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Post by dollartwentyfive on Feb 10, 2017 23:26:46 GMT -5
can you determine TDC by the alignment of the stator pickup?
don't forget, these scooters utilize the "wasted spark" scheme, so you might have to remove the valve cover to make sure you are at spark TDC, not end of exhaust TDC
when aligned properly, notch the crank on the variator side for future reference.
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Post by rockynv on Feb 11, 2017 9:04:06 GMT -5
Why can't you remove the timing check plug and use the timing marks? Its the easiest and most accurate way to go to pull the access plug on the flywheel cover and align the marks. have you tried this method? the timing hole is on the right side of the engine, but you must be on the left side to turn the crank. it was impossible for me. i got so fed up with it, i had to just "guess" when TDC was reached. i removed the plug, held my thumb over the hole, and turned the crank until i felt compression. i then gave the crank an extra 1/4 to 1/3 turn more. like i said, it's a guess, but apparently close enough to set the valves. if you ever do find the true TDC, then notch the end of the crank with a file. if setting the valves is your goal, then the following is even better: remove the valve cover. rotate crank until the rocker arms are on the low part of the cam (both rocker arms). replace valve cover. set valves. you don't need TDC, just make sure both valves are closed. To set the timing chain back in place you need to find the True TDC. I get it close based on feel and from the right side of the bike reach under to the socket wrench I leave hanging on the left side to more finely align it. 926 is installing a cam and needs to get the valve timing set. To adjust the valves I just eyeball for when max gap between the rockers and valve stems exists and set them to spec unless the engine uses valve shims. When shims are involved I will verify the timing mark as I hate working with shims and want to be as accurate as possible to ensure I won't be doing it again sooner than I want to. I really dislike valve shims which on some bikes can raise the cost of a valve adjustment by $100 if it has multiple cylinders. Been wrenching for over 50 years now so I am quite familiar with the process of how to get it done. |
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Post by dollartwentyfive on Feb 11, 2017 10:30:00 GMT -5
To set the timing chain back in place you need to find the True TDC. i think he can get it done by aligning the pickup on the stator with the rotor. but he would have to remove the valve cover to make sure he was at spark TDC. the CF250 doesn't use shims. both rocker arms are in the valve cover, and i haven't seen anything that looked like a shim. got ya beat, i've been wrenching on a chinese ride for about 5 or 6 years. i wouldn't trade that experience for anything. WAAAA, I WANT MY BIKE, I WANT MY BIKE [img style="max-width:100%;" src="  |
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Post by spandi on Feb 11, 2017 15:20:27 GMT -5
Why can't you remove the timing check plug and use the timing marks? Its the easiest and most accurate way to go to pull the access plug on the flywheel cover and align the marks. have you tried this method? the timing hole is on the right side of the engine, but you must be on the left side to turn the crank. it was impossible for me. i got so fed up with it, i had to just "guess" when TDC was reached. i removed the plug, held my thumb over the hole, and turned the crank until i felt compression. i then gave the crank an extra 1/4 to 1/3 turn more. like i said, it's a guess, but apparently close enough to set the valves. if you ever do find the true TDC, then notch the end of the crank with a file. if setting the valves is your goal, then the following is even better: remove the valve cover. rotate crank until the rocker arms are on the low part of the cam (both rocker arms). replace valve cover. set valves. you don't need TDC, just make sure both valves are closed. Good idea. Mine was marked on the side but not on the very edge of flywheel, I filed a thin notch in it then painted it in bright red. Problem solved. |
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Post by dollartwentyfive on Feb 11, 2017 21:07:40 GMT -5
Good idea. Mine was marked on the side but not on the very edge of flywheel, I filed a thin notch in it then painted it in bright red. Problem solved. i was thinking about the crank on the variator side. this would make it uber easy to get TDC. i haven't had any timing problems with my cf250, although i did set the valves a couple of times. it was a healthy engine that ran strong up until the day it choked, as far as the timing chain goes, you would still need to remove the valve cover to determine if you are at firing TDC. you would need to remove the cover anyway to get to the cam. |
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Post by spandi on Feb 11, 2017 21:14:56 GMT -5
Good idea. Mine was marked on the side but not on the very edge of flywheel, I filed a thin notch in it then painted it in bright red. Problem solved. i was thinking about the crank on the variator side. this would make it uber easy to get TDC. i haven't had any timing problems with my cf250, although i did set the valves a couple of times. it was a healthy engine that ran strong up until the day it choked, as far as the timing chain goes, you would still need to remove the valve cover to determine if you are at firing TDC. you would need to remove the cover anyway to get to the cam. Wait a second, I thought you said the scooter was in the back yard......Do you have more than one? |
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Post by dollartwentyfive on Feb 11, 2017 23:42:49 GMT -5
Wait a second, I thought you said the scooter was in the back yard......Do you have more than one? it is in the back yard, and like i said, it ran strong until it choked. the estimated top speed was about 70mph with 20 gram rollers. no, i don't have another scooter, i can't seem to scrape up enough money for one. someone local had a helix for sale for 800 bucks, but it was gone by the time i came up with the money. i figured even if it didn't run i could get one bike out of it and my old one. scrappy has engines for my bike, but after sitting so long i would need other things too, like master cylinders and maybe even brake calipers. maybe i can tie a rope around the handlebars and get my brother-in-law to pull me down the street with me saying "VROOM VROOM". |
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Post by cyborg55 on Feb 12, 2017 9:07:10 GMT -5
As long as the rockers are on the base circle of the cam the valve lash can be set
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Post by rockynv on Feb 12, 2017 20:56:11 GMT -5
To set the timing chain back in place you need to find the True TDC. i think he can get it done by aligning the pickup on the stator with the rotor. but he would have to remove the valve cover to make sure he was at spark TDC. the CF250 doesn't use shims. both rocker arms are in the valve cover, and i haven't seen anything that looked like a shim. got ya beat, i've been wrenching on a chinese ride for about 5 or 6 years. i wouldn't trade that experience for anything. WAAAA, I WANT MY BIKE, I WANT MY BIKE [img style="max-width:100%;" src="[img style="max-width:100%;" src=" Quote the full text instead of taking it out of context please. The comment about valve shims was a secondary comment and that was lead into with "To adjust the valves I just eyeball for when max gap between the rockers and valve stems exists and set them to spec unless the engine uses valve shims. When shims are involved I will verify the timing mark as I hate working with shims and want to be as accurate as possible..." I've wrenched on Chinese bikes too and really enjoy the difference you experience when working on a well thought out finely machined bike regardless of where its made especially when the maker has many fine examples of properly maintained bikes on the road with well over 100,000 miles on them. The Znen I had was not one of the better examples and its an experience that I would like to forget since it was a constant exercise in throwing good money after bad. My bikes don't sit rotting away in the back yard they get maintained to keep them running well. If the unexpected happens they get diagnosed to determine the root cause and repaired otherwise ones back yard could end up with more bikes and cars in it than the driveway and garage. Even the lousy 2007/2008 Znen was put back into working order after the straw that broke the camels back and traded in on something more reliable. It was in as good working condition as was possible when I traded it in and more likely than not running better and more reliably than when it was new however not daily driver 1,000 miles per month reliable. |
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Post by dollartwentyfive on Feb 13, 2017 4:15:02 GMT -5
Quote the full text instead of taking it out of context please. The comment about valve shims was a secondary comment and that was lead into with "To adjust the valves I just eyeball for when max gap between the rockers and valve stems exists and set them to spec unless the engine uses valve shims. When shims are involved I will verify the timing mark as I hate working with shims and want to be as accurate as possible..." i have no idea if the cf250 uses shims or not, i never seen any though. i don't even know what they are. i assume they would go between the valve stem and the rocker arm. my 250 was my first encounter with a chinese bike mechanically. that bike taught me everything i know about the step through twist and go design. lucky you. some of us are pretty strapped for cash. i'm hoping to get another one, maybe santa will get me one for christmas. [/quote] |
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Post by rockynv on Feb 13, 2017 4:56:29 GMT -5
I was strapped for cash and ended up even more strapped after dealing with the Znen. Three heads failed, bad gearbox, valve adjustments every month, oil changes twice a month, failed CDI, burnt out ignition pickup, defective clutch, weak variator worn out in 6,000 miles, 2 belts, failed muffler, headlamp burning out every 2 months, etc and the lost wages from being stuck on the side of the road and missing work on more than one occasion added up to costing more than just purchasing a new Aprilia when they were on sale for $2,999 at 0% interest. The Znen had 6,746.8 miles on it when I traded it in and cost me more than the past 30,000 miles on the Aprilia. The Znen kept taking back any savings I was getting by riding, to pay for parts, mechanics fees (needed a second opinion on all the head failures which ended up being poor quality casting) and time lost from work due to its poor quality.
The Znen ended up a wash with the savings from riding it for 6 months going towards keeping it running while the Aprilia after deducting tires and all maintenance that I have done on it since it was purchased 6 years ago has returned almost $20,000 in savings over driving my van according to the logs I maintain in an Excel Spreadsheet.
Some bikes use shims so I commented about them. The CF250 is not the only bike out there so you have to take them into account when making a general comment on eyeballing for valve adjustments. I will take that into account when considering a bike for purchase and will shy away from those that use valve shims.
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Post by dollartwentyfive on Feb 13, 2017 8:25:19 GMT -5
I was strapped for cash and ended up even more strapped after dealing with the Znen. Three heads failed, bad gearbox, valve adjustments every month, oil changes twice a month, failed CDI, burnt out ignition pickup, defective clutch, weak variator worn out in 6,000 miles, 2 belts, failed muffler, headlamp burning out every 2 months, etc and the lost wages from being stuck on the side of the road and missing work on more than one occasion added up to costing more than just purchasing a new Aprilia when they were on sale for $2,999 at 0% interest. The Znen had 6,746.8 miles on it when I traded it in and cost me more than the past 30,000 miles on the Aprilia. The Znen kept taking back any savings I was getting by riding, to pay for parts, mechanics fees (needed a second opinion on all the head failures which ended up being poor quality casting) and time lost from work due to its poor quality. mine wasn't quite that bad. actually, the engine was pretty sound, only had minor problems with it. overheating was the only major problem with the engine, but it was caused from a poorly designed cooling system. i also had a bendix problem but i fixed that too. i bet that's what killed the motor, the bendix locked up engaging the starter. at least that's what it sounded like when it died. the rest of the bike though, especially the body panels and the electrics, talk about bottom of the pile stuff. it ran great though, it sounded good too. it came with 11 gram rollers and that gave me great acceleration from a dead stop, it would beat anything off the line. i guess they were 11 gram, i weighed the least damaged one. the other five were in little pieces. i switched to 20 gram rollers to to give me top end performance, but i was slower at getting off the line. thanks for the heads up, i'll keep a lookout for those shims. |
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Post by rockynv on Feb 14, 2017 5:31:41 GMT -5
If your an occasional rider or just like to tinker rolling the dice on a Chinese bike can work out but for reliable 12,000 to 15,000 miles per year transportation they many times will cost more than a used or even new bike thats made of more sturdy materials.
Yes watch out for bikes with shims or you can end up with a bit of sticker shock the first time you have a valve adjustment done.
My boss put in free charging stations for electric cars this past September so I don't ride as much now since I no longer have to pay for fuel to drive to work after picking up for very low cost a used Nissan Plug In Electric Car that's almost as big as a CRV.
No gasoline, oil changes or mufflers to deal with. Braking is mostly from the regenerative system so the friction brakes last a very long time making scheduled maintenance an annual tire rotation and change of wiper blades along with a new cabin air filter. Battery is air cooled and made in Tennessee so it is not as dangerous as the Tesla battery and they are reused, once no longer fit for automotive use, as UPS batteries for Microwave Towers and to supplement the power grid reducing the use of backup generators.
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Post by spandi on Feb 14, 2017 13:49:10 GMT -5
If your an occasional rider or just like to tinker rolling the dice on a Chinese bike can work out but for reliable 12,000 to 15,000 miles per year transportation they many times will cost more than a used or even new bike thats made of more sturdy materials. Yes watch out for bikes with shims or you can end up with a bit of sticker shock the first time you have a valve adjustment done. My boss put in free charging stations for electric cars this past September so I don't ride as much now since I no longer have to pay for fuel to drive to work after picking up for very low cost a used Nissan Plug In Electric Car that's almost as big as a CRV. No gasoline, oil changes or mufflers to deal with. Braking is mostly from the regenerative system so the friction brakes last a very long time making scheduled maintenance an annual tire rotation and change of wiper blades along with a new cabin air filter. Battery is air cooled and made in Tennessee so it is not as dangerous as the Tesla battery and they are reused, once no longer fit for automotive use, as UPS batteries for Microwave Towers and to supplement the power grid reducing the use of backup generators. Very soon the gasoline engine (and it's overly complex systems) will be a thing of the past, relegated to the same place as steam engines and their enthusiasts are today. |
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Post by dollartwentyfive on Feb 15, 2017 21:00:01 GMT -5
If your an occasional rider or just like to tinker rolling the dice on a Chinese bike can work out but for reliable 12,000 to 15,000 miles per year transportation they many times will cost more than a used or even new bike thats made of more sturdy materials. it's really hard for me to classify all chines rides as "less quality". my 50cc never gave me a bit of problems, and i rode it almost every day. although i do have to admit, it left me stranded once, but that isn't really unusual. my 250 on the other hand was a beast to be reckoned with. i was beginning to wonder who would win, me or it. i finally got it tamed enough that i was fairly certain it could go cross country. then it just gave up. i debated expending any more time/effort in it, and there it sits. i'll have to agree with you. if you aren't mechanically inclined, then shop elsewhere. if you are, then chinese can be a viable alternative |
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