backfire / afterfire

[lee]

interesting read

Back-fire - Wikipedia, the free encyclopedia

 

[Gas Man]

You are a info hound lately...

 

[TCALZ06]

so What do you guys think causes the after fire? I seem to have both sometimes.

 

[lee]

it would appear it could be either running rich and / or an exhaust leak - both these answers are already on this forum in places and the attached document seems to back that up

 

[LamboV12]

Afterfire is usually timing - many of our bikes have non-adjustable timing, then I would suspect ignition - followed by carb (accel pump shaft, O ring, etc) followed by exhaust leak

 

[TCALZ06]

I sometimes have a backfire on start up which I believe the write up says is a lean condition. The after fire I get doesn't happen all the time either.

It seems like these carbs are picky and change as the temp changes and engine temp. Is a little of this just normal?

 

[lee]

I sometimes have a backfire on start up which I believe the write up says is a lean condition. The after fire I get doesn't happen all the time either.

It seems like these carbs are picky and change as the temp changes and engine temp. Is a little of this just normal?

it certainly seems a few of us have similar issues - and as you the carbs could be sensitive to temperature changes due to changes in the density of the air - i would of thought the temp changes would have to be fairly significant though

 

[lee]

doubling up on gaskets - I think I might try that

 

[Vegas]

The answer is yes, They are Picky and yes with Shorter Pipes and if you like most are running the V&H BR Pipe, then you are going to get decel pop. Sometimes you get Pop when you first start the bike due to excessive fuel in the bowl of the carb. Yes there are Bikes out there that do not pop but every single motor is different and has it's own characteristics. If it's excessive, 9 out of 10 times you have an exaust leak. I've also found that on the rear port where it meets the head, the stock gaskets are not enough, I double up the Exchaust Gasket on that head. Made a world of difference for under 50 cents.

Carbs change as you change in altitude and believe it or not 10 to 20 feet is Big. which is why we set world records at Englishtown raceway because we are at Sea Level here.

Elevation and temperature are a huge factor especially on these old carbs which honestly don't have enough ways to tune. I am sure that is why Sul loves his new carb. I bet it has atleast one more adjustment. That is the beauty of fuel injection, it accounts for conditions. You can get these S&S carbs close but not perfect.

 

[TCALZ06]

The answer is yes, They are Picky and yes with Shorter Pipes and if you like most are running the V&H BR Pipe, then you are going to get decel pop. Sometimes you get Pop when you first start the bike due to excessive fuel in the bowl of the carb. Yes there are Bikes out there that do not pop but every single motor is different and has it's own characteristics. If it's excessive, 9 out of 10 times you have an exaust leak. I've also found that on the rear port where it meets the head, the stock gaskets are not enough, I double up the Exchaust Gasket on that head. Made a world of difference for under 50 cents.

Carbs change as you change in altitude and believe it or not 10 to 20 feet is Big. which is why we set world records at Englishtown raceway because we are at Sea Level here.

Thanks. Mine isn't close to 9/10 and right now in AZ it gets down to the
40's and when my bike ran perfect it was anywhere from 90-110

 

[francoblay1]

Ehaust Gaskets?

I am after some Exhaust gaskets as I am going to install a new V&H Big Radius 2-2 exhaust system on my K9... it has the 117 ci engine.

Which gaskets are the best?
Which ones do you recommend, please?
Any suggested links where to order them?

Thanks.

Would those be the ones? [ame="http://www.amazon.com/Cometic-Gasket-Exhaust-Style-C9719/dp/B0012TWSFS/ref=sr_1_18?s=automotive&ie=UTF8&qid=1338615197&sr=1-18"]http://www.amazon.com/Cometic-Gasket-Exhaust-Style-C9719/dp/B0012TWSFS/ref=sr_1_18?s=automotive&ie=UTF8&qid=1338615197&sr=1-18[/ame]

 

[HMAN]

I got a set of tapered gaskets from J&P for my VH 2-2. Seem to work fine. Got to keep an eye on the flange nuts though. They do vibrate loose which makes for leaks.