The Basics of Porting and Polishing 4 stoke cylinder heads and intakes?

[200XMichigan]

I have been doing some looking online as to what it takes to port and polish cylinder heads. Seems like on 4 strokes it is really more polishing than removing any material like 2 strokes?

I bought a Trail 90 the other day that came with 4 engines two for it, two ATC 90 engines, and a couple extra cylinders and heads. There is also a ATC 90 frame and some pieces at the junk yard. And I figure with all these engines I should learn something new. So I am looking for some advice on how to go about porting and polishing a ATC 90 head. What I basically gather from reading is you want to just polish up the cylinder head will a real fine stone on a dremel, basically till it shines and remove any burs from intake or exhaust passages. But like I said I've never done this before. Any pictures of a finished product would really help.

[3WW Star-Yamahondaman]

EEEWWWW !!!! I have some pics of the BUSA i did .. i'll GIT em up soon for you .. like 2-stroke .. leave the intake rough and Polish the exhaust... some people remove the valve guide that protrude's in the exhaust port ... i dont.... "they" say NOT to HOG them out ... but i do.... the BEST thing that help's with 4-stroke porting is BIGGER Valves... don't use the stone ... use double cut insert's for your drimmel or die grinder

[200XMichigan]

What is hogging them out? Pics would be great.

[TheRealFatShady]

Has anyone added bigger valves to an ATC? If so, was it beneficial/difficult?

[Grizzlypeg]

From what I've read on porting work, its not "intuitive", and the effect of changes on flow have to be measured on a flow bench. If you start removing metal you could just as easily make it flow worse, than better. Once someone finds what works, its easier to copy it, but I'm sure they still flow bench it to ensure it meets previously acheived results.

[3WW Star-Yamahondaman]

Has anyone added bigger valves to an ATC? If so, was it beneficial/difficult?

YES to a 350x and the 400ex ... BIG Difference... i dunno who done it after i ported it but it was NASTY !!
200xMichigan...... "Hogging Out" is taking the MOST Alluminum out that you can without Hurting certain thing's.. ATV'S like BIG Volume.. i'll try and GIT some pic's up soon of the BUSA,400EX,GIXER 1000 and Triumph ... IV'E DONE EM ...... HOG IT OUT !!

[beets442]

Your not going to gain that much it's only a 90cc. The best thing you can do is clean it up(removing burrs and polish). If you want faster, buy a bigger machine...Good luck Beets

[shortline10]

Here is a pic of the intake side of last atc90 motor I just put together .

[thumper 14]

make it flow you'll see a difference