Tearing down my tx650

[JDS1]

I have a 73 tx650 and it was in pretty rough shape when I picked it up (it was free). I striped it down and have a tc brothers hardtail on it now. The engine was seized so I was going to tear down the top end and replace / repair what it needs. I have the top of the head off and down to the cam. I've done a search here to remove the timing chain but I want to make sure I don't screw it up. It all looks really good including the chain but the master link is stuck somewhere down below. Is it possible to slip the chain without breaking it or should I just cut the chain and plan to replace it later? I'm not trying to do this on the cheap, just right.

 

[pa23driver]

i've heard that if you completely loosen the cam chain tensioner it'll leave enough slack for you to wiggle the cam shaft bearings off which you can then slip the cam out without breaking the chain... i haven't tried it, i just went ahaed and broke my chain, but others have done it

 

[CDNTX650]

how many miles? i would break it and put in new guides/chain. no point cheaping out.

 

[JDS1]

Thats actually my plan, 1st over pistons, rings, and anything else that should be replaced while I'm in here, not trying to be cheap just careful.

pa23driver - Apache(Aztec) driver? I'm a cub man myself

 

[CDNTX650]

i would do a new one. i have done (2 honda cb SOHC4's ans 2 xs's) 4 separate bikes with peen links on the cam chain and they are all still running strong.

 

[angus67]

new chain. do you really want to go back in there after all that work?
it will aways knaw at ypu when you are full throttle up a hill. just do it.

 

[pa23driver]

Thats actually my plan, 1st over pistons, rings, and anything else that should be replaced while I'm in here, not trying to be cheap just careful.

pa23driver - Apache(Aztec) driver? I'm a cub man myself

yep, the ol aztec - i love her even though she tried killing me once, turns out there's a reason they have two engines...

i got my seaplane rating in an amphib super cub, definitely a fun airplane

 

[JDS1]

I got my timing chain off and pulled my cylinders. One side had gotten water in there at some point and resulted in rust of course. I noticed at the case where it meets the cylinder there were three small stress cracks in the case itself. Is this something to worry about?

 

[xjwmx]

Do they look like this? I've been told they're just casting marks.

 

[JDS1]

Yes they do, thank you. I got all worried there that it was all cracked up. Now for my next question. One piston is rusted solid in there and I'm trying to pop the cylinder off. I'm afraid to get too heavy handed and break something. Should I just go ahead and drill or break the piston up somehow? Thanks again..........

 

[nj1639]

Good penetratimg oil and a little heat. Check the plug threads, may have been there that the water got into the cylinder?
It's how mine was, right cylinder plug stripped. I figured it being left outside on the sidestand would let the water in....needed 2 over bore to get the rust ring out.

 

[JDS1]

Yea!! A little heat and the cylinder popped right off. Once that pesky cylinder was gone everything turned over nice and smooth. If anyone can recommend a machine shop in Michigan that can bore my cylinders I'd appreciate it. I just need to determine if I need to go 2 over and make up a parts list to order. Any thoughts on anything I should be aware of would be greatly appreciated.

Ben

 

[5twins]

Leave the old chain in place until you're ready to re-assemble things. Then remove the master link and hook your new chain to the old one with a small length of tie wire. Use the old chain to pull the new one into the engine and around the crank.

The master link is peened together .....

Easiest way to remove it is to grind the pin ends flush with the plate, then it pops off easy .....

 

[JDS1]

Cleaning everything up and getting ready to take my cylinders to the machine shop to be bored. I was going to paint (epoxy paint?) most everything black and polish all the covers, sides of the case, etc. and make it look pretty. I had thought of a big bore kit but apparently no one makes a kit for the 73 tx650. If anyone knows of a big bore kit available for this engine I'd appeciate the info. Thanks......

 

[XSLeo]

You might want to take your cylinders in and get them measured first. You need to know just how far they need to go before you buy pistons.
If you bore it then get pistons, they may not work together.
Getting the cylinders bored to match the pistons is the best way. They may cleanup the bores to get past the rust, then measure. That would work.
My cylinders were worn enough to need first over, but found a set of NOS second over pistons for $49 for the pair, so I went second over instead of first.
Shop around for your pistons.
It cost me $35 per hole at the local speed shop where the local racecar drivers get work done.