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Author Topic: Resurrecting the 250  (Read 9254 times)

silentjatt

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Resurrecting the 250
« on: January 06, 2011, 04:44:19 AM »

so i've decided to give this a whirl myself..

one day.. when i was coming home from couple hours ride(a bit of twisties and highway mixed in) was coming to a red light. started slowing down and the bike started to sputter. i pulled over to the side and the bike shut off on its own. tried to restart it. it was turning over but didn't start.

got it towed home. tried to start it again several times. first it felt like it would start if i gave a bit of throttle. but after several tries, that stopped too. and now the bike would not give any indication that it would start.

upon checking everything, when i checked the cam chain tensioner, the spring had let go. there was no tension in the tensioner.

from that, i concluded that the tensioner faulted and then as a result, piston and or rings might have gotten damaged when i tried to start it again and again.

sent it to a mechanic. he said timing was off. he said he fixed the timing but still no go. he told me 100% leakdown and 0 compression. he said the engine needs a complete rebuild or a new engine completely. too much money for me to invest. so it sat in my garage for the past 5 months or so.

after all this time, i still have no money to get this fixed. but spring is just around the corner now. so i've decided that i might as well try to give it a go and try to fix it myself with help from peeps here and my friend.

progress on tihs is going to go slow on this as i only get 1 day off from work every week. but im going to keep this detailed with pictures as much as possible and will need a alot of help from the experts on here. pretty please..

first thing, took out the engine with the help of my friend. well.. he did most of the work. i just watched and elp wherevr i could.

but we forgot to take out the oil first. so that was the next step..

put the engine on couple of paint boxes and drained the oil.




i am going to start with the front cylinder first. cuz thats where i heard the clinking noise from. and my guess is that the piston or the rings might have gotten damaged. but i have no idea where they are supposed to be and what next, they look like. so im going to open this apart, put up the pics up here and will ask what the next step is. the help will be much appreciated. :)

next step, open up the cover of the front cylinder.
open these 4 screws



note the marks so i can get the timing right after.


take out these screws. black circle are number 6 and red circle are number 7.




next, i opened the sator cover(i think thats what its called pls correct me if im wrong)
green colour screw is for the radiator. iopened that from here and from the other side too.
the ones in red are longer. than the others.



this is end of the day today. next, i have no idea what to do.. help please..
my goal is to get to the piston and check for the damage there. also one thing i havent figuered out is how to get the chain off. any tips?
« Last Edit: January 06, 2011, 04:57:38 AM by silentjatt »
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extermin8tor

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Re: Resurrecting the 250
« Reply #1 on: January 06, 2011, 08:19:50 AM »

I would begin by reading the service manual starting at page 44:
http://www.scribd.com/doc/16066620/Hyosung-GT125-GT250-Workshop-Manual#

Basically just take the camshafts out, remove the union bolts connecting the two cylinders with oil, loosen the bolts at the base of the cylinder head.

I would put the stator cover back on because it is unlikely to have a problem, and you are just setting yourself up for dust in the engine as well as losing bolts.
When you get to the point of removing the cylinder head, etc I would work on a clean surface such as a towel, preferably indoors in the laundry rather than a dirty garage.

There are also tricks such as stuffing cloth into the engine to keep dust out, as well as making sure that you dont drop the camchain into the engine, so that it stays on sprockets!
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bushpig666

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Re: Resurrecting the 250
« Reply #2 on: January 07, 2011, 09:02:40 PM »

Dude! Respect for giving this a go yourself 8)

I will be watching and learning very closely. Can't provide any help though sorry.
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silentjatt

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Re: Resurrecting the 250
« Reply #3 on: January 08, 2011, 04:10:34 AM »

I would begin by reading the service manual starting at page 44:
http://www.scribd.com/doc/16066620/Hyosung-GT125-GT250-Workshop-Manual#

Basically just take the camshafts out, remove the union bolts connecting the two cylinders with oil, loosen the bolts at the base of the cylinder head.

I would put the stator cover back on because it is unlikely to have a problem, and you are just setting yourself up for dust in the engine as well as losing bolts.
When you get to the point of removing the cylinder head, etc I would work on a clean surface such as a towel, preferably indoors in the laundry rather than a dirty garage.

There are also tricks such as stuffing cloth into the engine to keep dust out, as well as making sure that you dont drop the camchain into the engine, so that it stays on sprockets!


engine was already moved to a room in the backyard before opening. put the stator cover back on before i left same day to prevent any dust from getting in there. didnt tighten the screws but just put it on. covered it all up too.

i was reading the manual. thanks for posting the link here. more convenient. but its just open this, open that. doesnt really say how it should look and stuff. but also.. to be honest i wasnt paying that much attention to the manual. will do more.

im guna try to get some more work done this sunday after work.. will post more pics that time if i figure this thing out.
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silentjatt

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Re: Resurrecting the 250
« Reply #4 on: January 08, 2011, 04:14:07 AM »

Dude! Respect for giving this a go yourself 8)

I will be watching and learning very closely. Can't provide any help though sorry.
thanks! thats the idea man. im still learning as i go. hopefully this can inspire someone else if they are ever in the same situation.. will try my best to get this running again.
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silentjatt

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Re: Resurrecting the 250
« Reply #5 on: February 03, 2011, 05:56:01 PM »

a little bit more progress.

remove the carburator.
sorry. did not take any pics while removing carburator

remove the linking screws. i think there were 3 screws total linking the two pipes together. two pipes sharing oil for both cylinders.


remove the pipes. theres a washer on each side of the 3 screws. do not loose these.


remove the cam chain tensioner


the chain will come loose and then remove the camshafts.



remove these 3 nuts.


remove these 4 screws. these are very long screws. there is a washer at the end. do not loose it OR let it drop in the engine. carefully tip the screw while taking out the screw to bring the washer with thte screw.


take off the cylinder head.


fingerpointing to the seal.. do not loose it or bend it. note the perfect circular hole in the carpet. do not loose a bulb unattended.. lol




thats all for today.. next step remove the piston.

P.S> while removing the carburator, i found this rubber hose blocker thingy ripped. what is this? and what is its function?


« Last Edit: February 03, 2011, 06:01:46 PM by silentjatt »
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hotdiggerty

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Re: Resurrecting the 250
« Reply #6 on: February 03, 2011, 06:31:21 PM »

 :) wow, huge detail, well done. onya for having a go. dunno if shop bought w/shop manuals have more detail?
 i guess you know that you will need to check bore diameter for wear, a light hone would be the go. pistons don,t look too well -burnt?,nor valves. valves may grind up ok.[ @ $27.aust, ea. hyo.source]  new valve seats/seals are the go too.[hyo.source too], they have piston/ring sets too. think blocked off hose is to do with ais system,air inject. alantris seems very informed, hope he can chime in too.you think cam chain adjuster failure caused the problem? jeez, good idea to change to up-dated one, better check mine. great learning project.cheers mate.
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muppit

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Re: Resurrecting the 250
« Reply #7 on: February 03, 2011, 10:18:33 PM »

I have a feeling it's for the models with the charcoal canister. My bike had a had a pipe from that connection linked to the other inlet pipe. But when i orderd new ones they didnt have connectors on the inlet manifold , so i didnt fit the pipe.

Muppit
« Last Edit: February 03, 2011, 10:21:49 PM by muppit »
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stigger

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Re: Resurrecting the 250
« Reply #8 on: February 04, 2011, 04:27:17 AM »

If there's one on each inlet then they're probably for balancing the carbs...
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johnny ro

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Re: Resurrecting the 250
« Reply #9 on: February 04, 2011, 04:51:54 AM »

Great job. Photos will help reassembly. I almost hope something in there is really toasted now you are so deep into it.

I do hope you or mechanic checked spark and gas flow before you started this tear down. Like on any old lawnmower. Just sayin'.

The busted hose is a discrepancy that would hurt how it ran, so that's one thing found. It won't make it not run at all so keep going. Plan on examining all hoses for heat and ozone damage.
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