Gs 1100 ex porting

[4cyl h2]

Good idea or not. gs1100 e. To back cut the exhaust valves at the bottom of the factory 45? Stock 1100 23mm valves, radiused factory valve seats seated near outer edge of valve if so how much? any advice appreciated!

[4cyl h2]

51 looks and no thoughts? Or am I asking for for valuable info??

[Nessism]

Sit tight. There are only a few guys around here that know such things.

Personally, I'd leave a reasonable margin for wear. Why not lap or blue the valves to describe the contact face, then back up up to within 1 mm or so of the face? Not sure about the back cut angle.

[Guest]

If you search the board you'll find usefull information. In the section tips and tricks there's a topic about flowing 1100's heads. Your questions about back-cutting are answered there too

[Guest]

I looked it up for you, think it was in a different part, but hey, here it is

http://www.thegsresources.com/_forum/showthread.php?t=137631

[4cyl h2]

Much appreciated got a project going I think will be fun. Just hoping to make it a little better

[Guest]

Much appreciated got a project going I think will be fun. Just hoping to make it a little better

What kind of project? I'm currently building a classic superbike racer

[4cyl h2]

putting an old conversion cartire chassis back on the dragdtrip will be a ported stock valve 1100 head with a hi dome 1260 piston

[Guest]

Dats a small motor for a car tire bike

[4cyl h2]

1 of the reasons im looking for all the tips-tricks i can find to use

[gearhead13]

28mm 1150 intake valves are bigger and can be found cheap. That and some Neway seat cutters to open up the seats. Thats what I used.

[Guest]

Why stock valves? Why not put a set of lighter 28.5/24 stainless valves to give that little motor some power to push that huge tire and rim. I mean if your gonna spend the $$ on porting it why not?

[gearhead13]

Why stock valves? Why not put a set of lighter 28.5/24 stainless valves to give that little motor some power to push that huge tire and rim. I mean if your gonna spend the $$ on porting it why not?

It sounded to me like the guy was on a budget, he was asking tips and tricks

[headsbikesmopars]

Back cutting the valves is always a good idea when you have the valves out. Use some layout dye on the valve seat area on the valves themselves and lap the valves in. You will see the seat contact area very clearly. Take them to a GOOD head shop and have them (intake and Exhaust) back cut to 37 degrees. What this does is open up more valve area and picks up the flow thru the port earlier in the lift cycle. It gets the moving column of air moving sooner. You will have the same flow at .050 as it was at .100, same at .100 as it was at .150 and so on untill around .300 lift, at this lift value the valve is open enough to where the valve shape isnt a factor . this will creat MUCH torque production and torque is what we want on the street. Expect to pay about $20.00 to $40.00 for this cheap mod. I never charge more than $20. for a set. 37 degrees is what Hemi chambers like , the Kawasaki's will flow better with 35 or 36 degrees as does Honda but The GS's LOVE 37 degrees. Just FYI wedge chambers (auto) like 30 degrees, if you cut these to 37 it will hurt flow. Low lift flow IS what we are after.

Terry

[Starion007]

Can you do the back-cutting on a lathe with carbide? or do you need a grinder.
I'll have to chuck up a couple used ones and give it a try.
Thanks Terry that's some really good info.

Mark