KZ900A4-is this bike really hopeless?

I just brought my KZ900A4 to a shop to replace the rear tire and tube. On the way she rode beautifully-responded quickly. Then I had to go over RR tracks and soon lost power, bogged and died when I stopped to turn left into the shop. This problem has just recently started happening. Last week I rode all day and never encountered this prob. A few days later this problem appeared as I coasted down hill and then went to accelerate once level. (I did encounter an occasional bog last year but she never died!) Also, one cylinder pops.
Last year we replaced the manifolds(?) which were original and cracking. I have electronic ignition-no points.
No major work has been done to this bike since the 80's,having had second gear repaired. The mechanic explained he found loss of compression, engine problems, no electrical. He said the engine needed to be overhauled to the tune of at least $1000 and it still may not run.
Now this bike has been on the road pretty much every year since 1976 to the tune of 21,000 miles. This year she only sat 2 mos. She's become mine since 2004 and I've ridden it year round. My husband has been the main mechanic thus far.
Should I trust a shop mechanic or would it still be better to troubleshoot and repair ourselves. I just downloaded the shop manual and will take a look at that. Any technical work we've done as a team and thanks to you guys some of the repairs were made simple.
Please give me your opinion. I was hoping to ride to Americade this year!

Post edited by: strider, at: 2007/05/17 13:12

It could cost as much as $1,000 and still not run???

I'd think about going to another mechanic.

Otherwise, I would start going through the posts and ask questions here to see if you can narrow down the problem. Maybe you guys can fix it yourself.

I don't know about you but I don't have the $ to spend and then maybe still not have a bike that runs.

Also, depending on where you are located, you might find a member close enough by that can look at it and give you some tips.

Just a couple of thoughts for what its worth. Good luck.

The beauty of these old Z's is that they, for the most part, are the essence of mechanical simplicity. This is one of the reasons that, even after 20-30 years, they still have a following. Always assume an easy, simple fix for an encountered problem. Unless you trust this mechanic, be leary of someone who says your bike needs an 'overhaul' and there can be no guarantee it will run, even then. Even I can do a topend overhaul, reassemble, and get my bike to run! With a minimal number of special tools, you (and your hubby) should be able to freshen the head, hone and re-ring...for less than $1000...parts are readily available, reasonably priced, and between the manuals and this site, you can bring your bike back to life:)

IF it is loss of compression it is probably an easy fix. I panicked when I got my bike and found only 30 pounds of compression in one cylinder but it only cost less than $100 to fix, all 4 are up to factory spec. If it has never been touched then it probably needs adjustment. Get yourself a service manual, a compression tester (pull all 4 plugs test each cylinder while cranking with the throttle wide open) write down your results. If you do in fact have low compression (more than 15 pounds difference from the other 3) in one or more cylinders pull the valve cover off. This is pretty simple. Then follow the manual for testing valve shim clearances. You will need a set of feeler gauges (Z-1 has a good set cheap), again write down your results for each cylinder intake cam and exhaust cam. The factory service manual has a chart to help you find the right shims. Z-1 also sells a full selection of valve shims and the tools to change them. I started by buying one shim to swap in and out of each bucket. Makes it much easier. It will take time, and some work, but if you can manage it between the 2 of you it will not cost much at all! Before going to that extent (I am assuming your mechanic did not make up the low compression, which can be a dangerous assumption) check all the simple things. Plugs, wires, fuel filter, etc first. Best of luck, I am SURE you will find you can fix it!

Sounds like a fuel starvation problem. My 900 will act the same way when the in tank fuel screen plugs up with rust etc. Take the fuel valve out and clean the two screens on the inlet tubes and the one in the small bowl too. I also run two inline filters between the valve and the carbs for insurance. If that doesn't completely cure the problem I would next check the float level.
I have 50K on my 900 and the motor has never been apart.It runs great so far but I do plan to rebuild it this year.
I would also question a "mechanic" that would charge me $1000 to rebuild a motor and say it "may or may not run afterward". That's criminal! I'm a profesional mechanic and would never even think of saying something like that. Find someone else or take the time and learn to do it yourself, you'll be better off.

2 inline filters John? Wow! I think your mechanic is a thief or something. I don't think there is a Kz out there that can't be fixed, they are easy fixers, even by there own owners. I like Johns theory on the fuel petcock being blocked. That downhill experience you had, I had that once when the gas was to low plus it will happen if compression is so low it doesn't activate the vacuum operated petcock. O downhill my gas went to the front of the tank and the bike shut off.

The OEM fuel valve on the KZ900A4 is a mechanical valve,no vacume needed,and has 2 fuel lines feeding 2 carbs each thus 2 inline filters. And yes, sometimes I think my mechanic has his head screwed on crooked:silly: :whistle:

Thanks, for the moral support. I just had the bike repainted so I replaced all the seals to the petcock(yes, gravity fed, very simple!). I probably need to replace any rubber seals and parts to the carburetor since most original rubber is starting to dry out and crack. I still think there's an electronic problem. A broken wire was replaced. At one point the headlamp wouldn't light after yhe repaint-I believe one wire may be in common with the ignition system. After moving "things" around the lamp was on as well as the starter switch. We'll have to go over the bike slowly and carefully to be more specific with symptoms-we just got kicked into panic mode!
Oh, yeah, by the way, I was able to purchase a lower left ORIGINAL pipe in great conditon all by itself.

Post edited by: strider, at: 2007/05/17 16:59

I've learned the hard ($) way and would'nt trust a mechanic until I had done some basic checks like the guys above describe. Intermittent cutting out does not really sound like poor compression. When that happened to me it was a loose connection at the negative battery terminal. Looked fine but was shakey.
Hopefully for you it's sometihng simple and cheap and your step by step approach will do the trick. Good luck.

JR wrote:

I've learned the hard ($) way and would'nt trust a mechanic until I had done some basic checks like the guys above describe. Intermittent cutting out does not really sound like poor compression. When that happened to me it was a loose connection at the negative battery terminal. Looked fine but was shakey.
Hopefully for you it's sometihng simple and cheap and your step by step approach will do the trick. Good luck.

I agree, and with the intermittant electrical problems I think I'd start there first! I did want to point out though, that even if it was somehow compression related it's not the end of the world, far from it! These engines have a reputation for being basically bullet proof. Standard service for police bikes I read is 50,000 miles before they sell them and they are driven much further after their service life. I thought my bike was toast when I had no compression, but with WiredGeorge and Z-1 it's better than ever and didnt even cost much!

thousand bucks!?

Must be the same bunch of criminals er.. highly trained and respectable professionals I tend to find!

My wife helped me do a top end on my 81 last year. Found someone to go through the head for me, but in retrospect I think we could do it ourselves. Of course I spent more than I wanted too, but I got bunches of new shiny things to put in my engine.

These are really easy to work on at home. I have accumulated a few tools over the years (how did I manage without all those 1/4" drive sockets?...) I think you already have the drive to fix it up. I find (almost) all my answers right here on KZRider.

All the advice above is excellent. I'm thinking electrical first as well. Check all the wires and connections as best as you can. You may have a poor ground or short some where that appears when you go over bumps, etc. Verify fuel flow, don't forget to make sure the fuel cap vent is operating properly (this can cause starvation). Check the spark plug cable caps (many times people replace coils and such when it is just the cable ends); and above all resist the temptation to fiddle with any settings on the carbs. I've bought several bikes that had "carb troubles" that were actually ignition related. Properly adjusted carbs should not need any attention other than occasional cleaning. The service manual is your friend!

Almost forgot: Get a new mechanic, and a KZ900 is NEVER hopeless!

Post edited by: lowbuck, at: 2007/05/18 10:42