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Post by usmcdoc on Jul 24, 2015 21:44:57 GMT -5
It fired up being 180 degrees out of sync? How did you do that..make it run 180 degrees out of sync without busting or bending valves? A 100cc kit..was it 50mm or 52mm? Did you use the stock head or a Big Bore head? Only time I have seen an engine have a flywheel rub is when the crankshaft bearings were nearly disintegrated...from using a 50mm or larger big bore with a stock 39mm head. However those 2 customers got about 200 and 300 miles on the engine before the ultra high compression and offset weight of the grossly overweight 50+mm big bore kits..took out their connecting rod and crank bearings.. Btw..be careful because the 50mm and bigger kits pistons weigh twice as much as the stock 39mm piston. The counterweights on the crankshaft are not designed to balance that much offset weight. Standard generic Chinese 50 and 50+mm BBK's have very thick and heavy piston crowns and therefore double the weight. Only 50 and 50+mm kits I have seen with a piston weighing near the same as stock and slightly lighter than the 47mm kits..are the Naraku and Airsal kits. Just a bit of info.. Glenn  |
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Post by backtrackbug on Jul 24, 2015 21:46:09 GMT -5
And this is a pic from the day I bought it, like I said, its just the run of the mill chinese scooter, 4t 50cc.  |
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Post by backtrackbug on Jul 24, 2015 21:54:29 GMT -5
Yeah, it'll fire up right now with the cam upside down, Ill take a pic of it tomorrow before I pull it out. Wont prove much because I dont wont to start it again for a video. The bbk came with a head with valve assembly installed. Is a 50mm piston. Yeah I did some research on the pros and cons of the 100cc bbk's on 50cc scooters. I know its a trade off on longivity and its rough on the rest of the motor and etc. My brother has been running a 100cc bbk for the past two years, The motor is still strong but he has gone through a few variators, clutches, belts. His front forks/tree snapped the other day at 40mph and he got pretty messed up but I think that was due to oversized tires and hitting the potholes too much.
I really hope its not crank bearings! Very well could be and thats whats causing the drag on the flywheel/stator!
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Post by Availien on Jul 24, 2015 21:54:39 GMT -5
50mm piston is 81.2cc with stock crank. I don't know why they round stuff like that. Even with a stroker crank shaft it would be 87cc.  That's a good cam, variator, valve head. I can't say much about the piston and jug quality. I have the same exact head, cam, and variator set. You might want to inspect the center of the outer variator plate in a few hundred miles. It's copper and wears out quick. I used 5g slider weights in mine. The kevlar belts are awesome. Get a puller from eBay. They're cheap and handy to have. I get most of my scooter parts from this guy now: www.ebay.com/usr/scooters_to_go?_trksid=p2047675.l2559He's a member of this forum and has a good reputation. High quality parts. |
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Post by backtrackbug on Jul 24, 2015 22:01:30 GMT -5
Cool, I saved his link Availien. I have been using this forum as my go to since I got the scooter and will definitely support him. I tried 5g rollers but it revved really really high before it really grabbed good and got to speed. I have three 5's and three 7's (36grams) in it now and its about right for me. I have a new set of 8's I may try once I get it back on the road. I put a magic marker line on the variator and the 5 and 7 rollers push the belt about a 1/16th inch from the top and was getting about 35-38 mph (gps) on flat ground. Kinda wishing I would of just left it alone at that point.
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Post by usmcdoc on Jul 24, 2015 22:02:28 GMT -5
50mm piston is 81.2cc with stock crank. I don't know why they round stuff like that. Even with a stroker crank shaft it would be 87cc. That's a good cam, variator, valve head. I can't say much about the piston and jug quality. I have the same exact head, cam, and variator set. You might want to inspect the center of the outer variator plate in a few hundred miles. It's copper and wears out quick. I used 5g slider weights in mine. The kevlar belts are awesome. Get a puller from eBay. They're cheap and handy to have. I get most of my scooter parts from this guy now: www.ebay.com/usr/scooters_to_go?_trksid=p2047675.l2559He's a member of this forum and has a good reputation. High quality parts. They are very good people...have met them in person and know them. Their shop is 30 minutes from mine. They sell QUALITY products.. Their competitor a few blocks from them sells generic Chinese parts with NCY..Bando..Gates..Malossi and many other parts with the companies loge etc.. But a close look tells ya right away it's phoney stuff. Still wonder how yours ran 180 degrees out of sync..and I hope the bearings are not bad.  |
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Post by backtrackbug on Jul 24, 2015 22:07:10 GMT -5
But wont a engine fire if the cam is 180 out? The plug fires twice for each stroke right? Fires at tdc and again at the bottom of stroke. I am prolly wrong, but it fired right up, two seconds of black smoke (from burning off cylinder lube) and the three seconds later it was fourth of july in my flywheel. It will still fire up, but the sound makes me cringe lol.
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Post by backtrackbug on Jul 25, 2015 7:55:53 GMT -5
Well, got up this morning and managed to get the flywheel off. Somehow a washer fell inside it and was stuck to the inside of the magnetic flywheel. Problem solved and no real damage, luckily. Then I flip my cam 180, so it is now in correct. Set the valve lash at .004 for intake and exhaust. Took it for a easy ride and a huge power difference, two different worlds. I did notice that my valves are a little louder that usual,but I'll give it about 50-75 miles of easy driving then reset them. And I also noticed that it has a pretty strong vibration through out the bike. That has me a little concerned because my brother has the same bike and same bbk and his feels a lot smoother.    |
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Post by katastroff on Jul 25, 2015 8:15:39 GMT -5
Vibrating scooter=chick magnet.
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Post by Availien on Jul 25, 2015 8:29:41 GMT -5
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Post by backtrackbug on Jul 25, 2015 8:51:37 GMT -5
Well, Im going to take it for a easy 30-45 minute cruise and see what happens. Hopefully it doesnt fall apart at the seams  |
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Moat
Scoot Member
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Post by Moat on Jul 25, 2015 11:23:25 GMT -5
Hey thanks for the tdc info on the cam, I have it 180 out. Will fix that first thing in the morning. Same difference... turn the crankshaft one full, 360 degree turn - and the cam should then be lined up properly. No fix needed! Bob |
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Post by Availien on Jul 25, 2015 15:28:17 GMT -5
Hey thanks for the tdc info on the cam, I have it 180 out. Will fix that first thing in the morning. Same difference... turn the crankshaft one full, 360 degree turn - and the cam should then be lined up properly. No fix needed! Bob How will that work? I'm not understanding this clearly. If he has the cam upside down then just simply turning it by hand will not fix the issue. The timing will still be off and the engine will not be "inhaling" and "exhaling" at the correct times. The cam will need to set correctly for proper function. |
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Moat
Scoot Member
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Post by Moat on Jul 26, 2015 0:48:14 GMT -5
How will that work? I'm not understanding this clearly. The camshaft turns at exactly half the speed (number of revolutions) as the crankshaft. So for each one turn of the crankshaft, the camshaft turns only a half revolution. Think about it... it's therefore impossible to time a cam 180 degrees off. One complete 360 degree turn of the crankshaft (flywheel), and voila... the upside-down cam will now magically be right-side-up.  The only reason to pay attention to position of the cam as being "180 degrees out" (i.e. - upside-down) during assembly is the added safety margin of additional valve-to-piston clearance at TDC at the end of the compression stroke (where the cam lobes are pointing away from the rocker followers) - in case you're initial timing is a tooth or seven off. That helps avoid accidental valve contact - as the valves are completely closed in that position, and a long rotational ways from beginning to open. IOW - Having the lobes pointing away from the followers when timing the cam affords some rotational latitude in finding the proper cam timing without bending a valve. That's all. Flip the cam 180 degrees from there ^^ (i.e. - upside-down), and it's perfectly doable... but riskier - as the lobes are then pointing towards the followers (actually holding the valves open slightly, if the adjustment screws haven't been backed out - that position known as "valve overlap") and any further rotation will open one of the valves even more. A couple of teeth off on timing, and they could possibly tag at/near TDC. But as far as timing goes, it's the exact same - either way. The real key is to not force anything... if something feels like it's hanging up, not turning without resistance - gently back off and figure out why. Valves are delicate! Bob |
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Post by backtrackbug on Jul 26, 2015 9:42:48 GMT -5
Ok, so after riding about 35 miles yesterday I am happy with the power difference. Has much more torque, gets up to speed much faster, climbs hills much stronger and is a bit faster over all. But I definitely have to zero in on some tuning issues. My top speed on flat ground is around 38mph (gps)And I really think it should be a bit faster than that. 50cc stock was running 35mph. I was expecting atleast 43-48mph top speed and was hoping for 50mph. One thing I have noticed is a sputtering in the exhaust when I decelerate. Its not back firing but the sputtering is moderately heavy.
As it is currently set up, it has the 50mm bbk, A9 cam, valves set at .004 intake/exhaust. Stock carb (18mm?) with a #90 jet, stock airbox and exhaust. Carb needle is still set in stock position. 6g rollers. Sputtering means its running lean,right? I tried adjusting the a/f mixture from two turns out all the way to about four turns out, none of it seemed to make a difference.
Any tips on a straight forward tuning process to get the tuning nailed down for top performance? I am going to go check valve lash in a little while and readjust incase it needs it from break in/valve seating.
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