Cylinder not firing - GT185

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bennymalta
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Suzuki 2-Strokes: Suzuki gt 185

Cylinder not firing - GT185

Post by bennymalta »

Hi,

So I'm restoring my 77' GT 185 and getting everything done I'm now trying to start the engine. The engine starts fine but I've discovered that the left cylinder is not firing. I've changed the spark plugs and plug caps but still nothing. I disconnected the left spark plug and the engine starts, then I disconnected the right spark plug and the engine did not run. Then I plugged in the cap of the right cylinder to the left one and the Engine banged, a blow of exhaust shot out of the pipes yet it did not run. After that I continued trying to crank it but nothing. What could it be?

I've narrowed it down to either:
1. No fuel is entering the cylinder,
2. There is no compression (but I doubt it as by placing my thumb on the plug hole proves there is compression),
3. Could it be incorrect timing or the point wore off or condenser is not working?

Just so you know I had replaced the rings of both pistons - that is basically the only thing I did to the engine.

Appreciate your ideas on what could be the issue.

Thanks! Ben
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tz375
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Re: Cylinder not firing - GT185

Post by tz375 »

I am completely unfamiliar with the GT185, so this is more of a generic approach than model specific.

I would start by removing the plugs to make life easy and insert them into the plug caps and lay them on the head. Next check the points and see that they are clean and set with the correct gap and that the open at the right time.

Then turn on the ignition and kill/run switch and flick the points open and closed with a screwdriver. You should see a spark on both.

If no spark on one side, turn off the ignition and test the continuity at the plug cap to see if the cap is open circuit. It is quite common for old caps to deteriorate and no longer allow electrons through. If the caps are dead, also trim 1/4" off the end of the plug wire to give teh cap fresh copper to dig into.

Test again for sparks as above.

Still no spark on one side, test the coil connections and for resistance.

If/when you get a big fat spark on new plugs at the right time on both sides, it it still will not start, look at the carbs but check for sparks first because even with perfect carbs, no spark, no fire.
bennymalta
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Suzuki 2-Strokes: Suzuki gt 185

Re: Cylinder not firing - GT185

Post by bennymalta »

Thanks for this.

Thing is, the right spark plug fires magnificently, so that means that the point/gap for that side + plug cap + ignition coil + condenser are all working correctly for the right spark plug no?

So how is it that when I tried connecting that spark cap on the left side it did not fire?


I will check the spark etc but theoretically if I have a good spark on the right spark plug, when I connect it to the left one it should fire the cylinder as well...no?

P.s. I have new spark plugs + new caps.

thanks.
karl pa
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Re: Cylinder not firing - GT185

Post by karl pa »

When the right spark plug fires, the left piston is at the bottom of the stroke, you may get a bang in the engine, but it will not run because you are not on compression stroke.
You may want to check the points are clean, they oxidize and prevent contact.
76 GT185
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bennymalta
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Re: Cylinder not firing - GT185

Post by bennymalta »

Could it be that the points need replacing altogether?

Cause I remember that a mechanic about 5 months ago had cleaned the points with a fine sand paper...so they might just need to be replaced altogether :/
Craig380
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Re: Cylinder not firing - GT185

Post by Craig380 »

bennymalta wrote:Could it be that the points need replacing altogether?

Cause I remember that a mechanic about 5 months ago had cleaned the points with a fine sand paper...so they might just need to be replaced altogether :/
Unfortunately, you can't really "clean" Japanese points that way. The point faces have a plated surface and the sandpaper messes it up, which means the points won't work properly anymore. Ask the 17-year-old me how he learned this :wink: :roll:

You could try using a residue-free electrical contact cleaner spray and a piece of clean white card to try and clean up the points surface. This can work sometimes. But if it doesn't, you need new points. If you haven't replaced the condensers yet, then I'd get a new pair of those too. Just to eliminate possible problems, and they cost peanuts anyway.
1976 GT380 - wounded by me, and sold on
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MarkH
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Re: Cylinder not firing - GT185

Post by MarkH »

I'm check the carb first. Sounds like a float valve issue, or stuck float.
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vman858
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Re: Cylinder not firing - GT185

Post by vman858 »

Take the left side cover off put a timing light on it. 185 has two marks, one for each side. I would bet that's it. Go through manual and set it by marks and test light.

Might try putting plugs back in and opening throttle while starting and kill switch off so it won't start, then check plugs for fuel. Also make sure oil system is working.

I just went through mine and am pretty familiar with it. I do have a few questions but start a new thread. When you put your thumb on plug hole does it feel the same on both sides or at least close?
vman858
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Re: Cylinder not firing - GT185

Post by vman858 »

viewtopic.php?f=2&t=11783&hilit=gt185" onclick="window.open(this.href);return false;

Good info
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