wrist pin needle bearing lubrication holes

Hi, first post here, great forum. I am rebuilding a new 70cc boygofast China motor and want to drill lubrication holes in the top of the con-rod to help lube the needle bearing. My understanding is that some motors have these holes but mine doesn't. Without having seen one with holes, I am planning to drill three 5/64" inch holes, one on top and others 45 degrees offset to each side.

Does this sound right and if not what sizes and positions are recommended. Sorry if this is posted somewhere, search yielded no results this time.

Thanks

I can't help you but i never saw it posted and have no idea what to tell you. Please don't worry too much about asking questions that have already been asked, we do it all the time. If there is a detailed answer someone might give you the url to it, but otherwise they will jump right in to help.

This sounds like a norman or bikeguy joe's kind of question to answer.

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Norman!!!!!!!!

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If it ain't broke, and you mess with it long enough, it will be.

What type of nedle bearng you going to use caged or the type that are in a can I call torrington needle bearings.
The caged shouldn't need extra oiling holes needle bearings are a low friction bearing and have planty of room for the premix that's being pumped through the engine. There is a **** of a storm of fuel/oil mix slinging around inside and getting on everything and everwhere inside. I'd hate to be inside and try to stay dry.
I've heard it is very hard to drill the rod some sort of very hard steel I don't know as I didn't try to drill one yet. But extra holes shouldn't hurt as long as you can deburr the hole on both ends. I'm not sure how a guy would deburr a torrington needle bearing housing on its inside there is the rub. Might be better to grind a opening and aline the opening with the rods holes before you press in that type of bearing into the rod.
Let us know how it goes.

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Thanks for the replies! Norman, here is my roller bearing, I guess it is the caged type.


After posting my question I went ahead and *tried* to drill one hole at the top of the rod. What you heard is correct, it is very hard to drill and exceeded the limits of my bits, snapped four. Drilling was easy 95% of the way through and the last 5% is either hardened or hard-chrome plated or something. I never was able to get through it. After reading your post I think the risk of finishing/properly deburring the hole is higher than the risk of lube starvation. This was all prompted by a friend who I've been corresponding with- he just experienced engine failure and attributed it to the cage coming apart associated with over-rev and lube starvation due to no holes.

Thanks again

yes.. Holes should be drilled 120 degrees apart. 3 of them. this is typical with roller bearing uppers. one hole for solid. Solid or Roller bearings can be best. Depends on the metal and roller bearing used. The beauty of a Solid bearing is that when it starts to go, it gives warning. Rollers typically give no warning, and when they go, they take the whole top end, and even the bottom sometimes. Rollers do the most damage by far when they go. As for drilling, I can tell you, the connection rod is super super hard steel. I am not sure you will be able to find a bit hard enough to drill through it. I am sorry to tell you that news.. You should have at least one hole already. Thanks..

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I think something was missed in China (imagine that) if you don't have one hole at least.

You should be able to drill it with a cobalt bit at reasonable speed and lots of coolant/lube. Finish with a diamond burr.

This is yet another reason even I don't recommend running these engines oil lean and I think a reason why most instructions say to use a synthetic oil.

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I know of two boygofast 70cc motors that don't have any holes. I'm off to the tool store to search for uber-bits...

I have a boy go fast kit and have no idea if there is an oil hole or not. I really haven't heard much about them blowing but if it does, I'll be sure that everyone knows about it.

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Well, a cobalt hard-metal bit didn't yield any new shavings from the hole. I ran it with coolant and low and medium speeds for quite a while. The cutters on the tip are showing signs of wear. It's frustrating because there is so little distance left to go. The upside is that the IDs of these connecting rods are HARD!!