Polishing the Intake Manifold Ports
By Loki #300 (Kirk Hilse)
Sep 14, 1998

OK, everyone, I went to TMIB's house on Saturday and we performed Lamont's Intake Manifold Polishing mod, and Chet's four-way flasher mod as well. Here's my experience regarding the manifold polishing mod; I did both TMIB's bike and mine, while TMIB did the four-way flashers on both bikes -- I'll let him report on the flashers.

For us very green people (myself included), the intake manifolds are the curved chrome tubes coming up out of the engine connected to the carbs up under the tank. They come off really easily -- at the top there's a black hose clamp that you loosen with a phillips screwdriver and at the bottom are two 8mm hex bolts. The ones on the inside are kind of hard to get to with a socket wrench, but I was able to loosen them with the 8mm wrench from the Valk toolkit and unscrew them by putting a short socket on the top of the bolt and using my fingers. On some of the manifolds there is a tube coming off a nipple on the back of the manifold. Some just have blank tube ends. Be sure and disconnect the hose, and keep the manifolds in order so you know which go back where. The tube going to the left-rear manifold connects to the tank on the other end, so if you've removed the tank this hose will be hanging loose in your engine. I'd thought I'd pulled the other end free from wherever by mistake. Good thing TMIB has done carb stuff many times before. After you loosen the hose clamp, remove the two bolts, and disconnect the hoses, you can just grab the tube and pull and it'll come right out with little effort -- it sticks about 3/8" into the upper hose and fits flush with the engine. There's an O-ring in the bottom of the tube; make sure you don't lose it, it's greased with something and will drop off when you're not looking.

The manifolds are cast aluminum and the wall on the inside bend on one of TMIB's manifolds was quite a bit thinner than the outside, but most are about 2mm thick all around. Plenty thick that you don't have to worry about sanding a hole in it.

For the polishing we used TMIB's Dremel with this keen 24" flexible drive cable which holds the bit at the end like a dentist's drill. We started out with the 1/2" sanding bit using (I think) 80-grit sanding cylinders. We burned through all three remaining 80-grit cylinders on our two bikes, so make sure you have at least two or better yet three new ones before beginning. After sanding down the chrome and rough casting finish, we put on the softer metal wire brush (flat disk type) and polished out everything pretty good.

During my return trip home I noticed a bit more pull at higher rpm's. I haven't ridden enough to do a mileage comparison yet.

In retrospect I think the beveled (bullet-shaped) grinding stone attachments would work even better for the rough work. I might try for a better finish this winter when my bike's apart.

I personally, in the cultural vacuum in which I live, could not for the life of me find a 1" flapper for a die grinder. Sooooo...

I used a Dremel with small 120 grit sanding drums like LOKI suggested. Buy a bunch of them. If you can, get a flexible shaft for your Dremel. About $26 bucks. It makes the job easier and with the increased fuel mileage, it will pay for itself and you will use it elsewhere besides.

Do everything Lamont says on his site, but use the Dremel and drums. "Scrub" the insides of the tubes, don't let the drum sit in one place for any amount of time. I went a step further on NightMare, and you need a Dremel with drums to do the second part.

I did one intake at a time to keep the dust out of the other ports. While I had the intake port open, I went down into the head to clean that up too. But, you must be careful not to leave dust in there.

I soaked some lint free shop towels with a little oil and stuffed it down into the ports as far and tight as I could. Then I went after the port in the head with the shaft and drum. Same method - "scrub" - don't hang in one spot. You can't get it all, but you can get a good amount of the rough casting off. Once done with a port, suck as much dust out as you can with a shop vac and pull your oily towel. Then, get a rifle bore cleaning rod and several swabs. Soak the swabs with oil and clean out the port of any remaining dust.

My intakes are totally free of varnish after several thousand miles of riding. They are also dry and free of any evidence of washdown.

For the doubters, take a look at Lamont's pics on his site (link above). That's VARNISH on the intakes (he's in California, so it's nothing to do with climate ;-). That golden greenish stuff in the stock intake. Dry or wet, it's VARNISH. Proof that there is washdown on the intakes. You will find that mossy stuff in the heads too. Mine are totally free of that now.

This is in response to some e-mails I have received. And, a supplement to Lamont's excellent write up.