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

TOPIC:

Centerline GPZ cams 26 Aug 2016 09:37 #740028

  • larslykkegaard
  • larslykkegaard's Avatar Topic Author
  • Offline
  • User
  • Posts: 39
  • Thank you received: 1
Hello

Im downgrading my kz1000/1200 from K410 cams to GPZ1100 UniTrack inlet cam and GPZ1100 exhaust cam,, i have put the Centerline to 109 on both but its like it dosnt rev in the high RPM - is 109 for these cams wrong??

Inlet is 32 BTDC and exhaust is 43 BBDC @ 0,40''/ 1mm.....


>What to do???

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

Last edit: by larslykkegaard.

Centerline GPZ cams 26 Aug 2016 22:03 #740100

  • Kray-Z
  • Kray-Z's Avatar
  • Offline
  • User
  • I need more power Scotty....
  • Posts: 583
  • Thank you received: 107
Try and locate the stock timing numbers for both engines and calculate the lobe centers from that. I would time both cams to the intake lobe center...
2-04 R1, 81 CSR1000, 81 LTD1000, 2-83 GPz1100, 3-79CBX, 81 CBX, 3-XS650, 84 Venture, +parts
Quote "speed costs money...how fast do you want to go?" (Which Z movie?)
Universal formula for how many motorcycles one should own = n + 1, where n is how many motorcycles you own right now....

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

Centerline GPZ cams 26 Aug 2016 22:36 #740103

  • Kray-Z
  • Kray-Z's Avatar
  • Offline
  • User
  • I need more power Scotty....
  • Posts: 583
  • Thank you received: 107
I have the '81 GPz1100 exhaust as open 68 BBDC and closed 32 ATDC.

Lobe center is therefore 108 BTDC (on exhaust stroke).

Your @ 0.040" lift timing for the 83 GPz intake doesn't make sense - opening 32 BTDC might be o.k. but closing 43 BBDC should be at least 62 ABDC if the cam is symetric...
If so, the intake lobe center is 105 ATDC...which doesn't seem right to me, but that matches the spec I have for the '81 intake cam....
2-04 R1, 81 CSR1000, 81 LTD1000, 2-83 GPz1100, 3-79CBX, 81 CBX, 3-XS650, 84 Venture, +parts
Quote "speed costs money...how fast do you want to go?" (Which Z movie?)
Universal formula for how many motorcycles one should own = n + 1, where n is how many motorcycles you own right now....
The following user(s) said Thank You: larslykkegaard

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

Centerline GPZ cams 27 Aug 2016 10:53 #740149

  • Tyrell Corp
  • Tyrell Corp's Avatar
  • Offline
  • User
  • "You were made as well as we could make you"
  • Posts: 1650
  • Thank you received: 260
Your @ 0.040" lift timing for the 83 GPz intake doesn't make sense - opening 32 BTDC might be o.k. but closing 43 BBDC should be at least 62 ABDC if the cam is symetric.


You are sure this is a GPz11 Uni cam? why just one rather that a pair that is matched in lift and duration?

There are a number of different grinds, the late GPz uni being the most extreme. FSM has cam identification details,

www.kzrider.com/forum/2-engine/590239-stock-j-model-cam-options



All the GPz's are very 'cammy' , the uni being most of all -at the expense of bottom end grunt. I would think setting them symetrically anywhere between 105 and 110 (assuming no interference issues) would be a good starting point.

Triva: the zx550 unitrack Gpz has an inlet lobe centre at something like 92 degrees, on 280 cams... strange but true.
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces

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

Last edit: by Tyrell Corp.

Centerline GPZ cams 30 Aug 2016 02:27 #740487

  • larslykkegaard
  • larslykkegaard's Avatar Topic Author
  • Offline
  • User
  • Posts: 39
  • Thank you received: 1
Inlet opens at 32 btdc and close at 71
exhaust opens at 43 bbdc and closes at 05

everything is measured @ 0,40 / 1mm lift

i use this calculation
inlet
71-32 = 39
39/2 = 19,5
19,5+ 90 = 109,5

exhaust
05-43 = 38
38/2 = 19
19+90 = 109

Got the calcultation with some cams from Joe/PSP

Does it sounds all wrong???

I heard the mix of these two cam was good if i wanted a bit more bottom torque compaired too only runing UniTrack cams

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

Centerline GPZ cams 30 Aug 2016 06:01 #740498

  • Tyrell Corp
  • Tyrell Corp's Avatar
  • Offline
  • User
  • "You were made as well as we could make you"
  • Posts: 1650
  • Thank you received: 260
1) Did you accuately find TDC using a positive stop? not good to rely on the ignition timing markings when dialing -in cams

2) If yes to above do it again then double check your lobe centres. For now Ignore any idea of duration or lift, purely about finding the point of max lift.
This won't be an exact crank angle but an angle of a few degrees that you turn through as the valve is wide open and seems not to move as the crank turns - it is just on the nose of the cam. Halfway between the this max valve lift 'sweep' gives you your lobe centre. Check that.

I've not dialed in GPz11 yet, but is there an indent for the cam chain tensioner top run like on some of the other gpz's?
( does the camchain top run dead straight or does the top run tensioner bend the chain down at all? ) If so you must to account for this. You could think you have correct lobe centres, then the cam cover tightens down and the top tensioner guide squashes the chain down so the inlet is now advanced -this would cause just the problem you have.

Dailing-in to a lobe centre means : valve clearances, camchain wear and possible head skim / head gasket thickness issues won't affect your valve timing.

In a perfect world if you know precisely the cam specs you could set set them both just using either the 0.40 opening or closing point, in reality it probably wouldn't be accurate due to inevitable wear and manufacturing tolerances.

Be really precise here, it is time consuming I know. Be wary of adding more lift if you aren't sure of your clearances - piston valve cut outs can be fly cut deeper if required. Things can go bang if you get it wrong. Use threadlock on the cam gear bolts.




With slotted cams you have a lot of timing options, for example 105 degree lobe centres for midrange, 110 for rpm power. With DOHC you can use asymmetrical timing, perhaps reducing or increasing the overlap.
Short overlap = grunt long overlap = rpm power.

The one zx cam has more lift, you could think consider this in your valve timing to reduce chances of piston valve interference. There is the option of symmetrical cam timing, or cam phasing. This book covers it really well and is really worth a read:


www.bokus.com/bok/9780857331250/four-stroke-performance-tuning/
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces

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

Last edit: by Tyrell Corp.

Centerline GPZ cams 30 Aug 2016 09:14 #740512

  • gpz1170
  • gpz1170's Avatar
  • Offline
  • User
  • Posts: 124
  • Thank you received: 10
83/84 GPZ cam center line 110' intake and exhaust
1974 Z1
1976 KZ900
1978 KZ1000
1981 KZ1000
1983 GPZ1100

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

Centerline GPZ cams 30 Aug 2016 12:55 #740545

  • Kray-Z
  • Kray-Z's Avatar
  • Offline
  • User
  • I need more power Scotty....
  • Posts: 583
  • Thank you received: 107
Lots of ways to calculate the lobe centers of symmetric cams. With most of the engines I put together I have to check piston to valve, and valve overlap / interference clearances, Because I need to "see" in my mind were the cams and pistons are relative to each other while the engine is rotating in the forward direction, here is how I do it.

I add 1 / 2 the total duration to the valve open number. Sounds easy, but you have to keep track of were in the stroke you are. Anytime the piston passes TDC, the numbers start at 0 again. You have to work with valve opening numbers that reference TDC only. For example, the stock 82 GPz1100 by the FSM: Intake opens at 35 BTDC and closes at 65 ABDC. Total duration is 35 + 180 + 65 = 280. 280 / 2 = 140. "Add" 140 to 35 BTDC = 140 - 35 = 105 ATDC (note that lobe centers always reference to TDC). The exhaust opens at 68 BBDC (180 + 68 = 248 BTDC) and closes 32 ATDC. Duration is 68 + 180 + 32 = 280. 280 / 2 = 140. "Add" 248 - 140 = 108 BTDC for the exhaust center line.
So the stock 82 GPz1100 cam centerlines are 105 ATDC Intake and 108 BTDC exhaust. Valve overlap timing is from intake open to exhaust close - 35 BTDC to (180 - 68 =) 112 ATDC, or 35 + 112 = 147 total valve overlap / duration.
2-04 R1, 81 CSR1000, 81 LTD1000, 2-83 GPz1100, 3-79CBX, 81 CBX, 3-XS650, 84 Venture, +parts
Quote "speed costs money...how fast do you want to go?" (Which Z movie?)
Universal formula for how many motorcycles one should own = n + 1, where n is how many motorcycles you own right now....

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

Centerline GPZ cams 30 Aug 2016 14:13 #740559

  • Kray-Z
  • Kray-Z's Avatar
  • Offline
  • User
  • I need more power Scotty....
  • Posts: 583
  • Thank you received: 107

larslykkegaard wrote: Hello

Im downgrading my kz1000/1200 from K410 cams to GPZ1100 UniTrack inlet cam and GPZ1100 exhaust cam,, i have put the Centerline to 109 on both but its like it dosnt rev in the high RPM - is 109 for these cams wrong??

Inlet is 32 BTDC and exhaust is 43 BBDC @ 0,40''/ 1mm.....


>What to do???

I'm sure that Joe has told you about needing to swap the cam sprockets for the two bolt cams....

Another note...the K410's can make pretty good mid range power if you have enough compression and advance the intake cam 2 deg (108 ATDC).... what compression ratio are you using?
2-04 R1, 81 CSR1000, 81 LTD1000, 2-83 GPz1100, 3-79CBX, 81 CBX, 3-XS650, 84 Venture, +parts
Quote "speed costs money...how fast do you want to go?" (Which Z movie?)
Universal formula for how many motorcycles one should own = n + 1, where n is how many motorcycles you own right now....

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

Centerline GPZ cams 30 Aug 2016 14:17 #740560

  • Kray-Z
  • Kray-Z's Avatar
  • Offline
  • User
  • I need more power Scotty....
  • Posts: 583
  • Thank you received: 107
I believe the intake cam on the "J" engines is advanced about 1/2 to 1 deg. by installing the top cam chain guide in the valve cover...
2-04 R1, 81 CSR1000, 81 LTD1000, 2-83 GPz1100, 3-79CBX, 81 CBX, 3-XS650, 84 Venture, +parts
Quote "speed costs money...how fast do you want to go?" (Which Z movie?)
Universal formula for how many motorcycles one should own = n + 1, where n is how many motorcycles you own right now....

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

Centerline GPZ cams 31 Aug 2016 01:33 #740625

  • larslykkegaard
  • larslykkegaard's Avatar Topic Author
  • Offline
  • User
  • Posts: 39
  • Thank you received: 1
those numbers Kray-Z, they give me some good guideing will try re adjust inlet to around 105 and check the exhaust centerline again..
i used a positive stop /reshaped sparkplug

Im runing a kz1000A engine so yes the sprocket is changed to the 2hole/30t

is a 1197cc with some german racing piston - it made 120WHP+ with the K410 cams, but was annoing to ride in the city traffic

will update

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

Centerline GPZ cams 31 Aug 2016 15:31 #740691

  • Tyrell Corp
  • Tyrell Corp's Avatar
  • Offline
  • User
  • "You were made as well as we could make you"
  • Posts: 1650
  • Thank you received: 260
And maybe tweak the exhaust cam too , if the object is to boost the bottom end then you don't want to increase the overlap.

Diid you actually acertain the lobe centres, or did you calculate these off your measured opening and closing numbers?
1980 Gpz550 D1, 1981 GPz550 D1. 1982 GPz750R1. 1983 z1000R R2. all four aces

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

  • Page:
  • 1
Powered by Kunena Forum