Buying a dome would defeat the purpose of this experiment.

Zero: There is no way in hell I would ever challenge you on engines. You are clearly a high perf Engine guy based on what I have read in any of your posts. As an Engine guy you are probably pulling your hair out right now. I can hear you scream over the internet. That being said, this post originally started as "lets see if I can run a badly damaged welded piston" TO "lets see if I can break it". This project has kind of run away on me. I enjoy experimenting. I don't care if I explode this grenade all over the side of the mountain. I'll tow it home and fix it. Also note that because of where I live, most full throttle runs are VERY short bursts because you will fly off a cliff or into some trees.

I don't have a depth mic so I do the best I can with what I got. I measured the deck at .079" so that works out to 2.03mm -- right ?? I don't own a Pilot so not sure what those run at. It's possible it is less like you say.
By the way thank you for that link to get domes. I didn't even know you could buy that stuff and if you could I thought it would be a fortune. Nice link thx. But I am still gona make my own for this project. Not sure yet if I am going to run that o-ring or use a stock gasket to drop the compression. By the way I am using used rings that I skived out of this piston when it blew up.

What liduno said.

Despite my initial lack of enthusiasm in your ''Making A Piston'' thread, I'm starting to understand you. I now fully support your inner mad scientist..lol

OK I guess I was confused between MM and ". 80thou would be 2mm. I was thinking .080 was .8mm and so I thought 2.03mm was too much, when its not. 2.03mm deck clearance is going to make a very loose squish (Probably 80 thousandths or more).

If you were making a high octane/performance Engine then I would still tell you to get the squish down to about 40 thousandths. You can accomplish this two ways:

1. Deck the base of the cylinder. Fr this you'd need to carefully heat and press out the sleeve, deck, then re-install the sleeve. In fact if you did do this; I'd actually recommend replacing the sleeve for an 80mm one.
2. Deck the top of the cylinder. Much easier done.

#1 - Deck the base has the added benefit of changing port timings. This would give you an opportunity to make lots more adjustments given some porting knowledge. #1 would be much harder for the layman Engine builder.

I just looked in my notes and previously noted my Pilot Engine has a .28mm (11 thou) deck gap. You being at 2.03... that's a number designed for air-cooled engines... Think about it.


Bottom line - I suggest you deck the cylinder top. By how much I cannot tell you exactly because ultimately it would need to be relevant with the squish band you'll be cutting into your head - which should be at about a 10 degree angle.

Thank you

No I can't build a performance Engine.
I just don't have the tooling or the technical abilities.
Decking and sleeving is way out of my skill/tooling range as I have not done either one of those.
This is just gona be a basic Engine with a welded up piston. Right at the moment I am leaning towards running that homemade head with a stock gasket which will really open up the squish but it will drop my compression to a reasonable level. Hell I might even start over and make another head with a deeper combustion chamber. Not sure yet.
Well off to the little city to help out my buddy. He got canned last Friday when the company he worked for decided to contract out the shop work. We gota go get his service truck. Adios for now.

Caveman style - use a belt sander. Mark around the inside and outside of the cylinder about 1mm depth and go to town. After, final wet sand it flat and true using a perfectly flat surface - like a slab of granite with 220 grit firmly fixed. Let gravity to the work and just slide the cyl in a figure 8 motion.

I have no idea bout the squish band angle but I just had my Engine rebuilt and it was originally at 9*, and was recut to 14* as that's matches the angle of the piston dome at the edges. my squish was set at .054"

When I cut the squish angle on my homemade head I set the compound vise on the lathe at 15' (as best I could). The reason is that I measured (the best I could) the angle on the stock head that is laying on the bench right now. It came in at 15'. I may be wrong but that's what I got.

Question: What happens if my squish ends up being .110" or .120" total ??

The Engine will be lazy. Less heat. Less power. Less burn quality. Less fun.

More reliable.

From what I understand, the squish centers the flame in the combustion chamber, and helps atomize the air fuel mixture through turbulence. The less effective the squish, the lesser the efficiency of the burn. Too tight you risk detonation, too loose you lose power.

Took a brake from that fooling around on the head thing because I was getting tunnel vision.
Moved onto the pull start because it was busted. Previous owner must have ripped the rope off, as well as the handle was missing and the aluminum bung and plastic nut were busted. What a retarded job this was. The previous owner of this Engine screwed everything up on this pull start set up. The spring an latch were also damaged and would not engage and the spring was bent on the end and grabbing the aluminum casing, scoring it up.
The rubber rope protector was also torn in half. So I bought some 3/16" paracord and a bicycle inner tube to use as a rope protector. I saw a picture here once where a guy used beverage tube as a rope protector as well.
Still have to make that aluminum bung under the pull start handle.

Edit: pull start rope is 3/16" x 70"

I hear you on taking a break. All that Engine stuff will give a guy a headache!

Looking good - I would buy a oem style handle. It is easier on your hand and it will also seal around the aluminum bung.

https://www.ebay.com/itm/HONDA-1985-FL3 ... :rk:4:pf:0

Is that a starrett scribe? I use mine often, handy tool to have around.

How did you mold the end of the inner tube to fit the recoil case?

It actually slips over and then you hold it with a tie wrap.
It's a snug fit and you have to stretch it to get it to slip on. The bell end of the cover is larger than the inside diameter of the inner tube. This was a brand new inner tube I bought and not a used one.
I will hold it with a tie wrap at the other end as well ---- when I get it made. Original Honda one was broken.

scribe -- yes
handle -- to cheap to buy stuff if I can make it, handle will never be used, my starters all work or I fix them

Well I got most of this Engine together now and am concentrating on finishing the head.
This head is turning into a "real project". Cutting the dome was a piece of cake compared to the rest of it.
There are several problems here.
1) Cutting the dome and the base plate are no problem at all but now the problem is that I have to cut 7 holes in this base plate for the head studs and they will be inside the water jacket. That's the problem. I want to be able to get at them. On the stock heads I liquid cooled I have 7 pipe plugs I take out to get at these nuts but I have to drain the system. I don't want to do that on this project.
2) If I cut 7 tubes and weld them in then they can't leak. If I use long bolts and bolt it down to the cylinder I can't have any leaks in those 7 tubes. Using bolts or studs -- same problem.
3) These tubes will be very close to the dome I made so not sure if the weld will clear.
4) This head will be square. I don't have a four jaw chuck for my lathe and even if I did it's to big of a piece to fit. I think I have an idea for that but not sure yet. So why not make it round you say. Well same issue, my lathe is to small for the piece to fit.

This is a big job. Now I know why they want 3 to 5 hundred bucks for this crap.

Can you make the water cooled part removable? Drill your holes as if it will be an air cooled head, then tap holes between each of those holes to bolt down the water cooled part. You can seal it with an o-ring just like the head.

Or go with the tube plan, but don't weld in the tubes, seal them with o-rings? Like these, but straight.
https://shop.advanceautoparts.com/p/dor ... lsrc=aw.ds

Well that's an interesting concept I didn't think about.
I think that would be complicated though. Have to give that some thought.

Looks beautiful!

I love the inner tube for the pull cord protector! I tried attaching 2 FL250 rope tubes together to make one FL350 size one, this is way better, and cheaper.

The inner tube was not my idea. It was the member Toby. He has not been on in a while. Lots of smart people here.
The paracord cost me $17 Canadian at the local gun shop.

I wouldn't have thought of the paracord either!!! That's why I love this forum! I just ordered some for my sled, that rope always breaks! I will be sure to replace my FL350 rope when it brakes also.

That old saying 2 heads are better than one. Good group of guys, full of ingenuity!

We could probably make anything... We'll, we should just get this Engine to not blow up for now!!!

I'm running avgas. We're golden

I still think you might want to open up that combustion chamber a little, but water cooling and high octane should definitely help.

When you get a minute, do a google image search on ''derbi tpr water cooled head'' It might give you some ideas on the head.

Yes I just looked that up. Cool. I am drooling. Wish I had CNC capabilities and equipment. https://www.treatland.tv/derbi-TPR-wate ... d-head.htm

But the issue for me is all those O-rings. Lots of potential leaks. Also I would have trouble cutting some of those o-ring pockets with the machines I got here.
I have decided to change tactics a bit. Right at the moment I am giving up on the square head.
The base plate will be square but the water jacket will be round. It's just a lot easier for me fabrication wise. Have to wait until next week when the machine shop is open, and then I can buy the stuff I need. Hopefully anyways. Hope they have stock.
I might try to bolt this head on before it is even complete, to do a compression test so that I can see where I am at.

Well ---------- Poo ----------
I bolted on the head temporary and it's no where near finished but I just wanted to see what the compression is. The Engine had no reeds installed but I see no reason for this anyways. Spun it over and got 135 psi. Rats. The old rings I used were from this piston when it blew up. Looks like I will have to buy new rings and didn't really want to do that since this is just an experiment. I guess I could bolt on reeds and try again but I think that is a waste of time.
At least I can do a leak down test to make sure the seals are still good. If those are shot then it will be a complete tear down.