So, the S3 low comp head arrived for my 2000 TXT 250, it's a work or art, half tempted to put it on the mantle piece but I'm sure it'll be more useful on the bike!

I've had a search online and I'm seeing different values for the torque required on the head bolts after fitting. I've seen everything fro 15 - 25 ft lb. I was expecting to see NM. Has anyone got a definitive answer for the older pre pro engine?

 

Cheers

Edited December 8, 20232 yr by carlanthony663

2 hours ago, carlanthony663 said:

So, the S3 low comp head arrived for my 2000 TXT 250, it's a work or art, half tempted to put it on the mantle piece but I'm sure it'll be more useful on the bike!

I've had a search online and I'm seeing different values for the torque required on the head bolts after fitting. I've seen everything fro 15 - 25 ft lb. I was expecting to see NM. Has anyone got a definitive answer for the older pre pro engine?

 

Cheers

8mm head bolts with O rings to seal head = 18ft/lbs = 24Nm   you need to lubricate the O rings with Silicone grease and lubricate the threads of the bolts to get a proper torque reading , Copper Slip Anti Seize is best to stop future corrosion and so for ease of future removal.

6mm head bolts with 1.5mm thick copper washers to seal head = 9 ft/lbs = 12.2 Nm.  Lubricate threads with copper anti seize as above.

Anyone looking for O rings you need FKM/VITON ones Nitrile is not as resistant to UV light. 

These settings are for a Standard GasGas Head.   I have had S3 heads on Gas Gas PRO motors an I used standard head Torque settings and had Zero problems If that is bothering you.

 

Edited December 8, 20232 yr by Tr1AL

Mate, that's exactly what I needed. Thank you very much. 

Copper slip is not recommend on aluminium, a specific aluminium anti seize should be used.

4 hours ago, b40rt said:

Copper slip is not recommend on aluminium, a specific aluminium anti seize should be used.

As the saying goes 'You learn something new everyday' , I have to say though In my Ignorance  I have been using Copa slip with steel to Aluminium For decades without consequence. and I have certain bikes that I have had for decades. Not a very good excuse of course for not using the correct type of product but it is a fact none the less. I need to stop digging. I never thought I would be judged by Mark Twain in my lifetime so that is something new also. Have a good day.

20 hours ago, Tr1AL said:

Anyone looking for O rings you need FKM/VITON ones Nitrile is not as resistant to UV light.

As long as we are picking nits here, I'd like to respectfully discuss this.

Where does the UV light come from?  The head to cylinder joint is pretty tight, so not from the sun.  I can imagine IR light coming from the combustion side, but UV?

I always use nitrile for the outer o-ring and typically silicone for the inner o-ring (because Yamaha did on the TZ roadracers).

1 hour ago, konrad said:

As long as we are picking nits here, I'd like to respectfully discuss this.

Where does the UV light come from?  The head to cylinder joint is pretty tight, so not from the sun.  I can imagine IR light coming from the combustion side, but UV?

I always use nitrile for the outer o-ring and typically silicone for the inner o-ring (because Yamaha did on the TZ roadracers).

Hello  Konrad , i think there may be a misunderstanding about the position of the O rings.  I am talking about the O rings that go on the head bolts not the internal ones that seal the head to the cylinder and cannot be affected by UV light. the ones that i am speaking of are the 8mm I D that are used to seal the  head bolts to the head and  when in place can have the edges exposed  to sunlight in their  position. This UV reference based on Technical specifications given by a seal manufacturer regarding their products. Too much detail I suppose but that is the human mind at work , probably my undetected autism is in full swing , who knows. Have a good evening.  Alan.

Thanks.  That's a very good answer.  It also explains why I have seen rapid degradation of the nitrile O-rings I use to measure fork travel.  Did not realize they cannot tolerate UV exposure.  Glad I asked.

5 minutes ago, konrad said:

Thanks.  That's a very good answer.  It also explains why I have seen rapid degradation of the nitrile O-rings I use to measure fork travel.  Did not realize they cannot tolerate UV exposure.  Glad I asked.

Thank you for your response Konrad , hopefully I have redeemed myself after my public disgrace as regards my previous  'little slip up' .