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Head Milling Question

J

johnod

Forum Mentor
Past Site Supporter
Am rebuilding top end, GS1000S, and have found some head pitting.
The machinist has suggested surfacing/milling the head, it is mainly pitting not warpage.
Is there any reason this can't be done, as I see no mention of it in the manual.


If it can be done, how much can safely be removed, and is there then any need to make changes to valve train geometry, such as valve stem length etc.?


Thanks
 
It can be done.
As long as minimal amount is removed, nothing else needs to be done
You could degree the cams to be sure

I'm sure Greg T had some experience in this
 
johnod said:
Am rebuilding top end, GS1000S, and have found some head pitting.
The machinist has suggested surfacing/milling the head, it is mainly pitting not warpage.
Is there any reason this can't be done, as I see no mention of it in the manual.


If it can be done, how much can safely be removed, and is there then any need to make changes to valve train geometry, such as valve stem length etc.?


Thanks
Click to expand...


i had .006" skimmed of my head mainly due to pitting as I was going to use the muttilayered stainless steel head gasket.
and whilst I was there I put in new piston rings and I gave the valves a quick lap in and renewed the valve stem oil seals with Viton seals and re- shimmed the valve clearances . One thing to note is do not attempt to rotate the engine when there is no shim in the buckets.
you could give renewing the piston rings a miss if yours are ok
But I would recommend getting Oem Suzuki gaskets and not copy's though, not forgetting you will need a cylinder base gasket as the seal will / have broken and renew the tear drop orings
The was no problem with assembly regarding your question other than the valve timing mark may not precisely line up this is due to the head being skimmed. It is obvious if you are a tooth out though.
 
Last edited:
fastbysuzuki said:
i had .006" skimmed of my head mainly due to pitting as I was going to use the muttilayered stainless steel head gasket.
and whilst I was there I put in new piston rings and I gave the valves a quick lap in and renewed the valve stem oil seals with Viton seals and re- shimmed the valve clearances . One thing to note is do not attempt to rotate the engine when there is no shim in the buckets.
you could give renewing the piston rings a miss if yours are ok
But I would recommend getting Oem Suzuki gaskets and not copy's though, not forgetting you will need a cylinder base gasket as the seal will / have broken and renew the tear drop orings
The was no problem with assembly regarding your question other than the valve timing mark may not precisely line up this is due to the head being skimmed. It is obvious if you are a tooth out though.
Click to expand...

What's the multi layered head gasket, I've ordered a stock Suzi part number? The rest I'm doing already. Thanks.
 
The older style head gasket was made out of an partly flexible compound the new style gasket is a multilayered steel gasket there is no need to put on any gasket sealer on that gasket it has an very thin layer coated on the surfaces which activates under heat.
The new head gasket should be the steel one unless the dealer you have ordered from has old stock in which case I personally ask for it to be changed for the new steel one.
one other thing is you do not use the oring that goes around the cam chain tunnel when using the steel gasket
 
The multi layer gasket appears to be the current OEM Suzuki replacement. It'll almost certainly be the type made for the late head with an extra stud in the front of the camchain tunnel. If your engine doesn't have this, it doesn't matter. use the gasket anyway.

Less than .010in off the head would be perfectly fine for a street motor using stock cam timing marks. It'll be a little off but you'll never notice.
More than that and I'd dial the cams.
 
GregT said:
The multi layer gasket appears to be the current OEM Suzuki replacement. It'll almost certainly be the type made for the late head with an extra stud in the front of the camchain tunnel. If your engine doesn't have this, it doesn't matter. use the gasket anyway.

Less than .010in off the head would be perfectly fine for a street motor using stock cam timing marks. It'll be a little off but you'll never notice.
More than that and I'd dial the cams.
Click to expand...

Thanks, don't know anything about dialing cams, is that in the manual?
It's night here, and it's in the garage.
 
johnod said:
Thanks, don't know anything about dialing cams, is that in the manual?
It's night here, and it's in the garage.
Click to expand...

Not in the manual. Several tutorials on line. I wouldn't bother if you're just having a very light skim done on the head.
 
GregT said:
Not in the manual. Several tutorials on line. I wouldn't bother if you're just having a very light skim done on the head.
Click to expand...

At this time it's just an estimate, but, 10 - 15 thou.

That a problem?
 
No.........It's going to retard the timing fractionally. Only a dyno will be able to tell the difference.
 
It's not necessary to remove all the pitting, just that around the critical sealing areas. The deepest pitting typically occurs in the vicinity of the stud holes because crud falls down. You don't need to remove all the pitting there and trying to do so won't add value to the process.
 
Nessism said:
It's not necessary to remove all the pitting, just that around the critical sealing areas. The deepest pitting typically occurs in the vicinity of the stud holes because crud falls down. You don't need to remove all the pitting there and trying to do so won't add value to the process.
Click to expand...


Frankly I was wondering what caused it.
 
When I went through my engine this past summer, the machinist took 0.002" off the top of the cylinder block and 0.009" off the head, for a total of 0.011". I did not take any measurements regarding cam timing, valve-to-piston clearance or anything like that, I just put the engine together. Could not tell anything different on how the engine ran, so I have to assume one of two things: 1. eleven thousandths less material does not really matter or 2. I got extremely lucky.

I agree that valve timing will be retarded just a bit. One of these days, I will take some measurements and do the math to see how many degrees.

.
 
Steve said:
When I went through my engine this past summer, the machinist took 0.002" off the top of the cylinder block and 0.009" off the head, for a total of 0.011". I did not take any measurements regarding cam timing, valve-to-piston clearance or anything like that, I just put the engine together. Could not tell anything different on how the engine ran, so I have to assume one of two things: 1. eleven thousandths less material does not really matter or 2. I got extremely lucky.

I agree that valve timing will be retarded just a bit. One of these days, I will take some measurements and do the math to see how many degrees.

.
Click to expand...

Camchain stretch has a bigger effect....
 
That's what I was suspecting. There's just something inside me that wants to know how many tenths of a degree the timing might be been retarded.

.
 
Nessism said:
It's not necessary to remove all the pitting, just that around the critical sealing areas. The deepest pitting typically occurs in the vicinity of the stud holes because crud falls down. You don't need to remove all the pitting there and trying to do so won't add value to the process.
Click to expand...

Yep. Glad to see someone else noticed this. On liquid cooled engines, you have all sorts of coolant passages to worry about, but on a GS head, all you need to worry about is the sealing around each cylinder, the four oil passages at the corners, and of course the tunnel in the middle. The pitting can get pretty deep in the other areas, but you don't really need to worry about it at all.

Also, with the newer Suzuki head gaskets you don't need the big square o-ring around the middle tunnel any more. Just leave it out and save yourself the $12.

I've degreed camshafts on a built-up KZ engine with aftermarket camshafts. The process is fiddly but fairly straightforward in theory.

You might have to dig to find a machine shop that will do a proper job of slotting the sprockets (we had a bit of trouble with this... not something you should just let Skippy the intern take a whack at with a Dremel). You've also just added another potential point of failure, so you have to make VERY sure the screws holding the sprockets in place a properly torqued with the proper thread locker, and re-check with every valve check.

We also learned, after an embarrassingly extended period of mathematical confusion, that there are two kinds of degree wheels, 180 degree and 360 degree. We had one kind, but the instructions with the camshafts assumed the other kind. Took us much longer to sort that out than it should have...

Overall, the difference a skim cut or two would make is very small. Plus, I'm not sure we have exact data on what the timing should be for some stock GS engines.
 
Last edited:
bwringer said:
..., I'm not sure we have exact data on what the timing should be for some stock GS engines.
Click to expand...
Could it be as simple as looking at the specs in the manual? :-k

Yeah, it won't be as accurate as actually measuring what's there, but it should be close.
dunno.gif


Just as an example, here is what I got using Web Cams calculator for my 850:



Cam Calculations - Lobe Center / Duration
Overlap: 64.00 degrees
Intake Duration: 276.00 degrees
Exhaust Duration: 272.00 degrees
Intake Installed Centerline of 100.00 degrees ATDC.
Exhaust Installed Centerline of 110.00 degrees BTDC.


The '79 850 had different timing, here are its numbers:
Cam Calculations - Lobe Center / Duration
Overlap: 54.00 degrees
Intake Duration: 276.00 degrees
Exhaust Duration: 272.00 degrees
Intake Installed Centerline of 110.00 degrees ATDC.
Exhaust Installed Centerline of 110.00 degrees BTDC.

I have not ridden a '79 850 to compare the powerband, but supposedly, the 10? advancing of the intake carb should make better low-end torque.

.
 
Cool, I had absolutely no idea the OEM specs would be in the manuals!
 
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