2001 Hyosung Sense 2T Issues
 

Hi all,

So I bought this 2001 Hyosung sense that had been sitting for 2 years. Replaced the spark plug, drained the old gas and replaced with new 94 octane ethanol free, removed/cleaned the carb bowl and sprayed out the jets with carb cleaner. I got it to run, but it does not run well at full throttle. It runs fine until it warms up, but then starts to sputter/backfire at full throttle and starts to smoke a fair bit when warm. Idles fine and runs ok at mid throttle, just full throttle is the problem.

I didn't disassemble the carb other than taking off the bowl, and there was definitely varnish/crud in the bowl when I removed it for cleaning. Should I pull the jets out and check them properly?

I'm thinking carb problem or maybe reeds, what do you guys think?

Cracked intake?

Is it designed for the anti-detonating POWER of 94 rated fuel...?

Hi
Welcome aboard
Pleased to meet you
I would give the carburator a thorough cleaning and tune up, add some sea foam to the fuel , run that tank and see if it clears up
http://www.seafoamsales.com/sea-foam-motor-treatment/
If not then we can look into other causes
Take care and ride safely
Yours Hank

Thanks for the welcome. I used to lurk on the old scootdawg forums back when I had a 139qmb 4 stroke, but this is my first foray into 2 strokes.

Conveniently I have a can of seafoam sitting around that I was going to use on an old car but never did. I'll throw some in the tank, clean the carb properly, and see what happens.

Thanks

Ok, so I pulled the new plug to check it, tightened the head bolts, cleaned the carb again, and put some seafoam in the tank as well as spraying it in the carb. I haven't had a chance to run it WOT yet to check my work, but it did start right back up as soon as I put everything back together.

Anyway, here is the plug:

Intake looks ok to me.

Ran it today, seems to run better now! No more backfiring at full throttle, but it does still smoke a bit. Hoping that will clear up with some riding around.

I'm no genius but I think the 2 stroke engine was designed to smoke just a bit...

Yea, I knew that, it just seemed like a bit more than I would expect, and didn't have the typical 2 stroke exhaust smell. I'm thinking a bunch of oily junk just built up in there while it was sitting and that I need to burn it out thoroughly. Seems like there used to be an exhaust leak as well, since there was some oil around the exhaust pipe flange. I tightened the flange bolts up though, should be good. Picking up a helmet tonight so I can register it and legally take it for a spin. :scoot:

Hi
Its good to see you got her running well, and its normal for them to smoke alittle and if you let them sit a while then carbon can build up and make them smoke more then normal, that should pass in time as the engine gets more use
Are you using a quality 2 stroke oil as that will help keep the smoking down
I use Royal Purple for my "April"
http://royalpurpleconsumer.com/produ...le-engine-oil/
Take care and ride safely
Yours Hank

Thanks Hank. Pretty sure there is crappy quality oil in there right now as it came with a mostly empty bottle of generic 2 cycle engine oil. The bottle does say ok for use with oil injected engines, but I will go to the local scooter shop and pick up the good stuff ASAP.

Finally got it out for a run tonight! Engine runs great, and the smoking stopped after the first 10-15min of my ride!

Tops out at around 60km/h with the blue CDI wire removed, so I'm thinking I need to get into the transmission now. Probably needs a new belt and some rollers/sliders to refresh things in there. Pretty good though for $400 and a few hours work! :D

Snapped a pic yesterday:

Very nice scoot!