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Discussion Starter #1
I'm having a weird issue with my 1980 cx500d, or at least it seems weird to me. Bike was more or less fine - it has been having some lagging issues under hard acceleration, but otherwise ran/started/idled fine. Then recently I went out to ride it and it wouldn't start. It'll crank hard for quite a while, probably close to a minute, and then let out a HUGE backfire - loud enough that my housemates came out of the house to see what happened. But never even chugs or sounds like its about to start. Some more information:

- did a full carb rebuild with Randakks kit and Larrys book around 1000 miles ago. I also have an inline fuel filter, although it's old. So I think the carbs should be fine

- the spark plugs did look black/wet when I pulled them, so I cleaned them off with carb cleaner and checked the gap but same deal. They DO have what looks to me like strong spark when grounded on the engine bolts.

- the bike does have pod filters (came without the air box from the po) and is rejetted to 78/118. Idle screws are at stock 2.5 turns out. Also to reiterate, I changed NOTHING between parking it around a week ago and trying to fire up again.

Help! I'm supposed to go on a ride with friends Tuesday after work so I'd love to get it running tomorrow evening if possible. Any tips are much appreciated, thanks
 

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Was the lagging issue showing up as the rpms came up to around 5k?
Do the stator test as shown in the FSM.
 

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As it's an '80, I'm guessing its a CDI bike?

Try unplugging the black/white wire near the CDI box
the kill switch may have got the weather in.
Do all the other tests by all means, it's good practise to monitor stator health
and there may be an underlying problem with it.
CDI boxes have been known to fail suddenly with no warning too, so a DC output test will help as well
 

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Discussion Starter #4
Thanks to both of you. I'll do some testing tonight. However, if the CDI or Stator were the issue wouldn't it not have good spark? Same with the kill switch? The lagging issue doesn't happen at any certain RPM - it seems to be more related to the amount of throttle applied. If I really gun it, from any RPM, it lags. But if I get on the throttle gently, it'll accelerate up to at least 6K. Also, when I pull the clutch it will almost always rev right up to the redline if I try, it only happens under load.

Good to know CDIs can fail randomly/suddenly. I was sort of ruling that out because I figured they didn't just go while sitting, but sounds like they can.
 

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Sounds as if you might have two possible problems.
1. carbs that need cleaning.
2. ignition system starting to fail.

A lag at any speed when the throttle is cracked open quickly is often a sign that the CV valves are sticking or the port is partially plugged/blocked.
If it is most noticeable around the 5k rpm range then you may have a failing stator coil too.
 

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Discussion Starter #7
Update - I push started it and it fired up, rode it around for about 40 mins and it felt GREAT, better than before. Brass rod upgrade seems to have fixed the lagging issue. Then this morning it fired right up on the starter and rode into work with no problems.

Who knows what the issue was, but a roll start seems to have fixed it at least temporarily. Maybe it was just flooded? We'll see, I'll park on top of hills for a bit so I can always roll start. Thanks for all the ideas.
 

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Me thinks your repreive is only temporary.

You better begin diagnosis by following all the offered suggestions. A series of multimeter resistance checks will tell much about the condition of the stator and all the other electrical bits.
 

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Discussion Starter #9
Me thinks your repreive is only temporary.

You better begin diagnosis by following all the offered suggestions. A series of multimeter resistance checks will tell much about the condition of the stator and all the other electrical bits.
Yep, definitely will do. Took it for 120 miles last night and it ran like a dream, but I know I'm probably working on borrowed time.
 

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Yep, definitely will do. Took it for 120 miles last night and it ran like a dream
Where did you go? Ever get over to the east side of the lake?
 
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