C90Club.co.uk

Concerning a 110cc Chinese barrel - I think I am right that this is a 52.4mm bore. Happy to be corrected if I'm wrong! If so does this mean that the head gasket should be...er...52mm?

Also, Is a copper head gasket considered preferable and, if so, is there a required thickness or is it safe to further assume any copper gasket (for a standard 110cc Chinese barrel and head) would be acceptable?

All advice gratefully received.

Most are 52.4mm, some time ago there were some 52mm cylinders around, but they have dried up, Dr atv sold a nice 52mm piston but finding the cylinder was a nightmare,
Try to use a 52.4mm head gasket, if the copper head gaskets come up smaller then see if they do over lap, but fit the dowls in the cylinder first to check,
Also if fitting a copper gasket then don't fit the oil feed dowl
On the bottom left head stud, you won't get it to seal right,
Just leave it out,
Also check your squish, don't go below 0.7mm.

Thanks Alan.

With regards copper head gaskets - 00 Racing are out of stock on all the useful sizes. Do you know of an alternative source? I found a European website advertising several, but the choices were too many for a bear of little brain. A link would be excellent.

Also. I've never seen fractional sizes, and thus the choice seems to be between too big and too small. I suppose I could get a 52mm item and spend some time with some emery cloth, but I fear the result would be unsatisfactory, which seems to indicate a 53mm gasket would be a better choice.

As for measuring squish, I've never attempted it since I've always stuck with stock parts and prayed (and never had an issue). I imagine if squish is too low then adding an extra base gasket is the seemingly clear way forward. But to be honest, I fear this whole area is above my pay grade. And I'm still working on the parts list!

Re the squish it's easy,
obtain some lead solder obviously about two or three mm thick, then remove your plug,
Poke the solder into the plug hole ( as a length) to touch the far side of the cylinder wall, then rotate the flywheel as to squash the solder, then remove the solder and measure the squashed portion,
Do this three or 4 times just to check,
Normally done just after a rebuild so no carbon in cylinder,
And with the head gasket I would go for the 52mm and check for size and enlarge,

You make it sound easy...

A quick search reveals a website selling leaded solder (not cheap!) in various sizes -

0.38
0.71
1.02
1.27
1.57

All in mm. So I imagine the last three would be the candidates - which one would you go for?

Also, you've stated a minimum squish tolerance but what would be a maximum allowance AND supposing the recorded squish was greater, what's to be done? Head skimming?

I've got 1.5mm and 2.4mm solder,
Doesn't matter about the maximum, your after the 1mm range,
This is why it's trial and error, testing.
Remove the head every time then re anil the copper head gasket,
You could skim. Or play with gaskets,
Depends what piston your using.
Also keep a eye on the piston pockets if it has any,
Re valve to piston gap.

"Trial and error". "Testing." These are not good words.

I'm not planning on going racing nor trying to build the baddest Honda Cub that existed in the history of ever. It's more just the notion of adding a big-bore kit instead of a standard re-bore / re-build in the vague hope that it results in a tad more go. Back in the day the fave mod, as I'm sure you know, was to add a 70 head to a 90 lump mainly because of the bigger valves (although I hear some engines were also stroked). This general idea is the primary attraction vis the 110 cc cylinder and barrel. It seems a well-travelled road.

00 Racing have so far been difficult to contact (either they are hella busy or the phone was left off the hook - maybe both). Otherwise I would ask them because after all it's their gear but... do you see a problem with these things being used together?

https://www.ooracing.com/head-e22-style ... valve.html

https://www.ooracing.com/cylinder-52-4m ... 108cc.html

https://www.ooracing.com/piston-52-4mm- ... n-pin.html

Checking squish I put little blobs of plasticine on the piston in the squish area , turn the engine over.
I then use the end of a vernier caliper to carefully measure the thickness while the plasticine is on the piston.
But watch out for piston rock at TDC this can take up maybe 0.3mm or more on running the engine.

I've bought complete 52mm top end kits from Petrol scooter Ltd in the past ,but I can't seam to find their site now,they redirect to eBay. Cheap for head/barrel/piston/gaskets/seals @£50 delivered.
Good quality but I always disregarded their wrist pin retaining clips in favour of genuine Honda c90 ones for a few quid.