Which head gasket for 1105cc pistons?

[ChrisB]

Hello all.
Just rebuilding a Z1000A1 engine which has a 73mm Wiseco piston kit. Rather than buy (and wait for) a Wiseco one piece head gasket like the one I found when I stripped it, I'm assuming I could just use a couple of standard 1100 gaskets. Anyone like to weigh in with their experience on this one?!
Thanks
Chris.

[ADRIAN H]

Unsure if a standard gasket from the 1100cc range would work, the engines were all 1089cc - with a bore of 72.5mm.

[DeadZedDave]

You can probably "get by" using the GPz11 gaskets which are, as another member mentions, made for 72.5mm pistons but also suitable after you've had your GPz rebored !! The bore holes are just big enough but you NEED to take care to keep them positioned around the bores when you put the head on, if they shift so the edge of the metal seal is into the bore a bit, the chance is that the piston will hit it at TDC and although it probably won't do any damage, it will probably start to blow / leak compression. ALSO the outer holes for the studs where the oil feed is have a bigger hole in the GPz gasket and ALSO no copper sealing washer built in like an early Z so you risk oil leaks here. I've done this "get by" back in the day (before we had internet) when you couldn't just easily order the proper gasket! To be honest though, I think if it was me, I'd just order the proper job and be done with it !! Just one other thing, assuming this is a NEW 1105 set up (and not rebuild) you need to be careful about CARBURETOR jetting. Probably ask on the forum and also it'll depend on what carburettors and other mods you have but just keep it in mind, back in the day, there were a hell of a lot of 1105's died pretty young as a result of holed pistons !! - even Graeme Crosby on his famous 1105 high bar race bike holed a piston going up the Mountain at IOM. Best of luck....

[Philippe]

Hello Chris

take my advice: buy a new Wiseco head gasket!
Take no risks.
GrtZ
Philippe

[ChrisB]

Thanks for these responses. In answer to DeadZedDave, I'm rebuilding an engine I've bought and found the 1105 Wiseco's in. It also had high lift cams which are water dameaged so i'm building it up with a standard head, standard cams, it'll have a four into one pipe as yet unsourced (I have a crappy Marshall for now) and i'll be using a set of standard 1000a carbs with pod filters for now but may change them for CR's if I can talk myself into the expense. I'll keep a close eye on plug colour but any experience on jet sizes would be greatly appreciated.
Also, where can I buy a new rubber camchain tunnel rubber gasket/o ring anyone?
And finally (Esther), i'd assumed the pistons won't get past the top of the barrel at tdc, even at max revs and therefore I might be able to use a smaller bored head gasket without the pistons hitting it. Am I wrong here?

[Philippe]

Hi Chris

if you use the standard Z1000 head gasket the pistons will hit the gasket. I experienced it myself.
A standard Z1100 gasket might do the job but take no risk: buy a Wiseco head gasket!
You don't have to invent the wheel again, it was invented a long time ago.
GrtZ
Philippe

[ADRIAN H]

Thanks for these responses. In answer to DeadZedDave, I'm rebuilding an engine I've bought and found the 1105 Wiseco's in. It also had high lift cams which are water dameaged so i'm building it up with a standard head, standard cams, it'll have a four into one pipe as yet unsourced (I have a crappy Marshall for now) and i'll be using a set of standard 1000a carbs with pod filters for now but may change them for CR's if I can talk myself into the expense. I'll keep a close eye on plug colour but any experience on jet sizes would be greatly appreciated.
Also, where can I buy a new rubber camchain tunnel rubber gasket/o ring anyone?
And finally (Esther), i'd assumed the pistons won't get past the top of the barrel at tdc, even at max revs and therefore I might be able to use a smaller bored head gasket without the pistons hitting it. Am I wrong here?

Crown of pistons passes top of barrels. You need a WISECO head gasket for the 1105cc pistons.

[DeadZedDave]

The easy bit... rubber cam chain tunnel gasket is normally stocked by Z-Power I think but also included in good top end gasket sets. However if you used a Cometic 73mm bore head gasket you wouldn't need the rubber - its a one piece fibre head gasket but check on line for fitting instructions on line e.g. APE.
Carb jetting for a none standard / big bore motor is less straightforward. I'd suggest you try to contact the builder / previous owner but as you point out, your'e making further changes going back to the standard head and cams so jetting will likely be different again. To try to offer a start point, a STANDARD 1015 with carbs from an A3/A4 - 28mm using pod filters and a good 4 into 1 I would put in some air corrector jets (available from a forum member) and put in 112.5 main jets - maybe 115's . ALSO, I bought a bike with an 1105 motor one time and it had 125 main jets and air corrector jets with an otherwise standard motor. (I'd be inclined to start with 130's or 132.5's and work back but ideally you need a Dyno - its hard to do a "plug chop" by killing the motor when you're doing 125 MPH !)
Building none standard AND using tuning parts which may or may not be further modified by previous owners is a challenge and you should expect it wont be straightforward / take a bit of time.
Regarding head gaskets DON'T use a gasket with smaller bores than the pistons.... Connecting rods DO stretch due to physics and the weight of the moving piston. A lightweight Yoshimura 73mm piston will stretch the connecting rod approximately 1mm at 11000 RPM (and thats just a missed gear change if I was going for it back in the day) so a piston set up at deck height (zero) a rest can hit the cylinder head if you're using a 1mm gasket - not good. I'd recommend do a dry build minus the gaskets (base and head) and make sure you still have 1.5 or so clearance all round. You can use an extra base gasket or two or even an alloy spacer to get more clearance if its needed.
Getting back to carbs though WHAT KIND OF PETROL do you plan to use ?? Those jet settings back in the say were set up using 4 Star with proper LEAD in it. Modern petrol is just another challenge ! This comment equally applies to the whole build !
It sounds like all you need to go back to relatively standard 1015cc is a block and pistons - then you could use standard gaskets and jet recommendations and just build the motor without to many more questions.It'll be a lot easier to put together and set up and probably a lot easier to live with! A good 1015 properly set up can be pretty good !!

[ChrisB]

thanks for your extensive and thorough reply there.
As the saying goes "there are no stupid questions" so I have another one!
Just got my new Wiseco head gasket. It's the multi layer steel type one piece gasket.
Question; Do I use a standard camchain tunnel rubber o ring, do I use nothing in there or do I fill the groove with some silicon?
When I took this motor apart it had a one piece (cometic ?) fibre gasket and had some orange silicon in the groove.

[zed1015]

thanks for your extensive and thorough reply there.
As the saying goes "there are no stupid questions" so I have another one!
Just got my new Wiseco head gasket. It's the multi layer steel type one piece gasket.
Question; Do I use a standard camchain tunnel rubber o ring, do I use nothing in there or do I fill the groove with some silicon?
When I took this motor apart it had a one piece (cometic ?) fibre gasket and had some orange silicon in the groove.

No! Don't use the 'O' ring but still fill the groove with RTV and slice flush with the head once cured.
I use VTech gasket maker.
Also with the MLS gaskets there's no need to re-torque .

[ChrisB]

Thanks for that. I'll get some ordered. I'm assuming 600 black,625 grey, 650 red, 700 degrees copper stuff is all adequate and you just buy the fastest colour!?

[Philippe]

Hi Chris

use the black version RTV . The melting point of aluminium is 660,3 °C, I hope the cylinderhead doesn't get that hot.
I'm pleased you bought the correct gasket!
GrtZ
Philippe

[zed1015]

As Philippe i prefer the Black 600 for the 'O' ring groove, crankcase joint and cam end plugs etc.

[ChrisB]

yes Philippe, sound advice, slowly taken.
Immediately felt better as soon as i'd spent the money.
I've gone off party line and bought the red 650 as much because if I need to remove/replace it i thought i'd be able to see traces of it better.
Might even get the motor back together and running this week. Thanks as always for input.

[DeadZedDave]

Certainly the best way forward ! Please let us know how you get on !! If its not already in the motor, would you mind measuring / posting the actual bore size of the new gasket.... its always useful to have such information !!
All the best with the build.
Dave