I call upon the rebel elders for clarification. - Honda Rebel Forum
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post #1 of 12 Old 11-29-2018, 07:37 PM Thread Starter
 
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I call upon the rebel elders for clarification.

Disclaimer: I'm new here and have little experience working on bikes.

So I am working on a Honda rebel bobber project. I've done the usual mods; new fenders, turn signals, spring seat, etc.

Next step get rid of the air box and install a pod filter. What I need clarification on is the breather chamber.

So basically this thing evens out the pressure in the crank case and occasionally spits out oil through the conveniently named "puke tube." In other words it's important.

Okay now my question. Why is the breather chamber tubed directly to the air filter? Ive done some googeling but havnt found anything. Is the breather chamber tubed to the air filter because it needs filtered air? Or is it because the breather/puke tube need some suction action and the air filter has a "sucky" effect when air is being pulled through it?

If I spent too much time in an unventilated garage and that didnt make any sense, Im asking if a separate filter attached to the breather chamber will suffice. Or do I need to splice the tube coming from the breather directly into the air filter pod?

Please, all powerful rebel elders, entertain my humble request.

It's an 87 250 if that matters.
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post #2 of 12 Old 11-30-2018, 11:30 AM
 
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Perfect sence, I'll make an attempt.
The rebel is a parallel twin, both pistons go up and down together. air goes out the crankcase when the pistons go down, air goes back in when the pistons go up. So a coffee mug's worth (232cc) of air has to go in and out of that breather tube every rotation. 24 times a second at idle.
Air going out has some oil spray in it, so you want something to prevent it getting all over your pants.

and air going back in has dust and bugs and cigarette ash and rain drops in it, so you want something to filter it so only clean air gets sucked into your oil.
so the 'breather chamber' lets oil spray settle out and collect in the puke tube, and the connection to the air filter makes sure only clean air goes back in.

hows that?
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post #3 of 12 Old 11-30-2018, 12:37 PM Thread Starter
 
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That's perfect. Everything makes a lot more sense.

So replacing the airbox with a pod filter should be fine if I put a small filter on the breather chamber, right?
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post #4 of 12 Old 11-30-2018, 02:27 PM
 
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Sorry wrong... This subject has been discussed a lot already . Putting a tiny filter on the breather loads it up with oil and water gunk on the INSIDE where you can't see the plugging happening. When it gets plugged up, the crankcase pressurizes from blowby gases and the pumping action of the pistons. This blows out the large oil seal on the crankshaft behind the flywheel resulting in a total loss of engine oil very quickly. As Kryton noted, the volume of air pumped through this filter is theoretically more than twice the volume of air drawn through the carburetor on each revolution . If anything, the breather filter would need to be twice as big as the inlet air filter. Bikes that have pod type filters from stock (none that I can think of) have some other type of breather system.
The Honda air filtration and breather system is well designed and works well. I would not change it to a system that will not do the job nearly as well and could cause you some heartache sooner rather than later.
If you insist on doing this mod, at least leave the ugly condensate trap in place and filter the tube that now goes to the airbox filter.
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post #5 of 12 Old 11-30-2018, 08:21 PM
 
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Your whole plan is not a good idea. The stock airbox/crankcase breather setup works very well, in fact it works great. It was designed by engineers, and they did a good job. Running a pod filter will seriously lean out your air/fuel mixture, and if you use the K&N gauze type, it will allow a LOT more dirt to get inside your engine, shortening engine life. Just putting a filter on the crankcase vent will work for a short time, till the filter becomes completely plugged up with oil and other gunk. At that point you have no crankcase vent. You would probably be better off running a long piece of tubing down underneath the bike from the crankcase vent, creating a "road draft" tube like what was used on old cars, before the PCV system was developed in the early '60s. The PVC system was intended as an emissions device, but it works great at venting the crankcase, since it uses actual engine vacuum to suck air through the crankcase vent. I don't know why this system was never used on motorcycles.

Anyway, I would rethink your idea. You will be damaging your bike if you do it the way you have in mind.
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post #6 of 12 Old 12-01-2018, 08:50 PM
 
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I realize that customizing a bike is intended to change then look. However, certain parts should be left alone, both to avoid damage to the bike, and for safety. The intake system is something you should not mess with at all. However, there are a number of aftermarket mufflers that can be used, IF the carburetor is retuned for them. Those little Emgo mufflers sold by Blue Collar Bobbers seem to be the most common, and seem to work well with the stock intake. Don't run open pipes, they are beyond the tuning range of the carburetor, and will fry your engine. One of the worst mods I've ever seen is replacing the rear shocks with struts. This is a serious accident waiting to happen, literally. Notice how the shock mounts are almost halfway between the rear axle and the swing arm pivot. The Rebel swing arm is very weak, and is designed to be used with springs. Hit a bump or pothole with struts, and the swingarm will crack right at the lower mounting point. And a home made hard tail is no better. Frame building is an art, and a lot of engineering is involved. A hard tail also provides a miserable ride. If you want one, it needs to be done by a qualified frame builder, meaning it won't be cheap. And after spending all that money, you probably won't ride it very much because of the pain it causes. Another thing is ape hangers so high you have to reach over your head tp put you hands on the grips. These are illegal, bu8t worse that that, they take away almost all control of the bike. You might be able to cruise down a straight road for awhile, but turning will be almost impossible. And if you get into a situation that require a quick evasive maneuver, you are almost certainly going to crash, and depending on the situation, you could even get killed. Those building custom bikes, and here it seems to be mostly bobbers, need to keep a lot of things in mind. When you start hacking up engines and frames, you are likely to get yourselves into a whole lot of trouble, possibly even killed. Modifying a factory made bike designed by engineers require a lot of thought and research. My motto is "if in doubt, don't" I have been all the way through the bobber picture thread, and I have seen a lot of very scary and potentially deadly creations.
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post #7 of 12 Old 12-04-2018, 07:28 AM
 
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@JakerHsnaker, Please don't mistake the passionate responses as reprimands, we really want to help you and share the wisdom of this collective.

Others have tried some mods on their rebels that worked great, and some that were disappointing, and some that led to more trouble then it was worth.
The left side crankshaft seal beneath the alternator is a MAJOR pain to replace, and it blows out and unseals when there is too much pressure in the crankcase that can't get in/out of the crankcase breather fast enough.
Some have found that the OEM air box actually gives the best take-off and top speed, and lost some of that with a pod filter.
Nearly everyone that tried changing the OEM sprocket ratio reported back that the top speed fell off, no matter which way they went.

We're not against you making your bike into what you want it to be, we just want to help you make informed decisions.
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"The bravest thing for me to do is admit when I am wrong" - unknown
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HRF Answer #2 You need to clean your carburetor
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post #8 of 12 Old 12-04-2018, 08:51 AM
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Excellent response, kryton.
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Keepin' all the left over parts. Gonna use 'em to build another bike!

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post #9 of 12 Old 12-04-2018, 06:42 PM Thread Starter
 
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Thanks for the words of wisdom, fellas!

Sooo after careful deliberation, I have decided against gutting the air box. I figure a matte black coat over the chrome side panels will give my rebel the bobber feel I was going for.

Follow up question:
How would I go about fixing a tail light wire? My rear left tail light wire seems to be dead. All the other blinkers work fine. And I know its not the actual blinker that is faulty because when I plug the rear left blinker into the other rear blinker wires it lights up fine.

I checked the front panel thing where all the wires connect. Everything seems fine, I think. That compartment is really a cluster**** though. The orange and blue wire connectors, the turn signal wires, seem to have all the appropriate wires connected. Anyone have any advice or suggestions? Also is that front wire panel behind the head light supposed to be packed so tight? I felt like I was squishing wires when I closed that thing.


Again, thanks for the help kind strangers.
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post #10 of 12 Old 12-04-2018, 07:08 PM
 
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Quote:
Originally Posted by JakerHsnaker View Post
Follow up question:
How would I go about fixing a tail light wire? My rear left tail light wire seems to be dead. All the other blinkers work fine. And I know its not the actual blinker that is faulty because when I plug the rear left blinker into the other rear blinker wires it lights up fine.

I checked the front panel thing where all the wires connect. Everything seems fine, I think. That compartment is really a cluster**** though. The orange and blue wire connectors, the turn signal wires, seem to have all the appropriate wires connected. Anyone have any advice or suggestions? Also is that front wire panel behind the head light supposed to be packed so tight? I felt like I was squishing wires when I closed that thing.
The rear tail and signal light connections terminate in a connection box which is part of license plate mount..
Accessed by removing bolt and cover at bottom of mounting box.. I have snaked in open wrench to remove 3 nuts of license plate mount, carefully twisting to expose the bottom access.. pita
removing rear wheel is also an option... bigger pita
The secondary rear wire harness runs from that box to connecting to Main wire harness under the seat..

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