What can a 650 I-4 be punched out too?

Several of the 750's I have looked at have had internal engine issues. THen I thought I had a line on a 750 I-4 that ended up being a 2 cyl.

I have started to expand my search to 650's, but am wondering if 10 over each cyl is doable, or is there some other tried and true bore that folks have done?

If I do bore it - what other considerations are there? Heads, cams, etc...?

www.flickr.com/photos/10256004@N08/4398249791/ [/img]

You can bore it out to 700cc max on stock sleeves. You'll have to change carbs but thats about the only thing you'll have to worry about.

Or, you can do what I am doing, bore to 810cc. It involves putting a KZ750 cylinder block on the 650 cases and boring those 3mm over. This will require carbs, head work, and probably cams. My build thread is down in projects, and a lot of members have this completed with success.

You don't have to change carbs, lots of guys run the smaller mikunis with the 700cc kits. Its best to put the 26mm or BS carbs on but the stock carbs will run fine if jetted properly. The stock bore is 62MM and the Wiesco pistons are 64MM so it is a significant bore job. The 810cc builds require 750 jugs and a early model 750 head, some simple modifications to the case, and you will want carburators if you go that route. The 750 can be bored out to 810cc and so you can (and lots of people do) build a 650 engine up with 810cc of displacement. It all depends on how much work you want to do?

You can buy a used 750 cylinder block with pistons on eBay quite cheap and just do a swap.

Champion Kawasaki in Costa Mesa Cali built a 1021cc motor based on the 650 barrel and cases for Superbike road racing back in the 1980-82 time frame. (Cycle World)

The bore was 73mm (+11) and stroke was increased to 60mm (+6) but it was for racing only. I believe the crank was stock but used longer rods and a spacer plate under the barrel. The motor was in a 650 chassis.

The biggest piston kit for the stock rods ever offered by an aftermarket supplier for the street was 70mm (831cc) but these required special liners and case clearancing... they are no longer avaliable.

I believe pistons above 69mm (810cc) for this motor are only avaliable as a custom order part... no suppliers at this time offer anything larger off the shelf.

The 810cc version of this motor is more than enough for the street when matched to a good flowing head and some cams.

Be advised that you cant just bolt 750 jugs and head to your 650 bottom end. the sleeves that protrude through the bottom of the 750 cyl bock wont fit onto your 650 bottom end without spliting your cases and boring the top one to accept the 750 block....that being said it is possable to use your 650 head, but find a 750 head to make it worth or while. None of this work is hard to do, but i Dont know what your budget is, but its gonna add up fast!! trust me!

id try punching out drunks at the local bar first then work your way up to the 650,aluminum is hard stuff!or maybe try kicking it 1st,oh engine boring you say? :laugh:

yeah yeah! I didnt just dremel tool my cases for fear of leaving too much clearance for oul to eventually work through and not too much as to do dammage when it all expands a bit when hot. i pissed enough money at this motor and wasnt taking chances. I guess im too frail to take on the alu-minnium!

Only the early models of the 650 need to be bored out to accept the bigger dia 750 sleeves, I think that if the motor is of the same years that they were making 750s the cases seem to be identical.

You can use an early model 650, 1980 and before, with an early model 750 head/cylinders, '78. or you can use the late model 650, 1981-82, with the later 750 heads/cylinders. The real issue is weather or not the engine has a roller timming chain or a hy-vo type. The 650 ran a roller timing chain untill the '81-'82 model year and only the early 750's ran a roller cahin the rest were hy-vo type. The head can be switched between the roller type or hy-vo and the cam sprockets can be swapped as well, but the lower end kind of dictates the cam chain you have to use because of the sprocket on the crank.

If you use the 650 head with 750 cylinders its pretty easy, but the 750 gpz is the head to use becasue of the bench flow numbers and the cams. So the best combination is to get a gpz head with cams, convert it to a roller timming chain and get '78 750 jugs and fit them with 810cc wiesco piston kit.

Or you can get the whole gpz engine, if your lucky with carbs, and put it in the bike with an 810 kit. The advantage is the oil cooler and a 6th gear.

There are a number of ways to build up the 650 to 810cc, and people pretty much figure out what parts they can get and go from there. I am sure there are other ways to do it. I have "heard" of 900 and 1000cc 650 builds but that is too much top end for the cases IMO.

...Or you can just run 700cc pistons in then engine you have now, or you can run a oem 750 pistons and cylinders, or... or.... or... you get the idea.

This forest green machine is a '79.

ORRRR better yet and I have heard of several people doing this most notably my next door neighbor but instead of all that work you could just shoe horn a z1 motor in to it and be all crazy about it. I hear they are a lot of fun to ride but I dunno. Never had a bike under 850 as my first and then 1000, 1100 back to kz 1075. I think you would have to pull the motor to change the plugs. Not sure on that though. It just seems so much easier and cheaper to get the 900-1000 and go from there. Of course you could just buy something fast to begin with but I assume that wouldn't be any fun if you don't have to work at it. :laugh: