Exhaust pressure

[antos]

Hi guys, Should I be able to feel the same amount of pressure coming out of both pipes? Pipes are not blocked, the one which isn't pushing out hardly any pressure was blocked with an oily sludge but I've drained it. Thanks

[antos]

Thanks mate, I've deffo got a problem then ,

[antos]

Thanks, well the side that has very little pressure (generator side) is a lot colder the can hardley warms up whereas other side is hot, stripped carb down 3 times blew threw everything with airline, including emulsion tube. Float is not punctured level is correct I'm fairly confident now it's not the carb, compression tested at 95psi, (both pots the same) swapped plug leads over (still the same) new plugs , pretty much stumped now to be honest.

[Yogi]

You could swap the carbs over and use a longer length of tube to join the balance pipe or block them off
Then you would know for sure if it's carbs
Matt

[antos]

If I get time I'll swap the carbs over tonight I've got spare fuel pipe, I've actually tried 4 different spark plugs in the no go cylinder, and used the opposite ht lead still nothing so that says to me ignition is ok, I'll report back lads thanks👍

[dusty350]

Is your head gasket good ?
I had an issue on a pv engine. Left pot not getting hot, and virtually no pressure from that exhaust. I had a stripped stud - I thought the head was torqued down but it wasn't tight enough, and coolant was being drawn in on that side. Right side was fine, but left was much cooler and exhaust pressure was nothing like the right side. 2 new studs sorted it.

Dusty

[antos]

Cheers dusty one to keep in mind👍 Well I think I've found the problem , I've fired it up and removed the carb rubbers to air box and put my hand over the carb inlet , the right cylinder wants to suck my hand in the left is not sucking at all so I reckon it's crank seal fooked. What you all think?

[antos]

Feb 7, 2017 16:41:07 GMT 1 dusty350 said:

Is your head gasket good ?
I had an issue on a pv engine. Left pot not getting hot, and virtually no pressure from that exhaust. I had a stripped stud - I thought the head was torqued down but it wasn't tight enough, and coolant was being drawn in on that side. Right side was fine, but left was much cooler and exhaust pressure was nothing like the right side. 2 new studs sorted it.

Dusty

 If head gasket has gone Wouldn't the pressure reading from the compression test I've done show a drop on the gauge on left cylinder?

[antos]

Cheers Tony yea that all makes sense to me, the engine hasn't been touched in all these years so it's a gem really no chewed screws etc, 22k miles on it pressure in both pots was exactly 95psi, stable too😊 So can't see any reason to suspect pistons or rings so unless there's a big hole in left crankcase somewhere to me it can only be the seal surely

[Tone]

Had this on my LC2 where there was a "pressure" pulse from the LH exhaust but not from the RH exhaust and also having trouble balancing the carbs on tickover as the throttle stop screw seemed to have no effect on the RH side. Eventually found that the top reed on the RH side wasn't closing fully and by turning it over the reed closed and sorted the problem. The standard metal reeds are fitted and when looked at from the side they are slightly "Concave" so if you fit them wrong you get a gap. It does very briefly mention this in the Haynes and Yamaha workshop manual about when reassembling the reed valve assembly to align the cutaway in the reed and reed stopper when installing the reeds.

Tone

[dusty350]

Hi
With mine, it showed no outward leak from the cylinder head, but was obviously leaking into the cylinder from the coolant passageway. I never got as far as a compression test - I pulled the cylinder head and could see a dodgy stud straight away. I changed a second one as it was borderline. That cylinder felt flat when running, and never got hot like the other side, and it was the fact that the right side ran ok that helped pull the left along a bit I reckon. If it had leaked into both sides I doubt it would have ran at all.

Dusty

[antos]

Feb 7, 2017 22:37:31 GMT 1 Tone said:

Had this on my LC2 where there was a "pressure" pulse from the LH exhaust but not from the RH exhaust and also having trouble balancing the carbs on tickover as the throttle stop screw seemed to have no effect on the RH side. Eventually found that the top reed on the RH side wasn't closing fully and by turning it over the reed closed and sorted the problem. The standard metal reeds are fitted and when looked at from the side they are slightly "Concave" so if you fit them wrong you get a gap. It does very briefly mention this in the Haynes and Yamaha workshop manual about when reassembling the reed valve assembly to align the cutaway in the reed and reed stopper when installing the reeds.

Tone

But even if the reeds were not sealing shouldn't there still be enough suction  from the crankcase ? Surely it's the suction that actually forces the reeds open?