Compression numbers.

[onethumb]

About to take the compression numbers and wanted to know what kind of figures are about right. I'll be using the kick start?
Thanks again. Steve


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[onethumb]

Here's what I got.
No 1.   60psi
No 2.   137
No 3.   148
No 4.   125.
I knew about no1 so that's not an issue. What about the other numbers?
Thanks. Steve



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[steff750]

  I would be a lot happier if they all read  between150 psi -170psi
just my take on it and yes no1 is an issue lol

[royhall]

Just a thought. You did do the tests with the throttle wide open?

[Trigger]

With the throttle wide open and some oil down the bores but, number one is not sealing.

[onethumb]

I did it with no carbs on and some 3 in 1 oil in the bores.


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[onethumb]

Engine is out now and on the deck ready for stripping tomorrow.


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[onethumb]

Just did them again with a bit of engine oil in this time. New numbers. After 3 kicks.         After 4 kicks
No 1.                30.                            50
No 2.              150.                          175
No 3.               150.                         175
No 4.                125.                         147

How do these look, do I need to look at doing the rings?

Thanks. Steve.





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[Trigger]

If your in the top end, I would check everything 

[onethumb]

Rightio trigger.
I've just ordered a Moore and Wright micrometer and a clutch tool so the checkover can begin.
It has had a rebuild at some time in its life so I don't know if that's a good thing or bad.
What do you think of the numbers?


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[MrDavo]

Factory manual says 175psi on a new one.

Whatever happens you know that #1 is well and truly up the pictures, the cause should be obvious once you're in there. Four doesn't seem too clever, if it were only normal wear and tear you'd expect them to be similar if low.

[onethumb]

Update. Right took the head off and the good news is there is no damage on the top of the pistons and the bores look good. Soaked the top of the pistons with a carb cleaner and wd40 mix for 2hrs and lost none.
Stripped the head but left the valves and springs in placed tipped it over filled the chamber with wd40 and lost it all though the inlet valve in no1 in about 5 seconds, lost most of it out of no4 in about 1 minute though both valves. Now I know I've got issues with no1 and 4 but I think I might get all of them redone.


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[Trigger]

Number 1&4 will have pitted valve faces and seats or bent valves. If pitted only, this is due to the tappets being too tight.

[onethumb]

Thanks trigger and mrdavo for the input. I'll leave it to the engineers to give me more info on what to do with the reconditioning.


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[onethumb]

Well trigger you were right. So the head went to the shop and he found pitting on number 1 along with a bent valve and two of the exhaust guides were gone. So it's been machined, new guides a new valve and the seats and valves re cut. Looks amazing.
Now the issue is: I've built the engine back and have done a test before putting it back in the frame and the numbers are weird. So before I was getting 1-4 40-150-150-125 now I'm getting 1-4 110-110-115-125. No plugs no carbs and a squirt of thin oil in the bores.
I did notice that the new head gasket that was from DS sat a little funny when on but flattened with the head in place. Could this be the issue? I'm getting a bit stressed over this. Help please.



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