Triumphrat

Hinckley · 07-14-2003

Kind of a dumb question.
I've been reading alot of posts in different forums on varying opinions of air/fuel mix. I've read that poping on decel is a VERY bad thing. What is the real scoop?
My bike has a minor poping on decel, not a loud bang just muted poping. Is this a bad thing? After all the money I spent on this motor, the last thing I want to do is hurt it.
It seems to be running fine otherwise. I have no other signs of a lean mix. As a matter of fact, I have more signs of a fat mix than a thin mix ( black around the ends of the pipes, hard starting, etc.)

Hinckley · 07-14-2003

Kind of a dumb question.
I've been reading alot of posts in different forums on varying opinions of air/fuel mix. I've read that poping on decel is a VERY bad thing. What is the real scoop?
My bike has a minor poping on decel, not a loud bang just muted poping. Is this a bad thing? After all the money I spent on this motor, the last thing I want to do is hurt it.
It seems to be running fine otherwise. I have no other signs of a lean mix. As a matter of fact, I have more signs of a fat mix than a thin mix ( black around the ends of the pipes, hard starting, etc.)

Hinckley · 07-14-2003

Kind of a dumb question.
I've been reading alot of posts in different forums on varying opinions of air/fuel mix. I've read that poping on decel is a VERY bad thing. What is the real scoop?
My bike has a minor poping on decel, not a loud bang just muted poping. Is this a bad thing? After all the money I spent on this motor, the last thing I want to do is hurt it.
It seems to be running fine otherwise. I have no other signs of a lean mix. As a matter of fact, I have more signs of a fat mix than a thin mix ( black around the ends of the pipes, hard starting, etc.)

MickMaguire · 07-14-2003

IMHO the popping is less of a worry than a rich mixture ( which it seems you have). It is caused by the design of the carbs when coupled with a racing pipe. Basicly the mixture goes so lean on overrun (butterflys closed) that you get a situation where the charge doesnt fire, but it then ignites in the exhaust. Personally I doubt that this causes any real problems as the engine is under reverse load.

An overly rich mixture, especially on an engine that is quite new can give you problems with bore glazing, you will also be losing quite a bit of power to it.

I would suggest that you get the bike to a dyno to find out exactly what is going on and whether a different jet combination would be right for the bike. A change to the primary jets may help allieviate or even cure the popping too.

MickMaguire · 07-14-2003

IMHO the popping is less of a worry than a rich mixture ( which it seems you have). It is caused by the design of the carbs when coupled with a racing pipe. Basicly the mixture goes so lean on overrun (butterflys closed) that you get a situation where the charge doesnt fire, but it then ignites in the exhaust. Personally I doubt that this causes any real problems as the engine is under reverse load.

An overly rich mixture, especially on an engine that is quite new can give you problems with bore glazing, you will also be losing quite a bit of power to it.

I would suggest that you get the bike to a dyno to find out exactly what is going on and whether a different jet combination would be right for the bike. A change to the primary jets may help allieviate or even cure the popping too.

MickMaguire · 07-14-2003

IMHO the popping is less of a worry than a rich mixture ( which it seems you have). It is caused by the design of the carbs when coupled with a racing pipe. Basicly the mixture goes so lean on overrun (butterflys closed) that you get a situation where the charge doesnt fire, but it then ignites in the exhaust. Personally I doubt that this causes any real problems as the engine is under reverse load.

An overly rich mixture, especially on an engine that is quite new can give you problems with bore glazing, you will also be losing quite a bit of power to it.

I would suggest that you get the bike to a dyno to find out exactly what is going on and whether a different jet combination would be right for the bike. A change to the primary jets may help allieviate or even cure the popping too.

07-15-2003

Hi.

I have a bit of a different view on this. In fuel's class, they taught us that riich = good; lean = bad. To greatly oversimplify, if you run too rich, the worst you will do is foul your plugs; if you run too lean, you'll burn up your pistons and valves.

We discussed pinging and backfiring in another series of posts. Discussion got pretty heated, with different views. Here's mine.

Pinging generally is caused by using fuel with too low an octane rating. This leads to premature combustion of fuel. Backfire through exhaust is caused by the less restrictive muffler. This leads to reduced backpressure that affects "scavenging" (intake and exhaust valve overlap) and effectively leans out the air/fuel mixture.

Unless you change timing or make other accommodations, pinging and backfiring are unavoidable consequences of using lower than recommended octane or going to off road pipes.

My two cents worth are to use the recommended octane and to go stick with the original muffler.....Jerry,

[ This message was edited by: jerrysussman on 2003-07-15 07:42 ]

07-15-2003

Hi.

I have a bit of a different view on this. In fuel's class, they taught us that riich = good; lean = bad. To greatly oversimplify, if you run too rich, the worst you will do is foul your plugs; if you run too lean, you'll burn up your pistons and valves.

We discussed pinging and backfiring in another series of posts. Discussion got pretty heated, with different views. Here's mine.

Pinging generally is caused by using fuel with too low an octane rating. This leads to premature combustion of fuel. Backfire through exhaust is caused by the less restrictive muffler. This leads to reduced backpressure that affects "scavenging" (intake and exhaust valve overlap) and effectively leans out the air/fuel mixture.

Unless you change timing or make other accommodations, pinging and backfiring are unavoidable consequences of using lower than recommended octane or going to off road pipes.

My two cents worth are to use the recommended octane and to go stick with the original muffler.....Jerry,

[ This message was edited by: jerrysussman on 2003-07-15 07:42 ]

07-15-2003

Hi.

I have a bit of a different view on this. In fuel's class, they taught us that riich = good; lean = bad. To greatly oversimplify, if you run too rich, the worst you will do is foul your plugs; if you run too lean, you'll burn up your pistons and valves.

We discussed pinging and backfiring in another series of posts. Discussion got pretty heated, with different views. Here's mine.

Pinging generally is caused by using fuel with too low an octane rating. This leads to premature combustion of fuel. Backfire through exhaust is caused by the less restrictive muffler. This leads to reduced backpressure that affects "scavenging" (intake and exhaust valve overlap) and effectively leans out the air/fuel mixture.

Unless you change timing or make other accommodations, pinging and backfiring are unavoidable consequences of using lower than recommended octane or going to off road pipes.

My two cents worth are to use the recommended octane and to go stick with the original muffler.....Jerry,

[ This message was edited by: jerrysussman on 2003-07-15 07:42 ]

MickMaguire · 07-15-2003

Hey Jerry, I don't know what it's called here but in the UK we referred to it as petrol wash. When the mixture is very over-rich gasolene condenses on the cylinder walls slightly and washes away the oil film so promoting wear and/or glazing.

In addition you will, as you say, foul the plugs more but you will also get more carbon buildup throughout the engine.

But the biggest sin will be the loss of power and lower gas milage. Hinckley has spent a lot of money on a performance engine, what a shame to waste that by running it too rich and lose a load of bhp.

All this is of course IMHO