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Moderator - Loves All Motorcycles
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Discussion Starter · #1 · (Edited)
So I got my CF Moto running beautifully and decided to find its new top speed. I hit 68mph then all of a sudden the engine started bogging down until it shut down with me still moving. I was able to get it started and got it home, and that was the last time I was able to ride the scooter. I have been able to start and run the engine so it appears to be fine.



Upon close inspection I learned I made a very rookie mistake. I got the scooter a new carburetor and cleared the bad fuel out of the tank, but I didn't replace the fuel filter that had turned into rust after having stagnant fuel sitting in it for who knows how long. Thankfully the tank appears to be intact and the rust was isolated on whatever cheap fuel filter this was. This means that while the fuel in the tank was now clean, it was getting contaminated on its way to the carburetor.



Last night I gutted the fuel system and replaced it. New lines (had to literally carve out the old ones), new filter, new carb.

It was when I was putting the bike back together that I noticed something weird:

This is the filter at the end of the intake tube that connects to the carb. That isn't rust, it's some sort of other material...



Alright, that wasn't like this when I first got the bike started. Uhhh, let's look inside?



It smells like old gas mixed with an additive like seafoam. The liquid has the consistency of honey.

Alarmed, I drained the tank, changed the oil again, and checked the coolant...all checked out. Oil was clean, coolant was clean, and fuel looked like fuel. Okay, so nothing appears to have exploded in the engine, so where the heck did this stuff come from?

Let's look at the inside of the air filter.



Upon close inspection, the particulate matter is either the lining of the air filter or some contaminant that got into the air filter (such as an animal nest). If you look closely, you can see the filter's actively falling apart...or whatever's in the filter's actively falling apart. I assume that when I was trying to reach top speed the engine was being choked of both clean air and clean fuel and just called it quits. The engine runs fine when I tested it on a clean system (pod filter and the cleaned fuel system).

I'll replace the filter before riding the scoot again. However, this doesn't explain where the liquid's coming from. Any ideas?
 

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Discussion Starter · #2 · (Edited)
Some self-studying reveals that a common problem with Helix scoots was that if you filled the oil all the way to the recommended specs, the crankcase vent would often shoot oil into the airbox. Mix oil with moisture (since I ride in the snow) and...milkshake, I guess? Studying my clone, the crankcase vent was another thing CF Moto shamelessly copied. *sigh*

I suppose my oil, water, and starting fluid soaked air filter started to fall apart and made a mess of absolutely everything.
 
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Save them all!
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Ya, I would guess oil from the crankcase vent while you were setting speed records on it.

Sounds like you have it figured out!
 

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Foam can break down and turns to mush, particles, and powder.
The foam in my old Bell helmet looks the same. Some engines seem to breath out more oil vapor than others. It is a crank vent, so pressure is possibly passing the compression ring or rings. There are nifty little filter things to place on the crank vent, instead of running the hose to the filter.
On my XS400 I run foam pod filters. The crank vent hose is open, and runs up the frame about 10 inches. Very little vapor comes out.
On my 68 Dunstall Norton, which had an external tank and breather hose, I ran the hose to a big block of foam in the tail section. It absorbed any vapor, which was like a fine mist, just slippery.

UK
 

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The vent on my Valkyrie goes to a T before connecting to the air box, with one leg smaller than the others. That smaller leg connects to the air box, while the other two go to the vent and a length of tubing that goes out the bottom. There is a plug at the bottom that is removed from time to time to let any accumulated water and oil from the vent to drain; messy, but it keeps that stuff out of the air box. You may want to come up with a similar arrangement for your scoot, if space allows.
 

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Discussion Starter · #7 ·
Thanks all! It's good to know I'm getting better with this diagnosis stuff. :)

Upon further investigation I think I have a long term solution. I'll vent the crankcase externally (with a tiny filter so I won't get oil everywhere when running on the highway) and plug the crankcase hole in the airbox. Hopefully this should be the end of my issues for a while.
 

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Save them all!
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That's how a lot of older bikes do it. Just make sure it stays away from tires and such.
 
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--

As you stated in post #7 is good. I have my vent going uphill under my seat with a filter on the end. Also, with two of my bikes, the factory fill level is too high and oil will shoot out after an oil change so owners of that model just put in one third quart less oil and no problems.

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Just a cautionary note, and it depends on the amount of oil film being vented. Oil on the rear tyre creates a slide like no other, except maybe a bald tyre on ice. The rear end can snap out so fast, it can dislocated body parts.

I rode many English bikes if you need to know. At the track, if ever there was oil on the track, the first bike the tech inspectors would check would be: guess who? the only guy dopey enough to be still running British junk. BUT, due to some experience with wayward oil ( see above ) I had developed a leak free and mist free system.
So I invited the techs to do a stem to stern inspection of the British bike, and then took them to the two stroke Yamaha road race bikes, that belched an oil mist out the throats of the carbs. Case closed.
It was often a cracked crank case or gear box or something that had dumped the oil.

Back to the matter at hand. Excessive crank case pressure, is the result of warn parts, usually the rings. But could also be something else that currently alludes me.

UK
 

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Discussion Starter · #11 ·
Thankfully it no longer spits out the milky oil stuff. I suspect it came from never really getting the scooter to running temp. My ride to work is only a mile. Couple that to our ever changing weather and too much oil... milkshake!

I decided to run it near redline for about 5 minutes and it stopped spilling out milky guts and most of the smoke is gone, too. Now it seems I need to correct airflow to the carb and that should resolve both my low top speed and the remainder of the smoke.
 

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American Legion Rider
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You do a major disservice to any internal combustion engine by only running it for 5 minutes at a time. If you can't run it for 20 minutes, don't run it at all. Take another route to get that engine to running temperature and keep it there for awhile. That not only helps burn of water vapor collected in the oil chamber but helps recharge the battery as well.
 

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100% agreement here, my wife used to have a problem with short runs, her ride to work was 1.2 miles, her engine would still be cold when she got there. it was bad for her car, it was probably worse for her bike. When she rode the bike she used to take a 20 mile ride home every day to give the engine a chance to warm up, I'd swap cars occasionally to get her car a good 70 mile run at least once in a while.
Now that we moved her commute is 13 miles, problem solved. :)

You do a major disservice to any internal combustion engine by only running it for 5 minutes at a time. If you can't run it for 20 minutes, don't run it at all. Take another route to get that engine to running temperature and keep it there for awhile. That not only helps burn of water vapor collected in the oil chamber but helps recharge the battery as well.
 

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Discussion Starter · #14 ·
You know, for some silly reason I figured the little 250 thumper would warm up faster. My GL1100 and my GS850 aren't even rideable without you letting them warm up first

Oof, this is a lesson sort of hard learned. The best way to increase the driving distance to work is to do a couple laps of the ring road. My actual distance from work is 0.25 miles but the building is separated from the condo complex by marshes with no trespassing signs on them. So you have to take the ring road to get around those areas.

Also in hindsight, I could have just added this to my main project thread. Do we have any active mods around who could merge the two threads?
 

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No worries running two threads, it keeps us sharp. I use the Subscription link above, to help with with the threads I have commented on. I am at the bottom end of my Island, with the village about 10 miles away at the other end. That gives the bikes a 20 run for the loop.
My XS400 is always screaming when I go down the freeway, and just about everywhere else too.
6000 at sixty, 7000 at seventy and so on.

UK
 

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Swamp Rat Rider
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Learned long ago if can't take the Bike 20 miles I don't even crank it up ...
 

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Discussion Starter · #17 ·
At this point I haven't found any logical way to make my work commute longer, so I guess I'm back to driving to work and riding for everything else. :)

Thankfully Mercedes-Benz's engineers factored short trips into their city cars. The worst monster you have to face is carbon buildup and that can be fixed by running it long and hard
 

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It's really easy to extend your commute...who cares about logic?

Let's say you work due east of where you live.
Get up an hour early, head west for 25 minutes, make a U turn, head east for 25 minutes, ride past your house and go to work, you'll still be early.
What's so hard about that?
Adjust as necessary for local conditions like mountains, lakes or oceans that might be in the way.
:)


At this point I haven't found any logical way to make my work commute longer, so I guess I'm back to driving to work and riding for everything else. :)

Thankfully Mercedes-Benz's engineers factored short trips into their city cars. The worst monster you have to face is carbon buildup and that can be fixed by running it long and hard
 
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American Legion Rider
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You got it Mike. Logic be damned. Just point the bike in any direction and ride. Then try to find a different way back. It's also called exploring so just give yourself extra time in case you get lost.:grin:
 
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Discussion Starter · #20 ·
Muahahaha! I do love exploring! Though Admittedly it would take a lot to get me to wake up an hour earlier. :D

However, it isn't impossible! I think I'll give it a try now that the holidays are over and I have time to go out on a nice long ride. :) At least 20 miles a day should keep the mechanic away! :D
 
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