Technical Popping exhaust
- Thread starter Flock
- Start date
Currently reading:
Technical Popping exhaust
Well, winter has arrived and the roads are heavily salted. So I put it in the garage knowing what to do when spring arrives. I'm happy knowing that I did everything that didn't fix the problem (learned myself how to service the engine this way) and probably know now how to actually fix it (the most obvious, exhaust gasket leak.)
That's cool, many thanks for the reply!
createcartel
Member
- Joined
- Jul 21, 2020
- Messages
- 13
- Points
- 54
I have recently fitted a mild steel Monza exhaust on my 500R and it very occasionally pops on overrun, when it starts playing up when hot. I’ve been through the engine and am assuming the coil is getting hot and not providing enough spark, so unburnt fuel is finding its way through.
smart51
Established member
A few months ago, a bit of the monza exhaust fell off my 500R. It was very loud and popped on the over run. I fitted a new exhaust and all was well again. I think on overrun, the mixture is a bit too weak to fire, so the fuel is prone to popping if there is something hot enough to ignite it in the exhaust and enough air for it to burn. I wonder if you have an air leak at one of the exhaust gaskets.
So I changed the exhaust gaskets, found out that the air I was feeling didn't come from a gasket, but from a tiny hole in the air vent compartment....no matter what I do, the popping on overrun keeps present after higher revs. So I took my wife to the garage, asked here what here opinion about the popping was. She told me to f*ck off and spend time on important stuff like the garden.
So from now on the popping is officially a special feature instead of a problem.
So from now on the popping is officially a special feature instead of a problem.
Wives are brilliant, my other half knows everything but knows f*ck all about engines! I'm still in the same boat, I bought new exhaust gaskets and I'm going to put it's own exhaust back on it and work backwards.
Can't the engine be manually cranked so both exhaust valves are closed and a shop vacuum be jury rigged to pressurize the tailpipe to aid locating the exhaust leak?
I've held a wet rag over mine and it will choke the engine so I don't think I've leaks but it's the common denominator in my case
the hobbler
Distinguished member
- Joined
- Jul 25, 2012
- Messages
- 4,084
- Points
- 1,013
If you have wasted-spark ignition, don't forget---you are producing a spark on the EXHAUST stroke as well the ignition stroke---I have wasted-spark ignition, and mine does the same sometimes.Hints of Soot on joins and welds..
It doesn't need much of a gap..
So I reverted back to the original exhaust and still the same. I think I'm up against timing and valve gapping.....again.
If I rev the car and hold it at revs then release the throttle it'll die unless I catch it with some acceleration. The mixture screw also seems to be limiting in that if I close it completely it does very, I've another carb with a rounded bottom, I'm going to try and make one carb out of the two while I'm in there. The joys of it all.
I think I've said it before.....I much prefer my 850!
If I rev the car and hold it at revs then release the throttle it'll die unless I catch it with some acceleration. The mixture screw also seems to be limiting in that if I close it completely it does very, I've another carb with a rounded bottom, I'm going to try and make one carb out of the two while I'm in there. The joys of it all.
I think I've said it before.....I much prefer my 850!
What do the spark plugs look like, as it sounds like weak mixture to me, not enough fuel.
Not an ideal test , but does the popping reduce if choke out a bit as a guide?
So (my wife was in the garden) I did a new test in the garage, inspired by the previous posts. I hooked up a bicycle pump to the exhaust, tape it airtight and pumped away. Guess what, I felt air through one of the gaskets I renewed a couple of days ago. Redid the gasket and test and it looked pretty airtight to me now. Couldn't start because my wife in het garden would hear that and than I had to explain why I had the bicycle pump up the cars ass. So hopefully I can drive a little this afternoon to see if the popping is reduced/gone.
Damn, still popping, even seems worse now when letting off the gas. I tried on my way fiddling with the mixture but that didn't help. I did notice that it seemed less if I slightly touch the choke handle while manually revving from behind. So with the choke a tiny little bit open it seems less popping (didn't do a drive test with that setting)
We're in the exact same boat. I'm going to have a look at letting out the mixture screw in the event it's too lean and I'm also going to play with the timing. They are the last two things for me to do.
Two cylinders of popping frustration!
If you can stop the car by putting a cloth over the tail pipe it will usually show up any exhaust leaks.
It is well worth doing a spark plug test after a fast?
run, to see if plugs appear to be running weak as this can be a cause.Another small point is that if it is running too weak for a length of time it can burn out the exhaust valves due to overheating!
Personally I don't think altering the idle mixture screw will make a great difference in comparison with the size of jets in the carb it's self, although others have different opinions re that.
On the previous exhaust I could stop it but at the same time I thought the bigger diameter exit may have been the cause over the standard.If you can stop the car by putting a cloth over the tail pipe it will usually show up any exhaust leaks.
It is well worth doing a spark plug test after a fast?
Another small point is that if it is running too weak for a length of time it can burn out the exhaust valves due to overheating!
Personally I don't think altering the idle mixture screw will make a great difference in comparison with the size of jets in the carb it's self, although others have different opinions re that.
I've pulled the plugs previously and they've been a nice light tea bag brown but I was going to richen it up to see if that made a difference and then look at timings.
I'm at my wits end with it. It's not ran right or been enjoyed in a year since all these issues developed.
Light brown plugs sound about right.
Not sure if tail pipe size would effect it or not.
Is air filter standard, "pancake or "boy racer type ones tend to allow more air through and so may cause weaker mixture.
The foam and gauze type ones I was always advised to clean with degreaser , blow out to dry with an air line and then squirt engine oil from an oil can into and shake off. The logic being it was clean but the oil would collect any dust particles.
If a little bit of choke improves the situation it would indicate carb running too weak to me.
Standard filter, no mods done there at all. I'll give it some choke and see what it does. It's falling down somewhere, give it a good rev and hold it then release it it will die unless you catch it so maybe it is too lean
