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Is this cylinder damage? TY 250 A


Tillerman6
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Guys,

  I started a thread asking about cleaning the tailpipe and got side tracked a bit.  Can anyone look at these photos for me and see if that intake side port opening looks damaged or modified or normal? in some way?

It looks to me that one side of the opening is lower than the other, and somehow it might have been caused by someone in there with a grinder?  The right side of the image is much shinier than the left side as well, so I don't know why that would be the case.  All I did was wash the whole jug with water and a solvent and I did not scrub this area on the right any more than I did on the left side.  So something has been in there either with a lot of heat or what is your esteemed opinion?  Before it was washed there were also tiny beads of silver colored metal stuck to the intake port surfaces but only on that same side.  These beads were on the order of .005" in diameter and resembled weld spatter from a MIG welder.  Any ideas?  I had some detonation issues while decelerating with the throttle closed (My bad) as I was thinking that the engine would cool itself down better with the throttle closed than by blipping the throttle with the clutch pulled in.

 

 

 

TY 250 A pictures 010.JPG

 

 

 

Edited by Tillerman6
Don't need but one good picture.
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Guy,

  Now that makes more sense than anything I could think of.  Reason I'm asking is that I have that cylinder sent out to Millenium Technologies for a rebore and Nikasil.  I don't know how many hours it has had on it, but when I had it in a local MC shop they ran a hone thru it to take out some of the scuff marks from the piston and rings.  The shop owner said the cylinder was a little out of round and you could hear the hone speeding up and slowing down presumably from the out of round condition.  I measured the bore in one spot above the output port and it was still right at 70mm, so I think the sleeve that is in there now has not been re-bored oversize.  But since that area on the right has been modified with a rotary file or some abrasive tool, it does probably mean that the aluminum outside the sleeve was not touching the liner so they ground down the liner until they had full support from behind.  I wanted to get as many eyes on that as possible before they call me from Millenium and say whatever they are going to say.  I am about 50-50 on trying to find a better cylinder to put the money into, and I think a re-sleeve would be several hundred dollars where maybe a cylinder that was worn but in better shape could be re-bored as is and end up costing much less out the door because it would not need to be repaired first.

 

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personally, I think you may be nuts! do you see any other edges that do not line up like a factory cyl? re-sleves are not that clean.

I am not even sure that you arebfixing anything here. you said your problem was a knock or ping on closed throttle decel did you not? trust me when I tell you that a worn out rattler does not know if they are on closed throttle decal, as they rattle all the time!

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12 hours ago, copemech said:

personally, I think you may be nuts! do you see any other edges that do not line up like a factory cyl? re-sleves are not that clean.

I am not even sure that you arebfixing anything here. you said your problem was a knock or ping on closed throttle decel did you not? trust me when I tell you that a worn out rattler does not know if they are on closed throttle decal, as they rattle all the time!

All the other edges in the cylinder line up perfectly. It was just this one spot that was low (high) because the pic was taken with the cylinder upside down.  I am not a 2 stroke authority at all, but I know that the rattle was getting LOUDER the more I ran the bike.

And I usually have to ride alone, in the middle of an area with sketchy cell service, so this thing HAS to work or I have a 10 -20 mile hike out of the woods.  AND a teardown when I get it home!-

If the piston had come out of that bore clean, then I would not worry, but it had an  area on the rings and directly below that about 1/2 inch wide and extended down the piston most of the way to the edge of the skirt. In that area the piston had seized before.  I don't know when, but it had seized at one time or another.

I don't have pictures of the rings, but they were nicked in 4 places near the ends where they pass by this red arrow area in the cylinder. Also some micro beads of metal were stuck to the inside of the intake port. (same area)

Knocking - I think that was my fault. The more I read on here the more it sounds like a bad idea to do any engine braking with a 2 stroke. And I was definitely doing that.

Rattling-  Well the rattling was getting louder and added to the loud bang when the cylinder would fire with the throttle closed.  It seemed like a good thing to go inside and have a look.

As it turned out, the piston to bore clearance was at the max limit after I had the bore honed to remove the glaze.  So at a minimum it would need a new piston and rings and an overbore anyway.

There are no cylinder boring services anywhere around where I live (North Idaho) and stock oversize pistons are not something you want to buy off of Ebay in advance of knowing what size you are going to need!

the Nikasil process is about 120.00 and I have read on here that the fellow that had his TY nikasil'ed liked it a lot, so why not try it?  It's supposed to reduce the friction and make the bike run smoother.  They would not offer that service if it was going to make things worse, and they do hundreds of cylinders a month of all varieties.  And they guarantee that the Nikasil will not flake off.

Anyway, I think it was good to have a look and it was time for a re-bore at a minimum. The bike is from 1974.   As I said before, I was trying to prevent being stranded in the woods and or blowing up my motor.  The damage during a seizure can go way beyond just the piston/cylinder in a heartbeat, so not being one to let it all hang out, this might be the way to go for me.

 

 

 

 

 

 

 

TY 250 top end teardown 006.JPG

TY 250 top end teardown 011.JPG

TY 250 top end teardown 012.JPG

TY 250 top end teardown 018.JPG

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8 hours ago, guy53 said:

I do agree with copemech that they are '' noisy '', also Nikasil ? What piston are you going to use ? I'm sure there is a cheaper and more standard way to fix your problem.

Guy

Noisy is one thing but this was more noise than I wanted to deal with.  I could hear it with my helmet on and the sound was bouncing off the trees in front of me. Not normal at all.

Then when I looked at the small end bearing it was missing a roller!  WTF?

I am leaning heavily in favor of the Wossener pistons right now.  They have 4 oversizes available in the Germany warehouses and the pistons are forged which is supposed to be stronger.

Millenium Technologies will decide which size to order.   I did find out that the same part numbers are used from the DT250 series if someone wants to use a factory piston and rings, But I don't know where all the sizes would be available on short notice in the States.  It's up to the technician to tell me what size I need after they get the boring process finished.

Thing is from my perspective, you can't save any money trying to jury rig a piston yourself.  You have to have the cyl bored, and that is what introduces some variables.  If the tech decides that the bore should go past the 1st oversize, then any stock or 1st oversize pistons that I might have stupidly assumed that were going to fit would now be useless.  So how are you going to save any money?

If you guess it right you are home free, but if you guess it wrong you have to go out and look for another piston and rings and try to sell the one (s) you bought?  Nahhhh!

 

 

 

TY 250 top end teardown 009.JPG

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13 hours ago, Tillerman6 said:

Thing is from my perspective, you can't save any money trying to jury rig a piston yourself.  You have to have the cyl bored, and that is what introduces some variables.  If the tech decides that the bore should go past the 1st oversize, then any stock or 1st oversize pistons that I might have stupidly assumed that were going to fit would now be useless.  So how are you going to save any money?

The usual technique to avoid wasting money is to get the person doing the re-boring to measure the cylinder and tell you which oversize piston kit to get before you order the piston kit

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When you ride with throttle shut you restrict petroil mix from the piston and hey presto you get piston nipping and score lines on the piston skirt. The porting photos look like there may have been a weld repair done and then a clean up. The honing marks look a bit course from the photo and what appears to be cleaning rag fluff. The port itself would benefit from a gentle clean up or smoothing. 

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About noise, I had just rebuild a D model, on start up it was crazy noisy. Lucky for me, I always use a lot of 2 stroke oil when I reassemble a cylinder. I noticed that the baffle ( the last piece of the exhaust ) was not '' smocking '' very much, but most of the smoke came from the joint between the muffler and the baffle, cleaned it and voila, normal sound

Guy

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Feetupfun and guys,

  Well, yes if I was close to anyone that could bore a cylinder I would walk it in there and have them tell me what piston to order,

Don't have that option. And I want the shop to fit the new bore to the new piston, not the other way around. 

It's a whole new can of worms to me. They have to bore until the cylinder wall cleans up plus enough for clearances on the next size piston that is available.  Nobody knows at what dimension that is going to happen until they start making chips.

I don't know if they can do all that in one setup. I would not want to try it without having the new pistons in my hand to measure.  Even then it would be a guess the first time.

Tough job to get it right.

I am not friends with Millenium Technologies in any way.  If it turns out that they let me down,  I will be the first one to let you guys all know it.  If they do a fine job, then that too will be widely known on here.

If the other guy that had the Nikasil work done on his bike would like to comment on his experience (who ever that was) I would be very grateful to hear all about it.

 

Wish me luck!

 

 

 

 

 

 

 

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7 hours ago, section swept said:

When you ride with throttle shut you restrict petroil mix from the piston and hey presto you get piston nipping and score lines on the piston skirt. The porting photos look like there may have been a weld repair done and then a clean up. The honing marks look a bit course from the photo and what appears to be cleaning rag fluff. The port itself would benefit from a gentle clean up or smoothing. 

100% agree and I won't be running like that from now on.  Point well taken.  But the bore is at the outer limits with this stock piston.  Time for plan B.

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7 hours ago, guy53 said:

About noise, I had just rebuild a D model, on start up it was crazy noisy. Lucky for me, I always use a lot of 2 stroke oil when I reassemble a cylinder. I noticed that the baffle ( the last piece of the exhaust ) was not '' smocking '' very much, but most of the smoke came from the joint between the muffler and the baffle, cleaned it and voila, normal sound

Guy

My cylinder is already sent out for repairs, but I will definitely be cleaning the hell out of the tail pipes.  And lubing all the parts well with 2 stroke oil on re-assembly   The pipes were clogged to some degree.I haven't got around to burning out the pipes yet, but that will happen soon. 

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