Seal testing bores and chambers?

Before I lift cylinder off Trixie pistons is there any down and dirty methods to check if rings or valve seats are an issue? Don't know what is normal to expect with various liquids.

A compression test on the cylinders might give a little insight, although I'm not sure what pressure is considered good for a healthy cylinder, Maybe like 145 psi comes to mind. Cj

Steve,

again, do a leak down test, it will tell you if it is the rings or the valves and which ones

if you don't know the methodology just ask

and yes, you do need to buy a leak down tester kit, they are cheap

again, ask and I am sure Jim Comstock or someone can point in the right direction for both the purchase and specific instructions to sleuth accurately

Appreciate the attention, ugh, even if I'd like to slap ya's around a bit on the reflex responses, as reveals ya don't care enough about me or poor Trixie Combat to follow the details of ongoing saga. Covered my flubbed failures of compression and leak down testing attempts last Sunday. If ya think you understand my dilemma being a mechanic, I double dog dare ya to find what air leak sound out of intake rocker box indicates when piston at TDC and both rockers rattle loose. Ugh.



Wes's JBW fitting was actually more useful to hear where sealing good or not.


Compression tester that don't screw in is about impossible to hold in our plug holes and kick it too, even with a helper. We got up to 140 PSI on RH dry side and 120-ish on L wet side. A good Combat kicked over fast should hit about 190 PSI. Leak down tests basically revealed gasket path of leak by blowing wet sump out the open oil tank mouth. Duh, I already knew gasket, so tried test to see if indications of more than just gasket but couldn't hear other air leaks till engine finally won and went off TDC to open a valve to carb or pipes. I have definitely fine tuned marked exactly where TDC is now as a tiny bit off > engine would turn either direction. The two of us are not men enough to do the full procedure which require rocking just off TDC ring reversal zone and tapping on valve stems to settle their seating. We held TDC by my full weight dropped on brake and Wes with rubber coated handles of huge channel locks.

Anywho was hoping to hear if say gas or alcohol poured in bore it should only leak down so fast as normal and if more suspect rings are new smokers too.
Watching smoke seems to go away on held throttle and more on trailing throttle and that the extra puff of smoke throttling up on a roll was merely the extra exhaust jets vaporizing the wetted pipes as mostly cleared up till slowing and smoking and throttling again.

[video]http://www.youtube.com/watch?v=JT5yUh3-rSg&feature=player_embedded[/video]









Too late now for vapor pressure testing, procrastinating to take bores to machinist to measure bores, piston clearnace, ring land size and ring end gap, to see if an issue and compensatable by special order TS rings as they have big range for this.

Hobot,
I thought it looked as though your head gasket was leaking badly between your pushrod tunnel and piston bore as that in my mind would be the cause for both air coming out the rocker hole and going directly to the sump and pushing oil out to the oil tank! Was your head and cylinder gasket surface checked for warpage?

I thought it looked as though your head gasket was leaking badly between your pushrod tunnel and piston bore as that in my mind would be the cause for both air coming out the rocker hole and going directly to the sump and pushing oil out to the oil tank! Was your head and cylinder gasket surface checked for warpage?

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Yep sir that is exactly all I think is wrong, but it may not be as straight forward as just looking at surface symptoms, like how I make living fixing folks no one else can. Wes is firm he thinks ring let go to over pressure the gasket seal till leaks contanstly and I did have intervals w/o air filter sealed and smoking on other side, almost as bad and the show stopping LH. My video was a let down surprise as the smoke is like half as much as tolerated on last long ride to meet riders on Polar Bear New Yrs run.

Seems some lighter copper areas and very slightly darker head surface show thin path of gas-oil escape. So do I just put on new flame ring, and ignore rings, or go w/o gasket and ignore rings, or try new rings too if gap shows too big?

Hobot,
I was once told there could be up to 4 thou. for every inch of bore for ring gap but have had almost 5 thou per inch once and got good seal. But it's all depending on how loose the piston is in the bore because if the piston is to loose it slaps around to much and won't let rings do a good job. A thou or two extra would be fine but I've got a manual around somewhere that says it should be rebored after 7 thou of wear so in my mind that was saying 4 thou piston clearance plus 3 thou. wear for a total of 7 thou. I'm no expert but that's how I took it.
Nortarly

Nortarly said:

Hobot,
I was once told there could be up to 4 thou. for every inch of bore for ring gap but have had almost 5 thou per inch once and got good seal. But it's all depending on how loose the piston is in the bore because if the piston is to loose it slaps around to much and won't let rings do a good job. A thou or two extra would be fine but I've got a manual around somewhere that says it should be rebored after 7 thou of wear so in my mind that was saying 4 thou piston clearance plus 3 thou. wear for a total of 7 thou. I'm no expert but that's how I took it.
Nortarly

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That's not really what .007" of wear means. It means the worn area at the top of the bore is .007" larger than it was originally. If you had .007" of wear, and started with .004" of clearance, you would end up with .011" of clearance at the top of the bore, and pretty close to .004" at the bottom of the bore, assuming the piston hadn't collapsed too much from use. The factory service manual says you need a rebore when the wear exceeds .005". They specify the measurement method as measuring the bore at the top of the ring travel area, where it is largest, and subtracting the bore diameter at the botton, below the ring travel area, where it is usually not significantly worn. That fits pretty well with my experience with race engines. I've run them with as much as .009" total clearance at the top of the bore, and still had the engines run well, but at that point, they are producing more blow-by and starting to smoke a bit, and I'm sure they aren't producing as much horsepower as they started with.

Ken

lcrken said:

That's not really what .007" of wear means. It means the worn area at the top of the bore is .007" larger than it was originally. If you had .007" of wear, and started with .004" of clearance, you would end up with .011" of clearance at the top of the bore, and pretty close to .004" at the bottom of the bore, assuming the piston hadn't collapsed too much from use. The factory service manual says you need a rebore when the wear exceeds .005". They specify the measurement method as measuring the bore at the top of the ring travel area, where it is largest, and subtracting the bore diameter at the botton, below the ring travel area, where it is usually not significantly worn. That fits pretty well with my experience with race engines. I've run them with as much as .009" total clearance at the top of the bore, and still had the engines run well, but at that point, they are producing more blow-by and starting to smoke a bit, and I'm sure they aren't producing as much horsepower as they started with.

Ken

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lcrken,
That makes sense Like I said it was just the way I took it. And you are right I wasn't at home to look and I shouldn't have posted .007 my manual supports your .005 thou tolerance. Below is from my manual.
An alternative (but less accurate) method of measurement is to place one compression ring in the bore, approximately 1/2 in. (12.70 mm) from the top and measure the ring gap with feeler gauges. Place the ring lower in the bore below the piston ring swept area and again measure the gap. Subtract the second reading from the first and divide by three to arrive at the diameter wear. The amount of wear should not excced 0.005 in. (.1270 mm) .
Excessive wear will necessitate reboring and the fitting of oversize pistons which are available in oversizes of + 0.010 in. + 0.020 in. + 0.030 in. and + 0.040 in.
Nortarly