Thoughts on street engine build for a 1980 KZ1000E

I am going to build a motor..or attempt to build a motor for my KZ1000E over the next several months. I can't afford to just go do it all at once, so I am trying to see what I can do to get started and I need realistic parameters.

I have many questions. I do not want a stock motor, but I do want it to be streetable. This bike will be 95% street ridden for sure, but will not be a serious form of transportation or be ridden on 1000 mile jaunts.

I'm not experienced at this at all, but I have a local mechanic (Wedman Motorsports) that is supposed to be really good and should be able to fix whatever I decide to break.

1) What is the biggest you would make a street motor and not have to worry about overheating or affecting its streetability?

2) What's the most compression you would run on a street bike?

3) If i bore out to 1075, 1105, or even 1200, do I need to change from the Mikuni 28's to a bigger carb to take advantage of the bigger bore? (would really like to hear wiredgeorge's opinion on this)

4) What grind of cam to run? If I were building a 440 mopar I would have an idea of cam grind, but no clue what you need for these bikes.

5) Does the shaft drive limit me in any way except being able to run a custom swing arm?

6) Are there any models of heads for the KZ's that will fit my bottom end that are inherently better than others, or is it all in the porting?

Sorry so long.

how many miles on motor?

Here's my E(ST) with lots of perfomance street mods.

Here are some answers/opinions:

1) 1045 and 1075 are good choices. Bigger is not always better or faster. This dosen't mean that you don't have to worry about heat especially if you are in stop and go traffic in warmer weather. I highly recommend an oil cooler.

2) 10.25:1

3) Not necessarily but there are some good carbs out there that may work better than the stock 28s depending on your setup. I'm running RS34s and I like them alot. Wired George will have other suggestions/opinions.

4) I'm running a drop-in-cam 0.365 lift. Execellent street performance cam and easy installation. A 0.410 cam would probably work very well too but requires cam lobe clearancing and possibly aftermarket valve guides which are shorter. I don't think the stock valve guides have clearance between the valve spring retainer and valve guide seal for more than 0.375 lift...Does anyone know if I'm correct on this?

5) It's heavy and less efficient. Also, Kawasaki did a good job of making the shaft model chassis stronger (and 50 lbs heavier) except at the rear swing arm. I pulled the swing arm and braced it because it was flexing from engine torque AND rear brake torque. The ST does not have a torque arm on the rear brake caliper!...so when you hit the rear brake hard the swing arm wants to twist. Why Kawasaki did this I have no idea? The MKII has a torque arm.


6) Be careful...the keys to streetable power do not lie in head porting alone. The right component selection AND PROPER TUNING will yield a very streetable engine with great throttle response, roll-on acceleration and 100+RWHP without hoging out your intake ports.

My ST: 1075, RS34s, 0.365 cam, 4-1 pipe, oil cooler, clip on bars, swing arm mods, progressive suspension front/rear, 94rwhp with 65lb-ft

It wasn't built as a 1/4 mile bike but I did run it last week at Englishtown NJ:
60' - 1.81
1/8 - 7.51
1/8MPH - 94.18
1/4 - 11.79
1/4 MPH - 112.48

i have a wiesco 1075 kit, .395 lift web cams good springs,s
some mild port work stainless vales, 29 smoothbores, older yosh pipe, complete dyna ignition system. ihave almost 30,000 miles on it in the last ten years mostly because of long trip's, i've never had a problem with it,last time i dynoed it made 114 horsepower 79 ftlbs torque. it has been a unreal street motor. i cruise all day at 80 mile an hour and never miss a beat . with a low lift cam like that you won't need to go to shorter guides and you wouldn't want to on a street motor anyway they would wear out to quick. i wouldn't go any more than the 1075 kit, like an 1105 the 1105 bore takes to much away from the sleeves it makes them a bit easier to warp when they get hot[go out of round]

PLUMMEN wrote:

how many miles on motor?

45K


Davel,

Thanks for the info. I like the painted swing arm on your bike. I'm pretty sure the shop I'm going to use for help could help me brace up the swing arm.

My mechanic also suggested 1075 but we have not talked much about it yet.

I've already bought some cylinders and I plan to keep buying parts over the next several months while riding the bike the way it is now.

timebomb33 wrote:

last time i dynoed it made 114 horsepower 79 ftlbs torque. it has been a unreal street motor.

Impressive numbers from that combo for sure. I've thought about the 0.395 cam from web. How does it perform in the low end (below 4000rpm)?

Out of curiosity, have you ever run this bike at the track? If so, any time slip info? Thanks!

I have not had any overheating symptoms with my 1135cc Wiesco kit. it has sleeves that can be bored to 1200cc, so there is lots of sleeve there to keep it from warping. u don’t want to have less than .100" wall thickness or u may have issues.
U need to really think about where u want your power band.
As u go bigger on the intake ports, carbs and cam duration ,u will move the torque range upwards.
You will need to have the head ported to take advantage of more cc’s at the higher rpms.
It will run fine without porting but the power will sine off early.
As has been pointed out . You can make a nice bit of power in the 1075cc range.
As u get above 1135cc's u have to think about when u ride,due to heat.i have a 1327 kit now and it runs at 220*F now. i havent had it running in hot weather yet.

the 1105 is the biggest you can go with stock 1015 sleeves,the 1135 kit works fine 2 but they involve boring out your stock block then redoing the sleeves as well, as far as time slips go for my street bike i tryed to run it once, but i kept forgetting i was on a street bike and kept launching it like it was my drag bike so i'd ether spin really bad or wheelie like crazy, sometimes my brain shuts off and i can do some really stupid things.so my et's sucked but i was getting 117-119 mph with 35 tooth sprocket on back,i'm going to run it this year because i finily bought a trailer big enough to haul both my bikes to the track so i'll let everybody know then.

Couple of thing;

410 cams work with stock guides. Head does need cam clearance, but if it is off the motor and getting springs changed, that is no issue.

Compression ratio.. Remember this is only a mechanical number. What you need to be concerned with is cylinder pressure. Comp ratio can effect cylinder pressure, but so can cam duration, cam timing, etc.

If you are going to install a cam with increased duration and/or overlap, that will offset some of the increase in static compression ratio, and hence, cylinder pressure.

You can reduce cylinder pressure by using a spacer under the block to lower CR, or retime the cams for more overlap.

So you have to consider the entire package and the way it will be ridden when deciding on the static compression ratio.

Jay