Hey everyone,
I am new on this site (introduced myself in new member forum) and I have been searching the forums looking for someone with a problem similar to mine but no luck. My bike is a 1981 KZ650 H1 CSR (first bike), I got it in the fall last yearand I am having some real problems. Sorry, but this will be a long post because I want to try and put everything I have observed and troubleshooted in it.

When I first got the bike, it ran just fine for a few days but then I tried to take it on the interstate to show it to a friend of mine who is really into bikes. It got to about 50mph and would go no higher and started cutting out. I barely got it home and it has been having problems ever since.

The problem is thatmy bikehas a real hard time starting (backfires from exhaust, but no smoke,and occasionally from carbs), then staying running. When it does run, the engine cuts out. Usuallydoes OK in first gear, but after that if rpm's get over like 2000, it runs like total crap. It also dies when it is coasting down from speeds over about 20mph.

I have pulled off the carbs and they are clean, has an inline fuel filter(replaced lastyear): clean,checked all fuel and vacuum lines: clean. I don't have the tools or know-how to adjust anything, but I do have a Clymer manual.

It will not start at all if the choke is on more than the slightest bit.
New battery, gets spark on the plugs, though they do get fouled quick.
It is missing the vacuum pump under the second carb and I am buying that this weekend. I also know that the diaphram in the accellerator pump is cracked. Also, the no.2 carb is missing the o-ring, clip, and valve weight. The person I bought it from said he had just cleaned out the carbs, apparently he was careless. I realize that timing may be an issue but again, no tools.

One wierd thing, the manual says that the petcock should not releasee any fuel in any position without the engine vacuum on it, but it does in all positions.

My first mainquestion is should replacing those partsmaybe solve the problem or does it sound more like a calibration issue?

Thank you for any help.

 

Sounds like the petcock valve's diaphragm is leaking. They make rebuild kits for them, so it shouldn't be a problem. Your carbs look to be the biggest problem on your bike by far. If you are absolutely certain your plug wires and coils are correct, then start tearing apart the carbs and rebuild them. (It is very common to mix up the plug wire configuration, making the bike backfire, and start hard.) When I first got my KZ750, the carbs were giving me about the same problems it sounds like you're having now. A good clean up and rebuild fixed the problem.

Good luck,
Mark.

 

Ok, so I am the dumbest person ever.
I did a re-check of my spark plugs and turns out my stupid *** measured the gap on the wrong side of my gapper (dumb, dumb, dumb, DUMB), so instead of like 0.7 mm I had 0.7 in..
After that, I should probably give my bike away and never touch anything mechanical again. I'm not going to do that.
So it starts ok now even with the choke on. But one of my coils is bad
Still acts up at high RPM's, maybe the accelerator advance?

Advice for rookies:
Check the stupid stuff first no matter how smart you think you are.

 

Trust me, even the best of the best over look the simple stuff.

Most importantly, you got the bike running! I think now we need pics of the ride!

 

The accelerator pump only gives the engine a small squirt of fuel to give it a little oomp to start accelerating, without it the bike will just take a little longer to start accelerating but should accelerate just the same after it starts moving. Like mark said check your carbs, do a full cleaning and rebuild. Never trust someone elses work, not even a shop or dealer, they screw up too. Let us know if you still have trouble.

 

For markmeinteil, I'll do that first chance but I have to borrow a digi cam from my brother.
For Prom, my bike is strange. Instead of having an adjustable timing system, it has an accelerator advance mechanism so the timing is not adjustable. The Clymer manual says if there is a timing problem, the accelerator advance mechanism is probably faulty. I am going to start working on the carbs soon though.
Would you happen to know how important an air induction system is? Mine was replaced with four independant air filters, one on each carb. I know this is letting bad air into the engine because the hoses are still there but they're just open to the air, no filter or anything.

 

ummm, yeah. I hope the previous owner changed the jets to match the filter pods. Having that little bit of extra air flow will mess with the way your bike runs if not jetted to match the higher air flow. Also, plug off the those emission tubes so dirt and other junk doesn't get in there. Some company out there makes block-off plates for the emission reed valve asy. on top of the valve cover if you really want to spend some bucks on it.

Honestly, I would reinstall the factory airbox assembly if nothing else was ever done to the bike. i.e. aftermarket exhaust, or like I mentioned above, larger jets. Your bike will probably run much better afterwords.

 

Ya, i was kinda planning on changing it back if its not too expensive. I figured there was probably a reason Kawasaki had it on there to begin with. I don't know if it has any aftermarket parts (guess I haven't thought to look that closely yet). By "jets" do you mean like the air screws because I know they need adjusted but I don't know how or what they should be adjusted to. It's not in my Clymer manual. If that's not what you mean then I'm lost.

 

I'm talking about the jets inside your fuel bowls. If they have been changed, you could either be running too lean or rich depending on what size was put into them. (If they were changed of course.) Most people don't know what they're doing when they install those air pods. They don't realize it will effect they way the bike runs. I bet you could find a whole complete original airboxasy. on eBay for cheap though. The KZ650 and 750 both use the same air box too.

The Idle air screws up top on the carbs have no aftermarket replacement. I also couldn't find a setting for them. After talking to a bunch of people and coming up empty handed, I just set mine at 1 3/4 turns out and fine tuned them until the bike felt right.

 

Well, I guess that's another job for me to do when i pull the carbs apart. No luck on eBay for the air box but I'll keep looking.
Thanx for the starting point on the air screws. Your bike is probably pretty similar to mine, right?