Boring - The Hole Story

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- Boring -

The Hole Story

The question - What is the hot setup for honing/boring? I do all of the work myself, except for cylinder boring and honing. Also, where's the best place to get the equipment?

The response - All I can say is, if you plan on boring your own cylinders, take them to a reputable shop. At $30-$50 a hole, you would have to bore about 200 cylinders just for the machine to pay for itself. It is easier to mic out the cylinder to double check the clearances, after you get the cylinder back than to by the equipment. I know it's nice to do things yourself, but in the case of boring and crank pressing, it is best left to the "professionals". I am like you, I do all of the work myself, but the crank and boring. I send my crank to Tony Doukas Racing, and I have my cylinder done at a local race shop. He does a lot of them and if he screws it up it's easy to catch, and blame is easy. I always double check tolerances after I get cylinders and cranks back, just so I know what everything is set at.

Eric

Finding a shop that can bore a round hole that's straight and true is more of a task than it would seem. Many places have a Quick-Way boring bar, but that doesn't mean they know what they're doing.

The hole not only has to be round - the top of the bore being the most critical on a 2 stroke - but it has to be perpendicular to the centerline of the crankshaft - exactly 90° when installed. That is to say it must not tilt to the right or the left because it would wear the piston and everything else quickly. Additionally it has to be concentric to the position of the original bore. If the hole is forward or behind the original hole, the timing will be off - or not the same as it was. In many cases this can be used to an advantage when done properly.

Torque plates work well on motors that are getting big bore piston kits or engines that are going more that 1 mm over size. If possible use them on every bore job - it is a quality touch.

I like what Eric said about double checking everything. A long time ago I got a bore back from a company that I trusted only to find that the hole was the same size as the piston. It would have been a instant disaster. Needless to say that company does not do any work for me any more. Parts are too expensive to replace as it is, add to it incompetence and that's just too much to tolerate. A company gets one chance to make a believer out of me - if they screw up one time - I go shopping. There are no mistakes - there are no excuses - I make it clear ahead of time what my policy is, that way there's no confusion if something goes wrong. Everyone who works on any of my stuff knows me by my full name - I like it that way. I have been referred to as "Rick The Prick." It should be "Rick who won't pay for incompetence."

Rick - [Please see TRX 270 cc Engine for more information about bores and sealing compression]

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The Hole Story
The question - What is the hot setup for honing/boring? I do all of the work myself, except for cylinder boring and honing. Also, where's the best place to get the equipment?
The response - All I can say is, if you plan on boring your own cylinders, take them to a reputable shop. At $30-$50 a hole, you would have to bore about 200 cylinders just for the machine to pay for itself. It is easier to mic out the cylinder to double check the clearances, after you get the cylinder back than to by the equipment. I know it's nice to do things yourself, but in the case of boring and crank pressing, it is best left to the "professionals". I am like you, I do all of the work myself, but the crank and boring. I send my crank to Tony Doukas Racing, and I have my cylinder done at a local race shop. He does a lot of them and if he screws it up it's easy to catch, and blame is easy. I always double check tolerances after I get cylinders and cranks back, just so I know what everything is set at. Eric Finding a shop that can bore a round hole that's straight and true is more of a task than it would seem. Many places have a Quick-Way boring bar, but that doesn't mean they know what they're doing. The hole not only has to be round - the top of the bore being the most critical on a 2 stroke - but it has to be perpendicular to the centerline of the crankshaft - exactly 90° when installed. That is to say it must not tilt to the right or the left because it would wear the piston and everything else quickly. Additionally it has to be concentric to the position of the original bore. If the hole is forward or behind the original hole, the timing will be off - or not the same as it was. In many cases this can be used to an advantage when done properly. Torque plates work well on motors that are getting big bore piston kits or engines that are going more that 1 mm over size. If possible use them on every bore job - it is a quality touch. I like what Eric said about double checking everything. A long time ago I got a bore back from a company that I trusted only to find that the hole was the same size as the piston. It would have been a instant disaster. Needless to say that company does not do any work for me any more. Parts are too expensive to replace as it is, add to it incompetence and that's just too much to tolerate. A company gets one chance to make a believer out of me - if they screw up one time - I go shopping. There are no mistakes - there are no excuses - I make it clear ahead of time what my policy is, that way there's no confusion if something goes wrong. Everyone who works on any of my stuff knows me by my full name - I like it that way. I have been referred to as "Rick The Prick." It should be "Rick who won't pay for incompetence." Rick - [Please see TRX 270 cc Engine for more information about bores and sealing compression]