Blown rings? - Suzuki TF125

**DeadeyeDent** · 12th January 2014, 09:14

Hi guys. On Friday night I headed off for a hunt using my TF125
To gain access to some otago high country. It was roughly a 20km
Trip with the last 9kms uphill mainly in 1st or 2nd gear. Just as I got
To the top the bike lost considerable power and another 400m later stalled completely.

I went chasing a deer thinking maybe it was just a bit hot after the big climb only to get back
A couple of hours later to find it would crank up and stall within a second. Changed spark plug
And same issue.

I could hill start it in 2nd and it would run although providing no power
Until I hit the flat or uphill sections then just die again. Managed to free
Wheel or push it most of the way out and had a mate with 4x4 come get me.

Trying to decipher the issue and whether it's worth fixing. Does this sound like simply
Stuffed piston rings or is it more likely the engine is completely poked?

**unstuck** · 12th January 2014, 09:16

Is the gasket leaking? Any water in the fuel? What checks have you done? Is there compression on the kick starter?

**The Reibz** · 12th January 2014, 10:07

Try a compression check. Then tip a small amount of oil into the cylinder and do it again. If compression builds up much faster than it did the first time. The rings are rooted

**fridayflash** · 12th January 2014, 10:12

sounds like a its nipped up, heat siezure or lean feed from the two stroke oil tank..or do you run it pre-mixed? as said before a bit of oil down the cylinder may free it a bit. iff buggerall compression whip the head and barrell off and check out the good news

**Katman** · 12th January 2014, 15:30

As has been said, sounds like a partial seizure.

New piston and (most likely) rebore time.

**DeadeyeDent** · 12th January 2014, 15:42

Just finished taking the head off - I'll try to upload pics shortly but the two rings on the piston seemed very 'loose' for lack of a technical term! In other words there was visible clearance where I assume they should other wise be sitting flush in place against the piston?

Sorry not very familiar with engine mechanics so hope I am describing things correctly. Pictures should explain it clearly will give uploading them a go now

Sent from my iPhone using Tapatalk

**unstuck** · 12th January 2014, 15:46

Click image for larger version.

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Loose like this you mean?

**DeadeyeDent** · 12th January 2014, 15:57

Here are the pictures as promised

**unstuck** · 12th January 2014, 16:00

That scoring does not look good, whats the barrel like? and for fucks sake put a rag or something over the crank.

**DeadeyeDent** · 12th January 2014, 18:40

Don't worry I might just be a back yard tinkerer rather than mechanic but I know enough not to leave the crank open to collect foreign shit

Those photos were taken within about 20 seconds of removing the head and it has since been completely covered!

Anyway, yes the piston is quite heavily scoured but the barrel seems to be in significantly better shape - some minor scouring I can feel with a finger mainly in one part of the barrel. Other than that, I cant seem to see much damage in there.

Do you think looking at the state of the rings on the piston a new piston and rings set may alleviate the current issue? I appreciate its bloody hard to diagnose via a key board but the bike didn't cost me much and to be honest I don't have a lot to spend on it. If it was a reasonably certain issue to fix I'd go ahead and do it. However I would prefer to avoid spending coin on a mechanic to pull it all apart only to find a number of issues or something really major. If that was the case id probably flick it off for parts.

**unstuck** · 12th January 2014, 18:49

Well there doesnt seem to be much scoring on the rings that I can see from the pics. Did you check the gaskets and mating surfaces? How about the plug, as in was it seated properly? See if you can find the ring gap measurement somewhere and see what thats like.

**fridayflash** · 12th January 2014, 18:59

looking at the front end of that piston it looks like it has nipped up alrite, ring wear is more to do with the edge which runs against the bore rather than how loose they look on the bare piston,does the big end bearing feel ok? working the piston and rod around a bit to be sure theres no undue slack.
also hows the small end bearings/gudgeon feel? sloppy small end could cause a nip up. id be pricing a piston kit, and rebore.

**Jjgres** · 13th January 2014, 05:07

Two-strokes will run with amazingly bad pistons/rings. You should replace both but I think your stalling problem is something else. Maybe fuel related. Water in gas? Filter? Vent on tank? Crud in Carb?

I could go on but I really shouldn't.

**Jjgres** · 13th January 2014, 05:27

Originally Posted by fridayflash

sounds like a its nipped up, heat siezure or lean feed from the two stroke oil tank..or do you run it pre-mixed? as said before a bit of oil down the cylinder may free it a bit. iff buggerall compression whip the head and barrell off and check out the good news

Also this. Oil injection not working (if you have it) or no oil mixed.

**unstuck** · 13th January 2014, 06:38

Originally Posted by Jjgres

Two-strokes will run with amazingly bad pistons/rings. You should replace both but I think your stalling problem is something else. Maybe fuel related. Water in gas? Filter? Vent on tank? Crud in Carb?

I could go on but I really shouldn't.

Thats what I was thinking, my ag is a lot worse than that and still runs ok. How blocked up is the exhaust?