Yamaha TRX850 Enthusiasts Forum

I modifid the head gasket (increased the holes so they corresponded to the bigger bore). Now it sems I have blown the gasket, the ccolant disappears, and I can see bubbles in the coolant reservoir. Luckily it only occurs when I am whipping the engine, so I can manage to drive home from the track in normal tempo...

How did You guys with 878 kit do with Your gaskets?
Would You be interested in buying '878' gaskets if I order custom built ones? I have no idea of the cost so far, but thought it's better to hear whether there's any interest at all.

I had the top of the pistons chamfered so I could use standard gaskets

I enjoy getting a response, but I don't understand it (My technical English is somewhat limited, could You please elaborate that a bit?)

The tops of the pistons have been tapered so that they clear the standard gasket

Maybe pointed makes sense?

My standard gasket worked just fine....

OK, tapered is actually a word in my vocabulary

I have still the old gasket, but before putting that in (season is quickly diminishing, I'll get a proper solution during the winter.)

But before I put that in, please help me explain a thing. I thought the reason for modifying the gasket was mainly that one doesn't want any sharp edges sticking out in the combustion chamber. But chamfering the pistons speaks for reducing the rsik that the pistons hit the gasket. And using the standard gasket means it's all just the same? What is true?

HansJ wrote:OK, tapered is actually a word in my vocabulary

I have still the old gasket, but before putting that in (season is quickly diminishing, I'll get a proper solution during the winter.)

But before I put that in, please help me explain a thing. I thought the reason for modifying the gasket was mainly that one doesn't want any sharp edges sticking out in the combustion chamber. But chamfering the pistons speaks for reducing the rsik that the pistons hit the gasket. And using the standard gasket means it's all just the same? What is true?

I can just add that when i got a quote from TTS on the JE 878 a head gasket was in the kit.
(so i guess they sell ´em?)

Kedo list one. 69.90 euro. Part number 30697 for 91mm bore 878cc.

[quote="Killerwhale
I can just add that when i got a quote from TTS on the JE 878 a head gasket was in the kit.
(so i guess they sell ´em?)[/quote]

Phone Paul at TTS - it's a standard gasket

As for overlap into the combustion chamber - 0.75mm is going to have no effect whatsover

TBH I looked at having gaskets made but I'd never trust anything other than OE head gaskets

martin young wrote:Kedo list one. 69.90 euro. Part number 30697 for 91mm bore 878cc.

Thanks, I have ordered one!

phuk72 wrote:
As for overlap into the combustion chamber - 0.75mm is going to have no effect whatsover

I thought anything sharp edged sticking out/in to the combustion chamber would possibly become to warm, and in worst case make the engine pre-ignite (Yup, I have learned the word here before, but managed to forget it again )