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Discussion Starter #21
Wow. Thanks for all the info everyone. This is all great reference and a lot to go through.

As far as moving forward, I'd happily let my mechanic shop take care of certain tasks if they could get me in there sooner. I called up a local machine shop too that does engine repair and asked about having the cylinder honed, but they told me no as soon I said the word "motorcycle" and told me to go to a motorcycle specific mechanic. I'm too impatient and curious to sit back for two weeks and not try fixing it myself so I will do what I can myself and keep my mechanic appointment in case I decide something is currently beyond me.

I can understand Prairierider's urging to use proper tools and not a chisel for removing the lock washer, but is there a proper tool for unbending washer tabs? If there is, please let me know and I will happily buy one instead of taking a chisel to the washer. I'm not especially eager to be chiseling away at a piece of my engine.

Thanks for the notes about lapping the valves. As this is going to be my first attempt at valve replacement, that is not something I knew to do but I watched a few videos and it looks like a very approachable task for me and the tool + compound to do so are cheap enough. I'm going to take the next few days to gather what I need and watch some videos, and this weekend get the engine back apart. I was going to hold off on the valves, but if evidence suggests they struck the piston and could be bent, I'll get them out to inspect them. I'll do the suggested leak test as well before removing them so that if they're not bent I'll know if they still have some life.

While a professional moto mechanic or machinist would definitely do a better job, I think I'm going to give honing the cylinder a shot so long as the measurements are still within spec. If it comes to having it re-bored and putting in a larger piston, I'll go to the pros for that. While probably not the ideal, is Willy's suggestion to go at the cylinder walls by hand with a Scotch-Brite pad viable for deglazing? I'm curious, but I plan to go pick up a 3-stone drill-attachment honing tool to do the job as I am all for learning new maintenance and repair skills.

When it comes to the piston rings, I have a set of OEM rings hanging around so I'm going to do that replacement (so long as I go the honing route). I have seen plenty of videos and pictures of people putting them on by hand so I'm going to forgo getting ring expanders, but what about a ring compressor? For those who have done this replacement, how difficult or risky is it to try reinstalling the piston into the cylinder without a ring compressor?

I will continue reading and re-reading through everything you've all shared. Thanks again, and I'll be sure to update as I move forward with the work on it.
 

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Wow. Thanks for all the info everyone. This is all great reference and a lot to go through.

As far as moving forward, I'd happily let my mechanic shop take care of certain tasks if they could get me in there sooner. I called up a local machine shop too that does engine repair and asked about having the cylinder honed, but they told me no as soon I said the word "motorcycle" and told me to go to a motorcycle specific mechanic. I'm too impatient and curious to sit back for two weeks and not try fixing it myself so I will do what I can myself and keep my mechanic appointment in case I decide something is currently beyond me.

I can understand Prairierider's urging to use proper tools and not a chisel for removing the lock washer, but is there a proper tool for unbending washer tabs? If there is, please let me know and I will happily buy one instead of taking a chisel to the washer. I'm not especially eager to be chiseling away at a piece of my engine.

Thanks for the notes about lapping the valves. As this is going to be my first attempt at valve replacement, that is not something I knew to do but I watched a few videos and it looks like a very approachable task for me and the tool + compound to do so are cheap enough. I'm going to take the next few days to gather what I need and watch some videos, and this weekend get the engine back apart. I was going to hold off on the valves, but if evidence suggests they struck the piston and could be bent, I'll get them out to inspect them. I'll do the suggested leak test as well before removing them so that if they're not bent I'll know if they still have some life.

While a professional moto mechanic or machinist would definitely do a better job, I think I'm going to give honing the cylinder a shot so long as the measurements are still within spec. If it comes to having it re-bored and putting in a larger piston, I'll go to the pros for that. While probably not the ideal, is Willy's suggestion to go at the cylinder walls by hand with a Scotch-Brite pad viable for deglazing? I'm curious, but I plan to go pick up a 3-stone drill-attachment honing tool to do the job as I am all for learning new maintenance and repair skills.

When it comes to the piston rings, I have a set of OEM rings hanging around so I'm going to do that replacement (so long as I go the honing route). I have seen plenty of videos and pictures of people putting them on by hand so I'm going to forgo getting ring expanders, but what about a ring compressor? For those who have done this replacement, how difficult or risky is it to try reinstalling the piston into the cylinder without a ring compressor?

I will continue reading and re-reading through everything you've all shared. Thanks again, and I'll be sure to update as I move forward with the work on it.
Wow. Thanks for all the info everyone. This is all great reference and a lot to go through.

As far as moving forward, I'd happily let my mechanic shop take care of certain tasks if they could get me in there sooner. I called up a local machine shop too that does engine repair and asked about having the cylinder honed, but they told me no as soon I said the word "motorcycle" and told me to go to a motorcycle specific mechanic. I'm too impatient and curious to sit back for two weeks and not try fixing it myself so I will do what I can myself and keep my mechanic appointment in case I decide something is currently beyond me.

I can understand Prairierider's urging to use proper tools and not a chisel for removing the lock washer, but is there a proper tool for unbending washer tabs? If there is, please let me know and I will happily buy one instead of taking a chisel to the washer. I'm not especially eager to be chiseling away at a piece of my engine.

Thanks for the notes about lapping the valves. As this is going to be my first attempt at valve replacement, that is not something I knew to do but I watched a few videos and it looks like a very approachable task for me and the tool + compound to do so are cheap enough. I'm going to take the next few days to gather what I need and watch some videos, and this weekend get the engine back apart. I was going to hold off on the valves, but if evidence suggests they struck the piston and could be bent, I'll get them out to inspect them. I'll do the suggested leak test as well before removing them so that if they're not bent I'll know if they still have some life.

While a professional moto mechanic or machinist would definitely do a better job, I think I'm going to give honing the cylinder a shot so long as the measurements are still within spec. If it comes to having it re-bored and putting in a larger piston, I'll go to the pros for that. While probably not the ideal, is Willy's suggestion to go at the cylinder walls by hand with a Scotch-Brite pad viable for deglazing? I'm curious, but I plan to go pick up a 3-stone drill-attachment honing tool to do the job as I am all for learning new maintenance and repair skills.

When it comes to the piston rings, I have a set of OEM rings hanging around so I'm going to do that replacement (so long as I go the honing route). I have seen plenty of videos and pictures of people putting them on by hand so I'm going to forgo getting ring expanders, but what about a ring compressor? For those who have done this replacement, how difficult or risky is it to try reinstalling the piston into the cylinder without a ring compressor?

I will continue reading and re-reading through everything you've all shared. Thanks again, and I'll be sure to update as I move forward with the work on it.
"For those who have done this replacement, how difficult or risky is it to try reinstalling the piston into the cylinder without a ring compressor?"

I have had more difficulty installing the piston wrist pin circlips. I typically install the piston to the rod and then install the cylinder over the piston. The bottom of the cylinder has a pretty generous lead-in taper, so the piston/rings can be persuaded in just using your fingers.
 

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^^^^

rings slide into cylinder from the bottom pretty easy with the piston already on the rod.
 

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I may have misunderstood you when you were talking about a chisel to get the valves out. I thought you were going to chisel the valve retainers and keepers. You must have been talking about the cam bolt retaining clip. A chisel is the proper tool for those lock tabs. Sorry for my confusement.
 

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PLEASE, PLEASE, PLEASE REMEMBER to stagger the ring gaps at 120 degrees. I usually start with the oil ring insert, IT SHOULD BUT, NOT OVERLAP!!!!! then the bottom and top segments staggered at 120 degrees with the inset but, keep on the non thrust side of the piston (rear of the engine) next the 2nd ring installed make sure it is the right way up, usually an indent on the top, or stamped TOP, if no markings, rule of thumb is inside bevel goes toward the top. Stagger this ring at 120 deg from the gap in the top segment of the oil ring. Top ring same as 2nd ring.
Just remember to clean out the ring grooves properly before installing the rings, use an old hacksaw blade by hand and with a sawing motion clean out all the carbon deposits that are there.
I like to use "Zeb" oven cleaner to clean the internal parts of the engine, just spray on leave a couple of minutes and rinse off with a high pressure washer. Just remember this stuff is highly caustic, but it cleans like a dream.
For assembly I like to use white lithium grease(spray can) or Wynns Charge or Assembly lube. Just a personal preference.
 

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Discussion Starter #27 (Edited)
Update. Tw200 is back together once again. Cylinder has been honed, piston re-ringed, engine gaskets and o-rings replaced (still have to match and replace valve cover o-rings), and timing has been properly set. I did stagger the piston rings, and I hope I did it right. I got kinda confused and eventually just decided it was close enough. Bike starts and runs on its own again. Engine compression checks in at 120 psi on a dry test.

I don't think that I'm quite in the clear yet. I took it out on a neighborhood test run and I have so far made two observations that worry me somewhat. First, torque seems down. I haven't gotten to ride it for awhile so I might just be remembering it wrong, but the bike feels weaker on acceleration than I remember. I popped onto a stretch of highway for a bit and I can still get up to 45+ mph but if feels like it is taking longer than I remember to do so. I'm gonna remove the cam chain tensioner again later and verify that it set properly.

Second, the engine is running super hot. I know the tw200 is known to run hot but it looks like that heat may be burning through my throttle cable. It. I was already aware of the cable fraying and have a new one on the way, so it could be blackening because of that prior damage exposing it the heat more. I will keep an eye on the new cable for any discoloration once it is installed.

I still have the appointment with my mechanic for the 25th. That appointment date means I have just under a week to judge how the bike is handling double check things and decide what I want the mechanic to focus on in the time I can pay for. Thanks again for all the advice and support this far. My appointment with the mechanic was originally set to have a leak down test performed. For the time being, it looks like compression is no longer my main concern, so does anyone have any suggestions for tests I should have the mechanic perform in place of the leak down test?
 

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If the engine runs hot and lacks power it might be that the cam timing is to advanced. Recheck the cam timing and try and retard it by 1 tooth. You can do that without removing the can gear, just remove the tensioner, then carefully work the chain over the gear teeth.
 

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Discussion Starter #29
Update. I have been getting 125 psi compression readings, not far off the standard of 128 psi, yet I was still have trouble getting the bike going from a cold start. I found a thread about altitude correction factors for compression tests and it finally makes sense. I live at about 7000 ft, so if I factor in altitude correction my engine is functioning at barely over 100 psi.

I finally was able to take the bike to my local shop today. They knocked out the leak down test and confirmed that my piston rings are still not sealing but everything else seems to be holding up fine. I was afraid of that but not especially surprised. I'm gonna take it back apart and give it another shot. If all else fails, the manager there told me which machinist in town they use for bore jobs so I now know where to go if I end up going that route. I might take this opportunity to try making my own gaskets as well.

Thanks again to everyone who chimed in to help me out. I've learned a whole lot in the process and hopefully I will be able to get the bike working properly this time around. It looks like I'll have a nice window of warm-enough days this week to give it another go.
 
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