Stainless steel 0.2mm gasket - my verdict

[QuickDraw]

Branching from a previous thread about cam timing where I mentioned the possibility of using a stainless steel head gasket, http://www.trx850.com/phpBB_forum/viewt ... 38#p103038, and having done a good amount of riding since, I am now able to report on how the stainless steel head gasket has performed so far.

The gasket is actually a de-laminated and cleaned stock-item (with no damage obviously) measuring 0.2mm in thickness. Compression ratio calculates to be a whisker under 11:1. With my bigger & longer cam profile, I figured I was losing actual compression with the increased overlap. Seemed radical at first but at Rod's suggestion of using a copper gasket, I was keen to keep my head original & un-skimmed. I was using originally using the stainless item for a test-assembly, then I thought "Why not?".

I've used Hylomar sealant on both sides. First time I've used it. Interesting stuff and tricky to get an even spray. It looks and smells like PVC-pipe cement (It doesn't set though... dries to a rubbery state). It certainly appears it will give a good seal. I reckon it will have added a small but measurable difference to the gasket thickness overall.

Before running the engine, I performed a compression test which indicated pressure within original spec. On the first run, I noticed slightly improved torque and response. After the first 250km went ok, I re-torqued the head and went a 300km each-way ride. It all felt strong and really good until a quick push at 6500 in top on the return run, when the engine started missing at higher speeds and was suddenly down on power. It felt like a fuel problem but I wasn't sure. Stopping to check, the small amount of hylomar that had squeezed out when the head was torqued, had turned from blue to green and was moist to touch. But there was not really any leaking to speak of. Made it home fine just cruising and did some checks. No bubbles in the coolant. Reservoir level was down only a small amount. The engine misfiring later proved to be a fuel problem... I didn't realise I'd lost the gauze from the fuel inlet.

IMG_2794.jpg

Still, I was concerned whether or not the Hylomar was up to the task. I re-torqued the head a second time and checked after every ride. Having ridden around 1000 kms since (and with reasonably high loads), there does not appear to be any further coolant permeation at the head gasket seal.