gs850 head shave?

[Guest]

would it do anything good or bad to shaved the head on the 850?...on my rebuild i wanna do anything that may help with power and or fuel mileage

[Steve]

If you are going to have the head off anyway, have it checked for flatness. If it is not flat enough, just shave it enough to true it up.

With the overhead cams, if you shave it too much, it will affect cam timing and you will have to make other adjustments, too.

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[Flyboy]

i wanna do anything that may help with power and or fuel mileage

Drop in a 1000G motor.

[tkent02]

Drop in a 1000G motor.

And the shavings will be about 15lbs lighter, too.

[gs850cafe]

And the shavings will be about 15lbs lighter, too.

have almost all gaskets for 850...

[Nessism]

There is a fair bit of meat on the head so you can cut it aggressively from what I've read here. Doing so won't do all that much from a performance standpoint though. When rebuilding my 1000 engine I had the head and cylinder surfaced to clean up the surface corrosion, and I couldn't convince the machinist to take more than just a clean-up cut on the head. Said no good would come from it. Cost me $100 to surface both parts and bottle brush the cylinder. Not cheap.

[Steve]

There is a fair bit of meat on the head so you can cut it aggressively from what I've read here. Doing so won't do all that much from a performance standpoint though. When rebuilding my 1000 engine I had the head and cylinder surfaced to clean up the surface corrosion, and I couldn't convince the machinist to take more than just a clean-up cut on the head. Said no good would come from it. Cost me $100 to surface both parts and bottle brush the cylinder. Not cheap.

Don't know about the "meat on the head" part, but the 850 is probably the worst engine in the GS (four-cylinder) line for horspower per displacement. Not that it is a slouch, by any means, it just does not have the neck-snapping power of some of the larger (or newer) bikes. Not that it's all that bad, though, it has a decent torque curve with very adequate power down to 1500 RPM. It will also rev very happily up to (and past ) the redline, so there is no excuse for being bored.

I's say that cost was about right, too. I think I was charged about $80 to have two broken exhaust bolts removed and the head surface trued.

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[Steve]

I just went back to the original post in this thread and was quite amused.

... i wanna do anything that may help with power and or fuel mileage

and then noticed your signature:


I think there is at least one way to improve your fuel mileage.

So, that leads to another question (or three): what mileage are you seeing now and what would you like to see?

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[trippivot]

very loose engines when stock

you can remove material from the head to increase compression. It is VERY effective and you have a lot to play with, but as with every thing there is a give and take.

one engine I went very aggressive and removed 0.090" from the head surface. Yes we went into the seat material - just a little... it made over 130HP. small port 1000 head... big D port 1100 can go farther.


technically after the material is removed from the head surface = the valve is going to be in a different place than stock when lifted off of the seat. it is the edge of valves to the edge of the pocket in piston crown where the interference is. you test fit all 8 valves with machinist dye and no head gasket.. ONLY a problem if you really get aggressive and your mods.

in reality -- this mod is Not going to be problem until you start to tighten up the engine a lot

high lift and low lobe center cam timing is how make an engine "tight" -aka- valve to piston clearance @ 10~12 degrees after T.D.C. overlap . that is when both valves are partially open at the same time and the piston is up in there

.. that is when the pockets have to be correct.

I have also tightened up my engines by running without a base gasket..

to do that you have to really measure for sling out, and 0.040" is the magic zero number for piston to head. valve to piston 0.060" valve to valve 0.060" those tolerances are as tight as you ever want to get for a racing 850/1000/1100 2 valve GS engine..

[gs850cafe]

I just went back to the original post in this thread and was quite amused.


and then noticed your signature:


I think there is at least one way to improve your fuel mileage.

So, that leads to another question (or three): what mileage are you seeing now and what would you like to see?

.

low 30mpg...never see above 35..be happy with closer to 40

[Steve]

low 30mpg...never see above 35..be happy with closer to 40

Keep both wheels on the ground and keep the speedo under 80, there will be no problems.

Just as an example, take the same basic bike, add about 75 pounds of "stuff", you will have this:


Add two people that total about 400 pounds, along with enough smaller "stuff" in the luggage to support those two people for a long weekend, and you have the recipe for disasterous mileage.

Left Glens Falls, New York on a Saturday morning, took an 850-mile loop around much of New England, returned Monday evening.



Overall mileage for the trip: 40.9 mpg.

No complaints here.

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[gs850cafe]

Keep both wheels on the ground and keep the speedo under 80, there will be no problems.

Just as an example, take the same basic bike, add about 75 pounds of "stuff", you will have this:


Add two people that total about 400 pounds, along with enough smaller "stuff" in the luggage to support those two people for a long weekend, and you have the recipe for disasterous mileage.

Left Glens Falls, New York on a Saturday morning, took an 850-mile loop around much of New England, returned Monday evening.



Overall mileage for the trip: 40.9 mpg.

No complaints here.

.

haha yea i need to stop that one wheel stuff...its so fun but no good on the bike...im sure once i return it to stock ill behave a bit better...or take the rear pegs off

i usually did around 75 or so on the highway...then again maybe a good in spec engine will do it good too

[Steve]

There is yet another reason to keep one wheel on the ground.

My son insisted he was not racing when this happened.





Need I say more?

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[JAG]

I have a spreadsheet for calculating how much to shave off a head for any given compression ratio. PM me and I'll send it you.

JAG