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Old 08-20-2013, 03:04 PM   #1
Firehawk989   Firehawk989 is offline
 
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New cylinder eating rings!

So I got a new Italkit cylinder kit for my Hyosung Sense 2T. Installed it, tried to start the scooter, and it ran poorly for a little while then made a loud click from the engine and stopped.

Took it all apart, found a broken top ring. Replaced the ring, put it all together again, started, ran ok, took it for a test ride and it ran around fine for a while. Then I left the back roads and tried to get it up to around 50km/h; again loud click, sputter, dead, compression gone. Probably another broken ring!

I didn't see anything wrong with the inside of the cylinder when I took it apart. Could the porting be done wrong or something? I didn't have any trouble installing the cylinder, and everything went together fine with no parts out of place. WTF is wrong with this thing!?



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Old 08-21-2013, 07:55 AM   #2
blueboy5000   blueboy5000 is offline
 
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Each time you install rings you must 'ream' the cylinder (hone) walls, even if you are using a brand new cylinder (jug).
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Old 08-21-2013, 07:58 AM   #3
blueboy5000   blueboy5000 is offline
 
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Also have you verified your low-end is okay (crank, rod and crankbearings) as excessive play in the bearings can cause a crankshaft to wobble, thus killing the rings (among other stuff).

Lastly is your oil-feed working correctly as oil-starvation is the #1 cause of 2t engine problems.
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2011 Roketa MC-23-150

4T 150cc 157 qmj

24mm carb w 115 main jet and paper cone air filter

Manual petcock w Tygon fuel lines

Scrappy Dog Scooters Retro-slash stainless straight-thru exhaust

RED spring clutch

Adjustable CDI (brand unknown, it's blue and red and works great!)

KOSO high performance variator w 12g sliders

Gates Powerlink 835-20-30 belt

GPS verified 65mph on flats.



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Old 08-21-2013, 04:41 PM   #4
Firehawk989   Firehawk989 is offline
 
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Hmm, had no idea a new cylinder needed to be honed. What is the procedure for that?

The bearings seemed ok when I had everything apart, no noticeable play.

Oil feed was working fine with the old cylinder, and I never took apart any of the oil feed system, so it should still be working fine.

Thanks for the tips!
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Old 08-22-2013, 09:04 AM   #5
buford1488   buford1488 is offline
 
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some were on one of the ports got a sharp edge. need to chamfer the ports.



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Old 08-22-2013, 01:42 PM   #6
Firehawk989   Firehawk989 is offline
 
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Quote:
Originally Posted by buford1488 View Post
some were on one of the ports got a sharp edge. need to chamfer the ports.
So just a light touch with a stone on the dremel around the upper edges of the ports? Can they be chamfered too much?
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Old 08-22-2013, 01:55 PM   #7
Guest_3   Guest_3 is offline
 
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Quote:
So just a light touch with a stone on the dremel
I wouldn't do that.

Go get one of these and do it right.

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Old 08-22-2013, 09:16 PM   #8
Firehawk989   Firehawk989 is offline
 
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Quote:
Originally Posted by scooterwayne View Post
I wouldn't do that.

Go get one of these and do it right.

Lol, yea, I won't be honing the cylinder with a dremel! That was about chamfering the ports.
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Old 08-22-2013, 07:24 PM   #9
4getful2   4getful2 is offline
 
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Proper ring-end gap.
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Old 08-22-2013, 09:16 PM   #10
Firehawk989   Firehawk989 is offline
 
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Quote:
Originally Posted by 4getful2 View Post
Proper ring-end gap.
Thanks, will give that a look too.
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Old 08-25-2013, 01:03 AM   #11
teddy554   teddy554 is offline
 
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All the ports you need to take a file to and kind of round the sharp edges if not the ring catch on them and cause damage
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Old 08-25-2013, 01:36 PM   #12
jct842   jct842 is offline
 
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When I was a kid I had a james motorcycle that had a very worn villiars engine in it. At the bottom of the stroke you could wiggle the piston sideways about an 1/8th of an inch. I used to replace rings with some for a briggs engine every 2 or 3 weeks.

At the top of the stroke there will be a ridge that has to be removed if it is there. Then as mentioned a ring can catch on a port. Also the ring gap has to be right. Put the ring in the cyl, use the piston to get it square and then put a feeler gauge in the gap. measure at the top of cyl and at the bottom where it would be if it was in the piston. Your manufacturer will have the numbers to go by, If the gap is too large the cyl would need either replacing or boring. If it is too tight you may have the wrong size rings. They can be filed if it is only a few thousands. And there are better instructions on the internet for doing this.
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Old 08-25-2013, 08:15 PM   #13
buford1488   buford1488 is offline
 
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i dont know were you live...but if by any chance you are in pa or nj bring the jug to my shop and i will ball hone it and port it...sorry thats the best way i could help ya out......thanks...buford.
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Old 08-26-2013, 07:23 PM   #14
Firehawk989   Firehawk989 is offline
 
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Thanks all, this all sounds like way more work than I was anticipating.

I thought the process was:

1. Buy new cylinder, piston, rings, etc. from scooter shop.

2. Install cylinder parts, decarbon old head, make sure gasket surfaces are in good shape.

3. Put everything back together.

4. Break in engine.


Howcome nobody ever mentions doing this honing/porting stuff when talking about BBK installs?

Anyway, I will probably just sell it, not too fond of the scooter from the start anyway. I just bought it because it was cheap, and figured it would be easy to work on like other scooters I have owned, but due to the design of the welded in underseat storage compartment, it is a PITA to work on the engine.

Going to start looking for something with better aftermarket parts support, like a Zuma, or maybe another chinese scoot. Finding parts for this Morini motored Hyosung is not fun!

Thanks for the offer Buford, but I'm on the West coast in Canada.
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Old 08-28-2013, 11:06 PM   #15
qwertydude   qwertydude is offline
 
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People don't mention honing on a bbk install because it's new. It's when you replace the rings on a used cylinder you have to hone it. New cylinder and new rings means honing shouldn't be necessary if they're quality units.
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