KymcoForum.com
Scooters - 125 to 300 => Bet & Win 150 => Topic started by: Rickster on July 30, 2022, 03:17:32 PM
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Over the winter, I examined and rebuilt/replaced everything on my 2007 B&W 150, except for the engine - new tires, antifreeze, drive belt, variator rollers... you get the idea. She was ready to sell. Wouldn't you know it, but on a test ride, I believe the engine blew. I have not opened it up to verify that, but I'm pretty confident of that issue. (Engine noise + engine stop = blown engine.) I have zero experience rebuilding engines, and I have no special tools needed for such a task. Obviously, I'm not afraid to get my hands dirty and enjoy a challenge. So, my options are: 1) Rebuild it myself buying the needed tools along the way. 2) Have a dealership rebuild it for me. 3) Have a local small engine repair shop rebuild it for me. 4) Replace the engine with a different one. 5) Sell it / trade it for a different scooter, as is.
I'd like anyone's thoughts on what you would do, if this was your scoot. Thx.
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I think the reality is paying anyone to do any type of engine rebuild on an older scoot will cost more than the value of the scoot. If that's your only option I'd probably just sell 'as is', for parts.
Before giving up on it I'd first want to see if the engine will even turn over. ...and not with the starter button but by putting a socket and wrench on the variator nut. Will the engine spin over? If so, you're in better shape.
Have you visually scanned the motor for any cracks, holes, major leaks, etc.? If it is truly gone it would be much easier to swap in a used motor, assuming any of those are available...not many used scooter motors available around me.
Having just completely stripped down and then rebuilt one of these (S200, air cooled, 163cc) I can tell you that it is actually a very easy process if you go that route. The things you'll need (other than any new parts) are a full gasket set, 2 crank seals ($60, total?), a flywheel puller and starter clutch nut removal tool (another $30?). There's an endless supply of Youtube videos showing how to disassemble and rebuild a GY6 motor.
So I'd first want to know if the engine was viable..if not, sell for parts and move on, swap in a used one or last option, rebuild the one in there, yourself.
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Thx for the reply IaHawk. You essentially confirmed what I was thinking - that I cant make any decisions until I inspect the engine. I hope to get to that project this upcoming weekend. If anyone is interested in what I discover during my experience along the way, I can document it and post it here. Maybe someone will get some use out of it someday.
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we love pics and finding the cause of problems..it helps everyone in the long run and adds to the collective knowledge!
You'll definitely want to pull your cvt cover to inspect the variator, belt and clutch to make sure that your engine problem wasn't really just a cvt problem.
Please do report back any of your findings.
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Iahawk,
I've been watching a lot of YouTube videos about overhauling a GY6 engine, but I dont think I have a GY6 engine. I'm not sure what I have. Here is the info found under the variator. Thoughts?
Thx
Rick
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Oh, and yes, I can manually turn the engine over using only my hands.
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our Kymcos (at least yours and mine) are not tagged with the generic GY6 engine codes like the Chinese (50cc & 150cc) scoots are. They are, however, based on the GY6 design with many parts interchangeable with generic GY6 motors.
Were you able to see anything out of the ordinary on your motor? Did you pull the variator cover and inspect everything there?
Have you also tried to start your engine since your engine 'blew'?
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Thanks, Iahawk.
I appreciate the feedback and support. I have not tried to start it since it "blew." What should I be looking for or pay attention to when cranking the engine that might indicate what is wrong with it? I'm concerned that additional cranking might further damage the engine. Am I wrong about that?
Visually I see nothing wrong anywhere on the engine.
Note that I have only a few minutes per day to work on it, so thanks for your patience.
thx,
Rick
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you might want to start with removing the spark plug so you can easily spin over the motor. Feel for anything binding or restricting the movement. You could also remove the valve cover (head cover) and look at the cam, sprocket, chain, valve springs, etc to look for any damage or anything odd.
If everything looks good and feels good you can try to fire it up.
There's really not a whole lot of moving parts in these...your crankshaft rotates and the connecting rod and piston go up and down. The chain driven cam operates the valves up top. You'll have a chain driven oil pump inside and with your liquid cooled motor, some sort of shaft off the engine turning the water pump.
Might be smart to remove the valve cover to inspect, first, before turning the motor over. If all looks good and you don't hear or feel anything funny while turning over by hand, give it a try to start.
I don't recall you saying what happened when the motor died, originally?
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While turning the variator by hand, I could hear it drawing in air.
Spark plug pulled, is clean and there is a good strong spark.
Valve cover pulled and everything looks OK to my inexperienced eyes. When turning the variator by hand, the valves lift and close as they should.
Rather than tear the engine apart, I'm first going to test the fuel pump. Process of elimination.
Thanks again for your guidance, Iahawk.
Rick
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that would be wonderful if it was simply a fueling issue!
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Agree if only a fuel pump issue. I'm willing to eat some crow for overreacting. Hopefully my embarrassment will be useful to other readers. I'll let you know the results when I have them.
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Rebuild it, and enjoy the challenge. Been there, and still riding that!
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Iahawk, another newbie question if I may? Because I have the valve cover off, I thought I should check and adjust the valve clearance, if needed. Per YouTube videos and per the service manual (see pic), I turn the flywheel until the T mark aligns with the index mark on the left crankcase cover. I swear that there is no T anywhere on that flywheel!! So, instead, I turn the flywheel until the hole in the gear is TDC. I'm fairly confident that this is the correct position for adjusting the valves, but I'd like some assurance that my assumption is correct?
Thx!
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You could be...or your might need to spend engine again to confirm you are on the compression-firing stroke , and not just half way to it!
You should feel a little bit of up and down on the adjusters if you are at TDC. If one or both are tight, you might not be at TDC.
Some use a straw in sparkplug hole to double check piston is topped up.
In short, if you feel NO movement in the adjustment arms....be very careful not to change the adjusters yet! Bring that hole in the sprocket around again....then check for movement.
Stig
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You could be...or your might need to spend engine again to confirm you are on the compression-firing stroke , and not just half way to it!
You should feel a little bit of up and down on the adjusters if you are at TDC. If one or both are tight, you might not be at TDC.
Some use a straw in sparkplug hole to double check piston is topped up.
In short, if you feel NO movement in the adjustment arms....be very careful not to change the adjusters yet! Bring that hole in the sprocket around again....then check for movement.
Stig
Great idea to check the piston position, Stig. Believe me, I've spun that engine over at least a dozen times, but I understand that I must get it correct before doing any adjustments.
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Thx, Stig. I rotated the flywheel as you suggested and no T mark. I've spun that bugger at least 20 times, so I'm confident that there is no T. I did see timing marks, but that does not help me. But, I really liked your idea of putting a straw in the sparkplug hole to make sure that the piston is at the top. But now I have new questions. What is the shape of the top of the piston? The reason that I ask is that when I first stick the straw in the hole, it hits something a few centimeters beyond the plug hole depth, but then the straw slides toward one side and goes down another 3 inches. I've repeated this "finding" several times and it seems very odd to me. Without pulling the engine and the head off, I cannot get a good look inside the plug hole to see anything informative. Attached is a photo of a GY6 piston from a YouTube video, and by the looks of it, the piston is essentially flat. So, now I'm concerned that I have a hole in my piston. Thoughts?
Thx,
Rick
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Doubt you have a holed piston.
What did you find with the rocker arm movement when your big hole on sprocket is perp to cylinder head?
Movement, yes/no?
Hole 90° and rocker movement = check your valve lash🙂
Stig
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Iahawk, another newbie question if I may? Because I have the valve cover off, I thought I should check and adjust the valve clearance, if needed. Per YouTube videos and per the service manual (see pic), I turn the flywheel until the T mark aligns with the index mark on the left crankcase cover. I swear that there is no T anywhere on that flywheel!! So, instead, I turn the flywheel until the hole in the gear is TDC. I'm fairly confident that this is the correct position for adjusting the valves, but I'd like some assurance that my assumption is correct?
Thx!
Your mark on this flywheel should look like that.
Pls see pics (arrow) and piston.
I don't doubt your words, but it would be unusal not to have such a T- mark on it. To see this, the second plug has to be removed.
A straw is not really advisable to check TDC
(turns aside/ bends), a more rigid piece of something like a thin screwdriver shows better results (if neccessary).
Take your cellphone and shoot some pics through the sparkplughole in different piston positions.
This is how your piston looks like.
For holed piston: I did not see any holed piston on a 4-stroke motor within last 25 years. Mostly 2-stroke engines are suffering from (lean gas mix/ bad 2-stroke oil/wrong sparkplug).
.
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I've always thought that the reason you adjust valves at top dead center is because both valves are closed and you can do both at once. In theory (and Donyboy73, small engine Doc on youtube, has always done this) you can adjust either valve, intake or exhaust, as long as it's closed and there's no pressure from the cam on the rocker. I've seen him do this many times..if you can't find TDC then spin the motor so one valve is clearly open and there's no pressure on the other. Check that adjustment and then spin the motor again to open that valve, and repeat.
and Rickster - your spark plug hole enters the motor at a 45 degree angle, so if you use something flexible, like a straw, it could very well hit the top of the piston and then slide across it until it hits the cylinder wall. A wood dowel would be ideal. It doesn't really matter where the dowel hits the piston, as long as it's hitting it. Turn the motor over a couple of times with the dowel in the hole and watch it go up and down. You'll see where the piston is at the top of its stroke.
TDC should be easy to spot. Cam sprocket in correct position (hole at top and horizontal lines parallel with head) and the cam lobes will be horizontal, not lifting up on either rocker arm.
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and thank you, Ruffus, for always having relevant pictures!