Will I get my 100 ready in time for Taupo?

[Yow Ling]

Are we all on the same page, is this the test we talking about ?
http://en.wikipedia.org/wiki/Leak-down_tester

cant see how you can do this with a blood pressure thing, can see how that would work for testing if an engine is sealed but not leakdown

[Ocean1]

http://www.ebay.com/itm/Dual-Gauge-L...cessories&hashUm, google ring leak tester. My other crankcase
leakdown tester uses a bicycle pump at 8 psi, but this is a different test altogether.

Does your rig literature say what orifice size it has Dave?

[bucketracer]

I leak down test every 2 stroke I build ... Have you tried an expander ring behind the piston ring? I use them when I have trouble with ring sealing (Suzuki RG 150's have them on the second ring, and you can cut them to suit.

An expander ring behind the top ring is unnecessary (unless your trying to mask a problem) as the top compression ring does not rely on its static radial pressure for bore to ring sealing. The compression and combustion pressure behind it pushing it outwards does that and no one has mentioned the all important sealing surface formed by the underside of the ring and the lower face of the pistons ring grove.

Interesting.... I use a modified blood pressure testing kit (similar to a Kart tilitson pop off tester) to hand pump, rather than a compressor, I have always felt that was too much pressure...

Are we all on the same page, is this the test we talking about ?

http://en.wikipedia.org/wiki/Leak-down_tester

I cant see how you can do this with a blood pressure thing, can see how that would work for testing if an engine is sealed but not leakdown

Looks like, not everyone is on the same page, for a cylinder leak down tester, you need a constant pressure source like a compressor and pressure regulator and a way of forming a pressure differential. A hand pump like a blood pressure thing would not work that well but could work great for a crankcase leak tester.

I assume that you are 100% confident that the leak is from the cylinder sealing rather than anywhere else (exhaust port is very common),

I am not sure why anyone familiar with 2 stroke engines. who pressurizes the crankcase would be surprised that air will leak at the exhaust port or inlet. As the bore is hopefully round and parallel while the piston is neither round or parallel cold and not much better hot, the piston has never been intended to function as a good static seal.

Crankcase leak down is usually done with the inlet, exhaust and spark plug, plugged and looks for bad crank seals, case joints, head gasket etc and for completeness should be followed by a vacuum test.

I have personally never found an engine (yet) that hold the pressure for more than a few minutes (or less) particularly when cold, as it just eventually seeps past the rings, and have only done a few fast 50's myself, but I seem to remember that something like 10% was the norm in all cases (somewhat less than 35).

Anyone who has turned a good engine over by hand will have seen how quickly the compression pressure leaks past the rings, its a matter of a second or two, certainly not minutes and Leakdown % figures have no meaning when compared between different engines unless your using the same leak tester and method on both.

Below was scraped from yhe Wiki link Yow Ling posted.

A leak-down tester is a measuring instrument used to determine the condition of internal combustion engines by introducing compressed air into the cylinder and measuring the rate at which it leaks out.
Compression testing is a crude form of leak-down testing which also includes effects due to compression ratio, starter/battery condition and other factors. Leak-down testing confines the results to cylinder leakage alone.
Testing is done on an engine which is not running, and normally with the tested cylinder at top dead center, although testing can be done at other points in the compression and power stroke. Pressure is fed into a cylinder via the spark plug hole and the flow, which represents any leakage from the cylinder, is measured.
Leakage is given in wholly arbitrary percentages but these “percentages” do not relate to any actual quantity or real dimension. The meaning of the readings is only relative to other tests done with the same design of tester. Leak-down readings of up to 20% are usually acceptable while greater than that requires a repair. Racing engines would be in the 1-10% range for top performance.
In the United States, FAA specifications^[1] state that engines up to 1,000 cu in (16 L) engine displacement require an 0.040 in (1.0 mm) orifice diameter, 0.250 in (6.4 mm) long, 60-degree approach angle. The input pressure is set for 80 psi (550 kPa), and 60 psi (410 kPa) minimum cylinder pressure is the accepted standard.
While the leak-down tester pressurizes the cylinder, the mechanic can listen to various parts to determine where any leak may originate. For example, a leaking exhaust valve will make a hissing noise in the exhaust pipe while a head gasket may cause bubbling in the cooling system.




A leak-down tester is essentially a miniature flow meter similar in concept to an air flow bench. The measuring element is the restriction orifice and the leakage in the engine is compared to the flow of this orifice. There will be a pressure drop across the orifice and another across whatever leaks in the engine. Since the meter and engine are connected in series, the flow is the same across both. (For example: If the meter was unconnected so that all the air escapes then the reading would be 0 or 100% leakage. Conversely, if there is no leakage there will be no pressure drop across either the orifice nor the leak, giving a reading of 100 or 0% leakage).
Gage meter faces can be numbered 0-100 or 100-0, indicating either 0% at full pressure or 100% at full pressure.
There is no standard regarding the size of the restriction orifice for non-aviation use and that is what leads to differences in readings between leak-down testers generally available from different manufacturers. Most often quoted though is a restriction with a .040in. hole drilled in it. Some poorly designed units do not include a restriction orifice at all, relying on the internal restriction of the regulator, and give much less accurate results. In addition, large engines and small engines will be measured in exactly the same way (compared to the same orifice) but a small leak in a large engine would be a large leak in a small engine. A locomotive engine which gives a leak-down of 10% on a leak-down tester is virtually perfectly sealed while the same tester giving a 10% reading on a model airplane engine indicates a catastrophic leak. The non standard size of the restriction orifice determines the reading which therefore differs for each design.
Some manufacturers use only a single gauge. In these instruments maintaining the input pressure is (hopefully) maintained automatically by the pressure regulator alone. Any error in the input pressure will produce a corresponding error in the reading.
In instruments with two gauges the operator manually resets the pressure to 100 after connection to the engine guaranteeing consistent input pressure and greater accuracy.
Most instruments use 100 psi (690 kPa) as the input pressure simply because ordinary 100psi gauges can be used which corresponds to 100% but there is no necessity for that pressure beyond that. Any pressure above 15 psi (100 kPa) will function just as well for measurement purposes although the sound of leaks will not be quite as loud. An engine pressurized to 100psi must be locked at exactly top dead center or it will rotate under the pressure. This presents a serious danger to the operator. Using less pressure is less dangerous and opens the possibility to test at positions other than top dead center.
Due to the simple construction, many mechanics build their own testers and those instruments function perfectly well.

[F5 Dave]

Well I don't think I have much to add after that.

Just waits to see if I destroy everyone tomorrow. 'Course would have helped If I'd stayed sober, but well that's not my style.

[koba]

Just waits to see if I destroy everyone tomorrow. 'Course would have helped If I'd stayed sober, but well that's not my style.

You too eh?

I've got mine ready for an in-frame crankcase leak test tomorrow morning at the track, the devcon will have set by then...


Oh, you said 'everyone' I thought you said 'an engine' as that's what I think may happen to mine...

[Pumba]

.............Oh, you said 'everyone' I thought you said 'an engine' as that's what I think may happen to mine...

Funny, I read his post earlier an that is what I read as well. Wasn't till your post that I picked it up.

[F5 Dave]

Well it all worked pretty well. Comes on pretty sharp. I'm kinda used to that delivery on the 50, just there's considerably more. Made riding in the wet a hazardous proposition & I got totally detuned & while starting out in the lead, the competition destroyed me when I went to pieces.

Must buy some wets made in this century. Sorry credit card, you're going to take one for the team.

Fortunately the weather dried up for the 30min enduro so I went out on slicks. There wasn't many of the fast guys there, but no one passed me & after maybe ten min I pulled in. No point wearing the bike or slicks out before the BOB.

Its fairly fast, just need to work on some more spread.

[F5 Dave]

We'll plan for tonight having fitted a new brushless water pump that runs 3x the flow the last one did for almost the same current draw and repositioning the temp sensor in the head and reconnecting the det sensor was to cal the sensor and try a curved ig map instead of the straight 15 deg line I have as a starting point.

but doom, the dyno stops working. Poo. Nothing obvious and no spare time or parts.

did manage at least to give the pump a shakedown and seems ok. Also got det sensor tweaked to at least where I was assuming that was best just off red flashing.

while I was at it I set the quick shifter on the Ignitech up. Seems to work fine but proof will be in the riding.

sadly I have a bored RGV carb complete with homemade solenoid almost ready to test. Might have to stick with what I've got for the BoB.

[richban]

We'll plan for tonight having fitted a new brushless water pump that runs 3x the flow the last one did for almost the same current draw and repositioning the temp sensor in the head and reconnecting the det sensor was to cal the sensor and try a curved ig map instead of the straight 15 deg line I have as a starting point.

but doom, the dyno stops working. Poo. Nothing obvious and no spare time or parts.

did manage at least to give the pump a shakedown and seems ok. Also got det sensor tweaked to at least where I was assuming that was best just off red flashing.

while I was at it I set the quick shifter on the Ignitech up. Seems to work fine but proof will be in the riding.

sadly I have a bored RGV carb complete with homemade solenoid almost ready to test. Might have to stick with what I've got for the BoB.

Quick shifter please. X 3.

[F5 Dave]

So what am I going to do? Maybe I'll have to get obsessed by handling instead

[Drew]

So what am I going to do? Maybe I'll have to get obsessed by handling instead

I've always thought this was where all race bikes, should get the builders first attention. Unless they're just throwing a bike together with whatever is lying around, as I do.

[F5 Dave]

Don't be silly. I come from the Wayne Gardner school of thought. Twist it & hold on.


. . .actually I'm not good enough to do that,

[F5 Dave]

Quick shifter please. X 3.

ok I've got some more on the way, I've had one in the van for when I next see you.

[F5 Dave]

Well no dyno time so had to work on the chassis. Mounted the rear Wet to confirm there is clearance (old one rubbed the pre94 sw unless you surgically set it up). Hurrah, the Bridgey wet is narrower so easy as. While wheel was out I took the time to fit the sharkfin. What a windup that was. Trying to drill holes without a RA drill in the middle of a swingarm is a right pain. Course I got it wrong & had to grind the rivets off & redrill the plate so it didn't hit the sprocket bolts.

Gave me time to rearrange the washers so the axle nut bites onto better thread and I can fit an R clip.

Redid the brakes, replaced the catchbottle & hose. Might even pass scrutineering with a smile.

Next need to fit the taller gearing, but a bigger sprocket is off being ground down to 415 & the 15T I used last time is the template for the 16T.


Working on dyno bits now to try fix, wouldn't mind another run or dozen to try a bigger carb etc.

[F5 Dave]

Well it loved the bored out (35mm) carb straight off a decent improvement on top & even upper midrange with 2hp from 9.5-11 so improvements all round.

However as the testing progressed the jet changes stopped making any difference & power was down say a HP. An all gears run confirmed that things were a little worse in the higher gears so I decided to pull the plug and go back to the 32 as its a honey in the tall gears.

I think its something to do with the powerjet & how its flowing. I was driving it wrong at first too, but had it unpowered at the start so its a bit confusing as it wasn't making a difference. I need to do some blow through tests.

However I'd also blown through the PJ at some point, maybe I'd cleared a blockage. You could see the fuel travel int he clear tube so it is working.

So safe is best for the BOB, but more testing required, with a decent promise of things to come.

Time to fit the fairing & front wet onto the wheel & its ready to go. oh yeah & fit my shift light again. Terminal broke. Wires next time.