It's a long way to 920 type(rary)

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Hi there,
Disapointed!! here are the results from the dyno runs I did to day:
62 BPH at 6.500 rpm with the 920 with the big valves, same result as in the pass with my 820... with normal valves at 6.000 rpm
And more: less torque with the 920 as with the 820
The carbs setting where spot on with the analizer and I try different ignition timing w/o noticiable changes.
So I can only think on a bad camshaft timing...
Your opinions please
Thanks
Yves
PS: Bruno will post the graphs later to day
 
Oh dear...

Yes, cam shaft timing would be my first thought, or ign timing. I know you tried different settings, but are you sure you set the baseline right? I got mine VERY wrong once, but the excellent starting and idle control functions of the Tri Spark masked the symptoms, well, enough to fool me at least. This cost 10 rwhp. I only noticed it cos I took it to the dyno. The bad results made me think something serious was wrong!

Or, the tight pistons as mentioned by JS in another post?

Or, something unexcpected, even silly, a tight tappet, duff spark plug, etc.

Or, something wrong / different with the dyno settings?

Or... and I hope this is NOT the case... Sir Comnoz showed in his cylinder head thread how a very subtle difference in porting work, especially around the valve throat area, can have a big detrimental effect. Did your cylinder head man make an error??
 
The camshaft timing usually works in conjunction with the exhaust system configuration. Even if the cam timing is wrong, it will usually work - just not as well, if the exhaust system does not suit it. If you have changed the exhaust, you might have to move the cam timing to suit it.
 
Fast Eddie said:
Oh dear...

Yes, cam shaft timing would be my first thought, or ign timing. I know you tried different settings, but are you sure you set the baseline right? I got mine VERY wrong once, but the excellent starting and idle control functions of the Tri Spark masked the symptoms, well, enough to fool me at least. This cost 10 rwhp. I only noticed it cos I took it to the dyno. The bad results made me think something serious was wrong!

Or, the tight pistons as mentioned by JS in another post?

Or, something unexcpected, even silly, a tight tappet, duff spark plug, etc.

Or, something wrong / different with the dyno settings?

Or... and I hope this is NOT the case... Sir Comnoz showed in his cylinder head thread how a very subtle difference in porting work, especially around the valve throat area, can have a big detrimental effect. Did your cylinder head man make an error??
Click to expand...
My cylinder man don't touch the original porting from FA
 
But he put big valves in Yves, so the original FA porting needs amending / blending to the big valve... if you re read through Comnoz’ “head flow testing” thread you should find the parts that I’m referring to.
 
acotrel said:
The camshaft timing usually works in conjunction with the exhaust system configuration. Even if the cam timing is wrong, it will usually work - just not as well, if the exhaust system does not suit it. If you have changed the exhaust, you might have to move the cam timing to suit it.
Click to expand...

Yves has not changed the exhausts. He has changed the cam, but only to one with modified ramps, but the same profile. So the cam / exhaust combo he is running is as before. The possible variable is the positioning of the lobes on the cam, ie the timing.
 
Hello all, here is Yves' disappointing dyno graph, with both 828cc and 920cc curves:

It's a long way to 920 type(rary)
 
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Fast Eddie said:
Yves has not changed the exhausts. He has changed the cam, but only to one with modified ramps, but the same profile. So the cam / exhaust combo he is running is as before. The possible variable is the positioning of the lobes on the cam, ie the timing.
Click to expand...
As you can see on the graph the to day power line (green) you can see that I lost a lot of power in the mid range compare with the 820, only at 6.500 RPM the engine ritch the same power as the 820, but with 500 RPM more, can this be a sign that the cam is to retarded??
Yves
 
I can't make out this graph. Why are the traces exchanged, or are they offset to the right?
 
Mr. Rick said:
I can't make out this graph. Why are the traces exchanged, or are they offset to the right?
Click to expand...

Good point, first test started at below 2,500 and second test at 3,000.

If nothing else, that shows a difference in the dyno operators approach surely?
 
Fast Eddie said:
Good point, first test started at below 2,500 and second test at 3,000.

If nothing else, that shows a difference in the dyno operators approach surely?
Click to expand...
Hi Nigel,
I think that the dyno operetor just put the computer later on
Can you explain me wats happens to your ignition timing?
As you can imagine I feel very sad at the moment and I must find the reason for this lost of power
This afternoon I will tchek the cam timing again, but I don't understand the video from Jim Schmidt very well, I says to put the engine at TDC and registred the difference of lift between in and ex valves, but the in go open and the ex go closed, in my understanding I have to turn the crank in two different way, one wat for each of the valves?
And if I find that the cam is retarded and I advance the cam, this will only bring the torque to lower RPM, but will this ad power?
Thanks for your help
Yves
 
Yves,

I can’t remeber the details, but, I had set the bike very retarded on the ign timing. It lost power everywhere in the range.

There HAS to be a reason for your power loss. Actually, you haven’t really changed very much if you think about it. Cam profiles, head, exhaust, basic engine set up are all the same. CR is not much different, either is piston weight.

You’ve changed the bore size, the cam shaft (not the profile design), the valve sizes.

Let’s look at what’s changed:

Bore size: because you have not significantly changed piston weight, this cannot be causing a big power loss.

Camshaft: the lobe design is the same (except for the ramps) so this cannot be causing a power loss. But where the lobes are on the shaft, ie the timing, could easily be. My understanding is that it is NOT as simple as saying ‘retarding will increase torque at the expense of power’ etc. The cam works in conjunction with your entire system. Any change from ‘optimal’ could easily cause big overall losses IMHO.

Valve size change: Comnoz has demonstrated that big valves, when properly installed, increase both torque and power. BUT the work done around the valve throat area is of critical importance. Small errors here can cause big losses.

Other changes: unless I’ve missed something, you’ve not made any other intentional big changes. So, the other possibility is accidental changes like ign timing, valve clearances, tight pistons, etc.

If I were you, I would check the cam timing, ign timing, tappets, and anything else I could think of. If everything seems OK, I’d put as many miles on it as I could, inc some hard thrashing miles to get it really loosened up, then return to the dyno.

If results are still disappointing, I would suspect the head work.

Sherlock Holmes said “if we illuminate everything else that’s possible, then what’s left, no matter how improbable, must be the truth”

In other words, a process of elimination is your best bet!

I am not qualified to offer detailed cam timing advice Yves, I suggest your discuss this with JS.
 
Salut Yves & All,

Yves, have you had a look at a post below (Piston skirt treatment study) where Jim S. says "Yves has this coating on his pistons now and he is heading into the dyno with only about 100 miles on his motor. The tight pistons may actually hold down his HP output until they loosen up".

Maybe some food for thought?

Laurent
 
This is way out of my wheel house so this is a question more that suggestion. First It looks like there was a 11 degrees Celsius difference between the two tests, could that have an affect. The right side of the Dynojet chart is cut off so I can’t see beyond that point.
Second, could the increase in valves and cc’s require larger carbs or velocity stacks
Pete
 
Deets55 said:
This is way out of my wheel house so this is a question more that suggestion. First It looks like there was a 11 degrees Celsius difference between the two tests, could that have an affect. The right side of the Dynojet chart is cut off so I can’t see beyond that point.
Second, could the increase in valves and cc’s require larger carbs or velocity stacks
Pete
Click to expand...

Pete,

The 11 degrees diff may make a small difference, as would humidity and atmospheric pressure. But no where near then kind of difference Yves is seeing.

Ref carbs, I think Yves carbs are big enough, but, even if they weren’t allowing the bigger motor to realise its max potential, they would still allow it to reach the potential it did before.

Gotta be something else me thinks.
 
Nigel,
Thanks for the info. Will be interesting thread to follow as I’m sure Yves will not give up on this.
Pete
 
ludwig said:
Yves ,
I haven't followed the entire thread , but I believe your compression pressure is way too low .
Should be more like 11 Bar .
If piston rings , valves .. seal well , then you have a problem with cylinder filling .
Could be camshaft related .

Komt gij woensdagavond naar Gerbrand ?
Click to expand...
Is er iets te doen bij Gerbrand?
Yves
 
Fast Eddie said:
Pete,

The 11 degrees diff may make a small difference, as would humidity and atmospheric pressure. But no where near then kind of difference Yves is seeing.

Ref carbs, I think Yves carbs are big enough, but, even if they weren’t allowing the bigger motor to realise its max potential, they would still allow it to reach the potential it did before.

Gotta be something else me thinks.
Click to expand...
Hi Nigel,
I was in the workshop this afternoon, of course not very entousiast, but after a few hours of working I am already the old one
Like you suggest I must tchek it step by step, so to day I tchek the ignition timing, I take the exhaust, the rocker covers, plugs and so on off
then I put a dial guage in the spark plug hole to find TDC, put the degree weel on the crank and turn the crank 28 degrees clockwise, put the degree weel off, put the primary cover on the engine and look at the degree scale and it was 28 degrees, so the timing must be good...
The spark plugs are looking good after the dyno runs at 6.500 RPM
Jim Schmidt says that the inlet valve must be more advanset as the ex valve at TDC when the valves are in balance, so I did a visual tchek (difficult to do) and I gat the feeling that the In valve is at least on the same level as the Ex valve and maybe retarded... depending from the angle you use to watch the valves...
On monday I will make the mesurments on the valves, this time I will make a bracket like Jim Schmidt use on his cam timing video, this will be more accurate as the magneet I was using the first time.
I remember well when I put the first JS 2 cam, not the JS smoothramp I have know, I did also a visual tchek to the valves and it was easy to see that the IN valve was more advanced.
Hope my wife will give me the time to work on monday and hope also that the problem is coming from the cam timing, this is easy to solve
If the problem is not coming from the cam timing, then I will take the head of and go to the flow bench, again $$$$
Keep you posted
Yves
 
Yves - when you make your dial indicator brackets to measure valve lift at TDC - be sure you only turn the crank in the direction of running rotation when you get close to TDC - if you turn backwards it will give you false reading.

Porting is just as important or more important than installing big valves and as Nigel said - with the bigger valves the port floor curve leading to the valve (and the sides of the bowl) must be re-shaped. The FA ports can use some cleaning up around the guides as well. For a 920 the ports could be improved a bit for more flow to keep up with the increase in volume.

see this FA porting video and pay close attention from 6:20 to 7:20
see the template at 6:40

 
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