Hey guys - NEED HELP! - Page 2 - Honda Rebel Forum
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post #11 of 28 Old 06-18-2019, 07:02 PM
 
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If the CM engine is like a Rebels, the engine will run without a battery, but it's generally not a good thing to do. If the alternator wire is gone, it would explain why the engine isn't firing since you have a weak battery to boot.

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post #12 of 28 Old 06-18-2019, 08:58 PM
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Tighten the bolt into the hole, and whack the bolt head with a hammer. If it doesn't break free, tighten and repeat. Don't try and use just tightening the bolt to remove the flywheel.

You can jump the bike from a car battery, just be sure the car engine is off. If it starts, your battery is definitely weak. I recommend Yuasa brand replacements. That's what Honda puts in them from the factory. While a few dollers more initially, they are cheaper in the long run because they outlive any other battery I know of.

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post #13 of 28 Old 06-19-2019, 12:29 PM Thread Starter
 
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UPDATE - got her running!
Idles and starts right up, but I’m now getting popping/backfire when I go past 1/4 throttle.

I’ve pulled the carb and cleaned/adjusted the jets multiple times but I’m still getting the same problem..
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post #14 of 28 Old 06-19-2019, 02:45 PM
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What did you set the air/fuel screw to initially? Have you tried opening it 1/4 turn at a time?

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
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post #15 of 28 Old 06-19-2019, 04:40 PM Thread Starter
 
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2 and half turns out from seated - since then I’m at around 3 full turns which seemed to help..

I still have yet to change the bad flywheel, it’s really on there.. the magnets are in pretty bad shape, so this is on the agenda for tonight..

After pouring over the wiring diagrams I discovered that my wiring (and everything else for that matter) seems to be identical to a first gen cmx250 - the stator I installed was from a 2nd gen.. the first gen has 2 wires going from the stator to the CDI while the second has one.. I found a thread where someone else had a similar issue and they solved it with a simple splice of the 2 wires into one.. once I did that, she fired, idled and even ran at low throttle..

My question is; could a bad flywheel be causing a weak spark at open throttle? I know that changing is a must, and I have the extra part so I’m going to do it no matter what.. I’m just getting very frustrated - every time I “fix” one issue, I uncover another one.

I also have a rectifier, CDI and starter switch from the second gen, but without the pigtail wires it would require some modification to get it to work.. if it’s not broken, I don’t want to mess with it.. the problem has been finding what it actually broken.

Thanks again for all your help guys - hopefully I’ll be riding again soon!
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post #16 of 28 Old 06-19-2019, 06:17 PM Thread Starter
 
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Also - something else I can find no information on;

My carburetor doesn’t have a traditional diaphragm. It has a floating metal piston which holds the needle... is anybody familiar with this?
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post #17 of 28 Old 06-19-2019, 07:55 PM
 
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If the magnets are in bad shape because they beat up that wire, I suppose it's possible the magnets could have been demagnetized by the wire as the wire rubbed against it. I'm not for sure. If you change the flywheel, I'd like to know what the difference is.

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post #18 of 28 Old 06-19-2019, 08:41 PM Thread Starter
 
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Once I get the damn thing off, I’m going to change it lol

I’ll report back later tonight. I’m also replacing the plugs, just in case the fried stator fouled them out.

For the sake of learning and possibly helping someone else down the road, I’ll try to start it with the new flywheel only, to see what kind of difference that makes before I replace the plugs.

My hypothesis is that there’s a weak spark - either from fouled plugs or a weak current from the stator due to a demagnetized flywheel.. enough spark to fire and idle, but not enough to keep up with high rpms, explaining my exhaust explosion.

Now, correct me if I’m wrong, but this engine is a parallel twin, meaning the pistons fire at the same time, correct?

If the new flywheel and plugs don’t work - could I have a valve that’s hanging up leaving unburnt fuel in the cylinder and then when it does spark there’s too much causing the backfire? Even as I type that, I still think the simplest answer is that the plugs are bad causing a misfire and the unburnt fuel is igniting in the exhaust.
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post #19 of 28 Old 06-19-2019, 09:11 PM
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I believe the engine is an inline twin. It has a wasted spark ignition system. Each time the pistons come up, whether on compression or exhaust, both plugs fire (e.g., the "wasted spark"). When one cyclinder is compressing, the other is in the exhaust cycle, so they don't fire at the same time.

It sounds improbable, but backfiring is a sign of a too lean condition, not too much fuel. A compression test would reveal if a valve is sticking or not closing properly. Have the valves been adjusted recently?

Keepin' all the left over parts. Gonna use 'em to build another bike!

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post #20 of 28 Old 06-20-2019, 12:04 AM Thread Starter
 
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No - but I do hear a slight valve tap. Idk if it’s “normal” or not, I know this is a noisy engine..

My backfire is definitely an exhaust explosion rather than the lean popping.

Pulled the plugs and they are BLACK.. I’m surprised it started at all to be completely honest.

Going to autozone to pick up some plugs in the morning. Will report back.

Also, the ONLY bolt I could find in m16x1.5 is a drain plug for $12.. which isn’t a lot of money, but it’s more than I wanna spend on a bolt. So, my flywheel project has been postponed for the time being.
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