Boring to oversize at home?

[erik_w]

Hello!

If I want to bore a cylinder out to oversize at home, what would be the best way of doing it?

Where I live overbores are very expensive (100$ per cylinder or more) and therefore I am thinking of doing it myself.

1. Is it at all possible to get a good result at home?
2. If so, what Tools are needed?

Thanks!

[sparkman]

Spend the money. An accurate bore is one of the most critical aspects of an engine build. I used to charge one hour of labor ($60 at the time) for each bore and most shop rates are around $100/hr now.

[rodekyll]

It's easy.  Just buy a machine shop and staff and you're there!

Or as an alternative, rent one for an hour.

[charlie b]

First, it depends on what engine you are working on.  If it's an engine block then you need a big milling machine and the ability to set it up correctly, including the proper holding fixture for the block.  Or go to an engine shop where they have a boring machine that will do it in a 1/10th the time it would take for you to read up on how to do it.

If you are looking at a motorcycle, it is frequently cheaper to buy a used engine than to have one bored (if it can be bored, some cannot or should not).

You can reduce the cost a bit if you do the other work at home, like honing the cyl after boring.  But, if you don't know how to do it properly you can ruin the nicely bored cylinder with a bad honing job.

[charlie b]

So, making a guess that this is the 2stroke bike that you are having trouble getting to start.  Is there enough meat in the cyl to allow for an overbore?

If so, you could do the boring job on a std milling machine.  But, again, you'd have to know how to set it up.  If you have not done any machine work before then paying the $100/cyl is worth the money.  A good shop will charge you almost that much to 'rent' their machine (if their insurance/union would even permit such a thing).

PS machine both cyl to same size.  Only doing one to save money will result in a badly running engine.

[erik_w]

ok ok ok , i get it 

I'll go to the shop and have it done right

[Turin]

You could take it to a shop, or you can go in this direction.
https://www.youtube.com/watch?v=bT1nRq-cM7M

[Lannis]

You could take it to a shop, or you can go in this direction.
https://www.youtube.com/watch?v=bT1nRq-cM7M

He was funny the first time, and maybe the second ...

[charlie b]

I still like him.  I don't watch the full video or I will fast forward through them and I usually have the sound turned off.

[Rough Edge racing]

 I have a rack and pinion drive hone like the one in this photo. With patience and guidance using a hand held drill motor it can hone out a cylinders .010 and keep out of round and taper to less than .001. But it will follow the path of the existing bore... I have used it successfully on low performance vintage car engines...It might be a tool of last resort on a high performance engine...

       

           

[Silver Goose]

Erik, What are you building? Have you ever rebuilt an engine? Do you have the skill set and the equipment to do the work? Have you bought the piston(s)? This would be first on my list. If you have the piston(s) then bore the cylinder(s) to make sure of the tolerance between the piston and bore.

$100.00 is looking cheap,


Good Luck

[O]

You could take it to a shop, or you can go in this direction.
https://www.youtube.com/watch?v=bT1nRq-cM7M

"Adhesive assembly piston shim material, from Nickel Town Customs"...brilliant!  Perhaps my favorite one yet.

[cruzziguzzi]

Send the proposed pistons (matched and oriented) along with proposed rings to a competent shop.

Save the hassle and don't get dis-cumbobulated with advice wavering between the situations of "over-bore" and "honing".

Todd.