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Discussion Starter #1
So the intake adjuster lock nut backed off and got loose in there. i fished the nut out and it is has some dings on it, but otherwise seems ok. i bought some replacement nuts and reset the valve lash...and got no results. removed the covers again doublechecked the clearances; all good. bad news is that with the covers off i can hit the starter and see no action from the rockers. i'm guessing the nut rolling around in there either broke the cam or the chain.



any suggestions for how to troubleshoot past this? i've never had a head off a motor, but i guess an old-tech motor like this is probably one of the best to give it a whirl. looking to any and all suggestions / tips. thanks



ahm
 

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Discussion Starter #2
really, no suggestions? engine was running fine, then died. no bad noises noted, but clearly something bad happened. after resetting the valve clearance and thumbing the starter, i see no movement from the rockers. i take that to mean one of a coupe bad things might have happened:



1) cam chain broken / derailed (not sure if thats possible)

2) cam itself broke.



looking for guidance on a) theories on broke, and
a process to take the head off that is likely to cause the least amount of further damage. is it as simple as removing the head/frame bolt and the 4 long bolts going through the head, then lift off (assuming chain is not still intact)?



i really don't want to take this to a dealer as i know they'll end up charging me as much to fix it as buying a new tw would cost
 

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Discussion Starter #3
[media]http://molaver.org/tw200.camchain1.jpg[/media]



[media]http://molaver.org/tw200.camchain2.jpg[/media]



so, more info to the pile. it would appear that when the valve adjusting nut spun off the adjuster, it managed to lodge itself between the upper cam gear and its keyed nut, causing mayhem. i can see that the gear's keyway is beated to death, as is is the keyed nut.



thoughts at this point? scrap the motor? is the cam gear driving the cam directly (ie, the cam itself is dicked) or...? suggestions on how to proceed?
 

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there is link to service manual download in the technical section. you should be able to find an exploded view of you engine mechanical workings.maybe you can replce cam only?
 

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Discussion Starter #5
i've got the service manuals, but they are a little light on the 'noobie, do this first' type of instruction
i've got the cam out, and it is clearly trashed. the dowel pin broke out of it, which mangled the keyway in the camchain gear. i can order the parts and probably even put them back in, but 1) how do i 'time' the chain to the new gear, and 2) any way to know if there is any valve damage? i'd hate to put it all back together and realize i broke a valve.



i just don't see the description of a process to remove the head in the service manual. am i missing it?



ahm
 

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i've got the service manuals, but they are a little light on the 'noobie, do this first' type of instruction
i've got the cam out, and it is clearly trashed. the dowel pin broke out of it, which mangled the keyway in the camchain gear. i can order the parts and probably even put them back in, but 1) how do i 'time' the chain to the new gear, and 2) any way to know if there is any valve damage? i'd hate to put it all back together and realize i broke a valve.



i just don't see the description of a process to remove the head in the service manual. am i missing it?



ahm


No way to tell about valve/piston damage without either pulling the head or installing the new cam and hoping for the best. In either case odds are some schrapnel found its way into the bottom end through the cam chain tunnel, so I'd pull the motor out of the frame, drain the oil and pull the sidecovers and give it a good solvent flush, minimum.
 

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Discussion Starter #7
managed to get the head off (just those two little allen heads plus the 'big 4' and carb boot), and inspected the valves. they all look clean - no chipped edges, piston top looks good. have pictures of the cam and cam gear - not pretty. the dowel from the cam is just gone. i wish i could just post pictures here w/o having them hosted somewhere else, but whatever. while it may come back to bite me, i'm not going to solvent flush the bottom end. i'll dump the oil, fill it with cheapo stuff, run it for 10 minutes, dump it and clean the filter, repeat. i know you have the more thorough plan, but i just don't have the inclination.



anyone know if you order the cam, the dowel shows as a separate part - must it be pressed in to some spec, or...?



ahm
 

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anyone know if you order the cam, the dowel shows as a separate part - must it be pressed in to some spec, or...?



ahm


Hi AHM,

I recently had a similar problem in the Spring when my engine ran like crap and died on me 15 miles from home. I pulled the head and found the intake nut and screw had come loose and were found in the bottom of the valve cavity. My cam and chain were OK but the intake valve and guide was broken. I bought the parts from Powers Edge :

http://www.powersedge.com/pages/parts/viewbybrand/2/Yamaha.aspx . Look up your year and you will be able to tell what parts you need. Make sure the valve adjustment screw will thread OK. My rocker arm was boogered up in the thread and almost made me have to tear the engine down again. I made a special tool to pull out the intake rocker shaft. I bought a 2ft threaded rod and bolted a block of wood to the end. I threaded the rod into the end of the shaft and had the other end with the wood block in the jaws of a vice. This let me slam the head toward the ground with the block of wood stopped by the vice (same as a slide hammer). The shaft made its way out easily and without damage. I had a machine shop install the valve guide. the parts were less than $85.00 and the machine shop was $90.00 (which I thought was kind of expensive). I recommend buying an new adjusting nut and screw since the threads are so fine they are easily damaged and don't forget a new head gasket. Check over the head carefully so you only have to place one parts order. Good Luck,



Dave
 

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Discussion Starter #9
[media]http://www.molaver.org/tw200.head.jpg[/media]

[media]http://www.molaver.org/tw200.cam.jpg[/media]



sorry to hear about your troubles. this sounds like the two possible outcomes of the nut coming off; yours, going down the intake tract, and mine bouncing off the rocker and heading for the cam/chain/gear.
 

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wow keep us updated, I am new to this bike, so I have no suggestion, other than take your time, but it sounds like you are an experienced, self proclaimed newb.



Also Photobucket does an excellent job if you need a picture host.
 

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[media]http://www.molaver.org/tw200.head.jpg[/media]

[media]http://www.molaver.org/tw200.cam.jpg[/media]



sorry to hear about your troubles. this sounds like the two possible outcomes of the nut coming off; yours, going down the intake tract, and mine bouncing off the rocker and heading for the cam/chain/gear.


Hi AHM,

Looks like you are going to need a new camshaft, dowel, and sprocket at least, assuming the collar is OK. Cost will be about $135.00 +shipping from Powers Edge. The camshaft comes out easily after you remove the holddown bracket. Position the old sprocket on the shaft and bolt it back, then give it a yank. You can look for free movement of the rockers after that. I don't think you are going to be able to test for valve movement until you install your new parts and can turn the sprocket by hand. Check for thread damage at the bottom of the rocker. Once the adjuster bolt falls out the rocker will be banging on the top of the valve assy. Come to think of it, something would have had to jam a rocker so badly that it totally ripped out the dowel. That is a lot of force and worth taking a careful check of the condition of the rockers and valves/guides. I'll bet your dowel is at the bottom of the case. You should really pull the left case after you drain the oil and find it. It did not just vaporize. I would guess that a new dowel will just press into the sprocket with a vise or a C clamp.

Best,

Dave
 

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Discussion Starter #12
yep, the cam, dowel, sprocket, and collar are all on order. hoping they get here today, but we'll see. the AMA discount at bikebandit almost negated the 'expedited' shipping. the rockers themselves seem ok; while the nut backed off, the threaded adjuster did not come out of the rocker (by some miracle), so no damage to those parts.



you're right about finding the dowel...dangit. thats the one piece of shrapnel that scares me - could get lodged anywhere.... i'll filter out the oil as i drain it and hope its in there. what do you mean about taking off the 'left case'? is that the cover that came off when replaced the front sprocket / can it be done with the engine in the frame?



thanks for the help!



ahm
 

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yep, the cam, dowel, sprocket, and collar are all on order. hoping they get here today, but we'll see. the AMA discount at bikebandit almost negated the 'expedited' shipping. the rockers themselves seem ok; while the nut backed off, the threaded adjuster did not come out of the rocker (by some miracle), so no damage to those parts.



you're right about finding the dowel...dangit. thats the one piece of shrapnel that scares me - could get lodged anywhere.... i'll filter out the oil as i drain it and hope its in there. what do you mean about taking off the 'left case'? is that the cover that came off when replaced the front sprocket / can it be done with the engine in the frame?



thanks for the help!



ahm


Hi AHM,

By left case I meant the left side lower cover- the one that you had to take off to replace the front sprocket. The dowel is probably sitting in the bottom and will not float out when you drain the oil. You don't have to take the engine out to get the lower cover off as you know already. You will have a much easier time of getting the chain and sprocket back into place with that cover off.



There are 3 critical things you must be aware of when you put this all back together. The plastic cam chain guides need to be in their receiving holes when the head is inserted on. I did not have the lower case off so I could not directly look at the bottoms of the guides. The next thing is the critical alignment of the cam sprocket with its mark at the top and the crankshaft timing mark at TDC. The piston must be at the top of its travel with the crankshaft mark lining up with the last mark on the on the right showing up in the lower case inspection hole. The camshaft sprocket will need to be pointing up with the correct rotation having both rockers able to tap with their clearances on the valves. The cam chain needs to have no slack on the left side (towards the front of the bike). [I had noticed the position of the timing marks before I disassembled the sprocket and the marks, it seemed to me, did not line up exactly. When I reinstalled the chain they did and the engine runs better than new.] Lastly, the chain tensioner needs to be installed correctly. The newer bikes have an automatic tensioning which I did not understand at first. Under the tensioner cover is a slotted rod. You take a screw driver and turn the rod counterclock-wise to retract the tensioner as you are bolting the tensioner into place. When you release the rod it is forced clockwise by the spring and puts a constant pressure on the rear cam chain guide. When the chain stretches the spring keeps the same pressure on the guide. If the tensioner is not installed correctly the engine will start but won't run or idle (don't ask me how I know). Hope this helps.



Dave
 

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Discussion Starter #14
Dave - just wanted to say thank you for all the help. I finally made the time to attempt the repair and have come up short
The damage appears to be more significant than I first thought. I replaced all the parts, made sure to take care of the cam chain tensioner (weirdly, mine was reverse from yours - clockwise retracted it), lined up the cam gear, etc. It wouldn't start so I pulled the cam gear cover to watch it when I hit the starter..and discovered it isn't rotating in time with the crank. It will spin a little and stop (while the starter is cranking), then start moving again. I only 'bumped' the starter twice, so hopefully I haven't done any more damage, but I'm guessing the cam chain gear on the crank is trashed, which may or may not mean the crank itself is trashed (haven't looked at the diagrams yet). I haven't decided if I have the heart to try and rebuild it (never taken on a project like that) or try and find an engine to 'drop in'. Sad




ahm
 

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>>>I haven't decided if I have the heart to try and rebuild it (never taken on a project like that) or try and find an engine to 'drop in'. Sad



Yeh it is sad, cause the TW is such a lovable little bike but bear up it's gonna be OK. Just one of those things we have to work thru. To put it in perspective...I've had a similar thing happen to a fresh rebuilt $20,000 airplane motor. I survived that. Just figure out the best thing to do and "git after it". It'll be history before you know it.
 

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Hi AHM,

Sorry for your extra problems. I have experienced that before on my vehicles- just a downer. I can almost guarantee taking it to a shop is going to cost you almost the value of the bike (or would seem like it). Since riding season is almost over (depending on where you live) this might make a good Fall/Winter project. You can order or download the Service manual and you have the Yamaha or parts suppliers parts listing. (will resend the links if you need them). You are going to have to do a bit more detective work to find out how far the damage goes. Hopefully it stops at the crankshaft gear for the cam chain. You seem to have enough moxie and skill to work with the upper section of the engine- I don't see any reason to stop now. Reminds me of when I lived in Santa Clara, CA.. My housemate pulled his VW Bug engine and worked on it on the dining room table (It was a sturdy table I made out of redwood planks).

Good Luck,

Dave
 

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Hey all, just wanted to add my two cents in and share some of the pain, since I will soon be going through the same process...



My intake adjuster backed out while riding (again). It also sheared in half this time. I don't know which happened first. Both times, it was triggered by over-revving the engine. The first time was a missed shift, this time was the back tire losing traction on dirt. It wasn't a drastic over-rev by any means... The wheels just kicked out for a second before I could get off the gas to get it back under control. It was a new adjuster and lock-nut (less than 500 miles since the last one). I managed to find half of the adjuster screw behind the intake valve. Unfortunately, the other half and the locknut is no-where to be seen. Fishing with a magnet didn't come up with anything either.



I assume it's somewhere else in the head that I can't see, or it's traveled down the timing chain channel and is in the crank case somewhere.



The plan is to drain the oil, pull the left side cover and go fishing. If that doesn't work, pull the timing chain cover. If no luck there, pull the entire head. If that doesn't uncover the little beastie, I'll figure out something else.



Assuming I find it and don't have to go through as much as pain as is in the rest of this thread... what do I do about the valve adjuster backing out? This is the second time and is pretty critical, IMO. I can't trust the bike till I can figure something out. Do I locktite the frigging thing and just replace it every time I do an adjustment? Or replace the rocker arm in hopes that the threads in the arm are the issue?



I'll post up progress and fishing expiditions as I go. Any objections to continuing this thread (since Ahm and I are pretty much doing the same thing, and probably at the same level of mechanical experience), or should I make a new one?
 

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Hi Smthng,

Just post here. Sorry for your problems. I found the other parts of the adjuster and nut in the exhaust side of the head. You may have valve damage like I did (hope not) or thread damage on the bottom side of the rocker from beating on the top of the valve. I would do a compression test before you run the engine to make sure you don't have any other damage.



I just got back from a 65 mile ride and the thought on my mind was a valve clearance check is needed soon- one blown engine is enough. My suggestion would be to use a drop of Lock-Tite (red or blue) on the screw and nut on the rocker. I hadn't planned on it myself, but will be doing it myself now that it seems to be going around.



Dave
 

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Just post here. Sorry for your problems. I found the other parts of the adjuster and nut in the exhaust side of the head. You may have valve damage like I did (hope not) or thread damage on the bottom side of the rocker from beating on the top of the valve. I would do a compression test before you run the engine to make sure you don't have any other damage.


I fished around in both valve sides of the head with just about every magnetic and pick-type tool I could find and came up with nothing, so I pulled the head off yesterday. I don't know where that missing part of the adjuster screw and locknut were hiding, but they fell out when I turned the head over. Luckily, that means nothing fell into the crankcase. The piston looks good, with the exception of a little bit of carbon deposit. The valves also look fine to me, but I don't really know enough to say for sure. I can tell that there has never been any valve to piston contact and that the cylinder walls look good.
I assume the rocker arm threads are all bashed up... it was difficult to get the adjuster in last time this happened. I rode almost 30 miles after it happened this time, so I'm sure it's completely toasted now.



I just took the whole head assembly to the local shop to have them replace the intake rocker arm and check the valves. I'd rather have a new arm and be sure that's not the issue than to go through this again. Oh, I ordered a handful of gaskets and bolts too... I know some of the stuff won't seal right without it and I might as well replace a few rusty bits while I'm at it. Hopefully, I'll have everything back by the middle of next week.



Here's the original culprit:





Here's the headless TeeDub...





Sorry, that's all the pictures I got. I only had the cell phone camera, so they kinda suck.
 

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Discussion Starter #20
sorry to hear about your misfortune smthng - it was no fun at all! i am going to use a drop of locktite from now on on that adjuster and another on the nut.



so i 'won' / bought an '88 motor (kicker and all ) on ebay...and i realized i'm not 100% positive the motors are REALLY the same throughout the years (at least up to my '04). can anyone verify they really are identical (other than the kicker-related parts) or not? will it really bolt in after swapping over the carb/cdi, etc?



for $290 shipped, i had to give it a shot. assuming it works, i'll feel a lot more confident tearing down the old motor and trying to fix it. i sure hope the '88 motor is actually good - will be quite dissapointing to go through the process of swapping it only to find out its not functional... oh well, no guts, no glory. i guess the worst case is that i got all the kicker components and can swap them onto the '04 motor (assuming it can be resuscitated). i sure hope to have the little beastie out in the snow again this winter!
 
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