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Discussion Starter · #1 ·
hello everyone i recently redid the piston and rings on my tw200. finally got all back together then when i went to fire it started and ran like turd for a little bit. then out of nowhere it just went dead and lost all compression.. i dont know if i messed up a valve or what to do from here .. please help where do i start ? looked up videos on how to put everything together but who knows i may have screwed it up ?? where do i go from here .....
 

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2021 TW
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Your gonna have to go back over your work.Sounds from here like valve timing or a stuck valve may be the culprit. Or a valve adjuster has backed off.If it started and ran I doubt if its rings or a gasket, but stranger things have happened.Pull the cam cover and the tappet covers and check.
You may be able to find a shop manual for nuthin. Use the search community box at the top of the page.
And welcome to the forum.
 

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My 2003 Kodiak ATV would not start one day....felt like there was zero compression, so I thought...."It's dead Jim". SIL took it apart and the timing chain was broken....replaced it, and it runs great. Not saying yours is broken, but it could be a timing issue, or as stated a valve issue.
 

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hello everyone i recently redid the piston and rings on my tw200. finally got all back together then when i went to fire it started and ran like turd for a little bit. then out of nowhere it just went dead and lost all compression.. i dont know if i messed up a valve or what to do from here .. please help where do i start ? looked up videos on how to put everything together but who knows i may have screwed it up ?? where do i go from here .....
Why did you rebuild it ? You have to fix engine damage along with what caused it !
 

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Discussion Starter · #6 ·
so what i have figured out is that where you put the timing chain gear onto cam there is a nipple with a groove on the cam. somehow the groove broke off and now the timing chain gear will not stay in place .. would i have to get a whole new cam ? or how would i fix that ?
 

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From the parts diagram it looks like a dowel pin locates the timing chain gear to the cam. You should check for damaged parts and try to figure if it sheared or spun out or an errant assembly. Or just what the cause was.
 

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the pin is there its the centering of where the bolt goes (on the cam) that broke
If your cam looks anything like mine did, then you'll need to replace it. See below. If the cam sprocket is in good shape then you won't necessarily need to replace it unless it was also damaged.
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If your cam looks anything like mine did, then you'll need to replace it. See below. If the cam sprocket is in good shape then you won't necessarily need to replace it unless it was also damaged.
View attachment 224965
My TTR225 cam now looks like this after I replaced a leaky valve seal. The cause is because I failed to tighten the bolt that holds the cam gear to the cam. All the pressure was on that pin and after a glorious few minutes of smoke-free idling and revving, I let loose.
When yours broke, did you find the missing dowel pin and chip off the cam? So far I have not found mine and not sure what to do at this point.
(sorry for the hijack)
 
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You would think the parts would go down the cam chain side and end up in the stator case somewhere. Have ya looked down in there to see if maybe the parts are on the rotor magnets?
 

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You would think the parts would go down the cam chain side and end up in the stator case somewhere. Have ya looked down in there to see if maybe the parts are on the rotor magnets?
There's a BIG, FAT hole at the bottom of the case just made special by Yamaha so small parts fall into the crank. No shit.
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Discussion Starter · #16 ·
Now that the bike is running again im looking for ways to make more torque .. looking to do a couple little ways to get more lower end.. not an expert but thinking pipe, air filter , not sure what all i can do any help would be appreciated
 

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I replaced my cam with one off a YFM250. That is a Yamaha Big Bear/Timberwolf ATV that has the same head as a TW200. The cam is an easy swap and you can replace it from the head side cover. The YFM250 cam has lobes to develop more torque at lower rpms than a TW200. I have one in my bike as do a couple others.
Do a search on this forum to read more on this mod
 

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SkiPro set me up with a complete YFM250 head and its cam duration seems to generate noticeably more low end torque. A nice improvement over both the stock TW as well as the stock TTR225 heads which all have performed well on my TW.
Other than rebuild a TW head with cam issues or bent valve I would recommend searching for a complete replacement head from one of the other Yamaha models that share the same basic head architecture... XT225, TW200, TTR225, YFM250 (and possibly TW125 & TW225 but Have no experience with those heads).
 
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