Honda Spree and Elite 50 Forums

I've heard of people having there heads milled so you can use an o ring instead of a head gasket. Anybody kno how this works? Is it worth it? What o ring do I use?

A lot of the high quality heads come that way with the oring slot already there. You can get the orings from the different maunfacturers like malossi. Graphite 9 I'm sure has them and can order the heads. I have a couple of the malossi heads they are really nice stuff. You can have a head machined with the groove in it for the oring at a machine shop. I'm not sure what machine shop prices are like where you are but depending on the head that you have it might be better to buy a new head already done. The new heads are also machined with a particular chamber shape that the head you want to mod may not already have. Just things to keep in mind.

You shoud remove ur head gasket and use some copper rvt gasket maker, run that first to make sure the bike even benifits from more compression and also wont blast a hole in ur piston. Test b4 getiing ur head milled and doin' all that.

Greetings:

Melo's suggestion is spot-on. You can't run pump gasoline if compression is much above 145 or so. If you don't mind midnight trips to the county airport for some LL100 Aviation Gasoline, you can proceed up to 170PSI or so.

Flash 2's stock head was machined for a Viton O-Ring that was kindly donated to me by another member. The machinist and I "estimated" the diameter, depth and width of the groove and it worked out. But the best way may be simply to obtain a Malossi or Corsa head that already has the ring groove cut into it, as long as your piston has a 47mm diameter too. If you have some other slug, you will use your existing head and have the groove machined to the same dimensions as the Malossi or Polini head. I think I still have a Corsa head somewhere. If you remind me, I'll try to dig it out and measure with some pics.

You shouldn't use rtv where fuel is present. Read the instructions.

Greetings:

I wonder if Melo meant just to assemble it in order to check compression. I wouldn't rely on ANY goo where fuel AND heat are present in running status, but it'd give you a compression value at least.

Wheelman-111 wrote:Greetings:

I wonder if Melo meant just to assemble it in order to check compression. I wouldn't rely on ANY goo where fuel AND heat are present in running status, but it'd give you a compression value at least.

Sounds like it to me

So, the o ring mod raises compression? Are the heads universal, would a malossi o ring head work on a non- malossi jug? I have an afo5, so my head options are limited to a malossi or modded stock I think, but I have several machine shops and a small airport w a gas (100ll) nearby so I'm cool w raising the compression.

And no copper rtv (coppertex) on the head gasket? I don't have it but some guys do I guess.

1man8scoots wrote:You shouldn't use rtv where fuel is present. Read the instructions.

i use copper sealant on my 125 race scooter. it seems to hold just fine.

no head gasket

How big a difference in performance does raising the compression have? Is it worth the av gas?

Greetings:

Higher compression increases theoretical heat production and therefore maximum power output. Tuning correctly is critical, and finding a way to ensure reliability in an air-cooled engine is challenging.

The O-Ring mod eliminates about 0.5-0.7mm of thickness of the normal metal head gasket. You wouldn't think such a small decrease in combustion chamber volume would change compression all that much, but depending on the head volume it could rise by as much as 20-30PSI. An undamaged head gasket on flat unmarked mating surfaces does just fine sealing in the combustion Fury. There isn't any need to add goo. Doing so adds 2 possible planes of leakage, above and below each layer of semi-solid Goo.

If the tube says clearly on it do not use where fuel is present I would believe the manufacturer.

Don't forget about squish. Compression is only part of the issue without using a head gasket. I build engines that last forever not for a few runs. Do it correctly and you won't worry. Ensure squish is not below .7mm and not above .9 mm if you want good power. I literally do 8 Honda verts a month for people all over the US and they're all absolutely perfect and I even give warrantees, that's how much I trust my standards and practices. I don't doubt TJs skills but I also follow.instructions from manufacturers. If you're going to use anything use copper spray or red loctite. Both are intended for this use and Vespa even uses red locate from the factory.

Red loctite on the metal head gasket? Or no head gasket w red loctite?