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Post by wolfbane240 on Nov 18, 2018 17:42:13 GMT -5
Thx for all the answers. As an update I found the intake valve head in the sump like someone said. I didn’t see much movement in the piston rod so I took my chances and went ahead and put in a 80cc kit. Got it up and running but I’m real hesitant to run it far from home yet. When I put oil in I get what seems like a air bubble that kicks out some of what goes in. I checked the sump for debris and used a magnate to collect any shavings before I put the kit in. Found some but not as much as I expected. Anyone have an idea why I’m getting the push back when putting in oil? It’s holding just under the halfway mark which is why I’m being real cautious about running it too long.
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Post by FrankenMech on Nov 18, 2018 18:33:47 GMT -5
There is all kinds of grit in the bearings. I would not ride it until everything was cleaned up and replaced.
Is there lots of blowby from unseated rings?
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Post by GrumpyUnk on Nov 23, 2018 10:42:25 GMT -5
wolfbane:"When I put oil in I get what seems like a air bubble that kicks out some of what goes in."
If you pour the oil in too quickly, OR you don't have the front wheel on the ground while on the center stand, the oil has to displace air in the sump. Some can get out the cam cover vent, but not as quickly as the oil can flow in. If you have the rear wheel on the ground, the top edge of the dipstick opening can be sealed by the oil, and cause bubbles as more is added. I'd put it on the center stand, front wheel on the ground, and pour slowly. When checking the level, do not screw the dipstick into the opening, just insert it until it contacts the upper surface of the block opening, then remove and check. You should be able to get 750ml of oil into the sump without problem. Some suggest 800ml. I have never figured out the contradictory specifications, and they cannot agree on valve clearance adjustment specifications either, so I guess you'll just have to go with your gut. Given that there may be a few chunks of aluminum in the sump, perhaps even bits of Fe, I'd swish around with a magnetic probe as much as possible until I was not getting anything else. I would also seriously consider getting a magnet and stuffing it inside the 'filter' or oil pickup screen fitting. I'd want one that could not be sucked up into the oil passages, but could sit there in the midst of the flow, and grab anything on its way into the pump. After doing as much fishing as possible for particles, I'd consider a few other options. One would be to add 1/2qt of oil, and let it flow out the strainer and drain openings, hopefully the flow pushing out anything on the bottom. If the cylinder was off, I'd consider getting some brake cleaner and using the longest 'straw' I could find, sluicing out the ball bearings at either end of the crankshaft. Given that the engine only ran(rotated?) for a few seconds after the valve self destructed, there'd not be much chance to get particles into the ball bearings from splash, or pressure lube for the big end of the connecting rod bearing. I'd want to 'feel' how the crankshaft rotated without the reciprocating load of the piston to see if there was any roughness in the bearings. Harder to tell pushing/pulling the piston & rings around, even more so turning the cam and moving the valve train. Given not much to lose, doing a decent cleanup of the crankcase might leave you with something that will work. Only one way to tell. If the crank bearings have eaten some debris, you will soon find out as any roughness of the races or damage to the balls will tend to increase quickly. There is a youtube showing how ball bearings die when fed just a little bit of grit. The balls fit so tightly they tend to put grooves in the races trying to get around bits of grit put into their path of rotation. Once they groove the races, there's more deformed metal in the way of the ball's journey, so more deformation occurs, and it gets bad very quickly. You will find out soon if it will live or die. tom
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Post by wolfbane240 on Nov 24, 2018 8:46:44 GMT -5
Thx for the tips GumpyUnk. Will definitely check again with the front wheel down. My driveway is gravel so the scoots been sitting pretty much even with the back tire mostly touching. I’ve ridden it for over a week now and put over 100 miles on it so far with no issues except a little oil leak but I suspect that’s from the chain tightener not having a gasket (the kit didn’t have one). Otherwise, I’ve gotten a 10 mph boost and a steady 25 to 30 uphills which is a big improvement seeing I weigh almost 250lbs.
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Post by GrumpyUnk on Nov 27, 2018 10:45:37 GMT -5
You can remove the timing chain tensioner assembly and use some Great Stuff or 'gasket maker' type RTV silicone to seal the cover. Make sure the surfaces are both clean, apply a thin layer of RTV/gasket, spread it around like it was peanut butter, and let it rest for ~5 minutes or so. RTV cures in the presence of water, accelerated by heat(breath on it and it will maybe form a 'skin' as you do so). Install the assembly, tightening the bolts enough to snug the cover to the engine, but not as tight as you'd do in a final assembly. Wait until the 'squeeze' out is semi-cured to touch(you can't smear it), and tighten the rest of the way. Is should stop leaking oil. An alternative is to get a Cheerios box, and cut out a gasket using scissors or a knife. It just has to fit generally, and allow the tensioner to extend down to the chain, and have holes for the mounting bolts. You can also use Trix boxes, or other thin cardboard. If you have manila folders, that material is also good for home-cut gaskets. (used to be called Oaktag, I think) tom
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Post by wolfbane240 on Dec 5, 2018 6:18:52 GMT -5
Ok...so here I am again this time totally new issue. After running my scoot for close to 500 miles after the kit replacement it shut down on me. I’ll admit I was running it hard, just zipping around town this past Sunday. About after an hour it started to shake between 20 and 30 mph. I figured I’ll check the rear wheel when I got home. On the way, I stopped at an intersection with a bit of an incline. I hit the throttle and it actually got out from under me, but I was able to maintain control and brought it back down. A half a block up the road it just lost power and left me stranded. I got it home and tore down the engine. As someone commented, there was a little build up of carbon at the top of the cylinder, which was most likely caused by not tightening the head bolts right. Otherwise, everything else seemed ok. No binding in the cylinder, when it turns over I can hear compression. I thought the timing chain may have jumped because it seems like it wants to start but doesn’t. I’ve checked spark and fuel and it’s getting both. My question is could the gears be somehow out of wack, and could that be causing the problem. I haven’t opened the gear box to look yet for lack of time. And if it has nothing to do with it then why bother. Thanks again for all the advice so far and any further help will be greatly appreciated.
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Post by GrumpyUnk on Dec 5, 2018 14:08:23 GMT -5
When 'it starts to shake between 20 and 30 mph' do you mean vibrate as if a tire is out of balance? Or, do you mean that the engine seems to lose power then regain power so you are speeding/slowing causing acceleration/deceleration shake? For the former, I'd remove the CVT cover and inspect for loose parts or a damaged belt. For the latter, it could be a fuel supply problem, delivery volume down, or contaminant(water?) that makes it fire irregularly. The failure when it lost power could be a fuel problem, or loss of compression. You noted deposits of carbon on the top of the cylinder. If you are seeing carbon on the cylinder, outside the area of the combustion chamber, then you likely have a bad head gasket. You might want to invest in a composite head gasket that has a 'fire ring' around the diameter of the cylinder rather than the black sheet metal head gaskets. You might also want to check that the head is nor warped. Take a steel straightedge and determine if there is a gap in some areas across the bottom side of the cylinder head. If you can fit a feeler gauge between the steel and the head, you have warpage. Two choices to solve: new head, or, using 200 grit or higher AlOx paper, on a flat surface, wind the head in patterns to level the surface. I'd look real closely at the area of the head next to the cam chain opening. They seem to warp there for some reason. If you figure you still have enough compression without doing the above, you might want to check that your idle mixture screw is in the range of 2 turns out from fully tightened. Plus/minus 1/2 turn should be the norm. The throttle plate must be just barely opened, and the temperature high enough to have the engine run after twisting the throttle open a half dozen times. The accelerator pump will squirt some extra fuel at each twist from closed, and you'll have fuel right there for the engine to burn. It may start and die, so you may have to be quick on throttle after it fires. In most cases, you can't open it much without it stalling, so you end up playing with it to get it to go. To check the gearbox(unlikely problem area), remove the CVT cover, and rotate the back wheel. You should see the clutch 'bell' spin quickly. Feel how smooth the torque is transferred from the wheel to the bell, checking for gear irregularity(bad teeth) or grinding in the ball bearings. Things should spin freely, whether you spin the bell by turning the wheel, or sping the wheel by turning the bell. The bell will spin freely as the clutch 'feet' are retracted until the rpms are high enough. 90Gtvert did a youtube on how to check your gearbox final drive ratio which also shows how things turn as above. tom
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ratdog
Scoot Enthusiast
Posts: 342
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Post by ratdog on Dec 6, 2018 9:55:24 GMT -5
As I understand your post, your saying the engine is not running, right? If that is right, the only “gear” you would be looking at ( to make the engine run) is the timing gear. If you had the head off and back on, I assume you set the cam timing when you did that, so that is not an issue. I also assume you replaced the head gasket, RIGHT? And re set the valve lash? This sounds over simple, but have you changed the spark plug? I have had spark plugs that would spark when they were out of the bike, but would not spark under compression in the bike. I would also like to see a close up pic of your spark plug. Just wondering as I don’t recall you saying anything about re jetting. If you could post a picture of your spark plug, it would be helpful
I would recommend you completely drain the tank and put some fresh premium gas in it ( you are running premium gas with the BBK, right?). Dump the gas out of the car as well. With the fuel line pulled off the carb, (and fresh gas in the tank) spin the starter. You should get a good flow of gas out the fuel line. ( I’d replace the fuel filter too).
Now we know you have good fresh gas getting intot the carb, and you say you have spark (I would try a different spark plug just because). If it still won’t start, then I’d try spraying starting fluid into the carb. If you have spark and compression, he starting fluid should give you fire. If it dosnt, then he one thing left is compression. I’m guessing you didn’t think about it at the time, but, while you had it off, you should have turned the head upside down and filled it with gas to see if your valves ere sealing.
I have a little tool that makes finding problems so much easier. I plug it into the spark plug cap then the other end goes on the plug ( sorta like an extender for the spark plug wire). It flashes when the the plug sparks. Makes it so easy to “check for spark”. I think I paid about $3 for mine, but that was years ago. If you happen to see one cheap, you might want to pick it up.
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Post by SMALL CC TEK on Dec 8, 2018 0:29:43 GMT -5
Looks like a good old fashioned dropped Valve to me ! Running wide open downhill with a Tailwind ! lol Valve lock failure or spring failure or worn springs or a combination of all .
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