Cross hatching
 

In years past i've rebuild snowmobile and bike motors. When replacing rings/pistons I used a 3 stone tool and kerosene to cross hatch the cylinder.
Do you guys do this to these small motors and if so, with what?

Edit,

Also, as you make changes and try out different mods after reassembly, do you use new gaskets each time or coat the old ones?
Can you just coat the head gasket for testing purposes?

RE: Cross hatching
 

Cross hatching is for iron cylinders, not chrome or Nikasil...You want smooth so as not to wear out the piston rings...If you had cross hatching on a chrome cylinder the rings would not wear the chrome smooth, the peaks on the cross hatching would wear the iron rings out in short order...The lines you see in a chrome cylinder are the valleys left from the original machining operations...
Old gaskets seal just as well as new gaskets, why not use them ?

RE: Cross hatching
 

Ok, thanks
Does this apply to the head gasket as well?

RE: Cross hatching
 

Most of the motors you convert will be one piece cylinders with the "head" integrated. There is just a base gasket for the cylinder and a gasket between the crank case halves. Only other gaskets in a typical engine are the one s between the intake block and the cylinder and the carb and the intake block.

RE: Cross hatching
 

Ok im off to tear down some homelites!
I found 2-25's and 1-30 to play with
The 30 is the one I want to use I think....

Thanks

RE: Cross hatching
 

Have I been putting a gasket on the exhauast outlet needlessly?

RE: Cross hatching
 

I got a brand new Homelite 30cc leaf blower early last fall. I am running it in blower, but so far it just does not rev up good like others. I wonder if maybe they made this one to start and run nice but just forgot about top performance!!! Its a dog. This spring...its comming apart to get a hop-up and back in blower to break in some more. Capt,n[:-]

RE: Cross hatching
 

Best sealer for exhaust parts is Permatex Ultra Copper silicone...Won't burn out...Gaskets compress and get loose...doesn't take much....[8D]

RE: Cross hatching
 

Ralph,

What's the best sealer for the engine case and case to cylinder surfaces?
All of the old gaskets disintegrate upon removal.

Thanks

RE: Cross hatching
 

I can't believe I was asking about head gaskets! LOL

Foamcut - The exhaust sealer mentioned should be good for the entire motor.
Personally I have some permatex aircraft grade sealer that I use. Its black and really sticky
Cant remember the number right off hand but when I dig it up I will post it.
I've used this with great success over the years in a multitude of applications. Never on exhaust though.


Oh well... got the 2 25's tore down and they both look pretty good. They both had good compression and spark with just a hand flip of the mag wheel.
I figured I would work on these first before tearing into the 30. They are all around 1990 vintage or a touch older I think.

2 questions:

1. What is the best way to make the aluminum bright again? I've tried all the chemicals under the sink and on the net all I found was Tarragon/Vinegar combo that does not work.
I also tried oven cleaner but that darkens it. Sure sanding and polishing would work but there must be some common chemicals that work that everyone has around the house.

2. Is there a hotter coil to use with the stock mag setup? I know about the CH ignitions and all of the others, but I was curious if more could be gotten out of a stock setup for easier starting etc.

RE: Cross hatching
 

That black sticky stuff is maybe Permatex. It is hard to remove. Try Yamabond for clyinder to base or for metal back-plates. Be sure and remove any oily film first. I use carb cleaner or lacqure thinner.. Capt,n

RE: Cross hatching
 

jrjr2u,

Thanks for the feedback on the gasket sealer. I just want to make sure I don't have any leaks when I re-assemble. I've seen some really resiliant sealer on McCullogh chainsaw engines so I figured that might be the way to go. Let us know that permatex number when you find it.

The best way to make the aluminum bright again will be an mechanical / abrasive polishing. The surface oxidation of the aluminum won't be removed chemically without further etching the underlying aluminum. I would recommend a buffing wheel on your drill or bench grinder and a tube of Flitz or other wheel polish. Of course once it's polished you'd have to seal the surface to prevent it from oxidizing again.
I'll polish up a case this afternoon and post some pics to demonstrate.

If this were a ferrous metal I'd use a product called Evapo-Rust to remove the oxide but even then a mechanical polish would still be necessary to make it shine.

RE: Cross hatching
 

I found my sealant. Its by NAPA and called Aviation Form-A-Gasket part#765-1210

http://www.napaonline.com//MasterPag...ant+-+Aviation

It says max 400 degrees though so it would not be good for exhaust applications but has served me very well over the years in non exhaust applications.
Thin with denatured alcohol so that can probably be used for clean up too.

Edit:
I just tried cleaning up the can with Isopropyl and it came off with a little scrubbing.
This stuff may not be Glo Fuel resistant

RE: Cross hatching
 

jrjr2u,

I ran short on time this afternoon so I did a quick buff / polish on a a small section of a Mac25 case.
I've attached 4 pics below.
The first one is the original surface.
The second one is the surface after a buff with black emery on a 3600 RPM cotton wheel.
The third and fouth pics are of that same surface after a polish with 1200 grit rouge on a 3600 RPM cotton wheel.

I'm not aware of any chemical means that would allow you a polished finish without mechnical buffing / polishing. Chrome or nickel plating might acheive your goal but certainly would add expense. You could check with Caswellplating.com. They have an excellent tutorial on polishing and will sell you top quality plating chemistry and supplies.

RE: Cross hatching
 

Yea it looks good! I'll send mine right over :)

I thought there might be an easier way but I guess not, but polishing is not really that hard either....
Rather than polishing and then clearing/sealing the motors, I think I will paint them with header paint.
Will post some pictures when I get it done.
Just a quick going over with 400 paper makes them look pretty good though.

RE: Cross hatching
 

Shine is nice but it does slow down heat transfer.

RE: Cross hatching
 

Very true but I don't see it as an issue with the constant prop wash

RE: Cross hatching
 

I'm going to use a beadblasted finish on my stuff to eliminate the oxide coating and to create texture that increases the total surface area. This should promote cooling from a theoretical perspective. From a practical perspective these engines are going to be getting more airflow than they were probably designed for already.

Great input...thanks