GS-650 Tappet Clearances

[Guest]

Hi Guys,

We have a '81 650GX Katana.

It was bought as a complete dog, that had been sat in a barn somewhere for years and has been restored over the previous 13 months.

I'm a bit of a virgin when it comes to buckets & shims - I cut my teeth on rockers and hydraulic lifters.

When we got it, it seemed very low on power - ie try to pull away and it would try and die. Rev it and slip the clutch, and you could just about get it to move. This I put down to blocked jets (turned out only the pilot jets were blocked). On having the engine apart, I gave the shims and cams a visual check over, and all looked good (no wear apparent on either). I couldn't check the clearances at the time, as my feeler guages were out on loan. And yes, I kept the buckets/shims in the correct order when I took it apart and rebuilt it!

Fast forward to now - The engine has been rebuilt, carbs stripped and cleaned, new air filter etc etc. The top end sounds very tappity (I'm aware of the timing chain noise on these), and the power delivery is the same as when we first got it home, pre strip down.

The book says the tappet clearance should be 0.03-0.05mm.

The lowest my feeler guages will go, is 0.038mm and when I try to slide it between the back of the cam lobe and the shim, it won't even go through the gap. On all 8!

I'm just wondering if somebody, somewhere in time has re shimmed it with the wrong shims, and that was one of the reasons for the previous owner getting rid of it, as according to the title document (V5 in the UK) he only had it a few months before selling to us.

The manual says that if the clearance is too tight, it will result in loss of power... Do you think that's what is happening here?

Thanks,

James

[tkent02]

The clearances usually get tighter with wear. It's the valves that wear into the seats, not the cams or the shims wearing.

The clearance spec is .03mm to .08mm. Most of us use .10mm as the maximum. If they are under .5mm I go with a smaller shim, that way it won't get too tight before I check it again..

Do this, with the cam in the proper position for checking a pair of valves, try to spin the shim in the bucket with your finger. If it spins, you have at least some clearance, go with one size smaller shim. This should put you between .05 and .10mm. If the shim will not spin easily, there is no clearance or negative clearance, go with two sizes smaller shim. This should put you under .10mm. You could have one or two that are even worse, where two sizes smaller is still too thick, but it's a start.

Lack of maintenance is what leads most of these bikes to be parked for decades. Not adjusting the valves as they get tighter is one of the most common areas of neglect.

Too tight valves will result in burnt valves, and no power at all as it won't run with burnt valves.

[Agemax]

quite possibly. reset all the clearances to the higher end of the spec. try and get them all as close together as possible

[Nessism]

As Tom alludes, the valves tighten with mileage so it's critical to tend to the valves otherwise damage will ensue. A LOT of GS's hit the scrap heap because hack owners never adjust the valves. By waiting until running problems are experienced before tending to the valves the engine will have already suffered damage. I'm surprised to read here that the engine was "rebuilt", but you didn't check the valve clearance during the process? What's up with that?

[G0FHM]

Thanks guys!

I've had the cams out, and all but 2 are 2.8 mm, with 1x 2.75 and 1x 2.70.

The only ones that are between 0.038mm and 0.051mm (my feeler guage sizes) are 3 inlet and 1 exhaust, so it looks like I need to do some shim buying!! Any ideas as to where I can get them from? I've seen them on ebay from US sellers, but they work out to about UK£8.00 each, with extortionate postage (more than twice the shim price!). I don't mind buying from the US, if I can get a sensible postage rate, as I expect it will only be a Suzuki agent in Europe that will have them.

Secondly, I've double checked the cam timing.

I have the bottom mark on T1.4

Now, the book says to make sure arrow 1 on the exhaust cam sprocket is flush with the gasketed surface. Easy enough.

On mine, there is no exact lining the arrow up. It's either advanced so that the 1 itself is flush with the gasket surface, and the arrow is out of sight, or the arrow is slightly higher than the gasket surface. This difference equates to 1 tooth. Would I be right in wanting the arrow slightly proud of the gasket surface? I feel that with the arrow out of sight and the 1 flush with the gasket surface, will be a tooth advanced.

I've attached a pic of the cam - It's obvious this one has good clearance!

James

[tom203]

So #1 is flush/parallel with gasket surface, #2 mark is pointing at pin and #3 mark is 20 pins later ?

[tkent02]

Thanks guys!

I've had the cams out, and all but 2 are 2.8 mm, with 1x 2.75 and 1x 2.70.

The only ones that are between 0.038mm and 0.051mm (my feeler guage sizes) are 3 inlet and 1 exhaust, so it looks like I need to do some shim buying!! Any ideas as to where I can get them from? I've seen them on ebay from US sellers, but they work out to about UK£8.00 each, with extortionate postage (more than twice the shim price!). I don't mind buying from the US, if I can get a sensible postage rate, as I expect it will only be a Suzuki agent in Europe that will have them.

Secondly, I've double checked the cam timing.

I have the bottom mark on T1.4

Now, the book says to make sure arrow 1 on the exhaust cam sprocket is flush with the gasketed surface. Easy enough.

On mine, there is no exact lining the arrow up. It's either advanced so that the 1 itself is flush with the gasket surface, and the arrow is out of sight, or the arrow is slightly higher than the gasket surface. This difference equates to 1 tooth. Would I be right in wanting the arrow slightly proud of the gasket surface? I feel that with the arrow out of sight and the 1 flush with the gasket surface, will be a tooth advanced.

I've attached a pic of the cam - It's obvious this one has good clearance!

James

Sounds like you may be in England...
Try a motorcycle breaker, they should have the shims in large quantities.

[G0FHM]

Tom,

The 20 between the 2 & 3 arrows is not a problem.

The problem is that getting the 1 arrow directly flush with the gasketed face with the T mark lined up results in either the 1 arrow disapprearing inside the cam chain tunnel with the 1 flush with the gasket surface, or the arrow being just a tad over the gasket surface. I'd rather go with option 2! Either way it's 1 tooth difference.

@Nessism

The engine was stripped and checked, new rings fitted as well as new stem seals, and the valves re ground. I couldn't check the clearances at the time, as my feeler guages were out on loan, hence why I'm doing it now, before it goes out on the road.

I've done the "finger test" and all but Inlet 1 and Exhaust 3 turn freely, so I'll go down by 0.50mm on those. Inlet 1 is semi tight, and exhaust 3 is extremely tight with a 2.80mm shim. I1 has a 2.70mm, so I'm going to go 2.60mm on I1 and 2.70 or maybe even 2.65mm on E3.

Does that seem to make sense?

J

[tkent02]

Tom,

The 20 between the 2 & 3 arrows is not a problem.

The problem is that getting the 1 arrow directly flush with the gasketed face with the T mark lined up results in either the 1 arrow disapprearing inside the cam chain tunnel with the 1 flush with the gasket surface, or the arrow being just a tad over the gasket surface. I'd rather go with option 2! Either way it's 1 tooth difference.

@Nessism

The engine was stripped and checked, new rings fitted as well as new stem seals, and the valves re ground. I couldn't check the clearances at the time, as my feeler guages were out on loan, hence why I'm doing it now, before it goes out on the road.

I've done the "finger test" and all but Inlet 1 and Exhaust 3 turn freely, so I'll go down by 0.50mm on those. Inlet 1 is semi tight, and exhaust 3 is extremely tight with a 2.80mm shim. I1 has a 2.70mm, so I'm going to go 2.60mm on I1 and 2.70 or maybe even 2.65mm on E3.

Does that seem to make sense?

J

Go down by .05mm, not .5. What size is in E3 now? Other than that it sounds good.

[SVSooke]

Ask Steve for one of his handy shim spreadsheet http://www.thegsresources.com/_forum/member.php?u=484 .Email him,it's in his contact info.

[G0FHM]

E3 is currently a 2.80mm, so I'm thinking 2.70....

I1 is a 2.70mm so I'm thinking maybe 2.65mm bearing in mind it's only semi tight (ie with a bit of finger pressure it will move).

And I meant 0.05, not 0.5... Decimal places were never my strong point at school! :-)

My feeler guages only go as thin as 0.038mm, and although the shims will turn freely on the rest, the 0.038 will not slide in - Apart from I3 and E1 where it will slide in freely. 0.051 (the next size up) will not fit, so I'm assuming they are good and can be left alone?

I have found 2.65mm and 2.70mm on ebay in the US at reasonable rates, I'll try the English sources first (the guy at the bike shop down the road may have a box of them), and as a last resort I can buy the US ones. I'll even try the local Suzuki agent, but I suspect their prices will be laughable :-)

Thanks,

J

[G0FHM]

Incidentally, I've just tried the 2.70 that came out of I1 in E3, and it's still tight. I can turn the bucket via the tweezer slot with the tip of a screwdriver, but it still takes a bit of effort.

Thoughts please? I'm thinking 2.60mm... Or would you suggest thinner?

J

[Agemax]

if you are taking one shim out to try in another slot, what are you using to fill the vacant gap? DO NOT turn the engine over with no shim in the bucket!
also what "tool" are you using to remove the shims?

[G0FHM]

I'm using a proper tool, borrowed from a mate a with a GS Thou....

I'm not daft about turning it over with no shim... I popped the 2.8 from E3 in there... Turned over very gingerly to avoid any risk of piston/valve conflict!

There was none

J

[Agemax]

its not piston/valve conflict you need to worry about, its cam lobe/bucket conflict that will do the damage!