Author Topic: ZG1000 won’t pull above 7500 rpm  (Read 2525 times)

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Offline racer1735

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ZG1000 won’t pull above 7500 rpm
« on: December 31, 2017, 11:19:15 pm »
This past summer my son and I resurrected a neglected ‘99 Connie. SISF redid the carbs and, for the most part, everything was a success.  Bike starts right up, has great drive ability and pulls hard in gears 1-4. Initially it had a slight bog in the midrange on hard throttle, but experimenting with the foam as part of the 2-minute mod cured that issue.
One item wasn’t discovered until later....it won’t accelerate or pull above approx 7509 rpm/80 mph. Lower gears will pull redline, but in higher gears such as on the highway, it tops out at that point, even if still opening the throttle.
Is it starving for fuel (there is no roughness or hesitation). Or is this an air box issue.  I’m not sure which way to go for a cure. Aim satisfied with the carb job (not placing blame on that). Just thinking it’s a setup issue somehow.

Offline SteveJ.

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #1 on: December 31, 2017, 11:48:19 pm »
I noticed no mention of checking the valve clearance. Have you? It is an important part of a tune up.
Yeah, if you want true ram air tuning, you better be willing to ram some air! (SiSF)
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Offline racer1735

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #2 on: January 01, 2018, 01:09:44 am »
Yes, that was done while carbs were out for servicing.

Offline Mettler1

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #3 on: January 01, 2018, 01:47:37 am »
  Maybe a kink in the fuel line- Petcock working ok? An inline filter dirty??  Throttle cables opening the carbs all the way? Just throwing out things to check.
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Offline connie_rider

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #4 on: January 01, 2018, 02:40:19 am »
First things first; Rule some things out.
   Check the compression and while your at it, measure piston height to assure you don't have a hydrolocked engine.

Next check that you have only 1 vacuum line hooked to the petcock.
Checked for kinked fuel hoses.

Then move on.

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Offline Boomer

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #5 on: January 01, 2018, 09:21:26 am »
Once you've eliminated the obvious air/fuel starvation issues, check the valve timing. Having the intake cam one link out can gave this effect.
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Offline racer1735

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #6 on: January 01, 2018, 03:07:54 pm »
Engine runs great, crisp except in upper revs in top gears (bottom 4 gears pull string). I have an in-line filter installed due to residual debris in the tank. I’m wondering if there is a kink that flows fuel, but not enough when the carbs are trying to pull more?

Offline Brooke_Benfield_OR

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #7 on: January 01, 2018, 04:10:32 pm »
Brakes dragging?

Wheel bearings bad?

You mention difficulty only in the upper gears and at speed which makes me wonder about sources of friction. The other suggestions about fuel, etc., are also spot on.
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Offline connie_rider

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #8 on: January 01, 2018, 04:21:55 pm »
Racer, I really hope I'm wrong, but a damaged engine needs to be ruled out.
Best of luck.

Reason;
I had an engine that ran as you described.
Lower gears seemed ok, higher gears didn't have sufficient power to pull.

After troubleshooting other things; I discovered I had 1 piston that was 1/16" lower then the other 3. {due to a previous hydrolock)

I highly suggest; Check the compression and measure piston height to assure you don't have an engine that was damaged by a hydrolock.
{NOTE: Steve has an excellent video on how to do this. NO special tools are needed).

Ride safe, Ted

PS: Are you located near Canyon lake? I'm in Houston.
« Last Edit: January 01, 2018, 04:49:38 pm by connie_rider »
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Offline Pbfoot

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #9 on: January 01, 2018, 04:44:20 pm »
Engine runs great, crisp except in upper revs in top gears (bottom 4 gears pull string). I have an in-line filter installed due to residual debris in the tank. I’m wondering if there is a kink that flows fuel, but not enough when the carbs are trying to pull more?
  I am running a 90 degree filter due to residual debris as well. Bike will maintain 130mph no problem. Cleaning the fuel cap vent would be my first choice followed by a hydrolock test as Ted has suggested.
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Offline racer1735

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #10 on: January 01, 2018, 05:36:28 pm »
Thanks guys will do various checks. I ran the fuel line a bit long to prevent a kink but I may have a slight pinch. Will remove the filter and re-check.  If that fails will check piston height.
FYI- I’m in Canyon, TX, 20 miles  outside of amarillo.

Offline connie_rider

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #11 on: January 01, 2018, 05:47:27 pm »
From what I recall, a longer line is more likely to bend/kink when the hose gets hot.
Could be your problem.

I didn't realize there were 2 Canyon Texas.
  My Buddy lives in Canyon Lake Texas.

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Offline RodWpg

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #12 on: January 01, 2018, 08:09:31 pm »
leave the gas cap popped a bit and try, c10 known for venting problems as well
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Offline racer1735

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #13 on: January 01, 2018, 08:15:33 pm »
New gas cap(screw on type). Will ride it without screwing down tightly.

Yep, Canyon land Canyon Lake. Just 493 mikes apart. And in the same state

Offline VTconnie

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #14 on: January 01, 2018, 10:43:21 pm »
leave the gas cap popped a bit and try, c10 known for venting problems as well

New gas cap(screw on type). Will ride it without screwing down tightly.

Yep, Canyon land Canyon Lake. Just 493 mikes apart. And in the same state

I put my money on this, as well as shortening the fuel line and losing the filter!
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Offline Mettler1

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #15 on: January 02, 2018, 12:24:38 am »
  Been using  this filter for a lot of yrs. Run the fuel line under the tank to the 3006 filter and then the fuel line from the filter down to the carbs. NO kinks in the fuel line!!

           https://www.napaonline.com/en/p/FIL3006
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Offline cra-z1000

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #16 on: January 02, 2018, 03:23:49 am »
  Been using  this filter for a lot of yrs. Run the fuel line under the tank to the 3006 filter and then the fuel line from the filter down to the carbs. NO kinks in the fuel line!!

           https://www.napaonline.com/en/p/FIL3006

+1 Autozone has a cross reference equivalent to this filter also .
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Offline racer1735

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #17 on: January 02, 2018, 12:42:23 pm »
  Been using  this filter for a lot of yrs. Run the fuel line under the tank to the 3006 filter and then the fuel line from the filter down to the carbs. NO kinks in the fuel line!!

           https://www.napaonline.com/en/p/FIL3006

This is the filter I have been running

Offline WillyP

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #18 on: January 02, 2018, 01:05:51 pm »
Possibly the fuel filter is partially clogged? Does your screw on cap have a vent? If so, does that vent have any restriction? If not, have you provided for tank venting somehow? Have you tried running without the cap yet? Without the fuel filter? (substitute a short piece of line... as short as possible without kinks... temporarily) Holes rips or tears in the diaphragms?

Just throwing some ideas out there for ya!

If all these 'easy' ideas don't work, I'd try experimenting with the foam some more.
« Last Edit: January 02, 2018, 01:13:28 pm by WillyP »
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Re: ZG1000 won’t pull above 7500 rpm
« Reply #19 on: January 02, 2018, 01:42:49 pm »
The OP stated, "Bike starts right up, has great drive ability and pulls hard in gears 1-4 <snip> it won’t accelerate or pull above approx 7509 rpm/80 mph. Lower gears will pull redline, but in higher gears such as on the highway, it tops out at that point, even if still opening the throttle."

Can someone explain why a fuel line restriction (i.e. kinked fuel line or inline filter issue) would be a problem only in higher gears when it was stated the bike will run redline and operate OK in lower gears. It seems to me that fuel starvation should happen in any gear if engine fuel demand is greater than fuel supply flow. What am I missing?

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Offline mgoodrich

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #20 on: January 02, 2018, 01:46:47 pm »
Well, the thing I am missing is that the original post equated 7500 rpm to 80 mph.

My bike is turning roughly 4800 rpm @ 80mph, in 6th gear.

7500 is closer to 120 mph I believe, and my bike will top out their as well.  Only way I can get above that is to cut down the windshield a bit.

If you are maxing out at 7509 rpm, then your bike is pretty typical.

Edit here is what I was looking for, from past forum discussions (Rev Ryder):

20mph   1197
25mph   1496
30mph   1795
35mph   2094
40mph   2394
45mph   2693
50mph   2992
55mph   3291
60mph   3590
65mph   3890
70mph   4189
75mph   4488
80mph   4787
85mph   5086
90mph   5386
95mph   5685
100mph  5984
105mph  6283
110mph  6582
115mph  6882
120mph  7181
125mph  7480  Connie's advertised and generally observed actual top speed 128mph
130mph  7779
135mph  8079
140mph  8378
145mph  8677
150mph  8976
155mph  9275
160mph  9575
165mph  9874
170mph  10173

Of course I could be missing that in 5th and 6th it tops out at 7500/80mph. Which is really weird that 1-4 can go to red line?
« Last Edit: January 02, 2018, 02:09:24 pm by mgoodrich »

Offline Amotek

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #21 on: January 02, 2018, 02:20:04 pm »
I totally concur with the above!

Offline JPD

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #22 on: January 02, 2018, 02:55:27 pm »
Look into that new fuel cap. It is part of the fuel delivery system. Ask me how I know. Running down the interstate at about 80 and the bike just stops running. Cycle kill switch, ignition, cold start  system, reserve, no help. I had over 1/4 tank of gas but popped the cap and looked anyway. Closed the cap and the bike started and ran the 50 miles home no problem. For the next month when ever I rode over 60 for several min. the bike would go flat. Finely heard the tank sucking air when I parked the bike and the cooling fan shut off. It turned out than I had a bubble of loose paint (repaint by P/O) that would suck up onto the intake of the tank vent system. It would restrict the fuel flow only at high speed extended rides.
Also replace or remove the fuel filter. If it is restricting the fuel flow into the carbs the effect may not be evident until you get to the higher gears as the float level drops.

Offline Daytona_Mike

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #23 on: January 02, 2018, 03:14:08 pm »
I used to run that napa filter too. Nothing but problems. Restricted fuel flow- vapor lock. ( I am not saying this is your 80mph problem-
 pulls hard in gears 1-4 is what I dont understand - loss of fuel due to poor  venting or  fuel flow  restrictions usually is like hitting the kill switch- total loss of power- until the bowls fill again )
I agree with the compression check and /or  bent rod check and cam timing check

 IMHO is makes no sense to run an extra 20 micron fuel filter when the screen in your tank is also a 20 micron fuel filter.
Why run two?  It cant  filter out anymore.


 
« Last Edit: January 02, 2018, 03:50:04 pm by Daytona_Mike »
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Offline Bob_C_CT

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Re: ZG1000 won’t pull above 7500 rpm
« Reply #24 on: January 02, 2018, 04:09:21 pm »
I don't get the 1-4 gear going to redline thing either.
Sounds speed related then.
If you had to add foam to get it to run smoother, maybe you are making up for an air leak somewhere.
At the higher speed maybe the higher airflow is affecting something.
Are you sure the boots don't have a tear and are attached all the way around on the carbs, no crack in the bottom of air box. How about the gasket surface at the air filter hatch? Air filter properly installed.

When you are stuck at this brick wall rpm what speed are you at?, this happens at the same rpm in both 5th and 6th gear? Does the engine seems to be running smoothly at this brick wall rpm?

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