850 head can go how big?

[Guest]

I'm just wondering if this head can be punched over, and if anyone knows if parts are available to do so

[TheCafeKid]

If im not mistaken, the early 850 jugs were just punched out 750 jugs. With that in mind, they're already going to be thinner than stock 750 jugs. IF there is a bore kit available, going any LARGER with THOSE jugs could result in bad times, as the cylinder walls would be really thin at that point, and lead to overheating. You trying to make a drag bike out of that thing? You havent even got the 850 kit on it, and its already not enough power for you? Why dont you sell it and buy something bigger? Market is pretty soft right now, I bet you could sell that thing for a grand or so, and then pick up a 1000E or G in good running shape for 1500ish...

[crapwacker]

If im not mistaken, the early 850 jugs were just punched out 750 jugs. With that in mind, they're already going to be thinner than stock 750 jugs. IF there is a bore kit available, going any LARGER with THOSE jugs could result in bad times, as the cylinder walls would be really thin at that point, and lead to overheating. You trying to make a drag bike out of that thing? You havent even got the 850 kit on it, and its already not enough power for you? Why dont you sell it and buy something bigger? Market is pretty soft right now, I bet you could sell that thing for a grand or so, and then pick up a 1000E or G in good running shape for 1500ish...

You got a point. I was fishing for info on that head, and that was what I was looking for. I haven't done the swap, and wondered if it could go and larger. going to the 850 will give it a little more umph, but like you say, this is a good time to buy.

[49er]

If im not mistaken, the early 850 jugs were just punched out 750 jugs. With that in mind, they're already going to be thinner than stock 750 jugs. IF there is a bore kit available, going any LARGER with THOSE jugs could result in bad times, as the cylinder walls would be really thin at that point, and lead to overheating. You trying to make a drag bike out of that thing? You havent even got the 850 kit on it, and its already not enough power for you? Why dont you sell it and buy something bigger? Market is pretty soft right now, I bet you could sell that thing for a grand or so, and then pick up a 1000E or G in good running shape for 1500ish...

The early ('79) 850's aren't punched out 750 cylinders. They were re-cast and have 3mm wall thickness sleeves. You can further punch them out safely to 71-72 mm, but you need to go custom pistons to do that!!

As said earlier, buy a bigger bike if you want mega performance.

[Nessism]

I'm just wondering if this head can be punched over, and if anyone knows if parts are available to do so

Sorry to nit pick but the head is never "punched over", it's the cylinder that's bored out so larger pistons can be fit.