- Location
- Sicamous, BC
anybody have any pictures of a stock head with o-rings installed? how do you seal the around the mounting bolts, it doesnt look liket there is enough room to install an o-ring here as well?
o-ring stock head 61x 701
- Thread starter twinty
- Start date
- Location
- Rincon Beach
Removing the Head gasket on an oem yamaha head reduces the combustion chamber volume by over 5cc , aftermarket o-ring heads compensate for this by redesigning the combustion chamber and adding volume to compensate for this
also the design of the stock cylinder head chamber is not the best for high performance applications
Db
also the design of the stock cylinder head chamber is not the best for high performance applications
Db
- Location
- Columbia River Gorge, Wa.
Just use a head gasket and call it good.
- Location
- Sicamous, BC
thanks, but that is not what I wanted to know!
I know about the volume you lose that is why i am doing it, I am building a budjet ski. I have a lathe and am also going to reshape and cc the head when I cut the groove for the o-ring. We do this alot at the shop where I work, although to snowmobiles, but same physics. The yamaha head looks alot like the skidoo 800r and ho head and we cut these down 0.050" all the time to raise compression. I could do the same to the yamaha head but I would rather not use a gasket, this way I can pull the head numerous times to check piston wash without ruining a gasket every time.
What I simply wanted to know is how others are sealing the outside sealing surface when you o-ring the stock head, I have seen numerous posts saying people are doing it, but no pictures or solid evidence to back it up. I will probably end up sealing it with some 5910 flange sealant since this is what we use at work.
cheers!
I know about the volume you lose that is why i am doing it, I am building a budjet ski. I have a lathe and am also going to reshape and cc the head when I cut the groove for the o-ring. We do this alot at the shop where I work, although to snowmobiles, but same physics. The yamaha head looks alot like the skidoo 800r and ho head and we cut these down 0.050" all the time to raise compression. I could do the same to the yamaha head but I would rather not use a gasket, this way I can pull the head numerous times to check piston wash without ruining a gasket every time.
What I simply wanted to know is how others are sealing the outside sealing surface when you o-ring the stock head, I have seen numerous posts saying people are doing it, but no pictures or solid evidence to back it up. I will probably end up sealing it with some 5910 flange sealant since this is what we use at work.
cheers!
Freakrider
X247
- Location
- Tampa Bay area
pro tec heads with same oring set up use ultra black hi-temp rtv silicone made by permatex PX # 82180... I have used it and it works real good no leaks !
Last edited:
- Location
- Sicamous, BC
Thanks Alot! Exactly what I wanted to hear!:brap:
SUPERTUNE
Race Gas Rules
- Location
- Clearwater Fl.
Yamaha 650/701/760 have a freestanding sleeve design.
This design hates a stock head that just been o-ringed and not using the stock headgasket.
If you do this modification to the head you will need to special machine the cylinder block deck.
The stock headgasket has a folded metal ring over the gasket around the combustion chamber/sleeve. This folded ring gives you the additional 'CRUSH' around the sleeves verses the rest of the top of the deck, this is why in stock form they work pretty good.
As soon as you try and bolt on a flat head with just an o-ring, guess what... no crush to seal around the the freestanding sleeve, this won't last a weekend or two if you run engine pretty hard.
In order to achieve some success in doing this, you must mill the outside of the rim of cylinder .003-.004 thousandths more than the top of the sleeve to attain the crush needed to get a o-ringed stock head to seal to the sleeve.
Back when I was doing these mods I used RTV high temp copper silicone to seal the head down.
23 ft-lbs of torque on stock headbolts with a extra set of flat washers under the headbolts .
The stock 701 head is 34cc's, the stock .052 gasket is about 5.5cc's
You will need to lower the squish ratio on the stock head when tightening up the squish clearances, also use a 2 degree more angle.
These are to time consuming for me to do anymore and the rules let us run aftermarket heads now, Just buy a ADA head and bolt it on and go riding...save the headaches later at the beach when everyone's riding and your sitting there watching from a blown out head oring.
This design hates a stock head that just been o-ringed and not using the stock headgasket.
If you do this modification to the head you will need to special machine the cylinder block deck.
The stock headgasket has a folded metal ring over the gasket around the combustion chamber/sleeve. This folded ring gives you the additional 'CRUSH' around the sleeves verses the rest of the top of the deck, this is why in stock form they work pretty good.
As soon as you try and bolt on a flat head with just an o-ring, guess what... no crush to seal around the the freestanding sleeve, this won't last a weekend or two if you run engine pretty hard.
In order to achieve some success in doing this, you must mill the outside of the rim of cylinder .003-.004 thousandths more than the top of the sleeve to attain the crush needed to get a o-ringed stock head to seal to the sleeve.
Back when I was doing these mods I used RTV high temp copper silicone to seal the head down.
23 ft-lbs of torque on stock headbolts with a extra set of flat washers under the headbolts .
The stock 701 head is 34cc's, the stock .052 gasket is about 5.5cc's
You will need to lower the squish ratio on the stock head when tightening up the squish clearances, also use a 2 degree more angle.
These are to time consuming for me to do anymore and the rules let us run aftermarket heads now, Just buy a ADA head and bolt it on and go riding...save the headaches later at the beach when everyone's riding and your sitting there watching from a blown out head oring.
SUPERTUNE
Race Gas Rules
- Location
- Clearwater Fl.
Yes, The success with Pro-Tec heads were BECAUSE the heads are way thicker than a milled stock head casting.
Before aftermarket heads were allowed in limited class racers used to weld and oring the stock 750 heads. When the superjets started to become popular around 93 I remember having one done to my 94 superjet. I just used 1211 sealer for the water jacket. I had no problems. I remember that the only head that could use a gasket over 200 psi was the triton billet head. I ran 215 psi on my limited with no oring problems on the stock o ringed head.
- Location
- Rincon Beach
Kawasaki's have a supported cylinder and only used an .011 gasket so they are a completely different animal but the following still applies
A BIG issue with losing the head gasket and trying to run an o-ringed STOCK head, is you loose all control of the cylinder cooling . The cooling holes/passages in the gaskets, and in aftermarket heads are sized and placed to get proper cooling around the entire cylinder, with out these the coolant flow is uncontrolled and takes the path of least resistance, and creates hot spots in the cylinder which leads to a host of other problems
not trying to discourage you in any way. however countless hours of research and development and $$ have been dedicated to this exact topic.
Db
A BIG issue with losing the head gasket and trying to run an o-ringed STOCK head, is you loose all control of the cylinder cooling . The cooling holes/passages in the gaskets, and in aftermarket heads are sized and placed to get proper cooling around the entire cylinder, with out these the coolant flow is uncontrolled and takes the path of least resistance, and creates hot spots in the cylinder which leads to a host of other problems
not trying to discourage you in any way. however countless hours of research and development and $$ have been dedicated to this exact topic.
Db
- Location
- Sicamous, BC
Thanks all, I think I will just lathe about 0.050" off the head, reshape the chamber to 20 degrees and re-cc to 35cc and run a 50thou gasket. This sounds way more reliable than the oring thing on a stocker. If I didnt have access to a good lathe I would now just buy an aftermarket head! gotta save the money for the pipe and prop though!
cheers,mitch
cheers,mitch
#ZERO
Beach Bum
- Location
- Florida - U.S.A.
You might want to purchase a girdled aftermarket head anyway so your cylinder doesn't crack.
SUPERTUNE
Race Gas Rules
- Location
- Clearwater Fl.
Oh no! That's not right, you want about 31 cc's, so when you add the gasket (5.5cc's) your about 36cc's total!
The stock head is 34cc's plus the gasket= about 39cc's!
Chuck
- Location
- Sicamous, BC
my bad, in my head i was including the gasket in the 35cc total, :doh:
sometimes i dont type exactly what i am thinking
thanks!
sometimes i dont type exactly what i am thinking
thanks!
SUPERTUNE
Race Gas Rules
- Location
- Clearwater Fl.
Oh I didn't catch that...14 degrees is about right for a stock piston.
- Location
- Sicamous, BC
will do, as she is going under the knife tomorro at lunch. Will start at 15 degrees and cut the head till the surface is flush with the squish band, I will be measuring how much I take off to get there. Then to cc it and see where I ended up and how much more or less I should have taken! Good thing stock heads are cheap! Hopefully the squish should end up around 0.062-64 0.052+0.012
cheers
cheers
- Location
- Sicamous, BC
So I ended up reshaping the squish to 15 degrees and then as it turned out I only needed to take 0.040" off the deck to get even to the squish band I had just cut. I havent cc'd it yet but put it on and torqued it down to check the squish and ended up at 0.080" still too loose for my liking. It makes sense though as to my original reading of around 0.120" minus the 0.040 I cut off.....I am thinking of making a thinner base gasket now to tighten up my quench but I dont think I can get rid of 0.030" without completly removing the gasket, which I have done before on other 2 strokes, but it is kinda sketchy to do cause as everyone knows what happens if I get even a small air leak in the case.....meltdown! I also dont like the fact that lowering my cylinders with a thinner base gasket is going to change my port timing and alter my compression reading and take away the low end power I am trying to achieve by rasing the comp in the first place... Anyone know if there is a thinner head gasket available? like in the 0.020 range? aarg...try to save some money and look at all the work!