APE or rebuild original?!?

I am about to start the process of rebuilding my '77 KZ 1000A. It has low compression and a leak down test tells me its the rings. I want more power but still a nice streetable ride. I am wondering whether the APE 1015 kit with K410 cams and valve springs would be worth the money. Or should I simply buy new rings? What else would be invloved? Any advise would be greatly appreciated.

IMO...
Get it apart and see what you have to work with. If liners are too worn, you'll need oversize rings and pistons so you may as well go for more displacement. If still in spec, rings are cheap and you can keep eye out for a 2nd engine to build while you ride.

Well, I already have a 2nd engine from a parts bike I bought last summer (78 1000 Ltd) and I have a bike to ride (when it's warm enough to do so). This will be for my 'go fast' rides and my 1980 750 Ltd is my daily rider.

You need to get it apart to see if cylinders are worn out, if so a boring, honing and new rings and/or pistons are in order..then you will good to go fast.

1045

Your kz1000a already has 1015cc displacement and 70mm pistons so unless your bores are pristine, you do NOT want the APE 1015 kit. If you do go with it, you'll get some compression increase. You'll want to open her up, have a look, and then decide which way to go. Up to 72mm shoudl be fine. 72.5mm is pushing things a bit but can be a cheap if you acquire some good used kz1100 pistons and don't increase the compression much.

-Duck

Post edited by: Duck, at: 2007/01/27 22:55

OK, then. I'll get it all apart and check things out. What exactly should I be looking for? How and what do I need to measure? How will I know what direction I need to go?

If you decide to go the 1075 Wiseco kit route, a local machinist has a kit on the shelf that he got stuck with that he told me he would sell for $300.00.

He originally thought it was for the J, but when we checked it we found it was for the 1015 motor. I was going to buy it for a J, so I was a little disappointed.

the 1015 kit is gonna cost same as a 1075 kit except the boring.if you are going to do it id reccomend pulling the bottem end apart and checking everything and throwing in a cam chain while you are at it,that way you dont have to worry about it;)

visual inspection tells a lot.
if cylinder walls are scored or have any discernable ridge at the top you'll be going oversize.

if you want to measure bores you'll need a 3" micrometer and a transfer bore gage . i usually measure near the top and near the middle, front to back and side to side. specs are in the manual.

it takes a little practice to get used to handling and reading these tools. absent some precision gage blocks, take the reading of uncalibrated tools with a grain of salt. not a big deal because it's the variation that's of concern in measuring your bore and pistons.

You can get a decent 'made in china' set of micrometers 0-1", 1-2", 2-3" and a set of transfer guages for about $50 total. IMO, if you can get s Czech made set for not much more, grab it.

wireman wrote:

the 1015 kit is gonna cost same as a 1075 kit except the boring.if you are going to do it id reccomend pulling the bottem end apart and checking everything and throwing in a cam chain while you are at it,that way you dont have to worry about it;)

I couldn't have said it better myself.

Dollar for dollar..all things considered....the 1075 motor with even a drop in cam makes a hell of a street motor...relatively cheap to build...power output is excellent....reliability is excellent and I've never known anyone who said..." I don't really see much difference over my stock 1015 motor" my all time favorite KZ street motor.

Post edited by: larrycavan, at: 2007/01/28 14:52

Go with the 1015. Are you tearing down to the crank?

Wow... lots of good advice except that the person who needs the advice should understand the STEPS for making a good decision. THE FIRST step is MEASURE the cylinder bore... measure in three depths and in different directions so you can tell if the bores are ovalled or round. Measure about 1" below the surface, in the middle and 1" above the bottom. Measure then turn the bore gauge 90 degrees. You should get the same bore measurement both ways. To measure cylinder bores, the easiest/best way is to use Tee gauges. These fit in the bore and expand/lock at the diameter. You then pull the gauge out and measure (transfer) the width of the gauge to determine the bore diameter.

ONCE you understand the condition of your cylinder bore, measure your OEM ART pistons. They are measured just below the piston pin holes on the sides. The DIFFERENCE between the cylinder bore measurement and piston diameter is the CLEARANCE.

If the clearance is within spec, you can install new rings after honing and expect to renew the original performance of the engine as far as the ring seat goes.

OK... IF the cylinder bores are consistent and within spec, you can also go with a set of aftermarket pistons/rings as well to raise compression a bit to increase performance and just hone the cylinders but if the bores are not within spec, you will need to rebore. Since aftermarket pistons don't come in rebore sizes, such as .020" over but only in OVERSIZE, you will need to go with a 1075cc set of pistons or a kit. You will need to buy the kit plus have the cylinder bored by a good machine shop and this will cost between $150 and $200 in most places. You will find that the small increase in displacement doesn't add much performance unless you go with 10.25:1 pistons AND add performance cams (and springs) which will now offer a noticeable performance bump. The 1075cc displacement at the original 8.25:1 compression with stock cams won't feel a whole lot different than a 1015cc engine with stock pistons and new rings.