everything is reading as it should, I'm going to have another try with the bike today, as this has to be something simple, surely.
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Old 03-16-2007, 09:15 AM
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Default Re: No spark with compression tester

And the compression reading is normal, that's weird. Did you replace the anything before you started having this problem. Or did you start on the stator, CDI, etc. only after having this issue?
/Mike
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Old 03-16-2007, 11:31 AM
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Default Re: No spark with compression tester

Yes compression is bang on 150psi and I've replaced absolutely nothing to date, I've tested the components but obviously not under load as the bike won't start.
The only thing I can think of is, when the plug is out and the plug hole is left open, when you kick it over you can obviously move the piston quicker, which in turn is turning the crank over quicker and therefore, maybe generating a better spark, when the plug is in then the engine is'nt turning over as quick, so either I'm not giving it enough of a kick ( I'm sure I am, as I also own a Honda XR650r and I can kick that over without using the decompresser) or one of the ignition components is faulty.
Does the CDI, actually control the Spark?.
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Old 03-16-2007, 01:46 PM
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Default Re: No spark with compression tester

ya the CDI is charged by the pulse generator and when the CDI is charged it sends current to the ignition coil when the piston is TDC(top dead center) the ignition coil sparks the plug. when you said that the piston moves more freely without load and it generates a good spark maybe the ignition coil is gone, have you checked it? Try jump starting it, my coil is weak and when i take the plug out of the cylinder and kick it over i see a spark but when i put it back in i cant kick start it, i have to jump start it. so once you stall it in the trails or on the course your screwed.
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Old 03-17-2007, 03:55 AM
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Default Re: No spark with compression tester

Hi,
yes I've tested the HT coil and the resistance readings are well within what Suzuki specify, but like you said it may be a different story under load, maybe it is weak and breaking down.
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Old 03-17-2007, 10:55 AM
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Default Re: No spark with compression tester

Karl,
If the plug is in the head,and connected to the coil, and you get no spark I would agree that you may have a weak electrical component. If the plug is not in the head and subjected to compression, and is instead placed on the outside of the engine and truly grounded, and there is no trace of spark then something you are doing is preventing it. The CDI smart as they are have no way of knowing at that point (with the plug not subjected to pressure) whether there is 1 lb or 10,000 lbs in the cylinder. You may well have something wrong with the electrics, but the phenomena you are describing isnt an indication.
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