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

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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


Hi Jim, I first want to tcheck the cam timing, I don't understand your camshaft timing video: When you are at TDC with the valves in balance, the inlet is underway to open and the exhaust is underway to close, so if I understand I must turn the crank clockwise to have the mesurment for the IN valve and counter clockwise to have the mesurment for the exhaust??
Thanks
Yves
 
No
You only turn the crankshaft in the same direction that it runs (clockwise when viewed from the timing side). At TDC the intake valve is opening and the exhaust valve is closing. When you approach TDC slow down and stop at exactly TDC. The intake valve should have about .025" more lift than the exhaust. If you go too far, back up the crank more than you need to and start turning slowly in clockwise direction again (to get slack out of cam chain) till you get to exactly TDC. Don't worry if the lift is off only .002" or .003"

For example:
intake valve lift at TDC = .175" (starting/begining to open)
exhaust valve lift at TDC = .150" (just before closing)

Yves - you are thinking of lift as opening but the exhaust has lift that is becoming less lift when closing.
 
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It seems to me that visually checking the valves, by peeking into the combustion chamber, to try and ascertain if one is .025” more lifted than the other is a rather flawed idea.

Firstly, it’s very difficult to see clearly in there, it’s dark, you have very limited visibility and are viewing at a disadvantaged angle.

Secondly, if the exhaust valve seats have been cut deeper than the inlets, you could think the inlet valve has lifted more than the exhaust when in fact it hasn’t.

So, measuring lift using a gauge on the top of the valve stem or rocker arm seems the only way to do this and avoid such guesswork and potential errors to me.
 
The best way is to mount two dial indicators - one on the exhaust and one on the intake so you can see both at once. That gives you an accurate reading. Looking into the combustion chamber is just a visual check and it only works if the valves are level when they are on the seats with neither valve sunken or recessed. The visual check is really just to make sure the intake has more lift than the exhaust at TDC because usually the only problem is that the cam is too retarded. I use a small mag flashlight and optivisor manification.
 
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The best way is to mount two dial indicators - one on the exhaust and one on the intake so you can see both at once. That gives you an accurate reading. Looking into the combustion chamber is just a visual check and it only works if the valves are level when they are on the seats with neither valve sunken or recessed. The visual check is really just to make sure the intake has more lift than the exhaust at TDC because usually the only problem is that the cam is too retarded. I use a small mag flashlight and optivisor manification.
HI There, I spend the day to make a bracket to fix the dial guage and make the mesurments Here are the results:
Intake lift: .169 (must be .175)
Exhaust lift: ..139 (must be .150)
What now Jim and other specialist? is this still OK or must be the cam have more or less advance and how many degrees??
Thanks
Yves
 
That is only .005" too much lift on the intake valve. You have .030" more lift on the intake instead of the suggested .025" at TDC - slightly advanced but close enough. I would not touch it because the chain will stretch and it will be perfect. I would wait till the motor loosens up before doing anything else. You could do a leak down test to see if your cylinders are staying round and sealing well because 920 liners are a bit thin - other than that you can look at your port flow which has not been increased for the larger displacement and possibly reduce the exhaust restriction (temporarily remove muffler). Maybe try cleaning or removing the air cleaners.
 
I’m with Jim Yves, I’d put some miles on the motor and get those coated pistons fully loosened up before doing anything else.

If it turns out that the head flow is in question, you know who I would recommend sending it too! But that will take the bike off road for a while, so perhaps a job for after summer. Unless you can agree a specific time slot with him before hand?
 
I’m with Jim Yves, I’d put some miles on the motor and get those coated pistons fully loosened up before doing anything else.

If it turns out that the head flow is in question, you know who I would recommend sending it too! But that will take the bike off road for a while, so perhaps a job for after summer. Unless you can agree a specific time slot with him before hand?
Thanks Nigel,
I can find a flow bench here in Belgium, and with the video from Jim we can do some job, I will call the man from the flow tomorow and I will decide later
Of course the engine need more miles, but can this be the reason for sutch a lost?
I don't think that your man will agree with a time slot...
I feel realy tiered...
Yves
 
That is only .005" too much lift on the intake valve. You have .030" more lift on the intake instead of the suggested .025" at TDC - slightly advanced but close enough. I would not touch it because the chain will stretch and it will be perfect. I would wait till the motor loosens up before doing anything else. You could do a leak down test to see if your cylinders are staying round and sealing well because 920 liners are a bit thin - other than that you can look at your port flow which has not been increased for the larger displacement and possibly reduce the exhaust restriction (temporarily remove muffler). Maybe try cleaning or removing the air cleaners.
OK, I will do like you says
Yves
 
Hi there,
Here is wath I did to day for searching the lost horses
I take the head off, nothing special to mention, or maybe yes: on the 0.6mm cooper gasket, there was no hole for the return of oil, I think that the oil was going back via the push road tunels, but this can not explain a lost of power no?
After I take the cilinder off, also nothing special to see but I must tell you the true: I buy the 920 cylinder new from Maney, give a Nicasil treatment and after I paint the cylinder in black, therefore you must put the cylinder in the oven for one hour at 160 celcius, I put the cylinder in the oven, the case side on the floor; I was very surprised to see that the sleeves were coming out of the casting, nearly 2mm, not a big deal, I put the cylinder under a hydrolic press and put the sleeves back in place very easely...
After I water blast the paint from the cylinder and tchek the bore for ovality and so, we find a ovality from 0.01mm.
On the coated pistons nothing special, the coating is still in there, with no wear...
Here is what I plan to do in the coming days:
Go with the cylinder head to the flow bench
Go with the cylinder to Power Seal, the dutch Co that make the Nicasil treatment ans let him mesure the bore
And I will also order gapless rings from Jim Schmidt, I was very happy with those rings on my 850
So I hope to find something wrong or with the flow from the head or with the bore from the cylinder
Keep you posted
Yves
 
That is good news on the coating - no wear after some road use and a day of dyno runs. So they are probably still tight and holding down the HP. The coating is there to extend the life of the pistons. But that also means a longer run in period until they loosen up. The bare 920 pistons go in with .006" clearance because of their large size and because they're forged. Your coating brings that down to .003" clearance so you are probably losing HP until something loosens up a bit. You are having an interference fit when the pistons are hot because everything is still relatively new.

In extreme cases when the coating is too thick it will actually drag down the RPMS as the pistons heat up when the pistons are brand new in the cylinders. But it should not show any scuffing as long as the coating is still there. Race bikes either need a break in or a little more clearance if they're going straight on the track.

Please post a photo of the piston skirts.
 
If the sleeves can work their way up 2mm, what keeps them from coming up even farther?
Finding them up like that wd be a big disappointment to me.
 
nd I will also order gapless rings from Jim Schmidt, I was very happy with those rings on my 850
Yves

I was going to ask, because I recall you had said you were not going to use gapless this time.

Since we have a range of opinions ;):

I think you will need some work around the back of the valve in the port to make the big valves work.
I think you will want a little more compression.

Remember that it is often said that the valve angles of a large valve head are more compromised than a standard valve head. Hence the comment that you probably need some port work to get the best from the valves. Whatever else is said the jetting needs have probably changed a little, looks like you didn't do any work with them yet and I didnt notice mixture graphs with teh dyno figures.

I think maybe you do need to run the motor some more first when the weather is better.

It isn't all about dynos. Find out if the riding characteristics of your engine tie up fully with the dyno figures! What is the riding comparison between the two?
 
I was going to ask, because I recall you had said you were not going to use gapless this time.

Since we have a range of opinions ;):

I think you will need some work around the back of the valve in the port to make the big valves work.
I think you will want a little more compression.

Remember that it is often said that the valve angles of a large valve head are more compromised than a standard valve head. Hence the comment that you probably need some port work to get the best from the valves. Whatever else is said the jetting needs have probably changed a little, looks like you didn't do any work with them yet and I didnt notice mixture graphs with teh dyno figures.

I think maybe you do need to run the motor some more first when the weather is better.

It isn't all about dynos. Find out if the riding characteristics of your engine tie up fully with the dyno figures! What is the riding comparison between the two?
Hi steve,
Only fools never change there opinions, the only reason I don't order the gapless rings is that I was afraid that the Alton E start will not pass the compression
The port work will be down, tomorow I will know more.
More compression, maybe yes....
I will ask Bruno to send the mixture graphs
The riding comparison between the 820 and the 920 is subject to a placebo effect, for sure if you don't ride your bike the last four month and you think that the bike must be faster after all that work, then it will feel faster even it is not.
BTW: big thanks to everybody helping me on Access
I was complaining about how difficult it was to me to understand Hobot english, but I am wondering how all of you understand my english
Keep you posted
Yves
 
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