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Post by gingel on May 28, 2014 14:34:08 GMT -5
Hello,
I don't know if you remember, but almost a year ago my scooter hit the 100K KM mark.
It's now consuming more oil , around half of quart for 1000km (620 miles).
I am now at 110,000 KM (around 68,000 miles), and i think it's time to rebuild it.
The scooter is made by SYM.
I decided that i will replace the piston, piston pin, rings.
I will also rebuild the head completely, which means new valves, springs, valve seals and guides.
I never rebuild a scooter engine, it will be the first time for me.
That's why i can't decide if to open the engine completly and also replace the crank bearings (is it possible),
and also replace the timing chain.
How many miles can the crank bearings do, considering that the engine was taken good care?
What about the timing chain? how many miles can it lasts?
Regarding the timing chain, is it possible to replace it without splitting the engine?
Is it possible to use a chain breaker and riveting tool to replace that chain?
Anyone knows what is the size of the timing chain, and especially the rivet size?
Thank you for any help and advice.
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Post by craisin on May 29, 2014 8:25:33 GMT -5
may be cheaper to consider a crate motor
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Post by gingel on May 29, 2014 8:54:56 GMT -5
buying a new engine will not be cheaper.
It's a SYM motor, and also where i live there isn't an option to buy a new engine.
Maybe i can find a used one, but i prefer to rebuild mine.
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Post by gingel on May 30, 2014 12:35:48 GMT -5
Anyone knows regarding the timing chain?
Can it be replaced without splitting the engine case?
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Post by geh3333 on May 30, 2014 22:18:36 GMT -5
Only way I can think of would be to open a link on the old chain " same with the new one " attach he new chain to the old one and mark here the new one begins , spin the crank and when the old chain is all the way out detach chains from each other and reconnect new chain .
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Post by gingel on May 31, 2014 15:43:41 GMT -5
But how do you reconnect the new chain? Do you use the same rivet you took out, or do you need a special "master link" ?
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Post by skyrider on May 31, 2014 18:20:06 GMT -5
When I did that on a Honda years ago the chain came with no master link so I used a chain breaker and removed one link from each chain, used a master link to hook them together, rotated the crank til the new chain was in place. Then removed the old chain and hooked the new chain with the master link. In that case all I had to remove was the valve cover. Worked perfectly and never a minutes trouble in all the time we had that bike.
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Post by phatboy on Jun 2, 2014 0:46:18 GMT -5
i would guess the crank bearings are well worn by now. putting in a new top end is going to increase compression and but even more strain those bearings. clearly you ride the scoot a lot you want it to last another 100k, id get a new crank and rod.
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Post by gingel on Jun 2, 2014 22:33:33 GMT -5
Getting a new crank will cost too much as this is a SYM part.
Is it possible to just replace the crank bearings and the rod bearing?
Do you need to rebalance the crank after that?
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Post by rockynv on Jun 3, 2014 4:08:37 GMT -5
It should be a pressed crank so replacing the rod bearing would require a machine shop to break it apart, replace the bearing and press it back together again then you would still have the potential that the piston end of the rod may not be up to spec. You may be better off checking if a company like Hoca makes a replacement crank and rod set which should also come with the new bearings already on it for less than $200 US and it will be all nice and clean too. Ebay UK has a good number of low mileage used SYM 125 engines starting at 100 British Pounds and new ones for about 400. www.ebay.co.uk/bhp/sym-125-engine |
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Post by jerseyboy on Jun 3, 2014 17:20:09 GMT -5
Wow,,
I cant believe he got 68K miles out of it,,SYM is good but not that good...lol
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Post by gingel on Jun 4, 2014 6:44:53 GMT -5
It should be a pressed crank so replacing the rod bearing would require a machine shop to break it apart, replace the bearing and press it back together again then you would still have the potential that the piston end of the rod may not be up to spec. You may be better off checking if a company like Hoca makes a replacement crank and rod set which should also come with the new bearings already on it for less than $200 US and it will be all nice and clean too. Ebay UK has a good number of low mileage used SYM 125 engines starting at 100 British Pounds and new ones for about 400. www.ebay.co.uk/bhp/sym-125-engineI'll check the cost of a replacment crank and rod. Buying a complete engine from over seas, is not an option for me, because where i live they are giving you hard time when you personally import an engine. The ministry of transportation want all kinds of certifications, plus the shipping cost (if any of the sellers will even want to ship to Israel) will be very high. I'll better buy the parts, and rebuild my own engine. Anyway, my scooter model name is "Duke classic 125", and i understand it has the same engine as the "Megalo 125" . |
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Post by gingel on Jun 4, 2014 6:47:03 GMT -5
Wow,, I cant believe he got 68K miles out of it,,SYM is good but not that good...lol I also was surprised it did so much miles, and it's still running. Just need to make sure there is enough oil inside.  |
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Post by jerseyboy on Jun 4, 2014 11:56:43 GMT -5
Wow,, I cant believe he got 68K miles out of it,,SYM is good but not that good...lol I also was surprised it did so much miles, and it's still running. Just need to make sure there is enough oil inside. Yeah man,, Mine is chinese and never uses any oil between changes(every 1000km),,might blow a little out of the vent when cruising over 45 mph but only a drip or two in a 40 mile trip,,prolly cause I have it slightly over filled  |
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Post by gingel on Jun 6, 2014 0:00:57 GMT -5
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