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

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Yves, flat works too, although a track is best. If you are really consistent then the 1/4 mile sprint gives good before and after info.
Most of us aren't that consistent with the start, so the rolling test is probably better.
Pick a point and roll to it then wick it on and shift at consistent points, say 6500.
Pick a point for end speed( could be a road sign 1/4 mile away, exact distance not important ) and record finishing speed. Use a GPS.
That's really what we're all after with tuning and mods, greater acceleration and speed. Squiggly lines on a dyno sheet are great for discussion but true added road speed means more power, pure and simple.
I realize it is too late for this type of before and after test with your mods.
It would be nice to know what the bike did before and what it does now on the same run.

Glen
 
Yves, flat works too, although a track is best. If you are really consistent then the 1/4 mile sprint gives good before and after info.
Most of us aren't that consistent with the start, so the rolling test is probably better.
Pick a point and roll to it then wick it on and shift at consistent points, say 6500.
Pick a point for end speed( could be a road sign 1/4 mile away, exact distance not important ) and record finishing speed. Use a GPS.
That's really what we're all after with tuning and mods, greater acceleration and speed. Squiggly lines on a dyno sheet are great for discussion but true added road speed means more power, pure and simple.
I realize it is too late for this type of before and after test with your mods.
It would be nice to know what the bike did before and what it does now on the same run.

Glen
The only record I have with the 820 is from the drag racing over 1/8 mile, but the next one would be on september
Yves
 
By then the 920 will be well run in . Should be a good comparison test.

Glen
 
Yves, do you have ‘before and after’ flow bench data to compare?

Overlaying this with your ‘before and after’ dyno data is what’s needed here.
 
Let’s hope he finds an answer.

And if he does... let’s hope you don’t thrash him too badly for causing all this work / stress !!
Yves, do you have ‘before and after’ flow bench data to compare?

Overlaying this with your ‘before and after’ dyno data is what’s needed here.
We take the flow on the original FA with the bigger valves, but so far we don't do any work on it
Regards
yves
 
Yves, what I meant to ask was did you flow test the stock FA head before fitting big valves? And then after fitting big valves?
 
Yves, what I meant to ask was did you flow test the stock FA head before fitting big valves? And then after fitting big valves?
Yes we test it before fitting big valves, and we did a short test with the big valves trusday eve, so far I dont receive any graph from it
Yves
 
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 ?
Yves, I know people are querying you with all sorts of thoughts on myriad subjects, but back to Ludwig's comment above, it seems suspect to have such low compression with over 10:1 CR. Since CR started at 10.1 and is now 10.6 seems you should certainly be in the 160-170 psi (11-11.7 bar) range rather than the lower range you observed. When you did the test was the 1st hit a good one like 90-100 psi (6-7 bar), or did it slowly creep up to a maximum in small increments? I don’t recall if you did a leak-down test or not?
 
Here's one of the drawing I sent to Yves in case he wants to massage the FA intake ports.

It's a long way to 920 type(rary)
 
Yves, I know people are querying you with all sorts of thoughts on myriad subjects, but back to Ludwig's comment above, it seems suspect to have such low compression with over 10:1 CR. Since CR started at 10.1 and is now 10.6 seems you should certainly be in the 160-170 psi (11-11.7 bar) range rather than the lower range you observed. When you did the test was the 1st hit a good one like 90-100 psi (6-7 bar), or did it slowly creep up to a maximum in small increments? I don’t recall if you did a leak-down test or not?
The first thing you must know, I did the compression test with a Motor Meter, to me the best brand in compression meter, with warm engine and with the two spark plugs out and carbs fully open, maybe the fact that I take the second spark plug out can influence the resulst from the meter??
Becouse the Motor Meter is from a friend, I don't did the test again after lowering the head gasket, sorry...
I did the test with the E start, and the meter show 9.5 bar after passing 2 or 3 times the compression.
Now with the engine open, I mill 0.1mm from the head
I don't did the the leak down test, I don't have the tool to do it, if you know a cheap way to do the leak-down, feel free to let me know please.
Anyway, I can do nothing before I receive the gapless rings from Jim and this can take two weeks (special order)
And before I ask the flow man to do some work, I must receive some explains about the strange graphs from the dyno man, this will be on monday.
From Belgium, the way to Tiperary must be short when you go to the North, I gat the feeling that I am taking the way to the Sud, all around the world...
Keep you posted
Yves
 
Hi there,
This morning I call Ruud, the dutchman from the dyno and ask me to explain me why the graph from the 820 start earlier (lower RPM) as the graph from the 920?
He sais that he take the mesurments higher in the RPM with the 920....
So the power curve must be exact as wel for the 820 as for the 920....
But don't tell me that at the road test I should not feel a difference from 8HP lower in the mid-range like you can see on the graph?? I agree that I will not feel 1 or 2 hp, but 8????
The head is at the workshop from the flowman and he will try to have a better flow, following JS instructions
I order gapless rings from JS, but it will take 2 weeks to be here, so long I can do anything on the engine....
Once the engine will be back togheter, I will re-tchek the cam timing, CR and so on and brake in 750 miles before I go back to the dyno
I start to believe that the engine as to low brake-in miles when it was on the dyno, I can not imagine another reason so far...
As you see, I am still in the darkness
Keep you posted
Yves
 
Yves, to get the optimum value out of my JS2 cam, we had to set the intake Vv at the recommended lift by JS and optimum clearance with the exhaust Vv then set the mechanical timing to suit.
This meant that my crank pinion to intermediate gear timing marks are three teeth on from standard and we had to hand shape a stepped key for the camshaft sprocket. It is a lot of messing around , but it gets the best performance from your cam.
In the recent past, a friend rebuilt his standard 850 and installed a PW3 cam and was surprised it was quick to 80MPH but then ran out of puff past that, I advised to check his timing and sure enough it looks like he will need a stepped key in the cam shaft as well.
PM me if you need any other details.
Regards Mike
 
Yves, to get the optimum value out of my JS2 cam, we had to set the intake Vv at the recommended lift by JS and optimum clearance with the exhaust Vv then set the mechanical timing to suit.
This meant that my crank pinion to intermediate gear timing marks are three teeth on from standard and we had to hand shape a stepped key for the camshaft sprocket. It is a lot of messing around , but it gets the best performance from your cam.
In the recent past, a friend rebuilt his standard 850 and installed a PW3 cam and was surprised it was quick to 80MPH but then ran out of puff past that, I advised to check his timing and sure enough it looks like he will need a stepped key in the cam shaft as well.
PM me if you need any other details.
Regards Mike
Hi Brooking, I did already the cam timing and give the values here, to JS it was good.
Tomorrow I will put the cylinder on the engine, search TDC and then search the lobe center with a dial guage on the push roads, whait and see...
Keep you posted
 
Hello Together,
I just had Yves on the phone and we agreed that I do some calculations on the compression ratio. Yves told me that he has a combustion chamber volume of 48cm³ (was that right????). With a bore of 81mm we get a capacity of 458,38cm³/ cylinder. By using the Formula: ε = (Vh+Vc)/Vc we end up at a geometrical compression ratio of 10,55 : 1, which is the maximum we want for road traffic. Your connection diameter of the cyl.- head to the cylinder is 81,4mm (I should know, because I machined it).
If you want to rise your geometrical compression ratio to 11 : 1 we need to mill 0,4mm off the cylinder head gasket surface.
We assume that we keep the cylinder head gasket with a thickness of 0,6mm.
Now, we had it somewhere before: The difference between the geometrical compression ratio to the practical one is, that we have losses of gas exiting the volume of the cumbustion chamber during the overlap of the valves shortly before top dead center. Maybe we wouldn't be too wrong rising the geometrical compression ratio to 11:1. But you can be assured that this not the reason for the lost horses.
Well, that was a bit of mathematical theory.
Best Regards
Klaus Monning
 
Just thinking out loud...

With two beautifully machined surfaces on the cylinder head and barrel, is it necessary to run a head gasket at all, instead just used a crushable material like Kevlar cord saturated in Wellseal or Pliobond?

I am of course making an assumption that the valves won’t clatter on the top of the pistons.
 
Just thinking out loud...

With two beautifully machined surfaces on the cylinder head and barrel, is it necessary to run a head gasket at all, instead just used a crushable material like Kevlar cord saturated in Wellseal or Pliobond?

I am of course making an assumption that the valves won’t clatter on the top of the pistons.

Not quite what you’re suggesting but close, have you seen the 0.003” copper rings offered by JS? These must presumably crush to virtually nothing when torqued up:

http://jsmotorsport.com/product/high-compression-003-thin-head-gasket-rings/

With any such method, something still has to be done to seal the pushrod and oil return holes.
 
I did nothing to day! I have to stay home, my wife is shopping the whole day, and I have to stay home for the delivery from a tri-cycle for my wife.
It's 4 PM and no tri-cycle!!
And my wife is shoping with my credit card... I remember the day that somebody steel my credit card, but I never go to the police: the teef was spending less money as my wife!
yves
 
Yves,
that's good for you, that saves you a lot of money. You can't spend it on the Norton. Well, with all that sadness you currently experience, you need a joke from time to time. Imagine, I have to cleen the house today. I'd rather do cylinder - heads.
Best Regards
Klaus
 
Not quite what you’re suggesting but close, have you seen the 0.003” copper rings offered by JS? These must presumably crush to virtually nothing when torqued up:

http://jsmotorsport.com/product/high-compression-003-thin-head-gasket-rings/

With any such method, something still has to be done to seal the pushrod and oil return holes.

You also use .005" wire around the pushrod tubes and oil return hole and pliobond to glue the wire and the thin .003" head gasket ring in place. The wire crushes but copper gaskets don't seem to crush (try measuring one).

When I raced I used only a .017" diameter copper wire around the cylinders. It fit into a tiny shallow groove so the wire protruded about half its thickness. The wire would crush. I did the same around the pushrod tunnels and oil return hole. It was absolutely oil tight. After that came the .003" thick ring below.

It's a long way to 920 type(rary)
 
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