I've seen MC21 grooved barrels too, but there's not a lot of room to machine them around the studs.
I doubt RS O-rings are the answer. You will most likely need a different diameter. Remember the lack of head gasket will need to be accounted for elsewhere to pevent detonation. _________________ Andy.
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Andy wrote:I've seen MC21 grooved barrels too, but there's not a lot of room to machine them around the studs.
I doubt RS O-rings are the answer. You will most likely need a different diameter. Remember the lack of head gasket will need to be accounted for elsewhere to pevent detonation.
Fat base gasket is what you would want for that (.06 or greater). Or a custom head with inserts cut to make up for the lack of head gaskets (VHM).
If your going to go with o-rings, your going to want to replace your o-rings much more then you would your head gasket on the stock NSR setup. _________________ Charles Gallant
A base gasket can't actually compensate for the head gasket. They are the wrong thickness.
To optimise the setup properly, the base of barrel will need maching, the head relieving, or as you say, VHM style heads with the correct inserts. The shape of the inserts though, as well as the compression ratio, can make a huge difference on the dynamics of the motor.
Nothing is ever that simple. _________________ Andy.
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I read about the head gasket being only 0.25-0.3mm. Someone on here- I think Matt@TYGA- posted that.
Stock squish is 1.2mm +/-0.1mm (Again Matt@TYGA). -0.25mm would give 0.95mm. Getting close to right for racing... Minus another 0.2mm(Sp heads/R cyls) gives 0.75 in theory. I'll be on avgas, with adjustable ignition, so that sounds bang on...
Again, I'll be measuring things on the bike before I fiddle-CC volume etc...
Andy wrote:A base gasket can't actually compensate for the head gasket. They are the wrong thickness.
To optimise the setup properly, the base of barrel will need maching, the head relieving, or as you say, VHM style heads with the correct inserts. The shape of the inserts though, as well as the compression ratio, can make a huge difference on the dynamics of the motor.
Nothing is ever that simple.
A thicker base gasket will raise the barrel up, raising the head and compensating for the thiner head gasket. of course it will also have a the side effect of lifting the ports and changing the power profile.
Machining the base of the barrel will bring the head closer to the piston reducing your deck height even further, forcing you to need a thicker base gasket to keep the ports at the same profile, and you will simple be in the same place with the heads.
Your honestly best to stick with the stock head gasket, or if your going to cut grooves for o-rings, go with the VHM heads with inserts to match the change.
This will keep your port timing the same and make up for the reduced head clearance from stock. _________________ Charles Gallant
You can't compensate for a 0.25mm head gasket with base gaskets that are in increments of 0.1mm!
If it's going to be done, it needs to be done right. Machining somewhere (other than just O-ring grooves) is inevitable. _________________ Andy.
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so what is the thickness difference of using a head gasket and using o-rings (assuming the grooves are cut to proper depth/depth = RS250 grooves)?
My assumption is that it will be less clearance using o-rings.To make up for the less clearance, you would want to use a larger base gasket to make up for that difference.
Depending on the difference between o-rings and gaskets, you could be adding more clearance from stock, or less clearance from stock (but greater clearance then stock base gasket with o-rings).
Of course you would also need to take into account the tolerance (or lack of) in paper/material base gaskets and a .6 may be a .59 or possible a .62. Then you take into account the differences in size of pistons.
This is why I measure my base gaskets (and pistons) and hand pick base gaskets to match the pistons I am using to make sure my deck height is what I want/need. I may go with a fat .6 base gasket, or a thin .6 to produce the deck height I am going after. _________________ Charles Gallant
Yeah, the lengths I would say you should go to on a GP bike!
The point is GP machinery is manufactured to much tighter tolerances, and if an NSR is going to be tuned to a similar degree, then it should be treated to the same level of setup.
The difference is going to be 0.25mm, as it doesn't matter how thick the O-rings are, the heads will still clamp flush to the barrels. Yes, base gaskets are available in 0.4mm, 0.5mm, and 0.6mm (and slight variations of each), but by the time you've bought all the base gaskets you can find just to find the one(s) with the odd 0.05mm, you may as well skim the base of the barrel to get it right or just stick with head gaskets!
It's not like NSR heads really need to come off every 5 minutes, unless you're making 75hp of course! Even then, you'll be replacing rings (and pistons) so often there's still not much point in taking the heads themselves off.
It was designed into the RS, but not on the NSR. I just don't see the point personally, and think time and resources are better spent elsewhere, but each to their own. _________________ Andy.
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Wow this is... Spirited
I looked at O-rings because it could tighten the squish without affecting the port timings
What squish do you run on your racers, and what fuel do they run them on? _________________ The Chopster
I run R barrels with SP heads with another 0.2 taken off, so 0.4 off stock which leaves a squish of 0.8.
That runs fine 50/50 avgas/95ron unleaded on either a PGMIV c/w HRC 030 card and mc21 flywheel or a stock PGMII.
Dan has o-ringed his NSR (he's done the heads), they're more problems than they're worth.
I've seen ones like this on yahoo Japan, don't know if it works any better or not, same bloke has also got a properly centre plugged head, shame the auction starts at 100,000 yen! _________________ Please do not PM me technical questions, if you can't find it on the Forum start a thread
Kieran wrote:
Wow this is... Spirited
I looked at O-rings because it could tighten the squish without affecting the port timings
What squish do you run on your racers, and what fuel do they run them on?
You're better off machining the heads to adjust squish. The port timing needs alteration to get serious power. _________________ Andy.
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Andy wrote:Yeah, the lengths I would say you should go to on a GP bike!
The point is GP machinery is manufactured to much tighter tolerances, and if an NSR is going to be tuned to a similar degree, then it should be treated to the same level of setup.
I would say if your going to tune an NSR to this level, you might as well just go with a real GP bike. It will be easier in the end
Andy wrote:
The difference is going to be 0.25mm, as it doesn't matter how thick the O-rings are, the heads will still clamp flush to the barrels. Yes, base gaskets are available in 0.4mm, 0.5mm, and 0.6mm (and slight variations of each), but by the time you've bought all the base gaskets you can find just to find the one(s) with the odd 0.05mm, you may as well skim the base of the barrel to get it right or just stick with head gaskets!
You would be suprised at the variations (+ and -) you will find in a small hand full of base gaskets.
Now I have a good 30+ pile of base gaskets all measured and noted so I can quickly grab the one I need based on the piston I pull from stock. of course I (was) buy(ing) pistons 10 at a time. But when they doubled in price I stopped that practice
Andy wrote:
It's not like NSR heads really need to come off every 5 minutes, unless you're making 75hp of course! Even then, you'll be replacing rings (and pistons) so often there's still not much point in taking the heads themselves off.
It was designed into the RS, but not on the NSR. I just don't see the point personally, and think time and resources are better spent elsewhere, but each to their own.
Yep, I totally agree. If you want a GP bike, get the full benefits of owning one. When it comes to jetting changes, top end rebuilds, pulling body work, tank, etc.. you will find nothing can be done to a street bike to make it as easy as a GP bike is from stock. _________________ Charles Gallant
The "spares" you have amassed I would say, in a strange way, are a "benefit" of running a GP bike! Like you say, buying consumables in the quantity required to maintain the bike is going to leave you with a wide range of, technically left-overs! The more left-overs acquired, the more use they become when you start to mix'n'match as you do.
The funny thing is, probably 75% of internal parts (beyond HRC RS service life) you remove from your motor would be fine to use in an NSR. _________________ Andy.
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