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Post by rockynv on Mar 29, 2016 22:43:05 GMT -5
Depends on overall condition of the motor. An older 2 stroke needs some TLC to make it right. First is to ensure that the reed valves are clean without any pitting and that the carb is pristinely clean. Was there an oil injection system on that model or are you mixing oil with gas in the fuel tank at every fill up?
20 mph uphill may be a pretty good number for that bike if its an accurate reading. A 50cc can bog down to even less depending on the hill and the weight of the rider..
In general exhaust ports on the cylinder carbon up and need to be cleaned out as part of normal maintenance especially on the older 2 strokes or they get restricted causing overheating and poor performance. That is why many insist on only using the better 2 stroke oils to prevent carbon build up and extend the time between exhaust port cleanings.
Also verify that you have the correct size tires on the bike. 5 mph deviation at 30 is about normal not 20 mph and hitting engine redline indicated by the tachometer at a true 31 mph is not really right on a 50cc 2 stroke scooter and would be more likely at a true 45 or 50 mph albeit while going down hill. So really look closely at tire sizes, stuck sheaves not opening and closing fully, worn rollers, streatched belt, etc.
As for max that a 50cc 2 stroke can do my 1972 Motobecane Mobyette would do 40 tops and that was an old school pedal style moped. The 50cc Yamaha scooter of the day would do 45 mph top without redlining. A more modern Aprilia Ditec 50 2 stroke can top out at around 65 mph.
Yes worn or cracked reed valves can tick.
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Post by rockynv on Mar 29, 2016 11:53:00 GMT -5
currently it runs rich on the piolet circuit may change when it gets hotter out won't know until weather temp goes up but I have to kill the fuel flow to shut her down at 41 degrees. I found if it still runs rich in the hotter 70s perfect for expansion upgrade but it's a cloned carby. She runs lovely I can red line not sure if this is correct but my GPS indicates 31.83 mph while dash indicates about 50 redlining. Hitting the red line means you're about to destroy the engine. You usually do not redline a near to 30 year old vintage ride. You really do not want a connecting rod coming loose and poking through the side of the block. |
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Post by rockynv on Mar 27, 2016 20:10:54 GMT -5
You have to keep it wide open to hold the rollers in place while installing it. If its not spinning when its closed then the rollers will not have centrifugal force to hold them in their fully outward position in the ramps. When its all assembled the spring in the clutch closes that sheave completely forcing the belt into the fully outward position on the clutch sheaves pulling the belt into the variator sheaves so it is wide open and keeps constant pressure against the rollers.
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Pyder
by: rockynv - Mar 27, 2016 12:44:37 GMT -5
Post by rockynv on Mar 27, 2016 12:44:37 GMT -5
With the traction control and the Y chassis geometry, Pyder has never offered to hydroplane. Of course it is prudent to slow down in downpours, but it has always felt planted.I do have to wonder about those around me though. With respect to the scooter I tried radials thinking about a better response in the rain. WRONG! The bias ply tires that were the original equipment were sooo much better. Just have to adjust for conditions, like any other motorized conveyance.  David Tread pattern is more important in the rain. Unfortunately bike radials tend to come more often in a sport slick configuration with fewer rain grooves than most of the bias tires. |
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Post by rockynv on Mar 27, 2016 12:39:20 GMT -5
Ah. We have more Romanized members than I thought. There are a few of us. I got tired of Znen iffy metallurgy on my Lance Vintage along with the monthly oil changes so I walked into the Aprilia dealer to play Oliver Twist since I knew I couldn't possibly afford an Italian bike since everyone knows that they are just too expensive. Got the Aprilia for a few hundred dollars more than the local Puma Dealer was selling the Znen 250 for and have had no problems with the bike in 30,000 miles much of it at 80+ mph on day trips down the Interstate. Found out that I was wrong. Italian bikes are worth it because they last so long and if maintained by the book are very low maintenance. So far its just been belts and rollers every 12,500 miles along with 6,250 mile oil and filter changes. Still on the original clutch and variator and by the looks of things will be for quite a while to come. |
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Post by rockynv on Mar 27, 2016 9:20:44 GMT -5
Guess again - 2009 Aprilia Sport City 250 with around 30,000 miles on it sitting in my garage. From Noel Italy.
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Post by rockynv on Mar 26, 2016 10:18:28 GMT -5
I agree with all of the above. After that is corrected, you might consider adding one of the cheap tach/hour meters, to your scoot. If you already have a tach, then just a plain hour meter. Lots of them available on ebay, and using an hour meter is a great way to keep track of maintenance. I recently purchased one of the combo models for $8 and change, will be installing on my Ural for just that reason. Don't know what a Ural is  Click HereBullet proof Soviet bikes can be fun. Can be easy to maintain. Just keep the fluids full is what some Eastern Europeans claim. Doesn't even have to be oil just a liquid so they tell me however I would not test that out on my own bike. |
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Post by rockynv on Mar 26, 2016 10:13:12 GMT -5
All I use in the shop is good ole Dino Oil. As already been send frequent oil changes is the best maintenance you can do Depends on the make and design of the Engine. There is no blanket answer. If you have a bike with an engine with full oil filtration made by the motorsport division of the Piaggio Aircraft Company to micro fine tolerances then you go by the book and use Synthetic and follow the oil change schedule. You will get 50,000 to 75,000+ miles from the newer Piaggio engines if you go by the book. On a filter screen engine made to looser tolerances use Dino and change it per the book which on some is every 500 to 1,000 miles or monthly. |
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Post by rockynv on Mar 26, 2016 10:07:11 GMT -5
... Now if Chinese scooter manufacturers adopt the new Briggs and Stratton EXI Engine Tech that could change everything as they are designed to not require oil changes, just top them off if the oil gets low: You're supposed to change the oil in your push-mower not just top off? Oops..... >'Kat The new Briggs EXI Engines are specifically designed to never need an oil change. Not sure how they pull that one off. Hope its not because they wear out before the first oil change would be needed. |
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Post by rockynv on Mar 26, 2016 10:03:47 GMT -5
Was that a new head that you put your old valves into or did you reuse the existing head when you installed the 72cc BBK? The 72cc (just checked eBay purchase and says it's 80cc - 47.7mm - not good with doing the math to come up with actual CCs) came with new head with valves pre-assembled. Ran it a while today and no smoke... may have a bit of an issue with pre-detonation now as when I give it gas (hard) I hear some knocking or pinging. Will try richening up tomorrow and see if it helps. Seems as if there is a bit of hesitation around 1/4 throttle but take-off is quick and low-end is screaming. lol Think the clutch is worn out and will slap a newer one on as well. @ pisonguy: Yeah... thanks for the input on machining the heads and all but it only cost like $50 and it was all a "get a donor scoot running" type of project. Refusing to put out thousands of dollars on some unknown metal that may or may not last long. Lapping the valves did the trick, though. New head with the valves factory machined and pre-installed. So much for leaving the factory machining of the new valves alone without lapping them. Don't forget that a loose valve is a happy valve. You need to have a little valve noise at idle or the valve may not release/seat completely at high rpms. Yep, sounds like you need to upsize the jets to burn richer especially at high throttle. |
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Post by rockynv on Mar 25, 2016 22:10:18 GMT -5
Lets insert that video:
I guess I have been fortunate with the Aprilia 250.
I was keeping up nicely on the Interstate riding with the traffic on the far left last Saturday when an OEM Aramid Mitsoboshi belt shredded at 2,500 miles instead of lasting past 12,000+ as it usually does. Local Sports Bike club member saw me broken down on the Interstate and sent someone out with water and to ensure I was safe until a tow company had me on a flatbed and on my way home at sunset. Real nice kid (Dominic was the name I heard). Most often on Country back roads and State Highways the Sport City keeps up so nicely that I get invited to come along. Most are amazed that its "Only a 250".
One thing that surprised me was how little speed was getting bled off after the belt broke. I attribute this to the basic dynamics of the bike with its 15 inch wheels but have to give Kudos to Puig for their Sport Fairings with their aerodynamic design. I coasted forever after the belt broke and easily made it across 3 lanes to the breakdown lane on the right hand side of the road.
Most we can figure is that the local dealer had some very old OEM belts hanging out of their original wrappers which they sold me. Unfortunately the timing cover seal on the crankshaft which is behind the variator was pushed inside the crankcase by the shredded belt so I need to procure a $170 press tool to pull that cover and then press it back in properly aligned to tension the drive chain on the oil pump after putting about $5 worth of new seals on it.
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Post by rockynv on Mar 25, 2016 22:02:53 GMT -5
Check that the speedometer drive is correctly attached to the wheel and that the cable has not broken and is still attached to the speedometer. Many times its simply that a full PDI was not done and the front wheel was not assembled or tightened correctly which can be a very big safety issue.
Be sure to check that the wheels are installed correctly and have not started to come loose before riding the bike again.
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Post by rockynv on Mar 25, 2016 21:56:22 GMT -5
YA I knew someone would come up with a Chinese manual that say to lapp even tho the same OE Does Not at the Factory. Pure Bunk. the "Book" is simply passing down misinformation of Old school thought. Currently the Big Five makers Do not advocate Lapping, were dealing with Allot of TI in Offroad and want to ruin a TI Valve fast lapp it. Why would someone think there perfecting fine machined surfaces with Lapping compound. Unreal and have No Clue what There Doing. I have work with every Factory MC Pro Show and None Ruin a Valve Job with Lapping compound. Yup, I'm one of those who gets Paid to be at races every weekend. You are pointing out that you simply have never done a proper valve job and don't know how or know what you are looking at. Piston guy didn't move from TX to NC for the BBQ. I have been involved with one of the Nations Highest End manufactures of Valves, Valve Seats, Valve Guides and retainers. Turn the TV on this weekend and you can watch a few thousand of that Valve Train Not Lapped. A Service Station Manual from Piaggio Aircraft Corporation or its subsidiaries is not "some Chinese manual". Not everyone has a full race shop with machinery for milling valves so grinding with lapping compound is the final step followed by a leak test especially when servicing an old head that's being re-used when your Joe Average working on a shoe string budget. How many here would have a clue on how to apply and then read Plasti-Guage or Prussian Blue to ensure a proper engine rebuild when checking bearing clearances or valve contact patches? You would have to be pretty much insane to pay for race machining of valves when installing an $89 BBK on a $399 scooter. On a $150,000+ Moto GP bike with a purse and endorsements at risk that's a different story but on a 50cc Chinese scooter that someones put a BBK into that's a bit extreme. |
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Post by rockynv on Mar 25, 2016 9:11:11 GMT -5
On the original issue could have been a poorly seated head gasket leaking oil or loose valve stems causing the smoke. Lean fuel mix and possibly valve clearance set too tight on the burned valve along with poor valve seating.
Was that a new head that you put your old valves into or did you reuse the existing head when you installed the 72cc BBK?
Laying the head on its side and filling the intake or exhaust port that's facing up with gasoline or a very thin mineral oil to check for leaks is my preference over a light test.
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Post by rockynv on Mar 25, 2016 8:46:23 GMT -5
Per the 2009-2013 Piaggio Scooter Factory Service Station Manual published and distributed by Piaggio - after covering how to check if valves and heads are suitable for reuse they instruct:
"If no anomalies are found during the above
checks, the same valves can be reused. For better
sealing results, it is advisable to grind the valve
seats. Grind the valves gently with fine-grained
lapping compound. Upon grinding, keep the cylinder
head in horizontal position. This will prevent
the lapping compound residues from penetrating
between the valve stem and the guide (see figure).
CAUTION
TO AVOID SCORING THE FAYING SURFACE, DO NOT ROTATE THE VALVE WHEN NO LAPPING
COMPOUND IS LEFT. CAREFULLY WASH THE CYLINDER HEAD AND THE VALVES WITH A
SUITABLE PRODUCT FOR THE TYPE OF LAPPING COMPOUND BEING USED."
For checking how the valves are seating:
"Inspecting the valve sealings
- Fit the valves into the cylinder head.
- Alternatively test the intake and outlet valves.
- This test should be carried out by filling the manifold
with petrol and checking that the head does
not excessively ooze through the valves."
Bottom line per one of the most highly respected makers of motorcycle, scooter and air craft engines and not by my personal opinion you lap the valves on a scooter if you go by the book.
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