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Discussion Starter · #1 ·
My 1991 ZX-11 has recently had some issues with running right. It ran really well about 2 months ago when I bought it. But it has always had some problems with the RPM's dropping down when I let off the throttle. It stayed at about 3,000 RPM, then would eventually drop down to 1,000 or so. The last time I rode it, it acted like it ran out of gas. Just dead after about 2 minutes of riding. Then it started back up and I rode for another minute or two. It ran great for that minute or two, then died. It continued this cycle of running and dying. So I stripped down the carbs (for the SECOND time) and took the individual jets and needles out and cleaned EVERYTHING. I check my fuel pump - it's good. I replaced the fuel pump relay just to make sure. Today I finally got everything back together, started it up, and it felt like it was running on about 2 cylinders. VERY sluggish. I checked the spark, and all 4 are firing fine. Then I tapped the float bowls of each carb a little with a hammer. All of a sudden, it came alive! I'm guessing a stuck needle. BUT now I'm back to the engine not idling right. If I set the idle screw so it barely idles at about 500, it does O.K. dropping back down after a rev. But if I adjust the idle at about 800-1,000 RPM (where it should be), when I rev it, it stays at 3,000 RPM for about 3 seconds, then falls back down. This is especially dangerous when I drive it, because even if I let off the throttle to slow down, the engine still drives the bike at 3 grand for a while before slowing down. THAT sucks!

There's no vacuum leaks.

Any ideas?
 

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Discussion Starter · #2 · (Edited)
Lotsokids said:
...it got really bogged down like it was running out of gas, then died. It would restart after a while of cranking, and would run pretty good, then 2 minutes later the same thing would happen. I got it home, and before I shut it off, it was barely idling and ran like it was only firing on 2 cylinders...
Well, after all this work, I'm back to square 1.:tard

- Replaced the #1 intake valve
- Re-shimmed ALL the valves
- Replaced fuel pump relay
- Fuel pump is good
- Cleaned carbs entirely (second time now)
- New fuel filter
- Sincronized the carbs
- All spark plugs are firing
- Fuel tank is vented

Just now I was checking the carbs, and decided to tie the vacuum on #1 and #4 together and plug the T fitting (does that make sense?) That's how it was when I bought the bike, but the T was not connected to anything causing a huge vacuum leak. As soon as I did this, the idle dropped back down just as it is supposed to (idle was hanging up at 3,000 RPM). I was amazed! So I grabbed my helmet and hit the road... only to push it about 1/4 mile home and threw it in the garage again. Once in the garage, it fired up and ran like new. IT ONLY SEEMS TO RUN IN THE GARAGE.

I thought I was a mechanic, but it looks like I'll be taking this thing to the shop. :angry
 

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Discussion Starter · #4 ·
Have you checked the carb diaphragms.

Assume air filter okay?
Well, the air filter is a little dirty, but I could see light through it. I should probably change it... another $50

The carb diaphragms did have some issues that I found on my second disassembly (the first time, I didn't tear it down that far). Sometime previously before I bought it, a couple of them got pinched in the cover. I noticed a couple very small tears (maybe 1/8 inch) where it got pinched, so I reapired them with sealant because the dealer said they cost about $125 each.
 

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Is the air filter not washable or is it just past it's best?

I've heard prices are a bit extreme for the diaphragms :scared
 

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Discussion Starter · #6 ·
ENGINE IS DESTROYED

I just took it out a few minutes ago, and when I hit second gear (not too aggressively) there was a loud BANG and what sounded like metal scrambling around in the engine. No oil leaks or holes, so who knows? I thought the timing chain broke, but it is still in tact. The crank shaft will rotate some, but locks up in a certain position (valve/piston interference).

DOGGONE IT!!! so my 3 options are:

1. Spend $1,700 on a used engine
2. Sell the bike whole and not running
3. Part it out
 

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if the idle hangs up before setting down then the idle screws are to lean[back them out a half turn] if the idle when blipped goes below idle then back to normal its to rich.
 
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