Blue smoke om WoT and strange compression readings

[bumper]

I vote the 1300

 

[one2dmax]

Remember they are smaller at the top then at the bottom/skirt area.

 

[RempageR1]

Remember they are smaller at the top then at the bottom/skirt area.

I see. What would be the proper way to measure this then with home tools?

edit:
To quote you in another theat: '.004 piston to wall clearance. Note: Clearance numbers are obtained from measuring the largest diameter of the piston, typically at the bottom of the skirt. All measurements should be taken 90 degrees from the pin centerline.'
I`ll be measuring that in the upcoming days.

 

[Rusty McNeil]

Boy when you dive in you really dive in!!

I'm impressed !

You've gone this far might as well do a full rebuild!

My arias pistons were quite non-symmetrical.

I don't remember the details from when I assembled mine but I think how far down the bore you measure matters as well. But maybe that's just for checking a worn cylinder, not a new one.

I had a really good quality caliper, which I felt was ok for checking the pistons.

Measuring the bore it was totally inadequate. Too much human error.
Would have needed a bore gauge to do it right.

Sean did all the thinking on getting the correct pistons ordered and machining the bore to match so I ended up taking it on faith. It worked out well.

I think using a flat feeler gauge like in the picture on a curved cylinder bore is not going to yield good results. The spring pressure of forcing it to curve to the wall might give a false feel, and feelers like that are kinda subjective to begin with I think.

I don't know what tool would do it with the piston installed, but I'm not a machinist either so maybe there is.

 

[bumper]

know anybody from a garage that would borrow you a t-mike. Or maybe if you could load it up and take it to them. You can see the taper in the cylinder. With the piston in you wont get the full taper but would get an idea of half or better. they look like this http://www.ebay.com/itm/Set-of-4-Ge...560?pt=LH_DefaultDomain_0&hash=item2c6ebbae00
Here is a set in the UK. http://www.ebay.com/itm/Draper-5241...by_BabyFeedingUtensils_EH&hash=item4d0647742b

A man just cant have enough tools. I have to monster tool boxes full LOL

 

[sdt354]

By the time your done with this head you'll be in deep $$.Seals and guides, maybe valves too. Sean usually has low milage heads. The piston clearance? Not easy to check with pistons installed. But, I suppose you could do it from the bottom. Checked at the bottom of the skirt, 90 degrees frfon the wrist pin. A dial bore gauge is the way to go for checking the bore. Much easier to use than inside mics.unless your proficient with them.

 

[sdt354]

i vote the 1300

+1

 

[RempageR1]

Hi all,

Thanks for the feedback. I agree the way I measured is not the best way, it was just a quick check. I`m planning on taking the pistons out and having the cylinders and pistons measured by a professional. After that I can decide how to proceed. There are a couple of Vmax specialists around here in the Netherlands so it might be the best way to go.

I`ll keep you guys updated!

 

[bumper]

Its not the best test but if you clean any carbon away on the top of the cylinder. You can see where the top ring stops in its travel. You might be able to feel a lip there ? If its very minor so is the wear. If you finger nail catches and it a fairly good grove there then you got some serious wear. the top 1/4 inch or so is where your going to find the most wear because of the force from the ignition of the fuel of power stroke. The bottom will typically have the least amount of wear unless you have a scored piston. Power stroke is where you have the blow by and lose your compression when the rings cant provide the proper seal for what ever reason.

 

[Rusty McNeil]

Its not the best test but if you clean any carbon away on the top of the cylinder. You can see where the top ring stops in its travel. You might be able to feel a lip there ? If its very minor so is the wear. If you finger nail catches and it a fairly good grove there then you got some serious wear. the top 1/4 inch or so is where your going to find the most wear because of the force from the ignition of the fuel of power stroke. The bottom will typically have the least amount of wear unless you have a scored piston. Power stroke is where you have the blow by and lose your compression when the rings cant provide the proper seal for what ever reason.

My engine, when I tore it down with 40,000 miles in it, still had the full crosshatch final hone pattern fully visible and no lip at the point where the rings are at TDC. The pistons easily came right out the top without hanging up

Don't know if that helps as a "typical wear reference"

 

[RempageR1]

Time for some more pics:

An engine missing both heads and one piston:

Top ring in place.

I never knew pistons were smaller at the top then down :biglaugh:.

With the ring in place, there`s a 0.50mm gap which isn't all that bad actually... Still have the same plan though, let an expert measure it all and verify what needs replacement.

 

[MaxMidnight]

I never knew pistons were smaller at the top then down :biglaugh:.

And they are oval as well.

 

[RempageR1]

Valves are still holding nicely:

And this is what the cylinders look like. Honing marks still visible on the sides of the cylinder wall but not in the front and rear. Some minor grooving but nothing you can feel.

Does anyone have experience with rebuilding an engine with the same kind of wear?

 

[one2dmax]

Looks like normal wear. May not have needed to be taken apart. Will need to mic the bore and see what it measures out like. You will measure in multiple spots along the depth to see how tapered or egg shaped it has become (if any).

Sean

 

[Rusty McNeil]

I would say that if the hone marks aren't visible then it would be silly not to bore it and put over size pistons in it since its already torn down.

That's not motorcycle specific experience speaking.

 

[RempageR1]

Hi,

So here are the results: 90 degree means measured at 90 degrees from piston pin axle, the other two are in line with the piston pin. Top is about 2 cm down, bottom is at the end of the piston`s stroke.

Cylinder                     1        2        3        4
Top, 90 degree             76.02   76.01    76.02   76.02
Bottom, 90 degree          76.00   75.99    76.00   76.00
Top                        76.03   76.01    76.02   76.00
Bottom                     76.06   76.03    76.07   76.03

All pistons were measured at 75,90.

From what I understand, the top row from my table can be used to calculate the piston-to-bore clearances.
That would result in pistons 1, 3 and 4 having 0.12 mm and 2 having 0.11mm. This means they are out of standard (0.055 to 0.075mm) but within service limit (0.15mm)....

Are these acceptable measurements?

If I blow the budget by redoing the bore and installing new pistons, it needs to justify the expense.

Thanks!

 

[one2dmax]

You would not want to hone it and install new pistons/rings. You can either put it back together and keep riding with the little bit of blowby or do the rebuild. I MIGHT have some stock overbore pistons for cheap but you can also do a little larger then stock bore and get aftermarket pistons.