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Discussion Starter #1
Hi! I've been reading through the forum for awhile have found a lot of great advice here, but I'm finally posting as I am have trouble finding any reference for what I'm dealing with both on the forum and in the service manual. Hopefully someone can help get me going in the right direction..

I have a 2017 TW. Engine compression had dropped to around 85-90. It would still run if I sprayed a little starter fluid into the carb, but it was sluggish at best. I knew at the very least I needed to replace the engine head gasket, so I decided to look into replacing the intake and exhaust valves as well since I had been running the bike pretty hard towards the end of last year. I took the engine head off, replace the gasket and accompanying o-ring, and got stumped by the lock washer that needs to be removed to change out the valves (anyone have an advice for getting it off?).

I decided to reassemble for now. I put it back together to a state where I could set and verify timing. I got everything set and began to rotate the engine through the crankcase to make sure the cam chain and sprocket turned with it.Once they had rotated to where the line on the cam-sprocket is around the 10 o'clock position, they stopped turning as if stuck. It seems this is where the exhaust valves should compress and open but it is struggling to do so. I can continue to rotate engine via crankcase and I can hear the piston moving. If use a ratchet on the cam sprocket bolt to rotate the sprocket, I can push it through valve compression and then it will turn again with the engine when I rotate via the crankcase, but this throws off timing and everything jams up again once it reaches the next valve compression.

I reset timing to where it should be right and decided to reassemble the bike to an operable state as I heard getting the engine to fire up might be enough to free stuck valves. No dice. Engine will not start.

If anyone has any ideas or insights, they would be greatly appreciated. If all else fails, I'm also gonna check with my local mechanic about bringing in the engine head to have the valves professionally changed out, but I'd much prefer to do the work myself if I can figure what to do and how to do it. Thanks in advance.
 

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Just to help verify what you've probably already verified. Make sure your timing is correct by checking your cam timing mark and the TDC mark on the flywheel (the upper smaller hole which I didn't mark in the photo)...and verify the piston is TDC through the sparkplug hole.
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If and when you get to removing the valves, hopefully, these pictures will help by bad grammar and word use. I made a homemade valve compression removal tool from an old C-Clamp I had on hand. I ground the top portion of the c-clamp so I could remove the valve locking thingys.
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Quick timing tip:
The open port just above Admiral's socket and breaker bar is a sight window that allow one to see the corresponding timing marks on the flywheel. Best to start reassembly with the crank at top dead center, verify with piston position. This is because I believe the TW200 piston will hit an open valve. This can result in broken valve guide where it protrudes into the head, and/or a bent valve, and/or damage to the piston. When done at speed valve heads have been known to break off and rattle around doing no good the cylinder walls too if they don't get immediately stuck piercing the top of the piston.
While downloadable service manuals as well as a lot of advice is available on the Forum to guide you through completing the valve job and re-assembly your idea of the mechanic has merit.
I would pul the head now and check for anything amiss while starting a parts list beyond new valves & gaskets.
tw.JPG
 

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Discussion Starter #4
Thanks for the tips and reference pics. I gave timing it another shot, so here's an update.

From trying to start earlier, the cam sprocket is locked up with the sprocket marker pointing to the 6 o'clock position. Removed chain tensioner, still locked tight, not able to move sprocket at all by hand.
Using a ratchet to turn the sprocket counter-clockwise it moves but seems to snap hard to several positions. Eventually it falls with the marker between the 10 o'clock and 2 o'clock positions. In this range there is no tension on the valve springs so I can freely turn the sprocket by hand so I am able to line the marks for tdc.

I rotate the engine via the crankcase so that I can see the timing marks through the smaller whole. In rotation it seems really eager to skip over the marks. I can get to the first set of marks for when the spark plug fires but I am having a hard time centering the tdc mark in view as it seems to want to jump past it with even a slight touch. I finally got it pretty close to center.

I put the sprocket back and make sure marks are line up both for the sprocket and in the crankcase. Cam chain seems loose to an extent that rotating via the crankcase has no effect on the cam sprocket without the tensioner put back on. I'm not sure if this is normal. With the tensioner back on the chain feels very taught and the cam sprocket will turn when rotating the engine via the crankcase. Once it reaches the 10 o'clock position however, it feels like then tension of trying to compress the valves springs is too hard so it forces the cam sprocket out of sync and locks it up while the engine can continue to rotate. Additionally, trying to tighten down the bolt on the cam sprocket by using two ratchets, one to keep the engine steady and the other to tighten the bolt, also forces the cam sprocket out of sync and causes it to again move freely between 10 o'clock and 2 o'clock positions.

It seems like either the valves a somehow putting out enough resistance to disrupt the timing of the engine or the rotation of the engine is not putting out as much force as it should be in order to keep the chain taught enough for the valves to compress and open. This has me worried that it is possible that either the cam chain is overly stretched and needs to be replaced, something is wrong with the chain tensioner, or that it has gotten somehow misaligned on its crankcase sprocket. I'm leaning towards the later two options. I don't know much about the chain how the automated hydraulic tensioners on the newer TWs work and the supplement manual has not struck me as being all that helpful on the matter. As for getting a look deeper inside the crank case, I don't have a flywheel remover tool.

Eventuallly, I line up everything to be in time and reassembled the bike. Tried to start. Doesn't sound good. Engine won't start. I remove the cam chain cover and try again, there is no movement Sprocket is caught around the 3 o'clock position. Closed t back up and called it a night. For the time being, I am left with more questions and I suppose I will have to make a serious decision between paying to have a professional work on it or go further down the rabbit hole of taking it apart and trying to understand how its working.
 

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Here are a couple of my thoughts after reading through your post several times:

- It sounds like you may be fighting against the compression stroke. Have you pulled the spark plug while trying to rotate your engine? Other comments lead me to believe that your timing chain is not properly engaged with the sprocket on the crankshaft.

- If you haven't already done it, remove your spark plug. Next rotate the engine using the breaker bar on the flywheel bolt. Observe the action of the rocker arms and ensure that both valves are opening and closing properly. Next, using a wooden dowel (or maybe a chopstick from Panda Express), insert it down the spark plug hole. Then rotate the engine and observe the position of the chopstick to determine when the engine is at top dead center (TDC) with both valves closed. Check to see if the timing mark on the cam sprocket is at the 12 o'clock pointer on the head casting. If it isn't, then your timing is not properly set and you will have to remove the timing sprocket and properly re-set the timing.

- Don't bother removing the flywheel, as it will not give you a look inside the crankcase and you can re-seat the chain onto the crankshaft sprocket without removing the side cover and flywheel (not easy, but it is possible).

Good luck and report back with your results. . . .
 

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Discussion Starter #6
Update. Back to work on the bike today and managed to get some life out of it. I took the engine head off again today to give it another shot. Once I got into things with a light, it turns out that the cam chain had indeed come off the sprocket in the crankcase. Due to this setting timing was impossible as the two sprockets were rotating independently of each other.

As TW-Brian suggested, I tried to re-seat it without opening up the crankcase. After a bit of work I managed to do so by taping a light to the frame shining down the camshaft, I slacked the chain in with plenty of wire on it to pull it back out, and using one of the long bolts from the top of the engine head I was able to maneuver the chain back onto the sprocket.

With the chain back on the sprocket, I was able to set timing and this time the upper cam sprocket rotated fine as I turned the engine through the crankcase and valve springs seemed to compress fine. With timing set, I reassembled.

After reassembly, engine sounded like it wanted to start but was struggling. I spray some starter fluid in the carb and it fired up. It lives! I let it run in idle for awhile to get the engine heated and then shut it down to run a compression test. It came in around 60, not a good number.

I still have some o-rings that I know I need to replace, but with the compression that low I'm fairly certain my next move has to be replacing the valves, replacing the piston rings, or perhaps both. For now it's nice to know that nothing is severely jammed up and that the engine can function, it just doesn't want to. I already have new sets of valves and piston rings on hand, so I'll just need to pick up a new lock washer for the engine head as I am probably gonna be chiseling my way through the current one to replace the valves and a set of a piston ring compressor and piston ring expander.

Thanks for all the suggestions so far. I made sure to snap some photos this time, so I'll try to get those up a bit later.
 

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Congratulations Mackenzie!

I am suspicious of your 60 psi compression test. I am not sure your engine would even run at such a low level. Also, what lock washer is it that you need to chisel off?

I wouldn't waste any money on a ring compressor or piston ring expander. I thought that I needed both of these but found it easier to just do it using my fingers (if you feel that you have to buy something, opt for just the ring expander).

Brian
 

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Discussion Starter #8
I kinda think my compression tester might be a off too, but I don't currently have access to another to cross check. Now that I can at least get it running, I'm thinking about taking it in for a leak down test so I can stop all the guess work as to why its compression is low.

Following the service manual for valve replacement, there is a lock washer (# 90215-06184-00) that needs to be unbent from holding the bolts in place so that the rocker arms can be removed for valve access. It's inside the engine head, behind the cam sprocket. It's the c-shaped bracket , and it has a tabs bent right up against each bolt preventing their removal. Here's a pic:

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The manual suggests replacing this washer during reassembly rather than bending the old one back and reusing it. I was having trouble trying to bend the tabs away as they are pretty much flat to the bolts. Looking online, the only suggestion I could find was to take a cold chisel to them by wedging it between the bolt and washer and hammering it to work the gap bigger until the bolts can be removed. A new washer is about $4 so I figure I'll buy one and then I don't have to worry about damaging the current washer in its removal.

As for the piston rings, I've never done a replacement so I'm only going off videos I've watched but they all urge the use of expanders and compressors to avoid damage to the rings. I'll look into it more before buying anything.

I'll include a few more pics from the work earlier, too.

Here's how the cam chain was before I got it re-seated onto that sprocket:
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Here's my piston, looking a little toasty:
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And here are my valves, also looking toasty:
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Discussion Starter #9
Another update. I called up my local mechanic this morning and they are swamped with work right now. Price for the leak down test is only $49 but the earliest they can have me in is two weeks from now. I locked down the schedule slot just in case, but for now it means that I am back to trying to figure this out by my own devices.

Since it's day time now and easier to get the engine fully warmed, I decided to re-do the compression test and try a few different things. I had to use starter fluid in the carb to get it going again but it did start up, so I already know the 60 psi reading from last night has to be wrong.

I let it run in idle for awhile and laid on the throttle for a bit to see how it was sounding, and it sounds off. There is some skipping and it just sounds like something is not sealing. Timing could still be a little off too, so I am gonna re-check that.

After its warmed, I shut off the petcock and let the engine run dry. Tried compression test again and got the 60 psi reading. That simply can't be right if it starts so I start thinking that the tester is not forming a tight enough seal. Instead of the brass fitting in my kit I decided to try a rubberized one it came with that requires physical force to maintain a tight seal. Re-testing with the rubberized fitting I get a reading of 90 psi which makes a lot more sense as to why it can start by combusting starter fluid but cannot do so with an air-fuel mix since its sub 100 but not too far off.

I follow this up with a wet test putting a bit of oil down the spark plug socket to see if it can give me an idea if it is the piston or valves that are more at fault. 125 psi! Looks like I'm gonna be installing new piston rings.
 

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Congrats on making it run again.

Based off those pics it looks like it’s burning oil. Is the piston bore shiny?

If it is I would suspect that is the cause of the low compression and oil consumption. You would need to at least have it honed and re-ring. If it were my motor I would bore one size oversize and fit a new piston.

I would not touch the valves unless you something is wrong with them. At first glance from those pics they look fine. I would consider changing the rubber valve seals while you have it all apart which will require dismantling the head.
 

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Discussion Starter #11
Thanks for the insight, jb. The bore is kinda shiny. Here's a pic (also posted above in earlier update). It's not the best pic so I will further inspect it and take more pics and measurements next time I have the engine head off.

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In terms of the valves, I am gonna hold off on them and focus on the piston for the time being. I do have new valve seals that came with the ring and gasket kit, so I will try to get those on when I eventually do take on that task.

Re-boring / honing is a subject I know very little about outside of some small mentions I've seen in forum posts and videos, so I do have a few questions. If you can answer or clarify any, it would be much appreciated.

Am I correct that if the cylinder has worn too much beyond spec that honing will not help resolve it and either re-boring it replacing it will be my only options?

If the cylinder is smooth, would there be much hope that installing the new rings I have on the stock piston would resolve the pressure leak issue?

Finally, I know for a fact that I am not equipped to re-bore the cylinder so I'd need to go to a machinist to have it done. How intensive is honing a cylinder as a DIY task in terms of specialty tools and equipment needed as well as skill? Is it something approachable by watching a few videos or is it more intensive and something I'd be better off paying a professional to handle?

Thanks again.
 

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Here are a couple of my thoughts after reading through your post several times:

- It sounds like you may be fighting against the compression stroke. Have you pulled the spark plug while trying to rotate your engine? Other comments lead me to believe that your timing chain is not properly engaged with the sprocket on the crankshaft.

- If you haven't already done it, remove your spark plug. Next rotate the engine using the breaker bar on the flywheel bolt. Observe the action of the rocker arms and ensure that both valves are opening and closing properly. Next, using a wooden dowel (or maybe a chopstick from Panda Express), insert it down the spark plug hole. Then rotate the engine and observe the position of the chopstick to determine when the engine is at top dead center (TDC) with both valves closed. Check to see if the timing mark on the cam sprocket is at the 12 o'clock pointer on the head casting. If it isn't, then your timing is not properly set and you will have to remove the timing sprocket and properly re-set the timing.

- Don't bother removing the flywheel, as it will not give you a look inside the crankcase and you can re-seat the chain onto the crankshaft sprocket without removing the side cover and flywheel (not easy, but it is possible).

Good luck and report back with your results. . . .
Sound advice (y)
 

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By the carbon tracks on the outer edge of the valves it looks like they made contact with the piston. While apart I would remove the valves (with proper tools, can be home made, no chisels please) then chuck them in a drill to see if they are bent.
 

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I checked my valve seating by just pouring oil into the head and seeing if it leaked the oil out. Mine leaked out so then I poured it into the exhaust port and it went right past the badly seated exhaust valve. The intake valve was ok but I had the valve job done at a shop. I thought that this was a quick cheap way to check the valve seating.
 

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I admire the DIY guy’s.
Yer burning oil. Maybe alota things.
Admiral showed you the C-clamp mod and valve seals are cheap. Ken had a great one for a free valve seat check. Cheapiest / easiest would be rings.

DONT remove the cylinder w/out getting a rag under the piston to catch any broken ring.
Razor blade that carbon ridge outta the cyl, then ScotchBrite/ 3m pad (yes by hand!) in a kinda criss cross pattern and reassemble .
You’ve cut a lot of corners so run whatcha got!
 

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Grinding the valves and seats by hand is not that hard.
Nothing like the satisfaction of successfully rebuilding your own machine.
 

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Thanks for the insight, jb. The bore is kinda shiny. Here's a pic (also posted above in earlier update). It's not the best pic so I will further inspect it and take more pics and measurements next time I have the engine head off.

View attachment 203579

In terms of the valves, I am gonna hold off on them and focus on the piston for the time being. I do have new valve seals that came with the ring and gasket kit, so I will try to get those on when I eventually do take on that task.

Re-boring / honing is a subject I know very little about outside of some small mentions I've seen in forum posts and videos, so I do have a few questions. If you can answer or clarify any, it would be much appreciated.

Am I correct that if the cylinder has worn too much beyond spec that honing will not help resolve it and either re-boring it replacing it will be my only options?

If the cylinder is smooth, would there be much hope that installing the new rings I have on the stock piston would resolve the pressure leak issue?

Finally, I know for a fact that I am not equipped to re-bore the cylinder so I'd need to go to a machinist to have it done. How intensive is honing a cylinder as a DIY task in terms of specialty tools and equipment needed as well as skill? Is it something approachable by watching a few videos or is it more intensive and something I'd be better off paying a professional to handle?

Thanks again.
Now that im in front of a computer that bore does look very shiny and worn. It should not be like a mirror. You are correct that if the bore is too worn for a simple hone that a bore and a bigger piston is needed. Thankfully they leave enough meat on them for 2 re-bores.

As far as putting new rings on with a worn cylinder, not worth it. They will never really seal properly and you will really end up with the same deal you have now. A good crosshatch is needed for the rings to seal and for lubrication.

As far as honing goes that can in theory be done with a hone kit and a hand drill. Personally i would leave it to a professional machine shop. The reason being is precision of the finished bore. The cross hatch should consistent and at a specific angle and the surface finish needs to be specific too, doing that is darn near impossible by hand. Even with a drill press or a basic milling machine it would never be as good as what a professional machinist could do with proper equipment. Can you do it by hand good enough to make it run better sure, but the professional job will always be better.

Same goes for boring it out. The tools are specialized and a home gamer will never be able to do nearly as good a job as a pro and the motor will never last as long before it needs to be done again. A pro can also gap the rings for you properly which needs to be done as well regardless if you re-ring or replace the piston. I actually have a machinist background and i still would leave this to someone that does engine machining professionally, its a specialized trade for sure.


One of our TW's( the one my girlfriend rides specifically) was in the same predicament as yours is in now. It was burning oil and the bore looked like a mirror. I ended up putting in a one size oversized Wiseco piston ( pn 4292M06750) in it. I had the piston fitted by a local engine shop and i did the disassembly/reassembly of the motor. The bore job and piston fitment was ~$100, money well spent in my opinion. That bike runs so much better than my other one which is stock, makes more power too. Like noticeably more power. Both bikes are setup the exact same otherwise, hers i can pull power wheelies on, mine not a chance....
 

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Judging by the pics I have to agree the valves and piston made contact. I use thinners, alcohol, meths or petrol (gas) to test the valve seal for the simple fact that it'll show very quickly if the level drops. My way is to turn the head upside down and fill the combustion chamber with said fluid and see if and where it leaks through.
If you decide to go for a re-ring, depending on the wear of the sleeve, try and find a ring set that has a chrome(not a cast ring with a molly insert) top, "scraper/Napier" second and the normal 3 piece oil ring. Reference to Napier rings: ttp://korihandbook.tenneco.com/en/section_19.htm
The honing cross hatch has to be a 30/60 degree pastern for the best seal and given that this is not a dragster that you need to hone with a torque plate you can get away by trying it yourself. Otherwise take it to the shop where you made the booking for the leak down test and ask them to hone the cylinder for you.
The head you can do yourself too, Admiral's valve compressor would be great, just remember that the valves need to be lapped if you replace them, also your mechanic could do that too. I saw a mod that makes sense to me, replace the aluminium bush on the front of the cam (gear side)with a 6005 bearing that fits the cam and head perfectly and get rid of the bushing.(I think there is a tread regarding that on the site somewhere) You need to modify/replace the "washer" with the tabs to keep the bearing in place.
Then fit the new rings and slide the barrel over the piston, hook up the timing chain (the right way :p ) fit the head and get going.
I'd replace the t/chain & guides if were to do a re bore, simply because the chain looks to be stretched a bit and the guides would also have been worn down.
 

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If you keep going...

I honed and replaced the piston and rings (stock size) on my 2015 TW with around 16,000 miles on it. It was burning oil. My piston top looked like yours and the cylinder bore was like a shiny mirror.

I used a drill and honing tool from Harbour Freight I believe. I WATCHED MANY, SEVERAL, LOTS OF YOUTUBE VIDEOS ON HOW TO HONE A CYLINDER BEFORE I TRIED IT MYSELF.

I've only put on 1,000 miles or so since the hone job as it's hasn't used a drop of oil since.

A couple of thoughts I have in pictures (again). :D

This is not a complete how to so you'll have to refer to the manual or your own experience.

Prevously shown I removed the valves and replaced the valve seals.
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Fast forward, I also cleaned the combustion chamber (and valves).
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Crosshatched the cylinder during the hone process.
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I did not use a ring instalation tool. I just spread them and slipped them over and into the proper grooves.
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The rings do have to be indexed.
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P.S. If you do take your engine apart again, based on the possibility of the timing being off, look for this. Bent Valve. I learnt from my mistakes.
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That hammer sure did a nice job cleaning the combustion chamber. 😁

Nice insights and pics.
 
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