Turbobeaver

Hi guy's.Just spent the last hour trying to dig up information on how to go about making a stuffing plate for the crankcase of a Homelite 25 or 30.Maybe it's the terminology I'm using under my search criteria thay isn't producing any significant results for me but at the risk of sounding reduntant(I sure hope not),can someone please tell me how you went about making your stuffing plate?I'm trying to use off the shelf materials to accomplish this task as I don't have a milling machine at my disposal(that would be too easy) so what I'm looking for here is what combination of materials did you use to construct it and what was your final clearance to the crank pin?
On one of the threads that I did manage to pull up in a search,it was by AV8TOR1977 and he says that he left a .020 clearance between the crankpin and the backplate.How close is too close here and how much risk is there of potential damage to the engine if there is any contact between the connecting rod and the stuffing plate?Any help or direction on this subject would be most appreciated gentlemen.

captinjohn

Turbo B. I would say .020 would be just about right. Find some plastic or aluminum or fiber material. Make a test piece first to make sure it goes in place and has the clearance needed. I think you need a flat spot for piston clearance on down stroke. You may be able to put the stuff piece in place...then drill 2 small holes through the back plate into the stuff piece. Take out and tap for 2 small bolts to hold it in place. You can cut your material with a jig saw with the right blabe in it. File any rough edges. Loctite the srews. Should work??? Good luck Capt,n

Turbobeaver

The problem is finding the right thicknesses of materials to use.Man,I'd kill for a piece of nylon or other high temperature plastic right about now.I'd run it through the bandsaw to get the required thickness that I need and be done with it.Seeing as most Homies have a similiar stock back plate and the internal clearances would be similiar,I thought there might be an established formula of sorts for doing this particular job without having to reinvent the wheel all over again.If only you could find,or better still yet, have on hand the types of materials required to do a proper job when you needed them...........................and then I woke up.

w8ye

My Feedback: (16)

The tolerences of the Homelite are lax. You cannot add a certain amount. You have to measure each engine and make the clearance .020".

Sometimes, nylon type materials can be found at the discount store in the form of cutting boards or other devices not intended to be for model airplanes. The filler on the back plate can be aluminum, red linin fibre, plastic, or what ever you can find? Sometimes, JB weld will come in handy?

Enjoy,

Jim

captinjohn

You can use a piece of modling clay stuck on the end of the crankpin to find clearance. Or measure with a strait edge and a depth caliper. Not to critical. Good Luck Capt,n

farley9n

Hi!
How about just taking the required amount off the back of the crank case. Then just trim up and use the stock back plate. Somewhere in this forum is an excellent thread on low buget souping of a Homelite. Follow that advice for engine mods and you should be quite pleased with the results and lack of complications.

captinjohn

farley: That sounds like the best idea. Easy if you got a mill!! Capt.n

Turbobeaver

Yup.I've read all those threads.That particular thread that you were referring to on souping up the Homie was done by AV8TOR1977 a few posts back.Excellent information to know but I'm not quite that brave to start hacking at the back of a perfectly good engine block.I'd rather build up the difference internally and not risk accidentally screwing up anything.If I had a basket of Homie 30's to play with I wouldn't give a hoot and I'd give it a wirl,but I don't.Finding 30's around my area is indeed a rare find.
The idea of using a cutting board has already been experimented with and eliminated by me.They are made of polyethylene plastic which has a fairly low melting temperature and wouldn't be able to tolerate the operating temperatures of these engines.It would be an absolute disaster if it ever melted and released from the crankcase cover internally.YIKES!![:@].....Teflon or nylon would be good choices if you can find them in the right sizes,thicknesses for sale.

captinjohn

Looks like to me the best way is to just trim off the area where back plate bolts on. I guess about .030 is all thats needed + or - a little. Good Luck Capt,n

skypupmut

Andrew Coholic make a very nice back plate for the 30 homie it is alwready made for the purpose of packing the base, cast al.

farley9n

Hi Again!
I have a friend who does them on a belt sander. Remember they are just a seal and don't need to be accurate in reguards to the bore or crank line. You could use a body file then finish with a fine sand paper and a piece of glass. Always worked on B&S heads but that was a hundred years ago. By the way the 25 and 30cc Homelites share all the same parts with the exception of the cylinder, piston, and rod.

Airborn

Well the conversion bug has got the best of me! I have settled on the Homie 30 out of a leaf blower. This will be my first conversion. After tearing the engine apart and doing some measuring I found the tolerances were better than I had expected, especially after reading some of the post. My engine has a metal backplate, If you pull the head off and remove the piston and rod you can reinstall the backplate and get an accurate measurement between the crank pin and the plate. I need to machine .032 off the back of the motor. As long as the pin does not touch the plate you should be fine.

w8ye

My Feedback: (16)

It normally doesn't get very hot at the back plate area of a Homelite. I know it doesn't get hot enough to soften the locktite on the screws.

The area is cooled by the incomming air/fuel charge as well as the large volume of air blowing over it in a model plane application.

Enjoy,

Jim

Turbobeaver

The crankshaft on the 25's and 30's are also different.The counterbalance on the Homelite 30 crankshaft is much thicker and heavier than the counterbalance found on the standard 25's crankshaft.I've read threads in here on people changing over there 25's to 30's by simply swapping the piston/cylinder assemblies over and then wondering why there engines vibrate so badly afterwards.It aint because the flywheels out of balance folks.

jetski_waxhead

OK i am new to this and i know its an old thread
my experience comes from building jetski engines

The main aim of the gain is to increase the area around the crankshaft not to make it smaller
The only reason to try and get higher primary compression isif your transfer ports are not up to the tax which on a homelite they are not.

However since pulling my 25 apart i can see the plate in the back blocks off most of the rear transfer
If this was to be shaped better to allow a better flow then you would be able to use the area in then primary compression area

The way to do that would be to use a nylon block and fit in the back of the case
when you have done that you can then cut the transfer area in it so it breathes better
then you can cut the back out of the block to reduce weight

you will get a better gain than trying to make one and 1/2 transfers work
if you want to go radical you can also put in external transfers as well
thats old 550 piston port days but it can be done and it wakes the engines up very well

you plumb into the crank case and then you drill the cylinder to take a pipe
they are then conected with solid hose sounds crazy but it works

also a modern tuned pipe with better scavenging will also create such a negative presure in the combustion area that you will need to a larger primary compression area so not to limit your engine hp
Better transfer port flow also means you dont need to up your compression ethier
its a win win situation
I am working on my homie now and will post pics of it when i am done

w8ye

My Feedback: (16)

People normally fill the back of the backplate with J-B weld and then relieve the top part for the port you are talking about.

Generally you want the back plate to come within .020" of the crank pin. You can screw a piece of aluminum on the back plate to accomplish this.

Enjoy,

Jim

rcglert

I use layers of ABS plastic secured in place with epoxy. This may sound crazy, but I have been running engines stuffed in this way for a few years now without incident.

Tom

captinjohn

On my 25cc Homelite I have .0156 + clearence from throw pin to backplate. It is easy to measure with jug and piston removed, but with backplate on. Take drill bits and pass them through like feeler gages to find distance. Good Luck Captin

av8tor1977

My Feedback: (6)

If I don't cut down the case, I just make plates out of aluminum to stuff the case. It seems like .125" aluminum (1/8") usually comes out about right. You can always fine tune things with thicker or thinner gaskets, or stacking stock ones if necessary.

Here's a link to a high performance back plate, as well as 30cc long blocks: http://www.whobbies.com/index1.html

Good luck,
AV8TOR

captinjohn

Av8tor: I went to site...did not want to read it all. Where do you find back plate data? Thanks Capt,n

av8tor1977

My Feedback: (6)

That plate is pretty pricey. It includes a mount for boat use. I think they used to have one that didn't have the mount built in, but I don't see it listed anymore. You might contact them, as I think the other back plate without the mount was much cheaper.

Anyway, go to the site, and part way down on the left side under "Products", click on "Accessories". On the page that comes up, in the blue links click on "Homelite Parts". Some of the parts prices are ok, some can be had cheaper from other suppliers. The $109.00 for a 30cc long block isn't too bad...

Good luck,
AV8TOR