Compression vs: Leakdown testing results -Want opnions on MY results, please & thanks

[MACH1SCJ]

Compression vs: Leakdown testing results -Want opnions on MY results, please & thanks

I first want to state!
Both tests have there place! If one person thinks one is faster, quicker, easier that is fine I do not want a debate about which one is better as they give slightly different information. I would like you to help me interpret the results.
Engine is a 1990 Rude 48 spl 2 cylinder model E48ESLESA

Compression 140 psi top cylinder 130 bottom cylinder max build (5 rotations with elec starter, both cylinders were @ 75psi on the third revolution of cranking)

Leak down 40% top cylinder 30% bottom cylinder.

It was hard to get the piston exactly @ TDC but, I was able to & hold the flywheel very lightly & get a good steady leakdown reading.

I have a poor idle & stalling issue I am chasing.

I opened the plugs from 0.025" to 0.037", adjusted idle needles & it helped. I also switched from the new NGK's with 2hrs run time to new marine Champions. It idled for 10 mins in gear in the barrel without stalling however rougher then I want it to. Idle speed in netural is @ 800 rpm & in gear is @ 630 rpm. Idle base timing is @ 3deg ATDC

The top cylinder is rock steady with timing light flashes. the bottom cylinder seemed to drop one flash out of @ 400 to 800 flashes (only droped a flash once or twice per minute). Will have to hook up a lab scope to check the stator/crank signal & power pack/ign module to coil signals.

Do you think the compression vs: Leakdown indicuates overhaul soon?

 

[Daviet]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Correct, they both have their place. I go by compression results on 2-cycle engines. I think your idle speed is a little low, by memory, which is getting pretty bad lately, I think it should be 700-750 in gear when warmed up.
With those compression numbers I don't think you are ready for an overhaul.

 

[boobie]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

And yes I do have a leakdown tester and only use it on 4 strokes. Always use a compression gauge for 2 strokes. Your difference in compression specs are well with in limits. I'd do a good decarb on it and then find out what the real prob is, being carb or ignition.

 

[Tim Frank]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

What plugs are you using now?

 

[MACH1SCJ]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

I was looking for 700 to 750 rpm idle in netural. If that spec is in gear idle will be much better, but netural idle will be over 900 rpm & base idle timing will be @ TDC or 1 ATDC

OMC manual should be here this weekend. I will link & sync (again) by the book this time.

I have done a decarb on it with seafoam, the tops of the pistons were clean when I bought it & still are.

Champion QL78C plugs are the current flavor.

It started right up tonight with very little throttle & only two quick chokes.

I found spark leakage at both the coil & spark plug, bad leakage on the top cylinder, might have been the flash reflection on the lower plug wire vs that one leaking too? could not tell for sure. Was halo style at the top plug & around the coil. I would like to think that is the cough/misfire it does, but doubt that is my rough idle issue.

Had a few dropped timing light flashes on both cylinders tonight, I will fix the plug wires & recheck. Hopefully I'll get a chance to hook up the labscope & check the stator & module patterns soon. Great fishing weather is passing me by

 

[Tim Frank]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Champion QL78C plugs are the current flavor.

Those are not the spec'd plug. OEM plug is QL78YC
Insulator projection is a bit more than the one you are using.

Further explanation is beyond my technical capability, so don't ask.
I am just a big believer in using the exact plugs spec'd, especially as part of an ignition troubleshooting sequence.

 

[MACH1SCJ]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

specs per champions web site.

QL78C = 14m Thread Size, 12.7mm (1/2") Reach, 13/16" (20.6mm) Hex Size, Gasket Seat, CDI Resistor, Copper Core, Heat Range 78

QL78YC = Racing Plug, 14mm Thread Size, 12.7mm (1/2") Reach, 13/16" (20.6mm) Hex Size, Gasket Seat, Resistor, Projected Tip, Copper Core, Heat Range 78

Guess which one is the projected tip... Funny how the heat range is still the same..

I though I had ordered the correct plug.... 0432981 Ql78YC is listed as a superseded number to the one I am using-

0432981 Part replaced by 0502179 Unavailable
0502179 0502179 - SP PLG QL78C

is that information incorrect?

 

[MACH1SCJ]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Should that be shown as a marine plug on the box?

 

[Tim Frank]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

specs per champions web site.

QL78C = 14m Thread Size, 12.7mm (1/2") Reach, 13/16" (20.6mm) Hex Size, Gasket Seat, CDI Resistor, Copper Core, Heat Range 78

QL78YC = Racing Plug, 14mm Thread Size, 12.7mm (1/2") Reach, 13/16" (20.6mm) Hex Size, Gasket Seat, Resistor, Projected Tip, Copper Core, Heat Range 78

Guess which one is the projected tip... Funny how the heat range is still the same..

I though I had ordered the correct plug.... 0432981 Ql78YC is listed as a superseded number to the one I am using-

0432981 Part replaced by 0502179 Unavailable
0502179 0502179 - SP PLG QL78C

is that information incorrect?

iBoats sells the "YC" per their website.

Did you get the obsolete info from Federal-Mogul (Champion) or the "fake" site?

As I stated, I can tell you the plugs are different....but I really can't say what if any symptoms you might notice.
I just try to go with the OEM spec.

If you came back and said "Tim, I tried the YC plug and that solved the problem" I would not be surprised.
If you came back and said "Tim, I wasted $20- on plugs and no benefit"....I would not be surprised.

I would suggest that Federal Mogul has`a pretty good tech help group and if you contacted them they could no doubt give you more info.

 

[MACH1SCJ]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Ya there seems to be conflicting info from where I ordered my parts & the Evinrude site. Local napa had them QL78YC in stock for lees then 7 bucks a pair, Needless to say I have two plugs in my pocket now.

I am a firm beliver in the correct plug with automobiles, but sometimes can't see the forest for all the trees around me. Thanks for catching that error & getting me back on the right path. I hope to have time tonight, My neighbors will love me @ 10 pm again.

I wonder if I do the CDI conversion if I should run the CDI resistor plug?

 

[Tim Frank]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

I think the resistor in the YC is OK from CDI systems.
If in doubt, check with F-D.

 

[82rude]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

yup what tim said ,watch out for that champion site as it could kill your motor with incorrect info.almost got me.

 

[boobie]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

What do you mean by " a CDI conversion" ??

 

[MACH1SCJ]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

No mad neighbors tonight.... found a cracked fuel bulkhead fitting

yup what tim said ,watch out for that champion site as it could kill your motor with incorrect info.almost got me.

I dont think I was at the fake site, I did not look up application there anyways just wanted the spark plug specs.
There was one result that did not look right at the top of the search, That must be what you guys are talking about.

I had looked them up on marineengines, and it appears that is where I got the wrong part number from.

---boobie---

Johnson, Evinrude 113-4489 Power Pack 6100 RPM Limit S.L.O.W. - CDI Electronics 113-4489

http://www.iboats.com/mall/partfind...d_poid=334581&gd_row=167&session_id=154512215

 

[boobie]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Okay, Got ya....

 

[MACH1SCJ]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

The OMC book came in today. The book lists QL78C as the correct plug. Go figure.... I pulled the carbs to check them & they were clean, not a spec anywhere. went through the link & sync by the book. got the idle up to 730 ish in gear in the barrel.

I found that pulling the top cylinder plug wire only drops the rpm a little. The bottom cylinder will cause it to stall. The top cylinder is not contributing as much as the bottom. I feel like i am banging my head against a brick wall.

 

[Daviet]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

I didn't notice anywhere that you checked the spark with an air gap tester, does the spark jump a 7/16" air gap and is it bright blue?

 

[boobie]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Have you tried a good decarb on the mtr yet ??

 

[MACH1SCJ]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

The spark will jump the length if the spark plug boot, with a sharp "CRACK" the top sounds slightly weaker then the bottom. Both appear blue cored with a yellow shield/halo spark.

I ran a can of spray sea foam through it.

Sounds great @ 1500 rpm and up. At idle the carbs sound different, the upper has a "huff, huff" kind of sound & the lower has a "pfst, pfst" sound. I see nearly no spitback with the new chris carson reeds. Covering the upper carb with my hand has less effect on engine then covering the lower.

I have had the boat in the water 3 times & it seems to have gotten worse each trip. As I could not get over 4500 rpm the last time out, I did have the motor trimed lower then prior trips, an extra 100 pounds & the water was very rough. So that might not be relevant.

It did idle better the last time as I turned the idle stop screw 1 1/2 turns up. I now have it @ 5 or 6 turns from where it was so something is going on. Still within base timing specs, well on the edge.

 

[Tim Frank]

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

Re: Compression vs: Leakdown testing results -Want opnions on MY results, please & th

The OMC book came in today. The book lists QL78C as the correct plug. Go figure.... I pulled the carbs to check them & they were clean, not a spec anywhere. went through the link & sync by the book. got the idle up to 730 ish in gear in the barrel.

I found that pulling the top cylinder plug wire only drops the rpm a little. The bottom cylinder will cause it to stall. The top cylinder is not contributing as much as the bottom. I feel like i am banging my head against a brick wall.

Is it the OEM manual or an aftermarket one?
Here is the official E'rude recommended plug chart.
I suspect that there is not really much difference between the YC and C versions, but there must be some or they would not make both.
Interesting that there are different published specs.

http://shop.evinrude.com/products/553609/2-Stroke