Replacing GS1000 cylinder head question

[Jackbob]

Hi,

I am having a spare GS1000 head restored currently (new valve guides, light decking, lap valves etc) and plan to install it on my 1978 GS1000 cylinder block.

The original head on the engine was standard fitted with 26mm VM carbs. The new head is also standard but later model 8V (Aust spec.) GS1000S i believe and factory fitted with what previous postings have led me to believe are 30mm+ VM carbs (IE not CV carbs) and definitely physically larger than VM26mm and VM28mm both of which i have compared.
It has larger inlet ports (around 33mm diameter), and i believe slightly different cams/timing.
It also has the extra bolt hole in front of the cam chain tunnel, whereas the original does not.

I have 3 Questions -

Does the extra bolt matter? (it wont be utilized as the current block has no extra hole).

Does any one have a listing of the std jet sizes for the VM30? The main jets in my bank are 105's. I have looked on the carb thread but unable to find.

The cam sprockets on the original head have a teflon rubbing/guide strip on each side of the sprocket whereas the larger head cams do not. Is this normal?

Thanks.

[rapidray]

Can you post a pic of the "new" head? Thanks, Ray.

[Jackbob]

Photo

Hi Rapid Ray,

I tried to upload a photo - the server directed me back to another thread i posted back in September - this has photos and some very good answers to my questions basically, plus a photo of a head like mine.

The thread title was "GS1000S Cam shaft + carbs"

Not sure how to link the thread sorry. The head is at the engine shop now anyway.

Sorry to waste your time i should have looked.

Thanks

[tkent02]

Not sure how to link the thread sorry.
Thanks

http://www.thegsresources.com/_forum/showthread.php?t=123745&highlight=GS1000S+Cam+shaft+carbs

[SqDancerLynn1]

The extra bolt at the cam tunnel & larger ports, id's it as a 1980 cyl head - USA would have CV carbs-BS 34. . If it was fitted with VM carbs it would be aftermarker install. Euro could be different ????

[psyguy]

the extra bolt was added as that area was prone to leaking
i'd say you'd be all right without it as it is not essential, just an upgrade

for the teflon thingies... maybe look up the parts diagrams at www.alpha-sports.com

i have a spare set of cv 34bs carbs, if you want to try them on

[Jackbob]

Thanks for the feedback chaps.

I have been advised that its a 1980 head with the larger ports/extra bolt hole and locally supplied new with 30mm VM slide carbs. The link kindly provided by Tkent shows a pic of my carbs and the 80 head like mine.

I will be installing these when the cylinder head is ready in a week or two + hope to post some pics later + advise how it goes (hopefully much better).

FYI Initially I was worried the bigger carbs might not physically fit under the tank, however my bike has a later model 80 tank fitted to it anyway so not a problem. The main difference in overall height of the carbs is below centerline so to speak.

Maybe catch up this weekend Psyguy? I will have to come along on my standby bike though.

Cheers.Jack
GS1000 1978

[psyguy]

Maybe catch up this weekend Psyguy? I will have to come along on my standby bike though.

yeah, would be good. keep an eye on KB site!

[Big Jay]

Hi,

I am having a spare GS1000 head restored currently (new valve guides, light decking, lap valves etc) and plan to install it on my 1978 GS1000 cylinder block.

If you are replacing the valve guides, you can not just lap the valves. You will need to have the seats remachined.

Jay

[Jackbob]

Quote - If you are replacing the valve guides, you can not just lap the valves. You will need to have the seats remachined.

Jay
__________________
Speed Merchant

http://www.gszone.biz

************************************************** *****
Thanks Jay-

I am having the head remanufactured by an engine rebuider with a very good reputation - both bike and V8's etc (they have built some post classic GS/GSX/CB/Z race engines for example) - yes they mentioned this would be required...
They are also going to set up the valve clearances using existing shims (by grinding the seat inserts to suit). This is going to cost me a couple of hours labour but saves mucking around with shims later.
Needless to say - i am not looking forward to the bill.

The reason they are replacing the valve guides is that one was broken off where it protrudes into the port - god knows how. They reckoned they may as well replace the lot (using specially made ones ex USA and cheaper/better than OEM apparently. I am happy to get this done as the bike is a keeper. Valves + springs well within spec so no need to replace them.
Jack.

[Big Jay]

Quote - If you are replacing the valve guides, you can not just lap the valves. You will need to have the seats remachined.

Jay
__________________
Speed Merchant

http://www.gszone.biz

************************************************** *****

They are also going to set up the valve clearances using existing shims (by grinding the seat inserts to suit). This is going to cost me a couple of hours labour but saves mucking around with shims later.
Needless to say - i am not looking forward to the bill.

Sounds like a huge waste of time as new valve jobs usually tighten up and require reshimming after a few thousand miles.

Jay

[Jackbob]

Ok Big Jay - but why is it a waste of time? The valves need to be set anyway and i doubt the existing shims i have will be correct.

I appreciate what you say about the clearances closing up gradually - do you think i should ask them to set them at the max clearance or a thou or two more even?

I am not a mechanic by any means but what the shop said sounds feasible, and it was their suggestion not mine. I did wonder whether setting the valve clearances on the bench by grinding the valve stem ends or cutting the seats or whatever they do (head off engine but camshaft caps torqued down) would produce the same clearance when the head is bolted to the block - but why should it change if the head is correctly torqued down etc?
I will check the clearances again of course after it is back on the engine. If nothing else it should be in the ballpark - and i have access to a lapping machine at work should the shims require a tweak later.

Cheers

Cheers.

[psyguy]

do you think i should ask them to set them at the max clearance?

if that bike is a keeper, thats what id do, definitely!
and i would go for the absolute max clearance - using the thickest shims available (2.8mm i think)

i'm doing it next time on my gs as my shims are down to 2.3mm and they dont go much thinner

there is however a limit on how much valve stem you can grind off as the spring keeper starts getting in the way (from memory 0.4mm is the max you can take off) - so it all depends on how worn the seats/vavles are on that particular head

[Jackbob]

if that bike is a keeper, thats what id do, definitely!
and i would go for the absolute max clearance - using the thickest shims available (2.8mm i think)

i'm doing it next time on my gs as my shims are down to 2.3mm and they dont go much thinner

there is however a limit on how much valve stem you can grind off as the spring keeper starts getting in the way (from memory 0.4mm is the max you can take off) - so it all depends on how worn the seats/vavles are on that particular head

Thanks Psyguy - this is a great suggestion - i have a good collection of 270-280 shims, some new at home. It would be a good opportunity to add mileage so to speak. I hadnt thought of doing this. They wont be starting the work for a week or so anyway. Most of the shims i had on the valves were in the 255-275 range. Thanks, Jack.

[hampshirehog]

Some of the 79s (VM carbs) had the extra bolt in the head in Europe. That extra bolt just gives a bit of extra security against oil leaks from the camchain tunnel - I've swapped stuff around with / without and it's been ok.

Your standard carb specs are: Mikuni VM30SS; pilot jet #20; needle jet O-7; main jet #97.5