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Time for a topend rubuild? What do I need?

  • Thread starter Thread starter UK-GT
  • Start date Start date
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UK-GT

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My 81 GS650GT (UK Spec) has started burning oil (nearly 65,000 miles) although it starts OK and still pulls well, compression is between 120psi and 125psi across all 4 cylinders (cold and warm), it does not smoke when started so I do not think it is valve guide seals, one of the plugs is sooty so what do you think, there is also a rattle from the engine (between 3k & 5k rpm under load) which is suspect is the camchain, is it time for a topend rebuild?

What do I need?? I am on a tight budget and need to keep the cost down:

New camchain - recommendations please for cheap supplier - approx ?40??
Gasket Set - recommendations please for cheap supplier - approx ?50
51mm - 177mm Cylinder Honer - approx ?25
New Piston Rings - recommendations please for cheap supplier - ?100 for a complete set
Cutting paste & Valve Lapping tool - approx ?10
Torque Wrench - already have
Piston Ring Removal tool/Compression tool set - approx ?15

I did think about fitting another engine but I can not find one in the UK, so would ?250 seem ok to do a topend rebuild myself?

Have I missed anything? Any advice and suggestions would be gratefully received.

Regards.

Andrew
 
you do realize that to replace the camchain you have to split the crankcases!

forget the piston ring tool, you dont need one.
if you are relapping the valves you should change the valve guide seals as a matter of course. buy a genuine Suzuki gasket set, complete. more expensive but far better quality and comes with all o rings and valve guide seals (i am pretty sure anyway)

splitting the cases i would replace all oil seals as well, while you are there, just to be sure.

also dont forget new oil and filter
 
I was going to try and replace the camchain by splitting it and pulling a new one through etc as I have read that is the easiest way to do it?
 
The camchain rarely wears out

More likely your tensioner needs a rebuild

If your compression is good, the valve stem seals are the likely culprit. They can be replaced without pulling the motor

I'll bet your #2 plug is sooty -you need a new fuel tap
 
Big T said:
The camchain rarely wears out

More likely your tensioner needs a rebuild

If your compression is good, the valve stem seals are the likely culprit. They can be replaced without pulling the motor

I'll bet your #2 plug is sooty -you need a new fuel tap
Click to expand...

I was going to do the tensioner at the same time, but its worth a try first.

Is 125psi OK for comression, I thought that was a bit low. Re stem seals, I thought oil would seep past them when the engine is off and then smoke on startup, but it does not do that, to be honest I am not sure where the oil is going as I have not got a leak and my mate followed me and did not see any smoke, but the oil is going somewhere as the oil level has dropped from max to slightly below min in 200miles!!

I think it is No 2 plug that is sooty, petcock rebuild ?15) or new one (?48)?

Regards.
 
UK-GT said:
I was going to try and replace the camchain by splitting it and pulling a new one through etc as I have read that is the easiest way to do it?
Click to expand...

that is not the easiest way to do it and is probably the worst method you could ever think of doing.
if you want to go that route then at least buy a proper rivet link chain (if you can still get one) but even that is frowned upon by most.
 
Last edited:
i have unknown mileage...75-80 in cyl 1-3 and 124 in cyl 4...my 850 still pulls good...it smokes and uses at least a quart a month....if you wanna go fast 2 quarts

mine clack clings and sounds like a chinaman yelling.......

you do hafta split cases to change chain as stated...id start with tensioner...which is what i need to do later today
 
Agemax said:
that is not the easiest way to do it and is probably the worst method you could ever think of doing.
if you want to go that route then at least buy a proper rivet link chain (if you can still get one) but even that is frowned upon by most.
Click to expand...

Fair enough, splitting the case it is then!!

The closest thing I have done to this is replace a valve on a lawnmower and replace a valve on a 1000cc mini, the electrics I can handle (ish) as well as the breaks etc, but I'm still wary of the engine, I can not afford to take it to the garage and I can not afford to replace it yet, so I thoght it was time to roll up my sleeves and get stuck in!!

The internet is a fantastic tool for research but sometimes the info is conflicting and you end up more confused than you started.

I think the first thing I am going to do is have a look at the camchain tensioner, then see which plug is sooting to ascertain if the petcock needs re-building.

I will take the bike out for a good run tomorrow and then take the plugs out and post a pic to see what the view is on them, what would you expect to see on them if its burning oil?

Regards

Andrew
 
Test that petcock if #2 cyl is the sooty one (second from left as you sit on bike). Plug the vacuum line at petcock end, run petcock on "PR" spot and see if sooty plug disappears. Remember to put petcock back to "ON" or "RES" when you're done testing.
Your tensioner might be frozen or improperly installed.Understand correct method of removing and reinstalling camchain tensioner.

http://members.dslextreme.com/users/storagecliff/images/engine_odds-n-ends.html#A05

Your carbs will be in way unfortunately, so lots of fun involved but anything is better than splitting cases (and finding out it was unnecessary !) Make sure you lock tensioner plunger in place before you remove it
 
UK-GT welcome to another UK GS owner.

When you get a chance put your location up and some details in your signature so pepes can see where you are and what sort of bike you have.

If you are on Facebook, post to other UK GS Owners here: UK GS Owners FB Page.

We also have a UK social group on the Forum here: GS UK Social Group.

Let us know if you are going to any shows or meets. You never know we might see you there.
 
but I'm still wary of the engine, I can not afford to take it to the garage and I can not afford to replace it yet, so I thoght it was time to roll up my sleeves and get stuck in!!
Click to expand...

I normally cheer on prospective engine rebuilders, but since you mentioned finances...

As a general rule, you will put way more money into rebuilding an engine will all the gaskets, parts, tools, etc required than you will shopping around for a new engine. Doubly true if it's your first.

I would try ruling out some of the easier stuff mentioned by others above before either doing a rebuild or sourcing another engine.
 
I don't think the engine is bad. Decent compression, burns a little oil, so what? Oil is cheap. If it isn't belching blue clouds who cares? Adjust the valves, fix the leaky petcock and the tensioner, do all of the routine maintenance, ride the snot out of it.
 
tkent02 said:
I don't think the engine is bad. Decent compression, burns a little oil, so what? Oil is cheap. If it isn't belching blue clouds who cares? Adjust the valves, fix the leaky petcock and the tensioner, do all of the routine maintenance, ride the snot out of it.
Click to expand...

I agree with tkent here. A new petcock is a better choice than a rebuild. Tensioners are cheap and easy to rebuild ( see Basscliff's site for tutorial). Check to see if it's blowing oil out the breather tube on top of the valve cover. Check to see if someone has removed the oil seperation screens in the valve cover as well. My screens were missing and when I replaced them it helped. There is on fellow on here who has over 90k on his 650g. They are a strong unit, servicable for many miles. I use about a quart in 1000 miles. No smoke. A pain to find a level place to check the oil when on a trip, but I get it done. Welcome to this site!

cg
 
I agree too. Petcock is most likely leaking down the vacuum line and into the #2 carb. When you see a lot of blue smoke and start fouling plugs, do the top end.
 
Job 1 Today: Carbs have been off and the camchain tensioner has been stripped and re-built, I did notice that their was no tension on the spring when I took it apart, it now has 1.5 turns on it, so that may be the cause of the rattle. Took me longer to get the carbs back on then to do rest!!

Job 2 Today: Rocker cover off. Measured valve/cam gap:

5 of the valves I could get a 0.04mm (smallest one I have got) gauge through but not 0.08mm
1 of the valves I could get a 0.04mm, 0.08mm and 1mm gauge through but no 1.2mm (0.04mm & 0.08mm together)
2 of the valves I could not get a 0.04mm gauge through but I could rotate the valves with my finger so they are probably about 0.02mm/0.03mm.

I have just ordered a new set of feeler gauges that go down to 0.02mm. I am not going to put the bike back together until the new gauge arrives.

I did take a shim out and measure it with my vernier caliper but its not that accurate, it looked like 2.4mm thick but it could be 2.35mm or 2.45mm!! Should I order some 2.35mm & 2.45mm shims or do you think it will be OK?

Andrew
 
while waiting for your feeler blades, buy (or borrow) a micrometer as well to measure the shims accurately. they are not that dear for a 0-25mm micrometer.

you cant really replace shims unless you know exactly what you are replacing
 
From the results i posted earlier, are they way out, would this explain burning oil?

Going to order a new micrometer as well.

Where is the best place (in the UK if possible) to get shims from so that I can get them quickly without spending a fortune on postage?

Regards.

Andrew
 
Probably cheapest to get them from Z1 in the US - they're about $6 there and ?10 here. Obviously keep an eye on the postage as that might kill it.

Or try Ebay.

Or put an ad in the wanted section once you know exactly what you want.

Did you Loctite the cam chain tensioner nut when you put it back on?
 
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