Correct me if im wrong...

[Streetwise]

So as the tittle says:

After a good few hours this morning, i loose top end speed, and i have no bottom end torque. No hard accelaration but a steady increase. No high RPM.
Stated to tune the carb a little but wasnt getting any responce.

Noticed i had a heap of fuel around the bottom of the engine case around the bottom of the exhaust outlet.
im thinking maybe the gasket has gone / going and the air leak from the will cause loss power ??
Im gonna tear the engine down, it could do with an overhaul.

Thoughts ?

 

[Trip]

Yes if you have an air leak whether it's an intake, case or exhaust, the motor will run lean.

If you have a blown gasket it will allow air to leak past it. That air doesn't have any fuel mixed in it so it leans out the air/fuel mixture inside the crank case. Potential for motor burndown or seizure is imminent.

Sounds to me like a bad base gasket, or more likely the pipe is loose. A Loose pipe will cause all kinds of weird behavior.

I had a slightly leaky exhaust and I was trying to set the ls needle. The idle was fine for about 10 seconds then it would start to drop, so I leaned the ls and the idle went back up. For about 10 seconds it was fine, then it started to drop again, so I leaned it a touch more, then it was fine for a few seconds then the idle started going up. Then it dropped for about 10 seconds. Then it started surging. I was wiggling stuff to see if anything was loose and it turned out to be the can was loose. I tighten it up and the idle went back to where it was supposed to be and all was well.
Weird!

 

[Streetwise]

Yes if you have an air leak whether it's an intake, case or exhaust, the motor will run lean.

If you have a blown gasket it will allow air to leak past it. That air doesn't have any fuel mixed in it so it leans out the air/fuel mixture inside the crank case. Potential for motor burndown or seizure is imminent.

Sounds to me like the pipe is loose. A Loose pipe will cause all kinds of weird behavior.

Hey Trip,
i tore down the engine, the head gasket looked like it had better days, the Piston was really black in colour, spark plug was too.
stripped the carb down, the gaskets on that looked good, will change them anyways.

I knew something wasnt right when i was trying to tune it ! it just wasnt responding to the needles !!

Eventually it just kept stalling so figured it was time to head home !

 

[Trip]

Black is good! When it starts to turn white and then covers your plug with silver bits and puts a nice ashtray sized hole in your piston is when you have a problem... :lol:

Glad you got it sorted!

 

[pipeous]

possibly the crank bearing is leaking too. check that for play

 

[sperera]

interesting, I wouldnt have thought an air leak was the problem.

air leak will make idle very high and make it run lean, but not stop it from revving.

are there any marks on the side of the piston and top lip?

 

[Trip]

If it's lean enough it it stop revving.

 

[sperera]

even when the plug is dark?

sounds like it lost comp to me.

 

[Streetwise]

even when the plug is dark?

sounds like it lost comp to me.

I was on off road gravel / grass so hard to power off from standstill.
Piston has no marks on it, the case gasket looks in good condition, i am a bit reluctant to split that apart if i don't have too.

On the bench before i stripped it down, it would rev high on WOT but didnt sound right, the needles didnt seem to be responding.

Ive stripped it down, give it a good clean through, carb as well. Thrown in a new spark plug, will wait for the head gasket to come in and re build - see what happens, my guess is i might have to go back to factory settings and re tune

Any suggestions for getting the remains of the old head gasket off ? the last corner bits are proving stubbon

 

[Trip]

Razor blade and a steady hand.

 

[Trip]

even when the plug is dark?

sounds like it lost comp to me.

I would have to hear what the engine sounds like... But yes I have seen a black pug on a motor running lean. The high end needle was way to lean, but the ls was too rich, it didn't want to idle with the carb so rich but it would clear out as the motor revved. Then it would lean out because the hs was set too lean, then he would let off and the motor would be overly rich again!

I reset the needles and smacked him upside his head, and scolded him! :lol: I taught him better than that!


Changing gas stations or oil manufactures can cause erratic needle settings too. That's why I stick with the same gas station, same oil and I mix my one gallon cans out of a 5 gallon can. Everytime I get gas I buy one gallon, I mix the oil in and dump it into the "Community" can. That ensures every tank will be thoroughly mixed with 5 gallons of gas for a through blend.

 

[Streetwise]

I would have to hear what the engine sounds like... But yes I have seen a black pug on a motor running lean. The high end needle was way to lean, but the ls was too rich, it didn't want to idle with the carb so rich but it would clear out as the motor revved. Then it would lean out because the hs was set too lean, then he would let off and the motor would be overly rich again!

I reset the needles and smacked him upside his head, and scolded him! :lol: I taught him better than that!


Changing gas stations or oil manufactures can cause erratic needle settings too. That's why I stick with the same gas station, same oil and I mix my one gallon cans out of a 5 gallon can. Everytime I get gas I buy one gallon, I mix the oil in and dump it into the "Community" can. That ensures every tank will be thoroughly mixed with 5 gallons of gas for a through blend.

Didnt think to take a vid of it
I do the same with the "petrol" D ) buying 5 litres at a time and mix my own oil
i got caught out last year from an old mix i had in the garage, it had been sitting around for probably over a year and a half. MY FG didnt like that what so ever, i got chatting to a friend, says that petrol can go off if sitting around for a while, unlike diesel fuel that can sit around for years and still be fine to use. !!

Never new that !

 

[Trip]

We don't even use Gasoline over here, we use filtered sick and diarrhea. Everyone says that it goes stale in a month or so, but I have ran gas that was well over a year old. As long as it still smells like filtered sick and diarrhea, it will be fine. But that's just me.. Make sure it's filtered or else it will plug your fuel filter.

 

[MrFnisse]

The gas should be fine after a long period of time. Its the protecting aspects of the oil that takes the beating from long time storage. Something about the enzymes in the oil getting broken down from the gasoline and the engine then wont get the protective coating from the oil mix.
I could be wrong though but that's how i recall it.