Blown rings? - Suzuki TF125

[DeadeyeDent]

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]

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

[The Reibz]

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]

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:wacko:

[Katman]

As has been said, sounds like a partial seizure.

New piston and (most likely) rebore time.

[DeadeyeDent]

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 (http://tapatalk.com/m?id=1)

[unstuck]

292244 Loose like this you mean?

[DeadeyeDent]

Here are the pictures as promised

[unstuck]

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

[DeadeyeDent]

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:wacko: 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]

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. :niceone:

[fridayflash]

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]

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]

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:wacko:

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

[unstuck]

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?

[DeadeyeDent]

cheers for all the replies so far guys - learning a lot from this thread and google/you tube!

Pretty sure there is no water in the fuel as the bike is kept in a garage and I filled it up with the same fresh fuel I used recently for the lawnmower which has had no issues. I did notice when I took the exhaust off there was a lot of loose carbon falling out of the exhaust - a few gentle taps with a hammer and a fair few big chunks were falling out. Anyway to give them a good clean or need to bite the bullet and look at a new one?

Will check the gudgeon pin etc. tonight when I get home from work and see if there is any slop in there.

It still has the separate two stroke oil tank. Assuming I get it up and running again is it an easy task to simply block this off and pre-mix the fuel and oil? Id much prefer the manual mix method for peace of mind that the oil is definitely getting in there.

[unstuck]

Blocked exhausts on 2 smokes can rob you power and cause all sorts of problems. Clean as much as you can out, then try it again. Easy enough to disconnect the oil pump.:2thumbsup

[Jjgres]

I don't know about your bike but some Suzukis have a oil feed directly to the crank bearings. If you run pre-mix they may not get enough oil.

[ktm84mxc]

Yep just cutting of the oil feed line will lead to other issues mainly the crank assbly not getting enough oil for the bearings to survive .
De-coke the exhaust, there's plenty of threads on here on how to do it.
Buy a new air filter and use it as per the owners manual, if not use a proper filter oil and when its dirty clean and re oil.
Fit a new top end-piston,rings,gudgeon,small end bearing,gaskets don't forget the exhaust gasket.
And it'll run for another decade.

[DeadeyeDent]

Yep just cutting of the oil feed line will lead to other issues mainly the crank assbly not getting enough oil for the bearings to survive .
De-coke the exhaust, there's plenty of threads on here on how to do it.
Buy a new air filter and use it as per the owners manual, if not use a proper filter oil and when its dirty clean and re oil.
Fit a new top end-piston,rings,gudgeon,small end bearing,gaskets don't forget the exhaust gasket.
And it'll run for another decade.

Hey thanks for this - sorry for my late reply Mrs has been admitted to hospital with pregnancy complications and aside from travelling to Dunedin and back I'm now doing the solo dad thing so this repair project is likely to go on the back burner a bit. I think I will leave the oil feed line to avoid causing any other issues. I have been pricing up the top replacement parts and have found a few options for piston/rings/gudgeon pin sets online but none of the depictions seem to have the small end bearing - does this usually come with the sets or do you have to ask for and order this part separately?

Also, and this may be a bit of a noob question but the crank when I pushed it up and down and was looking for excessive play was becoming coated in oil - presumably it can only be transmission oil and I was wondering if this should be present? My understanding was that transmission oil should only be in the trans/clutch pack and the engine/crank is lubricated by the oil in the fuel mixture, is this correct?

Also if anyone knows where I can get a workshop manual for a TF125 id be grateful for a point in the right direction as I can find one anywhere.

[ktm84mxc]

A thin film of oil on the crank assmbly is normal , excessive amounts can mean a leaking crank seal allowing gearbox oil to be sucked in this normally shows up as excessive smoke from the exhaust. Small end bearings normally not included in top end piston kits and have to be purchased separately.
Haynes and Clymer should do a service books on the TS/TF models check Technical books etc .
I can handle a top end rebuild and general repairs my self and only seek expert or shop work for case splitting , shock servicing etc. The joys of 2 smoke ownership.