Porting!

Awsome thanks. I was having a bit of a chat to friend whoz been doing port work to motors for a long time, he suggested that i didnt polish intake (obvious) or exhaust ports and that i used a sand blasted and a vacum cleaner to smooth it all out. I saw you had this done with your intake port but not exhaust...

As with the plan that was pretty much it. Take the head off, port it all, releve the seats, get the intake manifold all matched then the exhaustand put it back together. I was then going to advance the timing and start jetting it.

next step wud be increase the compression (if i dont do this in the first go) and start working the valve train.

"two or three stones for working around the steel guide"
do you leave the guides in there?

Yes the guides are mostly left in while working. I grind the guide down flush in the intake port. On the exhaust side, I grind about 4-5mm off the guide and trim down the aluminium around it. Some guys do grind the exhaust guide right down too, but I don't like that. The guide is the only way the exhaust valve can rid itself of heat. These motors already run very hot, especially in the exhaust region.

Maybe someone should make a porting guide and it should be stickied .
Was also thinking about advancing timing on my bike but not sure if it will make a difference on a stock bike? Also what other cheap mods are there for a stock mso bike?

I noticed a difference from a few cheap mods.
1. Grind out the excess weld in the opening to the exhaust.
2. When they upgraded the Mikuni they didn't put a larger inlet manifold to match. $16.50 off Ebay for the correect size which I honed and matched to head and carby. The walls on the stock one were too thin to be honed out to the necessary diameter.
3. You might also notice that the throttle cable adjustment won't take out all the play. I super-glued a correctly shaped piece of PVC onto the twist-grip insert and reshaped with a dremel. Just making the throttle immediate and responsive made a big difference to the feel of the bike.
4. NGK plug

The MSO's I have seen standard, have been running too rich. They really need jetting. There is no point doing that until you have finished doing any head work etc. It would be good to get a sticky thread guide to jetting as well.

well this thread is pretty much the guide to porting, especially after mac's responses to my questions. Mac if you just wrote a little about grinding method etc for those who are doing this for the first time this would be pretty much complete.

as for timing, yea it will make a difference. But increasing the advance your engine will run hotter, you also run the thread of pinging (pre-detonation of the mixture) which is the worst thing for any motor besides a 4stroke with no oil. Step by step instructions here: http://www.50mods.com/articles/mods/timing.asp

Im not sure how much advance it will give you by doing it that way, im sure there are other methods of getting more advance... that is the way i will do it (ream out the holes as far as poss). Make sure after doing it you listen for pinging, will sound like a nut rattling in your exhaust.

hey,

http://cgi.ebay.com.au/ws/eBayISAPI....MEWA%3AIT&rd=1

would that be a suitable tool for porting these alloy heads or is it a bit big?

Ive got a couple of stone bits, but they tend to wear quickly and sometimes clog... I will use those for the valve guide, but is that bit good for the rest?

yeah too big. what tool are you using?

Ive got a dremel, that takes 3mm (1/8") shafts, and was going to borrow a die grinder which takes 6mm (1/4") shafts. Should i just buy a few stone bits and stick to the dremel?

The dremel will be ideal. Use 1/8 aluminium cutters like these

Attachment 55Attachment 56

should be able to get them from bunnings. Use your stones on the guide, and 60 grit sanding rolls for the rest. Most of your work will be done with the sanding rolls. Shaping and tidying the port. Bunnings sells dremels with the extension handpiece for a little over $100. The extender makes it real easy to use. If you have this you'll be laughing.

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mite go have a look see what i can find. Im going to try a sand blasting method for the final finish of both the exhaust and intake ports. Put a vacum on the valve end of the port, then aim sandblaster down the intake... should get rid of all the little rough edges.

have you got any idea on the aluminium cutters, and what are the sanding rolls u talking about? Those little rubber bits that you slip a roll of sandpaper over?