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Discussion Starter #1
On my 1994 TRX300 fourtrax 4x4, I have had this problem for the past several years with my valve rattling. I adjust the valves and still have the same problem with the valves rattling when the engine is up to temp plus it seems to be down on power. It has 485 hrs and it doesn't smoke or use oil.
After last weekends ride in the mnts of NC I decided it was time to find out exactly what was causing the valves to rattle even after constant checking the valve lash of .006".
I pulled the head cover to get a good look at the valves, cam, and rockers. Here are the pics.
 

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Looks like it was starved of oil at some point to me.
 

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I would be looking into the oil pump for sure. Betting its wore out and not pumping enough pressure to reach all the places it needs to. Could also be really clogged oil filter screens in the bottom of the engine also. Either way almost 100% oil starvation. My .02
 

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Wow, thanks for those pics!!! That is the worse I ever seen of a head & cam run without oil, ever. Rod bearings are knocking like crazy before I ever get to see them that far gone... :-(

Thats a bummer though... hope you can get a good motor back in it and keep on riding...
 

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I agree with MAC on this one. no way it would last that long if there was a oiling issue.

Ive actually seen this kindof damage quite a few times. Most the time its from the oil filter in backwords. on the 300 engine, after the oil passes through the filter it goes straight up through the top end oil line in the head.
 

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Air cooled Hondas are super tough. I had a 200x run with a broken piston. Sorry to say, that top end is toast.

Rob
 
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What was between the cover and the head? Sealant or a gasket?


Sent from my iPhone using Tapatalk
 

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that is toast , the worst I ever seen ------- amazing how they just keep going and going , you could most likely put it back together and ride it with the tap for a couple more years
 

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Discussion Starter #11
Back about 10 years ago, I took my TRX300 to a privately owned local motorcycle/ATV shop close to where I live for an oil & filter change and to also change front and rear diff fluids. Shortly after I got it back from him a noticed the valves slightly rattling. I took it back for him to adjust the valves.
For a good while after getting it back from adjusting the valves I noticed the 300 just didn't seem to run right like it was down on power. I eventually took it to a nearby Honda shop. They readjusted the valves put a new sparkplug, plug wire and coil. The Honda shop said the valves had almost 0 valve lash. Convinced the 300 was "right" after this repair a rode the 300 for several years, mainly just Deer hunting and when it snowed.
Since this time last year I have been going on a couple rides in the NC mountains and a ride in WV on the outlaw trails with a group of friends. After this past weekends ride in the NC mnts, the 300 was really rattling bad after riding it pretty hard all day. That's when I decided to tear it apart for a better look at the cam, rockers and valves. That's when I found this mess.
If I had to guess, the guy that changed the oil & filter for me, installed the filter in backwards and once he found out he messed up, he flipped the filter around right and gave it back to me.
The cam journal is so badly worn, I now know it wasn't the valves rattling, it was the cam rattling in the head. The cam was sitting in the head at such an angle, it wore the cam lobes on one side and also the rocker pads.
I have ordered a used head and head cover from a guy in Texas (ebay) and they came in today and they look great for used parts. I going to also replace the old valves, valve springs and of course the camshaft. I probably going to go ahead and replace the piston & rings with a Wiseco .50mm over sized piston and have the cylinder bored while I have the 300 torn down this far.
 

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installed the filter in backwards and once he found out he messed up, he flipped the filter around right and gave it back to me.
That's just all kinds of wrong! Man i sure hate that happened to you, i can't say how I'd handle that situation, but you'll get her back in tip top shape, just do your own service from now, and if it's over your head, your in the right place for great help, and advise!
 
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She will run like new with all those parts replaced. Probably last another 25+ years

Rob
 

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Thats quite a story! I'm glad you are fixing it back up right rather than give up and junk it like so many others do. There will always be exceptional value left in a good 300!!!
 

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Case and point why i dont trust anyone but myself to work on anything i own. Way to many storys out there like this. Just the other day on my way home from work i notice a car in the ditch totaled. I see its a young teen girl so i stopped to make sure she had help on the way and come to find out she just had a hole patched in one of her tires and the lug nuts were never tightened back up at the shop. Broke every stud clean off. There are dumb people born everyday sadly.
 

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Discussion Starter #16
You guys are right, I now plan on doing all my maintenance and repairs. This way I know its done right and if something goes wrong I've got no one to blame but myself.
This TRX300 is in too good of shape to junk just because the topend is damaged. So far I have about $700 worth of parts on order. The head, head cover & camshaft came in today. I keep updates on the rebuild.
Meanwhile hear are pics of the head and head cover I bought off ebay.
 

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Good lord! It looks brandnew! Someone put in the wrench time media blasting that for quite a while! They could have sold it as brandnew and fooled anyone lol
 

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I would at the very least spec out the oil pump and clean the screens. There will be plenty of shrapnal in there. And i would bet atleast one piece has gone through the oil pump. And thats all it takes.
 

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Discussion Starter #20
That's exactly what I said when I saw them posted for sale. I jumped right on them and bought them. Only difference is my head cover has the decompression lever and this one doesn't have that lever. No big deal to me. I think I have used it maybe 2-3 times since I bought it in '94.
Head was $215 and head cover was $65
 
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