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1986 CMX450
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48 Posts
Discussion Starter · #1 ·
I recently got a new to me cmx450. I got maybe close to 800 miles on it. I've noticed some stuff which might not even be anything. Keep in mind I am new to motorcycle altogether so my questions might be stupid.

The engine won't idle unless choke is almost fully on all the time or it will cut out the motor. Does matter how warm the motor is or how long I've been driving it, It will die. I am driving with choke fully open on all the time if that makes sense.

I get about 40 gallon per miles. Not sure if it is related to choke being fully opened all the time. I'm not trying to nick pick my mpg as I have fun and that's all that matters to me. I love riding.

3rd and most serious complication is my battery keeps dying. On Saturday the bike died went home and brought a spare battery. It started right up again, then I disconnected the positive termenial and the bike was still running. Today the battery is drained again. I'm guessing alternator. I just bought a brand new battery. Ideas or suggestions?

I want my bike to be reliable. If not for the battery dying it would be reliable. I'll drive with choke on all day if it is reliable.

Thank you.
 

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85 CMX 250C, 82 GW Remember that you are invisible, treat all others accordingly. Avoids Road RAGE!
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750 Posts
40 gpm sounds like an old army tank! 馃槈
Most of these have set for years. The 450 was only made in 1986 and 87. So if it's only get 800 miles it's set an awful long time. It needs a carb rebuild for sure!!!
If the bike still runs with the battery disconnected, that means the alternator is producing plenty of power. I would look for the fault elsewhere.
 

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1987 CMX250C AC
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2,380 Posts
Welcome to the forum

Your battery went dead while positive cable disconnected??
or had you reconnected battery?
with ignition Off disconnect Neg battery cable, using a volt/multimeter connected between battery terminal and ground,, check for parasitic voltage draw..
there should be no voltage shown..

111120


Rebel 250/450 will run without a battery, though it is hard on volt regulator..

you are going to need to clean carburetors, at the very least idle jet/passages are plugged..
classic symptom of plugged idle jet is the need to use enricher/choke all the time..

111118
 

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1986 CMX450
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48 Posts
Discussion Starter · #4 ·
Thank you both^.

Yeah I was thinking it might need a carb rebuilt because at one point must had been sitting.

Thank you for the diagrams too. I'll get a multimeter and check.

This is a great start!

 

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85 CMX 250C, 82 GW Remember that you are invisible, treat all others accordingly. Avoids Road RAGE!
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A word of caution..
Clean it yourself. Avoid the issues many have had with "professionals" ruining one of the few remaining 450 carbs out there.
 

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1986 CMX450
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48 Posts
Discussion Starter · #6 ·
Ok. 馃榿

I think I have the confidence to clean it myself. If not I'll have pic and pictures. 馃檹
 

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When cleaning carbs, use rubber safe stuff. Brake and parts cleaner can eat a lot of rubber parts, and can ruin the tips of the needle valves. You might guess how I know this. On my CB750F, it has 4 carburetors, and the stealership wanted $30 PER needle. Thankfully I found them cheaper online.

Also, get yourself a set of welder tip cleaners, those are good for gently cleaning the jets of any solid gunk that may have built up.
 

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An ultrasonic cleaner, or extended soaking in Berryman Chem Dip should get the jets clean without the need for files.
 

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An ultrasonic cleaner, or extended soaking in Berryman Chem Dip should get the jets clean without the need for files.
I bought one of the gallon Berryman chem-dip things, and it gets those brass jets looking like new! Great stuff. Worth the cost, for sure.
 

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1987 CMX250C AC
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2,380 Posts
DO NOT run a tip cleaner or wire length ways through pilot/idle jet as there is a micro screen within which will be destroyed..
 

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I bought one of the gallon Berryman chem-dip things, and it gets those brass jets looking like new! Great stuff. Worth the cost, for sure.
And it will do many carbs before getting too dirty/diluted and no longer effective.
 

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1986 CMX450
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48 Posts
Discussion Starter · #12 ·
Bike died. Battery dead again. Something is wrong but I ain't got time. I rather be in the words and painting. I'll get the insight to what is wrong. I'll just charge the battery every night if I have to. Jog to work and home. Ride to relax close by. 馃榿

Maybe tomorrow I'll start getting serious about lubing the change, cleaning the cabs, and getting a multi meter to check what is draining the battery.

Dead right at the gate.
Tire Wheel Plant Automotive tire Vehicle

Table Paint Recreation Tableware Stationery
 

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85 CMX 250C, 82 GW Remember that you are invisible, treat all others accordingly. Avoids Road RAGE!
Joined
750 Posts
Like SoakedKarma said, parasitic voltage draw sounds like the culprit. I've always enjoyed troubleshooting, got paid many years to go to work for more fun! Found a lot of strange & interesting problems. Loved that job!
Point is, whatever you do, enjoy it. There's too much in life to bring us down.
Great looking bike! CLEAN & SHINY! Anything added that isn't factory?
One more question, it's not meant to belittle. I'm not sure if this is your first bike or not, I just want to make sure when you're shutting the bike off your leaving the key in the left position when you're taking your key out, and not turning it all the way to the right which is Park, (which would leave the tail light on). It may sound like a stupid question, but you wouldn't believe how many pieces of equipment I had to plug back in.
 

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1987 CMX250C AC
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2,380 Posts
I can't think of a reason engine would have quit.. the ignition/CDI doesn't depend on battery to create spark..
For that matter CDI isn't even connected to the battery..
Rebel system is very similar to aircraft engine which uses magneto to power spark
 

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1986 CMX450
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48 Posts
Discussion Starter · #15 ·
Hi. Yes first bike. I don't put the keys in park with the tail light on. I got it working again swapping the battery and went for a cruised already.

Everything seemed oem. It has less than 6000 miles on it.

I'm just reading and relaxing and thinking about it here and there.

Automotive tire Bumper Automotive exterior Gas Auto part

Test drive it 馃榿
Sky Leaf Hat Neck Tree

I'm just going to pray. I can't take it Heaven but I own it ATM.
Food Table Tableware Sky Cloud
 

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1986 Honda CMX 450 Rebel
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35 Posts
Seeing the photo of your disconnected accumulator.

Disconnecting is: minus first (-) !.
Disconnecting plus (+) first can lead to desaster. Like burning your bike entirely down the moment the plus cable, accidentally, contacts ground (frame)

If the battery ist to be installed, plus is to be connected first !
This is no "wise-guy-cracking" but first thing to learn when working with accumulators...and it is with good reason.
 
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Seeing the photo of your disconnected accumulator.

Disconnecting is: minus first (-) !.
Disconnecting plus (+) first can lead to desaster. Like burning your bike entirely down the moment the plus cable, accidentally, contacts ground (frame)

If the battery ist to be installed, plus is to be connected first !
This is no "wise-guy-cracking" but first thing to learn when working with accumulators...and it is with good reason.
I saw this and thought the same thing. This is valuable knowledge-facts and I received from my auto mechanic many years ago. Was told when removing any battery, disconnect negative first and when installing, connect negative last.
 

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85 CMX 250C, 82 GW Remember that you are invisible, treat all others accordingly. Avoids Road RAGE!
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That is of course unless you've got a car from the fifties or before that had a positive ground. I had one once, generator & all. I sold it years ago.
 
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