Gas Gas Cylinder / Ports

[Jakobi]

I'm yet to inspect the cylinder on my gasser but from those with experience, whats the quality of the casting like? Are there many dags? Is there much to be gained by some light sanding on the intakes, and a polish on the exhaust?

Considering giving everything a clean up while the bike is down for its top end but would like to get an idea before I make a start.

Regarding the exhaust side. How much effort is involved in removing the power valve assembly? I assume it would be best to take the valve out before doing this work, or could it be done while in place?

[Dude]

Mine had some serious cast flash in the transfers. like really bad. I mirror finished my exhaust port as i hate carbon buildup.

Also the jug/case matching was horrid. looks liek someone went in there with a dremel and just murdered it. Lots of cleanup on mine. Lots of power differences as well after cleanup.

[Jakobi]

Is it best to pull the entire power valve out and shine it up too? Is there much involved in removing it?

Looks like I could spend the best part of a day prepping the cylinder

[stainlesscycle]

transfer ports really can use some work usually.. i knife edge mine, and polish them smooth. and match intake to reed cage, and smooth exhaust.

[Jakobi]

I see I see.. This will be my first time in the engine and as such don't want to bite off more than I can chew.. aka farrrk something up

I have a dremel and a few different grades of wet and dry to use so will probably just inspect for a start and see how things look.

[stainlesscycle]

just don't adjust the port sizes in the cylinder wall, the nikasil can flake. the transfer ports, intake and exhaust are very easy to work - i use a die grinder and a wet dry vac for the mess. matching the cylinder ports to the cases and reed block will have a noticeable effect.

[Jakobi]

Not looking to widen any ports that I don't have to. Just clean up dags etc.

Whats the best method to match ports as you describe? How would you mark out the material to remove? I'm not looking at pulling the reed block for this top end.

[socalscott]

Originally Posted by Dude

Mine had some serious cast flash in the transfers. like really bad. I mirror finished my exhaust port as i hate carbon buildup.

Also the jug/case matching was horrid. looks liek someone went in there with a dremel and just murdered it. Lots of cleanup on mine. Lots of power differences as well after cleanup.

Case/cylinder matching is easy free power.

[Jakobi]

But how do you do it?

[stainlesscycle]

for the case to cylinder matching use your gasket as a template. grind the case/cylinder with a dremel/die grinder to match. what you want is smooth flow from bottom to top. no edges that interrupt flow.

you will see the transfer ports on the bottom of the cylinder have a divider, it is square edged/flat where it goes into the case. that square edge slows/causes turbulence of the mix. you want to make it smooth/blended and knife edged.

the exhaust port can be matched to the exhaust flange. the only polished surface you really need is the exhaust port. it stops carbon build up.

i gotta say this before you go crazy with your die grinder. stay away from the nikasil. it will flake. do not open ports in the cylinder itself.


you can really mess things up if you are not careful. that being said, if you do sensible grinding, you'll see an improvement. it is free power. it really helped my 200 motor. when i swapped the 300 in, i was in too much of a hurry to do the porting. over the winter i'll go through it pretty extensively.


there's vids on youtube.

here's a good one on the transfer ports. in fact i've only just skimmed this guys stuff, but it doesn't look like he's a hack..

http://www.youtube.com/watch?v=kKQ95VnP2bE at 5:45 he starts to knife edge the transfer split

for case matching, go about :30 seconds into this video to see.

http://www.youtube.com/watch?v=kFbMn...eature=related