Ex-500.com - The home of the Kawasaki EX500 / Ninja 500R banner

1 - 20 of 27 Posts

·
Registered
Joined
·
41 Posts
Discussion Starter #1
After reading the whole topic on How to Degree your Cams, I wanted to check the cam timing on my GPZ500. In the topic it is stated that the cams are symmetrical. That is why it is easy to find the lobe center. But after looking at the cams in my GPZ, the do not seem to be symmetrical at all. I've try to make clear pictures of the cams:





There does not seem to be any damage or scourging on the surface of the cams or the forks:





The cam profile does seem to be the same on both the IN and the EX, but than opposite. So the inlet has a "soft" start of the lift and a "hard" cut off. The exhaust looks the other way around: a "hard" start and a "soft" cut off.

Does anybody know what kind of cams these are? And how should the cam timing be approached in this case?
 

·
Registered
Joined
·
19,318 Posts
The lobe center tenique is viable even in your case.

FOG
 

·
Registered
Joined
·
398 Posts
In order to get symmetrical movement at the valve with this type of valve train, the profile of the cam lobe has to be asymmetrical. This is due to the fact that as the lobe "wipes" across the surface of the follower, the the rocker ratio continually changes. The intake and exhaust cam lobes are mirror images of each other because the intake and exhaust valve trains are mirror images of each other. They are most likely stock cams.

FOG is right; the lobe center technique will work fine.
 

·
Registered
Joined
·
41 Posts
Discussion Starter #6
One more question about degreeing the cams. I quote from the How To from Fog:

I can add here that you can use different settings that the stock ones but I’m not going to tell you, except to say expanding the spread of the cams will move the power up in the rev range, and closing the settings will do the opposite.
What is ment by the 'spread'? Is that the same as the overlap between the exhaust and inlet? Sorry if this seems a silly question. Because English is not my native language, I sometimes miss the nuances.
 

·
Registered
Joined
·
48 Posts
Have a look at webcam camshafts
how to degree your cams. If you don’t have much experience in this area I wouldn’t mess around with your cams.
 

·
Registered
Joined
·
41 Posts
Discussion Starter #8
thanks for the links to WebCamshaft. They had all the information that I needed.

Experience is not the problem, sometimes my understanding of the English language misses the fine nuances.
 

·
Registered
Joined
·
41 Posts
Discussion Starter #9
Thanks for all the help. It took quit a bit of time to measure and adjust the cams because it was the first time I did this. To be able to do this while the engine is in the frame, a motorcycle buddy helped me out with his lathe. We made a elongated bolt left threaded M10x1.25 and a spacer. This way, I could leave the generator cover on and did not need to drain the oil.





A lot of extra work, but it was worth it. The intake cam was 3 degrees late, the exhaust cam was almost 6 degrees late. I don't understand why there was such a big difference. The chain was still well within the wear limits. Could it simply be the factory tolerances?

After reading up on the tip of Kiwigpz at WebCamshafs, I decided to take this opportunity to experiment a little. The intake cam is now 0,5 degree advanced from original, so lobe center at 99,5 degrees ATDC. The exhaust is advanced 4 degrees from original, so lobe center at 109 degrees BTDC.
With the information I red, this would shift the powerband a bit more to the mid rpm range. Personally I prefer bottom and mid power over top power. So I'm curious to how this change will hold up on the road. Seeing it is in the middle of the night here in the Netherlands, a testdrive will have to wait until tomorrow.

The long term plan is to put the GPZ on a dyno to tune the cabs to the current situation. This will be the base line for future modifications. A second cylinder head is laying around in my garage. I've already modified the exhaust porting and valve seats of this head in the same way I did with a Yamaha TT600R. That bike gained 14% torque and 17% power with that modification. The next step is to modify the inlet ports in the way described by Moto Man. Than the cilinder head will be put on the GPZ and go on the dyno again for comparison with the original base line.
 

·
Registered
Joined
·
19,318 Posts
Be interested to know what your results are .did all this work to one engine and was disappointed with the results.
let me ramble a bit here. In 12 years of racing ex’s in a box stock class. I have never seen a modified ex go a fast ( lap times) as the stock ones.
jeff Wood took a new ex with only a penske shock and race tires around London in a time that would have qualified him on the grid for the last super bike race at loudon
 

·
Registered
Joined
·
41 Posts
Discussion Starter #11
I expected nothing else but for you to ramble a bit here 😉 Somewhere on this forum I already red something about how hard it is to get these engines to go any faster. That is not that surprising, considering that mister Kawasaki already managed to get 60 bhp out of a 500cc twin. That is equal to 120 bhp per liter capacity. For an old nineties machine I think that is pretty impressive!

Now is the main goal not to get more power, but get a more flattened torque curve.I think this start with the exhaust flow, contrary to what is commonly thought in the world of tuning. A fortunately byproduct with the Yamaha and also the Moto Guzzi, was more overall power. By only working the exhaust valve seats and ports, with both bikes the torque curve gained over the full rpm range. With the Yamaha that was 14% and with the Moto Guzzi that was 9%.
Now I'm really curious to what this technique does in combination with the mentioned Moto Man approach.

It might take a while before I'll post again on this subject. Work tends to take a major chunk out of my hobby time 😊 By the time the results are in (good ore bad), I'll start a new topic on the subject to keep it organised.
 

·
Registered
Joined
·
19,318 Posts
You got it right, “more power” that is more under the curve if yo calculate the area under the power line of a dyne graph, not just look at the peak number. You will get around a race track faster. I was often accused (jokeinlly) of cheating ,because I woul pull others coming out of the corners,

fog
 

·
Registered
Joined
·
41 Posts
Discussion Starter #13
Do you mean you manage to get more mid-range torque out of your race EX? If so, what did you do to get that result? I'm eagere to learn and take all experiences in with my own experiments.
 

·
Registered
Joined
·
19,318 Posts
I said a greater are under the curve, I you look at the diagram below of the power curve you can see that a greater area under the curb of the power band ,results in more push everywhere and that little bump at the top (Max HP) contributes little. Yes you could apply this idea to the torque curve as well. But just be wary of people quoting big HP/Torque numbers as you don't know what they gave up to achieve them.
BTW the chart below is from my race bike the day I designed the FOG MOD
FOG
51709
 

·
Registered
Joined
·
41 Posts
Discussion Starter #15
Thanks for sharing that dyno diagram! That gives me something to compare my bike with. I find it hard to find reliable data on the internet. Just like you said, a lot of quotes with marvelous numbers are found, but little are substantiated with a dyno diagram.

With my Moto Guzzi and my Yamaha TT600R I did a run before and after the modifications. This way I could see for myself what the effect of my modifications were. For that purpose I plot the different diagrams in one diagram in Excel. This way it is more visual to me what and where the change is.
The below example is from the TT600R.



Do you also have a comparison diagram from a stock EX to compare the Fogmod to? That would be intersting to see.
 

·
Registered
Joined
·
41 Posts
Discussion Starter #16
Now I almost forget to write up the change after degreeing the cams.

Today I made a short test run on the road. It is completally subjective, but I've got the feeling that the peak torque has shifted slightly to the mid-rpm range, around 5500rpm.
Normally the bike would have its greatest torque around 8000rpm. In comparisson to the dyno chart from Fog, that is a bit late. Maybe this was due to the cams being very late. 3 degrees for the intake, almost 6 degrees for the exhaust!
With degreeing the cams, I've set the intake cam 0,75 degree advanced over stock. The exhaust cam is advanced 4 degrees over stock. This would explain the shift of the peak torque to a lower rpm.

However it may be, it drives nice on the road. With my sporty drivestyle (pegs to the ground, at the edge of the tires) the bikes feels more manageble. All in all I'm happy with the How To about degreeing the cams! Thanks Fog.
 

·
Registered
Joined
·
12 Posts
Be interested to know what your results are .did all this work to one engine and was disappointed with the results.
let me ramble a bit here. In 12 years of racing ex’s in a box stock class. I have never seen a modified ex go a fast ( lap times) as the stock ones.
jeff Wood took a new ex with only a penske shock and race tires around London in a time that would have qualified him on the grid for the last super bike race at loudon
Fog, That was my EX and he ran 4 1.17's in a row in the gtl race. That bike had first over pistons, no base gasket and was running MR-9 fuel. Still, he went like hell. Certainly nothing I could have done. I barely made it out of the 1:20's. Dana Temple
 

·
Registered
Joined
·
19,318 Posts
HI Dana,
Thats the trouble with telling old stories, how much was true & how much wasn't , good to know there were other witnesses .
I wasn't aware of any mods on that bike. But it was still a ex with all the wobbles. My best ever was a 1:22 and I thought I was gonna die.

FOG
 

·
Registered
Joined
·
48 Posts
I have found good gains in porting this engine. Definitely the exhaust ports want opened up and the valve guide can be ground back to allow better flow
F3F7228F-F114-41AE-BD0C-7844B9AEE91E.jpeg
A9C74C24-B049-45F3-B2B6-4BC062253DEC.jpeg
C575CB8B-1616-4A52-8B49-58C08AC79ADE.jpeg
 

·
Registered
Joined
·
19,318 Posts
curiously I have not. they look like they needed it badly but when done shown no gains. most of the improvement comes from a good valve reseating.
how have you recognized any gain.

FOG
 
1 - 20 of 27 Posts
Top