so I have a pretty decent head for an xt 350. I have tried to sell it on ebay like three times and am giving up on selling it. I have recently noticed that my valve seals are leaking on my running xt. (smokes a little at start-up only). also I'm concerned that with 9,000 on the ODO, I probably need to go ahead and throw a timing chain and tensioner on it too... I also, to add to the fun, have a bad base gasket on the cylinder... see where I'm headed.. time to tear the top end down and rebuild I think.

Sooo now to get to my original question. since I have a spear head I was thinking I might be able to completely rebuild this head and have it ready to do a direct swap. My problem is that I don't have the original cam caps. XTBuck told me it is a very bad idea to replace cam caps from different heads because they are line bored. Firs,t is this true? second if it is true how big of a deal is it. Also since I have a head with matching caps, would I be smarter to just collect my parts and wait for winter and just plan on the old beast being down for a month.

Next question is, has anyone done a polish job on the ports on this bike? I have all the tools to do one and just thought maybe it might help the air flow to polish the intake and exhaust ports? or would I be wasting my time?

also if any of you xt guys are interested I have a few xt parts I'd like to move. exhaust, forks with triple clamps, caliper, passenger pegs, engine case halves, misc internal case parts, rear undertail/inner fender, red plastic front rotor guard. not looking to get rich make me a reasonable offer, I just wanna get rid of them to fund my rebuild and "hop-up", stator and magneto

You can not swap the caps. They are line bored as XTBuck said. The cam to cap clearance will be off. If you are lucky, the cams would just be loose and slowly destroy your head. If you were unlucky, they would be tight, and destroy your head in a few min.
This is why tou can only buy a complete head assy from Yamaha.

In the bright side, replacing the valve seals and base gasket are not that hard. If you don't want to mess with the seals yourself, buy a casket kit and take the head and seals to any motorcycle shop  It should only take them about a half an hour. once you have the head off, the base gasket is a snap.

I have built many top ends, I've just never been in a situation where I want using all the original parts. So I'll just pile up my parts and do it all at once. Next question, is there any benefits to running no base gasket to increase compression? And what about porting? Are these worth doing

you can clean  up the ports but doing any oversizing with stock exh and air box is kind of pointless.  what i would do is knock down the weld some in the y-pipe as the weld restricts the exh a fair amount.

i have porting on mine but i also have cams, intake and exh mods on mine.

my plan was to run straight cone filters on the carbs eventually, and I was going to order exhaust this week. I will re-jet as needed as soon as I figure out this stupid carb setup! where do i get aftermarket cams?

You cannot just buy a set of cams.   I sent a spare set to webcams to have them built for more midrange. I also have stainless intake and exh valves with titanium springs and retainers.  Talk about moving the redline up.  Now can bounce the tac needle off the bottom of the gauge with no valve float.

Hey Maim, what inspired you to put  so much work into an xt350 motor?  I have done a lot of work on old Porsche and VW engines, so can appreciate the passion, just wondering if there was something cool about the xt?  This is my first bike in a long time, am digin' playing with it.

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Seems you already found the cool factor . Who cares what anyone else thinks ...