the only problem i see is dripping on your garage floor

the benefit is not having to remember to drain it occasionally

i run my rebel without a cap

 

I have been wondering the same thing. Will be interested to hear the replies.

One concern I had was allowing moist/humid atmosphere to reach the inside of the crankcase?

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One concern I had was allowing moist/humid atmosphere to reach the inside of the crankcase?

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That, and dust too. How much will that affect engine longivity? I don't know, but don't want to risk it. Putting a valve in the tube makes draining it very easy.

 

I would think, over time road grime will plug foam filter #16 of the Breather Separator,
rather than dripping into Puke tube oil/water will be pushed to the inside of air filter canister where crankcase vent terminates...

oil and paper filters are not a good mix imho

 

Newbie here, just to put a bow on this thread, what is the puke tube and how often should it be drained if I keep the cap on?

 

drain puke tube every oil change..

 

I wonder how many hundredths or thousandths of a horsepower more we could get out of our neck snapping, rubber roasting Rebel if it weren't sucking in some amount of crankcase nastiness? Every hundredth of a horsepower counts when I line up next to a V Star 250 in a school zone and need to teach that lowly mis-angled 2 cylinder sap a lesson.

 

Ha!!!

This brings up a subject I have wondered about... How DOES the Rebel 250 stack up against the VStar 250, performance-wise??

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All else being equal, I think the Rebel would get beat, at least on the strip, and top speed too. Again, all else being equal, I would say the V Star would cross the line 1 or 2 bikes ahead, consistently. And top speed, maybe 2 or 3 mph maybe. It just has a skosh more power. About 2 hp more from memory. However, most riders rating them rate the Rebel as their preferred choice, I think because of ease of use, access to replacement parts and mods, stuff like that.

 

Biggest problem with the vstar 250 for new riders is the clutch engagement. It has a super short clutch engagement zone right at the outer edge of the lever pull that isn't adjustable. Makes this a difficult bike to learn on for the first time for new riders as gradually feathering the clutch to learn engagement methodology does not work like other bikes. Even as an experienced rider I have trouble with stalling and jerky shifting on this bike, the first time I rode one not knowing about this I was convinced there was a serious problem with the clutch on the one I rode until I talked to the owner then read more about it.

Unfortunately it is a design issue which cannot be adjusted out using stock options. Some owners have success twisting and mangling the clutch lever into a shape which gives them a bit more control. Others actually get used to it, then wonder why the clutch is so weird on other bikes.

 

Back to the puke tube cap situation.



Most people think keeping the cap off shouldn't harm any thing because of positive crank case pressure, but the problem en lies with the intake pressure. Most air-oil separators work using gravity and baffles. The crankcase gasses are suppose to flow into the intake and residual fluid is supposed to collect at the lowest point in the separator.


The problem with leaving the drain cap off is the potential for unfiltered air to make it into the air intake.


When the bike is running it may seem like air is puffing out of the tube, but it is also being sucked back in at a slightly higher rate. With the cap in place the intake pressure should be slightly lower than the crankcase pressure resulting in a slight vacuum on the crankcase.


The best way to go about not draining the tube is to delete the system, and just run a filter on the crankcase side.

 

Back to the puke tube cap situation.

The best way to go about not draining the tube is to delete the system, and just run a filter on the crankcase side.

The only drawback to that is gunk that would end up in the puke tube clogging the inside of the filter, which leads to increased crankcase pressure, which can blow the crankshaft seal.

In my experience, it would take a ton of WOT throttle running before the puke tube would come anywhere close to filling up. I often fail to drain the tube for over 5,000 miles. When I finally do, there's never been more than about a tablespoon of stuff that comes out. I've heard riding in the rain increases the rate of "puke" production. I try to avoid riding in the rain when possible, but got caught in the aftermath of Hurrican Harvey a few years back. It varied from an absolute deluge to light rain for about six hours. There was very little accumulation in the tube the next time I drained it.