hi!

I want to fit a rear head front and was thinking if it would be a good idea to

skimm them a bit but how much for a spliced+mod airbox bike?Or else

(I have an R motor) if i install 2 rear sp/se heads then i will have the better spark location front + 0.2 shorter heads.

Is it a good idea for a derestricted bike without pipes which is for road use?

I want to tune the bike in the aspeq of the blueprinting.

A. Can you be sure you can get high octane fuel EVERY time you fill up? Raising the compression ratio then using lower rated fuel (even just once) is a recipe for disaster.

B. It's not just a case of milling off material from the heads. Depending on the deck height of barrels, the heads may need different amounts machining off them. (The barrels aren't always the same height!)

C. Unless you have the full spec's, I would stick to standard compression ratios. They will see you well into the high 60's if the rest of the motor is set up properly.
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Andy.
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Of course, if you do get caught out and have to use lower octane fuel, just unscrew the spark plug a few turns, to lower the compression...
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Would it not then suck in air and run lean? Or fall out on the way home

Thanks for the responce!

I don't worry about the fuel cause i always put 100oct. and find it everywhere!

The barrels have been measured when i did my last overhaul and are the same.(luckily)

I believe 0.2 skimming isn't a big deal, is it?

But youre right i dont race the bike and want to do plenty miles with this motor.

Ok you have convinced me i'll just fit one stock rear head.

Thanks for not letting us newbies destroy our motors...

That's the best plan. A stock rear head (SP on an SP barrel, or R on an R barrel) is the way to go.

0.2mm can actually be the difference between detonation and smooth running!
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Andy.
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When I raced both the 3XV and the MC28 I cut a bunch of 0.05 brass shims in the shape of the base gasket so that I could get my head volumes and port timing etc just how I wanted it. Maybe a tad anal, but I had the fastest 3XV and also the fastest MC28, so I must have done something right.

But... Unless you have all the relevant HRC information to hand, and the resources to implement it...

A stock rear head (SP on an SP barrel, or R on an R barrel) is the way to go.

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Andy.
NSR-WORLD.COM

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Andrea is right of course. stick to the stock matched setup and it's the best base to start from.