i have my r100gs in bits and the gearbox out now and want to get the engine overhauled for an overland trip. i want to do the valves and would like to have big end shell's and timing chain checked out and maybe new piston rings. is it all necessary though or am i going over the top to try and get it perfect for the trip? my bikes got 40k on the clock and it runs ok, not very tight sounding compared to my friends though.
engine rebuild?
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If you get it done 100% then you won't be worrying about it in the middle of nowhere, aka inside the M25.
Just my £0.02
Just my £0.02
Sylvester
Registered user
Sounds like you are tighter than your friends bike though. I'd measure all the parts up first to see how much they are worn. Sound is not a good measure of mechanical tolerance. Then let the spending begin.
Buy a compression tester before you do anything else 
40k miles = exhaust valves and timing chain kit, check oil pump for excessive wear.
Valve heads DO snap off over 40k miles damhik
Then look at your shells and crank for scoring, if none leave well alone.
Be very careful putting crank oil seals in as it's possible to move front bearing
Nicasil barrels are good for 100,000, piston rings ain't
Pushrod tubes, replace with stainless steel if any doubt as they will Suddenly corrode away, seemingly overnight
Valve heads DO snap off over 40k miles damhik
Then look at your shells and crank for scoring, if none leave well alone.
Be very careful putting crank oil seals in as it's possible to move front bearing
Nicasil barrels are good for 100,000, piston rings ain't
Pushrod tubes, replace with stainless steel if any doubt as they will Suddenly corrode away, seemingly overnight
thats good advice. i've had the heads off today the exhaust valves look as if they're on on the way so i'm replacing those. will look at the chain tomorrow. is a new chain enough normally fine or is it necessary to replace the tensioner and other bits too? the barrels look sweet so i'm thinking i'll leave the rest of the engine undisturbed. don't know how to do the oil pump but will look in my clymer. hopefully i wont have to take the barrels and pistons off..
thanks
thanks
You will have to replace the exhaust valve guides as well. Its wear in the guides that leads to valve head failure as the valve heads don't seat properly due to the 'slop'.
What are the exhaust stubs like ?
If the threads are on the way out consider getting bronze threaded sleeves fitted (Motobins did my R80RT for me when the guides were being replaced).
Once you start . . .
Bob.
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