View Full Version : Mounting the two stroke head for milling

Bob Quale
12-14-2003, 03:52 PM
I thought there must be a lot of info that I am not aware of so,

What is the best way to mount a two stroke head for milling?

Should the spark plugs be in?


12-14-2003, 03:55 PM
before I mill anything, I remove everything that is seperate from the piece, I see no benefit to having the spark plugs in.
Ofcourse you want the head to be mounted in such a way that it will not shift, and has as much surface area as possible resting against the table or holder.
This is certainly a project I would not do myself, atleast not without having more expirience under my belt.

[This message has been edited by BillH (edited 12-14-2003).]

12-14-2003, 04:05 PM
Do you have a lathe? Check your other post and find the easy way there! Take out your spark plug and use that hole to hold your head!

12-14-2003, 04:40 PM
Having never done one, and having no idea what this particular one looks like, here are some WAGs, which may be totally bogus for your particular situation:

I'd clean the inside face (the one you're going to mill) with a wire brush or similar and get any crud off until it will sit flat and solid on the mill table. Clamp it down. Spot face the surfaces around the bolt holes so they're all the same height (they may be, anyway). Make a set of standoff bushings, all the same length, as many as there are bolt holes. Get a flat plate, maybe 1/2" aluminum, that you can use as a mounting plate. Put the head on it (upside down) and drill/tap through the head bolt holes into the aluminum plate, using the standoffs if necessary to let you do that. Then bolt the head to the plate, through the standoffs, with appropriate short bolts so you can then move the head+plate combination around and have to worry only about clamping that mounting plate.

12-31-2003, 01:48 PM
My Husband does heads like this. Chunk of Aluminumn. Lay Head on Top. Transfer punch hole pattern from head stud pattern onto alum. plate. Also include the plug hole. Remove Head. Drill and tap punched marks for a suitable suocket head cap screw whose Outside head diameter is large enough to not slip through the hole dia. of the head. Flip head onto socket screw heads. Now you can level the head by reaching through the head bolt holes with a bondhous allen wrench and hold it down through the spark plug hole into the hole you drilled and tapped through the plug hole. Works good, Audrey

Ragarsed Raglan
12-31-2003, 02:36 PM

I'd stick to 4 strokes if I was you! You get a nice flat face to work off from the cam/rocker box surface!!

However, having chosen a 2 stroke to work with, then I'd look at it this way:-

If the plug is vertical in the head and not angled, then maybe you can use an old spark plug body to thread into the plug hole and then bolt down with a stud through it. Use suitable side clamps can then be used to prevent the head from moving. Alternatively you can weld a piece of bar to an old sp body to use as an attachment for back bolting (after suitble drilling and tapping of a jig plate - along the lines as suggested in previous posts). Then again, I like the idea of using the head bolt holes with suitable pillars (especialy if the boses are 'level'), but to hold the head down using Allen bolts (or any other bolt) from the head face side will, as likely as not, intefere with the face to be machined. In this case I would consider, either machining a recess in the face to allow use of a 'top hat' bush nut (drilled and tapped, then bolted from the jig-plate side); or by using an expanding mandrel type pillar which is expanded by a suitable coned screw in the pillar (go look at the cheap Chinese made lathe expanding mandrels as sold by folk such as J&L, these use a 60* included angle type cone screw - maybe someone sells them separate? - otherwise it's a case of make them yourself!)

Basically, all this adds up to engineering a fixture (several hours work), for a five minute skimming job. Look on the bright side though, once you've worked this job out you can take on similar jobs with ease.


12-31-2003, 10:55 PM
I do like Audrey say's her husband does but
I locate everything from the spark plug hole
(assuming it's in the center). I have a threaded pin which sits lower than the combustion chamber this screws into the jig plate and head acting as a reference intial
hold down point. I would not put the spark plug in, it there was a problem and got caught on the cutter, you have ruined the head.
I also make a clay or wax mold of the combustion chamber before I make any repairs
{i.e. welding or reshaping) that way if I encounter a problem I can build the material back up and can reshape it the the original size.

01-01-2004, 09:45 PM
I do a number of heads every year for a customer who races his machines. In all cases I do them in the lathe. The set up is simple in the 4 jaw. I take off as much as .0300 in some cases. Is there a reason you want to use the mill? It seems to me all the clamping and truing would be excessive.

Bob Quale
01-01-2004, 10:34 PM
My lathe only has a 14" swing. The head needes a 20" swing. The squish band is at .040 which is perfect for this set up. So I need to cut the squish back the same amount as the head.

This could be a reason to buy a gap bed!

But in any case I need to use my mill on this one, I think?


01-02-2004, 09:29 PM
The heads I'm turning are for snowmobiles and fit in a lathe with a 10" swing. They must be some heads your turning. Your not trying to turn them with carbs attached are you? http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif