This Forum is now CLOSED use the link to get more details viewtopic.php?f=3&t=13924#p102587
#92949
float level is okay, but with the jet sizes recommended from the German enfield forum (48/125) it chokes..
now i have 30 idling and 118 main jet. Air screw reach is responding like normal, but still popping out of the exhaust when closing throttle in gear.. does it also with neelde more up and bigger idle jets on which it chokes..
The popping was a sign for too poor misture?
By Cranky
#92966
Yes the popping is perfect, it is an indication of a good mix.

If you dont like the popping you have the wrong carburetor. The carb you have is a simple Idle jet and needle jet carb.

If you had fuel injection the fuel is cut off completely on de deceleration, so they don't have fuel.

What you have is fuel going into the carb on deceleration with the idle and some needle jet. This is a very weak mix at 2000 RPM deceleration and the fuel is still trying to burn when the exhaust valve opens causing a pop.

If you had a CV carb they have a deceleration valve (or coasting valve if you are American). This is the three screw valve on the side of the carb. These carbs have a fuel idle jet needle adjustment and 2 separate air supplies, one being in the mouth and the other is under the diaphragm. The deceleration valve when under max depression when throttle is off will shut a valve and allow only one air supply to the needle jet making a richer fuel air mix so stopping the popping that people dont seem to like for some reason.

For me it is a sign of a good mix and normal for the basic idle jet --needle jet carb.
User avatar
By Presto
#92968
Here we go again. :o

A backfire in the exhaust system is caused by unspent air/fuel mixture passing into the exhaust port and being ignited in the exhaust pipe. This is usually caused by a weak idle mixture and/or air leaks – whether intentionally or in error.

Backfiring on deceleration is usually caused by a lean fuel mixture in the pilot circuit. The mixture weakens to such a degree that it either fails to ignite consistently or burns slower. This allows un-burnt fuel into the exhaust port. The un-burnt gasses then ignite in the exhaust pipe, causing the backfire – or ‘popping’ if you prefer.

I’d say popping is not perfect – but it seems some folk these days think it is.
Everyone to their own.
#92973
Presto wrote:
Mon Sep 14, 2020 3:36 pm
I’d say popping is not perfect – but it seems some folk these days think it is.
Everyone to their own.
I’m with you Presto. Yes in can sound creative, but it’s the sound of a bad mixture.
Moto GP bikes have it coming out of the pits, but that’s because they’re designed to produce optimum power at a zillion revs.

My Transalp has it a bit because the PO fitted a more free flowing after market silencer. On my old Oilhead GS I could tweak the TPS to correct it. The Transalp is not that easy. I’ll put up with the slight burble rather than bugger up the setting of the mixture.

A general purpose road bike, it should be possible to remove the burble/popping. But on a performance bike, then you may have some somewhere in the range. But again, with the correct carb settings, idle, right jets etc, you should be able to get silence.... but that’s probably what the lovers don’t want.


John
By Cranky
#92977
If you want to stop popping then you wont achieve that with a simple PWK unless you richen your idle circuit . This of course will stop the popping when you decelerate but the carb set up for riding will be wrong.

Popping is a sign of weakness yes. It is also an indication that you are not rich--- If the bike pulls well then by this method you can tell that you are close to perfect.

Such a lovely simple carb-- I wonder why they don't use them anymore.
By Cranky
#92996
Oh by the way popping in the exhaust can also be a retarded ignition, and a leaking exhaust flange as mentioned by some one,. Not so much for us CDI guys but the point guys maybe.

If its a late ignition and a weak mix it can most definitely be still burning when the exhaust valve opens causing a pop. This is not to be confused with a back fire thats like a gun shot nor is it the spit back through the carb usually when cold.

You got to get your spitting and popping right first.
#93123
Thanks folks (i do not get an notification is a reply is posted here?)
The engine runs fin but with a 30 idling jet i can start it whithout choke. alas there does not seem to be a smaller pwk idling jet.
In meanwhile very trsnage gearbox problem.. wil create a new topic çause some panic here..

Shop for accessories at Hitchcocks Motorcycles