81 kz750 e1

Hello, NOOB here, just picked up an 81 kz750/4 as a trade for some labor. It has 44k miles, stock as I can tell and has the vedder fairing (which I may remove).






I have been researching/lurking this site for a bit to figure out whats going on with it. Now thought its time to register. So heres my innagural post. I've been a sportsbike guy (fzr600,r6,r1) but this is my first streetbike. I had originally planned to sell this bike, but after a bit of riding, and research on the site/pics, it might be fun to restore this bike. First, the symptoms:

It is cold blooded, ie full choke, crank it for a bit, maybe a little throttle, it will start and run if you keep the throttle slightly cracked for about 30 secs. Then it will idle on full choke, but seems to do better if you drop it down to half choke. I can ride it fine on half choke, although it loses power approaching 5k rpm. If I try to lower it to no choke, it will idle itself down until it stalls, but only when stopped or coming up to a stop. I haven't noticed any difference riding, but haven't been out on the road much with it, just in town so I kept it half choked so it didn't stall coming up to a stoplight.

Heres my plan of action: I drained the gas from the tank, drained the bowls of the carbs, bike runs now as described above. before it wouldn't start. Tank looks rough inside (this may be another post, but I may have to clean/paint/replace tank in future).

Next I think I need to look at the idle screw, which I may have inadvertantly twisted while tinkering (I have a manual on order). If that does not solve problem, maybe lookin at checking sync on carbs. It definately appears to be a fuel related issue because if I get it "no-choke" and it idles down, I can give it throttle and it will keep running. Also, if it dies, I can start it back up on the "no-choke" setting with a slight throttle input and it will run.

To sum it all up...I think the idle is set too low, which requires some choke adjustment to keep it up. Then, with the choke on, it enters a too-rich situation approaching 5k rpm. Does this sound correct or maybe a larger underlying issue?

Thanks for any help and great site btw.
Chuck

Welcome fireman, nice looking bike. There are others here with more experience and I’d listen to whatever advice they offer, but did this bike sit for any extended period? If so a good carb cleaning might be in order. You may also want to check for vacuum leaks. With the bike running wave a propane torch, valve on, no flame around the intake boots (between the carb and head). If the RPM jumps you have a leak to deal with.

Good luck.

Welcome r6fireman1996.

If you just got the bike then a good going over is probably in order. Check compression, check valves. check electrical etc and like CSR chopper says check for air leaks. I hear WD 40 will also work.

Dont be afraid to play with the idle adjustment screw. It should be a black knob thingy between carbs 2 and 3 and you should be able to see it a bit behind the carbs and almost below. When the bike gets good and warm play with the adjustment until the idle is at about 1200rpm. Then leave it there

Normal starting proceedure, put the petcock on prime for a few seconds, lift the choke lever and hit the starter button. Within a few seconds you should be moving the choke lever down a bit. Half choke for the first few minutes then no choke.

If the tank is in bad internal shape make sure you have a fuel filter between the petcock and the carbs as even a tiny spec of grit in the carbs can cause problems...........or may be causing this problem.

Try the idel adjustment and tell us how it works out.

Good luck

ok, thanks for the info. I tinkered with the idle adjust, and it made a great improvement. I also don't use the prime feature, so I'll give that a try and see if it starts easier, however, it started alot easier last night after it sat for a while post adjustment. I rode it around a bit, and acceleration was great, right up and through 5k without hesitation. I'll keep ya posted on further improvements.

Real quick, what are some performance improvements that are typically done on the 750? Other than this site, its really hard to locate much info on these bikes. Seems like there aren't many out there? Anyway, I was wondering if the individual air filters on each carb helps the engine breath better, maybe with exhaust and jet kit?

anyway, thanks again for the help. C

Welcome r6fireman1996!

You have a mixture of what appears to be a 1980 E model and an H (LTD) model. Have fun with it.

Mcdroid wrote:

Welcome r6fireman1996!

You have a mixture of what appears to be a 1980 E model and an H (LTD) model. Have fun with it.

how can you tell? vin is of e1. and if its a mixture, do I have the "good parts" or is it bastardized? ha. thanks C

A quick glance indicates H model handlebars (standard bars are lower), cables (longer to accommodate the hi-rise bars), front fender (standard is longer and painted to match tank/tail piece), 16" rear wheel (standard would have an 18" wheel), and an LTD style seat (standard seat is flat). The PO may have gone with different bars/cables to better fit the Vetter).

On the cheap, I'd start with an in-line fuel filter (as JR said) and then run some seafoam through with the next couple tanks of gas. You might be able to put off the carb cleaning for a while if that works.

When I got mine, it took a carb cleaning and valve job to get it running right.

I'd also inspect the sprockets & chain. If they are in need of replacement, a common mod is to switch to a 530 chain instead of the heavier 630. There are lots of threads on that here.

Pulls good to 5k? You still got 4k to go until that old girl hits her stride. You called it a street bike, but I think once you get it running right, you'll see it's actually a lot closer to a sports bike than it looks.

Congrats on a nice score. It looks like there's a pretty nice bike under that huge Vetter :laugh:

Ahh Mcdroid you're so observant and so correct
Yes, the previous owner has made some mods !
Personally I would lose the fairing and get lower handlebars but that's just me. Altough I have a 4 into 1 exhaust and individual pods and maybe an 810 motor its just because thats the way it came when I bought it. You could bore out to 810cc, get gpz cams, pods, 4->1 but you are still going to be less powerfull than a modern 650. You have stock airbox and 4 -> 2 exhaust and I would leave it alone and enjoy it for what it is. A good running 750 E1 in stock condition should have a top speed of close to 124 mph and my own 2 cents is that in any mans language thats a damn good top speed

Have fun and enjoy. Glad the idle adjsutment seems to be working out.

Ya, the fairing is gonna go. I wasn't sure if that was an upgrade or not. I think its ugly myself, but its also the first bike I've had that has a front fairing like that. I've ridden sportbikes for so long, its weird not having the wind in my face.

124 is a decent speed, no where near the 165 my r6 did, but i think this bike will be a good "daily driver". It was struggling before to hit 60, so its doing better now.

I didn't take it much over 5k because I haven't changed the oil since I picked this up, and would feel more comfortable with fresh fluids before getting on it hard.

I just thought the pods and exhuast might make it breath better and improve throttle response? At least it did on my R6. Anyway, thanks for the info. I'll post up some pics when I clean the bike up a bit more. Also, anyone know where I can get a headlight and mounting hardware for this? The vedder is integrated.

Z1 enterprises are a good source for stuff
www.z1enterprises.com/
If you cant see what you are looking for give them a call or send an email.