Scooterotica

ok then, need to think out loud and ask the advice of the people on here

my motor is going back together, happy bunny

so I took a flier and guessed that with the new piston and all things being equal to the old piston, I would need extra base gaskets to gain the squish I have been advised by CamLam, and at least give me a starting point from which to work.

so with 3 gaskets, 2 paper 1 copper, I sandwiched the copper one, I got on first attempt a near ideal 1.37mm well 54 thou but converted for the youngsters here LOL

I dont like the idea of 3 base gaskets (seems a bit bodge it and scarper to me), so have ordered head gaskets, 0.65 and 1mm, had to sit down when I got the bill LOL

my question is that Im unsure of what ways the "ideal" the head is a good fit and seal with no gasket, no problems with leaking there last build, as was the bottom end, but is the mix of the 3 gaskets at the base a potential problem

Im reckoning that going to one paper base gasket and running the .65mm head gasket, I should be back in the right area for squish, but what I am unsure of is with regards to the pressures, is bottom end pressure lower? therefore 3 base gaskets not such a problem as I thought?

just trying to think about possible weak links and erradicate them.

I would try and work it so you dont use a headgasket, as this can be a weak area for thin head gaskets (flat the barrell face and head face where they meet by using say 400- 800 grit wet and dry tightly fixed to a pane of glass and use threebond on the joint) however i wouldnt use three base gaskets. Measure the thickness of the three base gaskets and see if you can get a packing plate for the base to take that measurement up (mb do them and rayspeed and others) or even a packing plate and a fibre base gasket with threebond on either side then re torque head after say 50 miles.
Others may disagree but i dont like running head gaskets.

I agree that you are better avoiding head gaskets if you can because they are likely to fail/blow at some stage in the future. You can use multiple base gaskets but you can also order alloy packer plates or thicker base gaskets from many sources, e.g. MB, AF, etc.

If ending up with a paper gasket either side of a packer (copper in your case) then I'd not fit using sealant but grease the gaskets before assembly. Provided gasket faces are flat then the paper gaskets are designed to give you the seal, rather than relying on sealant. You will also have the added benefits that the grease initially aids the gasket being able to move (finds its own best seat) and that there is a very good chance that the gaskets can be reused if you take it apart in the future. Whilst this 2nd reason might not sound like a good idea to some, sealant + paper gaskets normally rip to bits and leave cr@p all over the gasket face area when you take them apart. If you ever find yourself needing to perform a fix at a rally, e.g. take the side casing off to address a clutch problem, then you'll be thankfully of this bit of advice if you don't have a scraper or a replacement gasket.

Along the lines of the above advice, this recently helped us when we replaced a piston on the way to Euro Lambretta, having a replacement piston but no new base gasket. Thankfully, the greased paper gasket was in good condition and could be reused.

Adam

right oh, thats some info for my grey matter to ponder

wish I had asked before doing nearly 20 quid on 2 head gaskets

the greased gasket is good tip, Im removing the chaincase once top end all done, as I want to check the chain tension (was new and wondering if its stretched at all) and make sure nothing come loose since the build, so will grease the new gasket and fit that way.

thanks

A great example of not needing a head gasket is the Vespa P-range, renowned for its reliability, which uses no head gasket and only a copper base gasket (nb: other material base gaskets may also be available). Providing the sealing face of the head and barrel are in good condition then only a tiny touch of sealant (almost any) is required.

thanks, my muggy kit ran no headgasket from when I built it, it seems that its designed for that, but I was just concerned that to get the squish I would need the 3 base gaskets

so I started on my quest to learn and work out the potential issues with moving the barrel down via less base gasket and then adding a head gasket, whilst retaining the desired 1.3-1.4mm squish.

do you see any "issues" with my sandwiched base gasket setup (paper, copper, paper),

the paper gaskets are 19 thou (0.48mm) each and the copper one is 10 thou (0.254mm), both measurements are of new uncompressed gaskets.

until I try it properly Im unaware as to how much they will compress during torquing of the head and head gasket should I have to use one.

I had planned, copper and paper base gasket, then a 0.65mm head gasket.

or just the copper base gasket as I thought this the best route for the base originally, with a 1mm head gasket, however the lip in the head that locates it into the barrel is only 1.2mm, so very minimal amount of engagement twixt the two for alignment etc.

sorry for the rambling on, but with no mates that actually can help etc this forum has become my outlet, my thinking zone and pretty much my bible LOL

Tony.. Dont use multiple base gaskets unless you can help it ! .. you are just creating extra surfaces to be mated.. ie. extra possible weak points

No problems with running 1.0mm head gaskets to report here. EG current daily has no base gasketing, 1.0mm head and 23K + miles with no leaks to report. This is the round type. Isn't it just the thin ones that can be problematic?

BTW who supplies all these copper base gaskets and packers? P2, smallblockLam +?

Yanker wrote:No problems with running 1.0mm head gaskets to report here. EG current daily has no base gasketing, 1.0mm head and 23K + miles with no leaks to report. This is the round type. Isn't it just the thin ones that can be problematic?

Good call.

I use the 1mm & 1.5mm 'round' head gaskets from usual dealers...no issues. Had some 3mm head packers/gaskets made for certain applications, also machined into the head on others.....horses for courses, all depends on the requirements. I also use alloy base packers of various mm thickness, from 0.5mm through to 9mm....in various combinations......sometimes with, sometimes without 1mm paper gaskets each side....always with either three bond or Loctite (despite the mess) top and bottom for a sure-seal.

Get your port timings right, get your squish right, seal top n bottom using good gaskets and sealants.

Indeed, I too have had reliable running from motors that do use head gaskets, however, I have also had head gaskets fail. The one thing I can say is that I've never had a motor blow from the head once I've sealed a correctly flattened head and barrel gasket faces and no gasket. My attitude to head gaskets is that you can/should use them if you need to to get clearance and port heights correct (even then I'd rather use a stepped and dowelled head without gasket) but eliminating one more possible failure point is always worth doing.

Providing you have flat gasket surfaces, decent material gaskets, use a little sealant on alloy gaskets and grease on paper gaskets, fit to the corerct torque settings, etc. then just about any combination should work and prove reliable.

Good luck with it.

Adam