Spaceman Spiff

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About Spaceman Spiff

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    California
  1. Great advice... thanks. Also, does anyone know how to test the auto decompressor to be sure it is disengaging above ~800 RPM? I have heard that they can fail... I wished I knew enough to check its freedom before I put the cover back on... One thing for sure... it's a darn clever deisgn (with the anti kickback mechanism as well... great innovations) SMS (for a great diagram of the way it works, see: http://www.xr650r.us/tech/decomp.pdf )
  2. The theory I have is that a bad stem seal allows oil to run down the valve stem to the back of it, where it burns. SMS
  3. Hi all... '97 XR400 Did a little top end work, and the shop manual says something about turning the engine counterclockwise to TDC, and NEVER going clockwise. What's up with that? I wish I looked at the decompressor mechanism better... there were a couple of things going on in there that I didn't understand. One was the device on the cam that only rotates one way... and then the decompressor parts in the cover. The reason why I ask is... after getting it all back together, she runs fine... but there is more audible ticking from the valve area then I was prepared for, and I have little compression. The one odd thing that happened was the valve at the decompressor was tight when I went to adjust the valves. Not only tight, but really tight. I had to back off the valve screw a turn or two. The other valves were good. Right then, a smart guy would have said "hmm... the decompressor mechanism must not be in the right position." , but I didn't say that. I just adjusted the valve. When I started the bike, the clacking sound was frightening. Checking the valve again, that sucker was a good 3/32" loose. OK, I'm smarter now. That valve is readjusted again... much better. But still, the lack of compression and the ticking sound is a concern. I tried adding oil through the spark plug port... and see if it was rings... and it's not. The rings are good. Which brings me back to the decompressor and other mystery mechanisms. What is the purpose of moving the engine CCW, and never CW when lining everything up for installing the valve cover? What goes wrong when some damn fool doesn't follow these directions? I'm hoping the answer is there. SMS
  4. Thanks guys! At this point... I'll take the head to the shop and let those guys make the necessary determinations... Might as well do rings and all the gaskets while I'm in here. SMS
  5. Hi All... XR 400, valves. I have one INTAKE valve with crud in the back side of the valve. This seems to be telling me that the valve is partially open during the power and/or exhast strokes. Is this going to be a valve adjustment issue, or crud on the seat preventing closing of the valve? In any event, I'm guessing it's a "bad thing". I'd appreciate any help you can give me to understand this... Thanks! SMS
  6. I was wondering about how the oil system normally keeps frame oil (that is higher than the heads) from flowing slowly into the engine when it's not running. Is there a check valve or something? It seems like some oil should be able to pass the pumps... Thx, SMS
  7. Yea... I check it warmed up... stick inserted, not threaded, upright. When I ran it down (or it took a dump... it did catch me by surprise) it was below the stick. SMS
  8. Thanks for the link! Plenty of smoke when I start... less smoke when I ride. Ideas? Thx, SMS
  9. Hey all... Odd XR 400 problem... Recently, I ran my 97 400 low on oil... though it ran fine. The level had stayed stubbornly up for months... then one day it was less than adequate. But like I say, ran fine. So, I add some oil, get the level back up. I noticed that the engine started running rough as days passed... finally got tired of that and spent about a million dollars for a special tool to get to the spark plug... (which didn't work), so I called The Professor and got the plug out with a dinner fork, two feet of rope and a pair of coconut halves (don't ask :-) Anyway, the plug is oil fouled. Cool... I replace it... it runs *great*. A full day of riding... like new. So... I park it overnight, then go to play the next day. Right from the first kick... it's alredy oil fouled. Basically, it oil fouled during the night, just sitting. Now, this makes some sense... as the oil reservoir in the frame is *higher* than the plug/head. In fact, I have no idea what keeps the oil from entering the head all of the time! But clearly, oil is flowing into the cylinder while just sitting. My question(s): What prevents this from happening normally? Shouldn't the oil flow into the head all of the time? How does the XR oil system work generally? Finally, what has likely happened? Time for me to start turning wrenches... would like the benefit of someone's wisdom before I go charging in. Thx, SMS