Welcome, Guest
Username: Password: Remember me
  • Page:
  • 1
  • 2

TOPIC: Not perfect RPM range...

Not perfect RPM range... 08 Sep 2019 16:44 #810541

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36
In general the engine goes really well now.
I have had one issue left, but I only provoke it on high speed (more the the limit in Norway) and inn deep hill..,

4 or 5th gear
6-7RPM
Approx. 50% throotle

If I give 70-100% throotle the bike start to accelerate and at the same time the problem disapear. Also If give lees Throotle so the RPM goes down some 4-5 the issue disapear.

If it was eletrical issue I should feel it when I acc. From 0 to Redline?

If something is unclear let me know!
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 08 Sep 2019 18:05 #810544

  • M_a_t_t
  • M_a_t_t's Avatar
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 166
  • Thank you received: 25
What exactly is it doing?
83 KZ1100A (shaft)
17 Versys X 300 abs
90 Honda CBR600F (brother's)

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 08 Sep 2019 18:09 #810546

  • baldy110
  • baldy110's Avatar
  • Offline
  • Member
  • Member
  • Posts: 2110
  • Thank you received: 419
Huh?

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 08 Sep 2019 18:21 #810547

  • 73z1
  • 73z1's Avatar
  • Offline
  • Member
  • Member
  • Posts: 25
  • Thank you received: 0
If you open the throttle the motorcycle will accelerate, if you close the throttle the motorcycle will decelerate.
Please describe your problem if you have one.

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 08 Sep 2019 18:22 #810548

  • Scirocco
  • Scirocco's Avatar
  • Offline
  • Expert Boarder
  • Expert Boarder
  • Never change a running system
  • Posts: 2203
  • Thank you received: 1000
Sounds like your engine runs under lean condition. Whats your carb Setup?

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 08 Sep 2019 23:51 #810557

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36
hehe sorry for my English :)

It`s start to "cheat" not going even and pull constant force....

810 big bore kit

Carb VM24:
Pilot: 17,5
Main: 112,5
Needle: 4`th posistion (the clips is not on the highest point but second).
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 02:56 #810562

  • Warren3200gt
  • Warren3200gt's Avatar
  • Offline
  • Member
  • Member
  • Posts: 459
  • Thank you received: 130
VM 24's on 650's and VM26's on 900's are standard. At 810 your probably at the upper limit of useful size with VM 24's. A bigger engine needs more air and 24mm diameter can only let so much air through them that's why bigger engines have bigger carbs.
75 z1b, 77 z650 b1, 77 z650 b1 period custom, 77 z1000 a1, 82 z1100 elr, 89 zxr750h1, 01 zrx1100r

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 03:45 #810563

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36

Warren3200gt wrote: VM 24's on 650's and VM26's on 900's are standard. At 810 your probably at the upper limit of useful size with VM 24's. A bigger engine needs more air and 24mm diameter can only let so much air through them that's why bigger engines have bigger carbs.


I know my engine have "bigger" potensial when it comes to HP, but I think it`s to easy to conclude the symptom I have is related to restricted air flow. Its only in these range I have problem under or over its fine....

Its not only related to the throotle posistion, its the RPM range together with the throotle posistion.

High speed or deep hill, so you can setup the scenario where I have 6-7 RPM and around 50% throotle, maybe some more, 50-60% but not more... all scenario without these is working perfect.

Example 3-4 RPM 0-100% throotle works fine... example or 7-8 rpm with 30% throttle works fine....
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Last edit: by gordone.

Not perfect RPM range... 09 Sep 2019 04:19 #810565

  • Warren3200gt
  • Warren3200gt's Avatar
  • Offline
  • Member
  • Member
  • Posts: 459
  • Thank you received: 130
what happens at 7 - 8k rpm at 100% throttle?
Lets say for arguments sake that 1k rpm = 1 cubic litre of air consumtion.
At 3-4 k rpm you are drawing into the engine 3 -4 litres of air through a hole which is 24mm
At 7-8 k rpm at 30% throttle you are drawing in 2.4 litres of air through a hole which is 24mm. So quite similar air consumption.
At 7-8 k rpm at 100% throttle you are TRYING to draw in 7 - 8 litres of air through a hole which is 24mm. ie twice as much.
Air has a specific density at a specific altitude and can only pass through a hole of a certain size at its maximum velocity which is why I asked whats happening at 7 - 8k rpm at 100% .

I suspect you can't draw enough air.

Then use the same argument for fuel. it can only draw fuel through a hole (Jet) at a certain rate. If you try to draw more air than can be supplied or more fuel than can be supplied one of three things will happen. The mixture will become too lean and it will run like shit at high revs or it will become too rich and do the same. Which of those two is happening will depend on which has the restriction air or fuel. The third thing that could happen is fuel and air are BOTH restricted which means it will bog down until the revs drop to a level where the supply is sufficient.

The way manufacturers counter act these affects is bigger jets if its a fuel deficiency or bigger carbs if its an air deficiency.

There are other factors involved but in lay mans terms those are the basics.
75 z1b, 77 z650 b1, 77 z650 b1 period custom, 77 z1000 a1, 82 z1100 elr, 89 zxr750h1, 01 zrx1100r

Please Log in or Create an account to join the conversation.

Last edit: by Warren3200gt.

Not perfect RPM range... 09 Sep 2019 05:03 #810566

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36

Warren3200gt wrote: what happens at 7 - 8k rpm at 100% throttle?
Lets say for arguments sake that 1k rpm = 1 cubic litre of air consumtion.
At 3-4 k rpm you are drawing into the engine 3 -4 litres of air through a hole which is 24mm
At 7-8 k rpm at 30% throttle you are drawing in 2.4 litres of air through a hole which is 24mm. So quite similar air consumption.
At 7-8 k rpm at 100% throttle you are TRYING to draw in 7 - 8 litres of air through a hole which is 24mm. ie twice as much.
Air has a specific density at a specific altitude and can only pass through a hole of a certain size at its maximum velocity which is why I asked whats happening at 7 - 8k rpm at 100% .

I suspect you can't draw enough air.

Then use the same argument for fuel. it can only draw fuel through a hole (Jet) at a certain rate. If you try to draw more air than can be supplied or more fuel than can be supplied one of three things will happen. The mixture will become too lean and it will run like shit at high revs or it will become too rich and do the same. Which of those two is happening will depend on which has the restriction air or fuel. The third thing that could happen is fuel and air are BOTH restricted which means it will bog down until the revs drop to a level where the supply is sufficient.

The way manufacturers counter act these affects is bigger jets if its a fuel deficiency or bigger carbs if its an air deficiency.

There are other factors involved but in lay mans terms those are the basics.


I have 7-8k RPM and have around 50% throttle (problem is present), if I give more and more throotle the bike start accelerate more and more and at the same time the issue disapear.

If I go direct from 50% to 100% the bike fly away without any issue in acceleration… hehe

Was that accurate information, or do I misunderstand something?

If I give full throttle 100% in all gear and push it to the red line in all gear, there is no issue under acceleration.
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Last edit: by gordone.

Not perfect RPM range... 09 Sep 2019 05:37 #810569

  • Warren3200gt
  • Warren3200gt's Avatar
  • Offline
  • Member
  • Member
  • Posts: 459
  • Thank you received: 130
Okay, I think I have misunderstood your issue.
So, if Im reading your last post correctly
zero to 100% throttle in one QUICK action = no problem.
50% to 100% throttle in one QUICK action = no problem.
Zero to 50% throttle SLOWLY = no problem
50% to 100% throttle SLOWLY = problem.

If my reading of your issue description is accurate I can't think of anything carb related which would cause that.

The only thing I can think of which could cause that is a sticky ignition timing advancer. They work by centrifugal force. If it was "sticky" around 60 or 70% of the rev range it would cause the the timing to be retarded at that point. As the revs increased so would the centrifugal force to a point where it forced the sprung weights beyond the "sticky" point and then the ignition timing would be correct again. This "sticky" patch may not be evident when the throttle is opened quickly as the weights would have momentum to help them past the "sticky" patch.
You wouldn't notice it on deceleration because the cylinder firing at the correct time on deceleration is irrelevant.
75 z1b, 77 z650 b1, 77 z650 b1 period custom, 77 z1000 a1, 82 z1100 elr, 89 zxr750h1, 01 zrx1100r
The following user(s) said Thank You: gordone

Please Log in or Create an account to join the conversation.

Last edit: by Warren3200gt.

Not perfect RPM range... 09 Sep 2019 05:40 #810570

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36

Warren3200gt wrote: Okay, I think I have misunderstood your issue.
So, if Im reading your last post correctly
zero to 100% throttle in one QUICK action = no problem.
50% to 100% throttle in one QUICK action = no problem.
Zero to 50% throttle SLOWLY = no problem
50% to 100% throttle SLOWLY = problem.

If my reading of your issue description is accurate I can't think of anything carb related which would cause that.

The only thing I can think of which could cause that is a sticky ignition timing advancer. They work by centrifugal force. If it was "sticky" around 60 or 70% of the rev range it would cause the the timing to be retarded at that point. As the revs increased so would the centrifugal force to a point where it forced the sprung weights beyond the "sticky" point and then the ignition timing would be correct again.
You wouldn't notice it on deceleration because the cylinder firing at the correct time on deceleration is irrelevant.


Thank you, I will check up the timing advancer and report back.
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 09:24 #810581

  • baldy110
  • baldy110's Avatar
  • Offline
  • Member
  • Member
  • Posts: 2110
  • Thank you received: 419
I too have an 810 kit in my 650 with VM24 carbs. It runs perfect with them. It sounds like your trying to say the engine hunts on steady throttle. If so raise the needle up by moving the clip down one notch.
The following user(s) said Thank You: gordone

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 09:36 #810583

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36

baldy110 wrote: I too have an 810 kit in my 650 with VM24 carbs. It runs perfect with them. It sounds like your trying to say the engine hunts on steady throttle. If so raise the needle up by moving the clip down one notch.


I understand, yes, it only happens in a small "window", under normal driving and under 100kmh / 62mih I haven`t notice it, just when I goes up in high speed or deep hill in combination with some good speed...
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 10:50 #810586

  • Warren3200gt
  • Warren3200gt's Avatar
  • Offline
  • Member
  • Member
  • Posts: 459
  • Thank you received: 130
If it were needle setting I would think it would occur regardless of how fast or slow you opened the throttle. OP said if he whacks it open it doesn't occur. It only occurs if he opens slowly. :unsure:
75 z1b, 77 z650 b1, 77 z650 b1 period custom, 77 z1000 a1, 82 z1100 elr, 89 zxr750h1, 01 zrx1100r

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 11:45 #810589

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36
How quick/slow I open the throttle have no impact on the issue.

It’s the throotle posistion compare to the actual RPM, when you tryto have steady RPM in the 6-7 range.
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 13:36 #810594

  • Scirocco
  • Scirocco's Avatar
  • Offline
  • Expert Boarder
  • Expert Boarder
  • Never change a running system
  • Posts: 2203
  • Thank you received: 1000
If you have the stock air box, i would give it a try. IMO i don´t like pot filters. Looks cool but made a lot of probs.
The following user(s) said Thank You: 650ed

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 23:03 #810619

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36

Scirocco wrote: If you have the stock air box, i would give it a try. IMO i don´t like pot filters. Looks cool but made a lot of probs.


Need to purchase one then…

I will check up the advancer and will then have much time to test it out during the weekend.

What is the symptoms of to low needle posistion?
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Not perfect RPM range... 09 Sep 2019 23:39 #810620

  • Warren3200gt
  • Warren3200gt's Avatar
  • Offline
  • Member
  • Member
  • Posts: 459
  • Thank you received: 130
Hi Gordone, Im still unclear about your symptoms. There seems to be some contradicting posts. I understand that English is not your first language but if you type into google translate in your native tongue and then cut and paste we may have a better understanding or the issue and be able to give a more definitive direction.
We may be missing something in translation?.
75 z1b, 77 z650 b1, 77 z650 b1 period custom, 77 z1000 a1, 82 z1100 elr, 89 zxr750h1, 01 zrx1100r

Please Log in or Create an account to join the conversation.

Last edit: by Warren3200gt.

Not perfect RPM range... 09 Sep 2019 23:55 #810621

  • gordone
  • gordone's Avatar Topic Author
  • Offline
  • Sustaining Member
  • Sustaining Member
  • Posts: 966
  • Thank you received: 36

Warren3200gt wrote: Hi Gordone, Im still unclear about your symptoms. There seems to be some contradicting posts. I understand that English is not your first language but if you type into google translate in your native tongue and then cut and paste we may have a better understanding or the issue and be able to give a more definitive direction.
We may be missing something in translation?.


Do you have something spesific who are not clear?

I will try to explain another way :)

1. I have not noticed the issue when I accelerate.
2. I have only notice it when I try to keep steady RPM in approx. 6-7k RPM range.
3. I have a understand the issue in 6-7kRPM range only is presented when I have approx. around 50% throttle.
4. If I have 6-7k RPM and around 50% and the issue is present, and I freeze the throttle for a while the issue is there whole time… if I try to increase the throttle slowly the RPM start to pickup and then the issue disapear.
5. The problem has not been notified during acceleration.
6. When the issue is present in 6-7k RPM range and I accelerate to 9kRPM example, I have not tried to freeze the RPM at 9 to see if the problem comes back there also, but I don`t think so... will test more...

Under normal driving between 0-100km/h I don`t “see” the issue, only when I go in higher speed or combine with deep hill…

Between 0-100km/h is not often I need to use the throttle more then 50% in any gear…

So in city driving etc.. the issue is never seen.
My understanding the issue is present when I have high load and high RPM.

I will test more in the weekend, will have a long drive then…
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

Please Log in or Create an account to join the conversation.

Last edit: by gordone.
  • Page:
  • 1
  • 2
Powered by Kunena Forum