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Top end rebuild difficulty?

  • Thread starter Thread starter 80GS1000
  • Start date Start date
8

80GS1000

Guest
I'm about to rebuild the top end of my 1980 GS1000E with some new gear to make it a little quicker and to restore compression.

How hard is it to disassemble and reassemble the top end, meaning the cylinders and cylinder head, provided that the parts are on hand and all ready to go? Haven't rebuilt a GS motor (or any other) motor before.

I'd send out the head to be rebuilt with race porting, new standard sized exhaust valves, new +1mm intake valves, APE valve springs, bronze valve guides, stem seals, and a performance valve job. The head would be configured for use with the intended Web cams. It would be sent back to me fully assembled.

The block would also be sent out for boring to 1100 cc for a Wiseco piston kit.

New cam chain would be installed along with some #110 grind .395 lift Web cams.

New gaskets all around on the top end.

So is this something a novice engine builder can take on? Is this a bolt-on bolt-off deal? Any special tools needed?

Thanks,

PJ
 
you may find out the hard way why engine builders charge so much money.

other than that... it is a 10 on a 1-10 scale of difficulty
 
gs was my first engine re-build. i disassembled it and put it together completely just following the factory manual and asking a question on forums from time to time. top end i find even easier than the bottom. no tricks and no special tools.
however, some experience with tools and general engineering is needed.
if you get stuck these forums are a perfect place to get advice!
good luck
 
to replace the cam chain you need to take appart the whole engine, not just the top end. unless you have a way of cutting the old chain, attaching the new one onto it, cutting it again and connecting the new one together. factory cam chains are one piece, but some aftermarket chains can be shortened and re-attached using special tools.
 
Like anything - it's easy if you know how and gets easier everytime you do it. However, I learned the basics by pulling single cylinder 2-strokes to bits , then twins and triples, then OHV 4 strokes before tackling my first OHC job (Honda CB175). The thought of that cam chain and having to time the top end with the bottom end terrified me. I think if my first job had been a dohc 4 cylinder 4 stroke it would still be in bits and I 'd never have touched another engine. Mind, I was only about 15 - still remember my intrepidation with that old Honda (Ace little bike by the way outran our village policeman's CB200 with ease).
 
While it isn't a GS, I did a top-end rebuild on my EX250 last summer. It wasn't too difficult. It uses locknuts to adjust valve clearances as opposed to shims, don't know if that makes much of a difference.

You'll need a good torque wrench (possibly more to deal with the range of torque values - don't trust them in their bottom 20% or so is a decent rule), feeler gauges, etc. Nothing too strange.


Oh, and it's not at all a 10 on a scale of 1-10. I may have had to be more careful, but I'd rather rebuild the top end on that engine than replace the alternator on my car - it's a PITA to get to my alternator, but my point stands. Bottom ends are far more difficult than top ends, too.
 
Top ends are pretty easy just take your time & lay everything out in sequence as you take it off, for example dont mix the cam caps up make sure they go back where they came from :-D I always set the timing to tdc before starting a strip down, just to make sure its not been messed with before hand, dont turn the engine backwards tho, take digital photos of anything you are not sure of & make notes if need be :-D

basically if you are carefull & take note of the manuals its a 5 out of 10 job & gets easier every time you do it :-D

Re the bore job i'd check with the guy doing the job that he's going to torque down the barrels properly before boring, cos we dont want a bit of a chatter ruining an otherwise decent job do we lol :-D
 
Thanks for this thread.
I'm about to dive into the top end.
Is there a thread with details, pics of this kind of thing?
 
Billyboy said:
Thanks for this thread.
I'm about to dive into the top end.
Is there a thread with details, pics of this kind of thing?
Click to expand...
plenty of threads with details, but probably no pictorial as such
your service manual should be a good start, and ask here if in any doubt (and before possibly doing some damage 8-[ )
good luck
 
If it is going to be a street motor go with the 1085cc wisco street kit. Just have the valves redone no fancy porting or OS valves needed. Spend the money on a clutch basket rebuild & APE cam chain tensioner. Cam chain requires removing the crankshaft. Unless it has lots of miles it should be ok
 
Last edited:
trippivot said:
it is a 10 on a 1-10 scale of difficulty
Click to expand...

Harder than a lawnmower engine...
Easier than an airplane engine...
If you can follow directions, keep things clean, don't get in a hurry and ask questions when you need to you will do OK.
Pay attention to the little details such as ring end gaps, etc.
People have been rebuilding all kinds of engines at home for a long time.
 
Replace the cam chain guides, front and rear, while you're in there.

I don't think anyone has done a comprehensive guide, but certain steps, like getting the barrels back on, are well covered.

Take your time, read the manual, use the correct tools and it's not too tough. Be organized when you take it apart so you don;t end up with "extra" parts.

I agree on skipping the porting and oversize valves for your set up. Not really any gain there, except to empty your wallet. A bit of clean up and matching in the ports is all that's needed
 
Billyboy pix, top end tear down

Billyboy pix, top end tear down

Billyboy said:
Thanks for this thread.
I'm about to dive into the top end.
Is there a thread with details, pics of this kind of thing?
Click to expand...

Mr. 80GS1000,

Mr. Billyboy has indeed dove into his motor, and given us pictures. Check them out to get a little more familiar with what's in store for you. Thanks Mr. Billyboy!


Thank you for your indulgence,

BassCliff
 
Aren't these motors known for twisted cranks? If you're going to all the trouble of building a head & boring out the cylinders you might think about checking the crank for twist.
 
robertob said:
Aren't these motors known for twisted cranks? If you're going to all the trouble of building a head & boring out the cylinders you might think about checking the crank for twist.
Click to expand...

And Welding it.
 
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