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Ex-Military Spec 6JB compression issue


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  #61  
Old 02-13-2017, 01:20:25 PM
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Default Re: Ex-Military Spec 6JB compression issue

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Originally Posted by MadGutts View Post
it was in thou - i don't have metric feeler gauges!

Shouldnt both piston rings have a sharp edge though as the top one is rounded?

for got to say the flat plate has a hole in for the compression gauge to sit in so when the piston is at its furthest down i will then hold in the gauge to get a reading - this way i can rule out the top of the engine
You will have too much pressure by just having a flat plate on top of the cylinders. Your starter and other parts could be damaged. If you have a question about the valves sealing properly in the head then invert it and pour diesel fuel into each chamber area and check for leaks. Some very minor leakage with used valves can be normal.
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  #62  
Old 02-15-2017, 08:42:33 PM
MadGutts MadGutts is offline
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Default Re: Ex-Military Spec 6JB compression issue

ok i have re assembled the lower end of the engine and oiled up the rings and cylinders using my plate i got a good reading from the compression tester and this was on both cylinders, so i think the bottom end is ok now.. so i have just given the head to an engine specialist to check for me, he will pressure test/vacuum test it and skim it if it needs it... he did notice some discolouration on the valves indicating fuel issues too so once i have it back, i will get my colourtune in and test the fuel mixture
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  #63  
Old 02-15-2017, 09:11:40 PM
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Default Re: Ex-Military Spec 6JB compression issue

Colourtune-
Sounds interesting-
http://www.ebay.com/itm/Gunson-Color...dXtGwX&vxp=mtr
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  #64  
Old 02-15-2017, 10:09:17 PM
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Default Re: Ex-Military Spec 6JB compression issue

This thread makes my brain hurt...

Last you told us, one cylinder had no compression and hissing into the crankcase.

Now it's OK, and you checked it with a "plate", but you suspect the head?

Honing made the difference?

Hmm...

Hmm...

And why not just set the mixture per the Onan service manual, instead of a 'colourtune' ?

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Old 02-15-2017, 10:20:45 PM
David C David C is offline
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Default Re: Ex-Military Spec 6JB compression issue

Can you post some good pictures of both sides of the head gasket? With the head off, you can fill each port with gasoline / paint thinner to see if the valves are sealing.

David C.
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  #66  
Old 02-15-2017, 10:54:46 PM
John Hartman John Hartman is offline
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Default Re: Ex-Military Spec 6JB compression issue

I have more advice. Let this derelict talk to himself and end this thread.

He has it all figured out.
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  #67  
Old 02-15-2017, 11:06:04 PM
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Default Re: Ex-Military Spec 6JB compression issue

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I have more advice. Let this derelict talk to himself and end this thread.

He has it all figured out.
Be NICE!
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Old 02-15-2017, 11:12:50 PM
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Default Re: Ex-Military Spec 6JB compression issue

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Originally Posted by John Hartman View Post
I have more advice. Let this derelict talk to himself and end this thread.

He has it all figured out.
Remember he is in England. Things are different over there.
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Old 02-15-2017, 11:22:40 PM
Wayne 440 Wayne 440 is offline
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Default Re: Ex-Military Spec 6JB compression issue

I think all of us have at one time or another gotten "side tracked" and overlooked something that should have been obvious.

I went on a service call once, with the typical directions, "Take the first left off of Main Street go 100 yards you will see...". I get there and couldn't find the customer. It turns out that Corydon, INDIANA is a much different place than Corydon, KENTUCKY.
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Old 02-16-2017, 01:04:26 AM
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Default Re: Ex-Military Spec 6JB compression issue

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Originally Posted by lokay5 View Post
For those who do not know-
Colortune- A spark plug with a clear glass insulator commonly used on British cars of the 1960's-1970's. A handy accessory for "knight of darkness" (Lucas Electric) cars with Webber, Su or similar carburetors.

If a "performance" engine had multiple Webber or similar carburetors- typically one venturi per cylinder-, each venturi had to be individually set. An air/ fuel ratio meter and an exhaust gas analyzer gave you overall readings, but you could have cylinders out of balance - you used a "unisyn" for that, and twisted the throttle shafts or bent the linkages to equalize cylinder vacuums. Then you used a colortune(s) to set the air/fuel ratio for each cylinder so the plug showed a nice blue flame when the cylinder fired.

On a badly out of balance engine- say saturday a mechanic tuned it- the whole process would take a skilled mechanic hours. Those tools were necessary to properly set up Jaguar, Lotus, MG, Triumph cars of that period, but are totally useless on an engine with a single venturi carburetor.
I would set the engine up per the manual, and if in doubt, do a quick check with an air/fuel ratio meter.

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Old 02-16-2017, 10:45:10 AM
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Default Re: Ex-Military Spec 6JB compression issue

A bit of teasing is one thing. I get my dose of "poor form" comments from the political news feeds, we sure don't need it here.

So, we're back to ignition and fuel after the heads get put back on?
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Old 02-16-2017, 08:47:22 PM
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Default Re: Ex-Military Spec 6JB compression issue

Excuse me, I apologize for my poor form.

Oh, I forgot to give special consideration because this guy is from England. The people that developed Rolls Royce automobiles and the Merlin engine that helped win the last world war. Motorcycles that are still running. Cosworth engines that dominated auto racing for many years.

Colortune was not a compression tool, and was never very popular.

I will still lurk. I have no reason to post on this site again.
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  #73  
Old 02-16-2017, 10:13:27 PM
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Default Re: Ex-Military Spec 6JB compression issue

John in case you haven't noticed. We don't treat people that way. The terms they use in the UK are different than some we use. We have a rule on this site. No one is to be treated like an idiot and there is no name calling. We are just a bunch of folks trying to help others. Most come here to learn. So we try the best we can to help them learn. It may take longer than normal but we stick with the person.

If you can't see the value in that. Then maybe you shouldn't be here.
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  #74  
Old 02-16-2017, 11:45:40 PM
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Default Re: Ex-Military Spec 6JB compression issue

Quote:
Originally Posted by John Hartman View Post
Excuse me, I apologize for my poor form.

Oh, I forgot to give special consideration because this guy is from England. The people that developed Rolls Royce automobiles and the Merlin engine that helped win the last world war. Motorcycles that are still running. Cosworth engines that dominated auto racing for many years.

Colortune was not a compression tool, and was never very popular.

I will still lurk. I have no reason to post on this site again.
John, Please don't leave or not post a question if you have one. I myself have been amazed and pleased at the patience the guys here have for others and for myself when I didn't understand something. The BEST part is that we seem to be "Self Moderating" in that if someone might say something off color or harsh, we all try to re-steer that person easily as to not hurt feelings.
I got the saying "Be Nice" from my 84 year old, A.A. sponsor. It has certainly worked for me when I am told it by my wife or others.
It takes a Good Man to apologize for something he might have said. Stick around.......
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Old 02-17-2017, 02:01:32 PM
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Default Re: Ex-Military Spec 6JB compression issue

The color tune system is not new! Here in the US of A we has Beaconlite spark plugs. They too had a translucent blue glass insulator that you could see the combustion color thru. Blue, tinged with yellow was good. orange - too rich, purplish to white - too lean. If you used kerosene (paraffin to the Brittish), then you had a different set of colors to attend to. There were other clear glass plugs as well.
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Old 02-19-2017, 06:38:58 PM
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Default Re: Ex-Military Spec 6JB compression issue

...crickets...
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Old 03-01-2017, 08:38:23 AM
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Cool Re: Ex-Military Spec 6JB compression issue

Right ignoring most of the irrelevent posts, the head was back after a damn good de coke and despite us re grinding the valves in, one of the valve seats had "moved" - not something i could test of even see so the engineering company i took the head too rebuilt it and did whatever they needed to do to re seal the valve too...

So this is up and running again thanks to all that helped it would apear there were a few factors and the fact there was fuel in the oil meant there clearly was an issue with the piston rings...

I now need to sort the voltage and cycles out as to get 230v ac it only give 45 cycles and we use 50 in the uk...
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Old 03-01-2017, 12:27:34 PM
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Default Re: Ex-Military Spec 6JB compression issue

Glad to hear you have it back in service again.
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Old 03-01-2017, 01:25:19 PM
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Default Re: Ex-Military Spec 6JB compression issue

Fuel in the oil could also be a leaking fuel pump diaphragm, something to check. It is a very common problem with the mechanical fuel pumps on J series sets. If you are only getting 45Hz you need to speed up the gen a bit, Hz is directly proportional to engine speed. There is a squared bolt projecting out the front of the fan housing with a nut on it , if you tighten the nut it increases the tension on the governor spring and the engine speed goes up. Cheers Dan
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Old 03-01-2017, 03:25:17 PM
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Default Re: Ex-Military Spec 6JB compression issue

If you had a cylinder that was not firing, then fuel let in during the intake cycle would bypass the rings and get into the oil. The gas would also dilute the oil on the piston and rings, leading tom excess wear. I would run the engine for a little bit and then change the oil and filter, just to make sure all the fuel has been removed from the crankcase.
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