PDA

View Full Version : Back fire and popping??



Hadafew
11-06-2010, 2:01 PM
Need help my triumph is back firing and popping and seems to have lost a bit of power. Seems like maybe a intake leak but I tightened every thing up but still back fires. Any suggestions

fightclub
11-06-2010, 2:25 PM
not an expert by any means, but I had similar issues.My exhuast spigots were loose going into my head on both sides, was causing some popping when i got off throttle, could also be timing ,

Hadafew
11-06-2010, 3:11 PM
Thanks someone else said the same on my way to the garage now. Timing i was a fried of because i don't know how to time magnetos i will learn now.

Drewwoods
11-06-2010, 3:45 PM
I had a similar issue with my virago. It was my exhaust that was loose though.

cntrhub
11-07-2010, 6:40 PM
Need help my triumph is back firing and popping and seems to have lost a bit of power. Seems like maybe a intake leak but I tightened every thing up but still back fires. Any suggestions

lose exhaust pipes do not lose power. I makes more power you open pipe. So yes, you have a mag setting to figure out. Got timing crank marks? The big pad with slit down the middle is full advance. Hold the slit at the nail. Then open the advancer at the mag. Beak the points there and you get the idea where you need to see the points separate at that raised pad with the line dent dealie.

Torch
11-07-2010, 10:09 PM
in my opinion here are the things you need to check. easy things first.
1. spray carb cleaner or WD40 around the intake and see if it revs up, (intake leak)
2. check the timing and the advance mechanism operation
3. clean out the pilot circuit in the carb or carbs,
4. pull the head and check for blow through marks on the head gasket in between the cylinders.

it would be helpful if you told us what ignition and what carbs you have

cntrhub
11-08-2010, 10:07 AM
in my opinion here are the things you need to check. easy things first.
1. spray carb cleaner or WD40 around the intake and see if it revs up, (intake leak)
2. check the timing and the advance mechanism operation
3. clean out the pilot circuit in the carb or carbs,
4. pull the head and check for blow through marks on the head gasket in between the cylinders.

it would be helpful if you told us what ignition and what carbs you have

1. Spray - Agreed.. But he said he tightened the area.
2. Timing - Agreed.. He did mention a mag.
3. Carb clean ~ Disagree.. It starts, runs and that means idle an main are clean or no start no idle. But guess it idles with a pop so why make the guy pull carb and clean hello?
4. Head Blow-by ~ We have yet to hear compression between cylinders for the 10% tear down calls that percentage. But he is not saying there is a pop out the head gasket. There is no loss of compression as per if the bike runs and spits out the carb not the head. Again, a waste tearing down the head or carb is look at the running condition before one makes a fish market move.

WOT is c0ompression so we see a big tit and a flat tit is spit-spit is a poor balance and maybe just maybe we have dual carbs out of sync or on carb with an air leak WD is waiting. Compression test is waiting. Carb sync or single carb is popping air with a gap.

I am going to stick my neck out and say the carb needs adjust or mounting not cleaning.
The bike needs a compression test not a head gasket inspection is one assumes all without proper diagnostics looks the jj. LOL

Get in front of that fish list is not my problem you want arguments in the technical points.

Hadafew
11-08-2010, 12:52 PM
Great thanks for all the input back down to the garage to check the wd40 method. It is a 650 with a 750 morgo top end ,single Amal card and a joe hunt mag. The motor was rebuilt from the sludge up last year so I hope its not a compression issue. I tighten the craop out of the spigots and the intake but still popping and backfiring. I have never tried to adjust timing on the mag but I guess I will giv it a shot. Cntrhub lost me so can anyone give me a tutorial on adjusting a mag for dummies

KT
11-08-2010, 2:05 PM
lock the engine at 38 degrees btdc...insert a piece of cigarette cellophane in the points of the mag rotate the mag till the plastic wrapper pulls out lock the mag down this should have the points opening at 38 degrees then use a timing light with the bike running ....on the stator is a line or timing mark, slowly moving the mag till the needle lines up with the line ...use a battery from a car or truck to run the timing light ...

Torch
11-08-2010, 6:26 PM
It could be a lot of things, but one the most comon things we see at our shop is a plugged pilot circuit in an Amal carb, todays mostly acohol gasoline will evaporate and clog the pilot jet in as little as 4 weeks of sitting, the best way to spot a clogged pilot is turn the mixture jet in and out and if the motor doesn't change idle speed then chances are it's plugged. it should be set at about 3/4 of a turn out.
The pilot jet makes up the first 25% of your fuel mixture so with a plugged jet what happens when you crack the throttle you get a pop and then it will rev up. the engine leaned out because you are getting a great big gulp of pure air with no fuel in it until the needle lifts out of the needle jet,
and it isn't necessary to pull the carb to clean it, just the take off the bowl and remove the mixture screw, on the underside you'll see a small hole going up into the body, and spray cleaner and compressed air up there until it comes out of the jet and out through the mixture screw hole. (usually right into your eye)
and yes it could also be timing, so...
The thing that happens a lot with Hunt mags is like KT says the timing slips because the allen bolt is too long in the taper drive.
As for the blown head gasket, that it has a tendency to push combustion pressure from one cylinder on a power stroke into the other cylinder just as it has the intake valve open and is taking in a breath of gas, pow, out the carb it goes.. ( HELLO??? ) we have done compression and leakdown tests that it didn't show on. but when the motor is running the head lifts and it will leak.
Come on pulling the head takes a 1/2 hour, if you have tried everything else with no results just do it. If you see a black mark on the gasket in between the two cylinders then you know whats happining.

KT
11-08-2010, 7:49 PM
yep I did have alot of trouble with the tapered shaft that goes into the end of the came first the allen was just a smidge to long, then the taper was not making 360 degree contact all the way around inside the cam end ...with alittle help from tony on how to go about it I was able to fix it and things seem good now...With a 40 year old bike though it seems the" for now " statement is the tricky area ...

cntrhub
11-09-2010, 9:50 PM
The pilot jet makes up the first 25% of your fuel mixture... We agree to disagree. I am going to ask you, yes or no and fill in the blank(?)
1. If I hold my finger over the low speed screw, What is the vacuum out of the main jet? Is it the same vacuum number over the low speed screw - Yes or no.
2. If I clog the main jet with a hair strand cut off; this is an open jet hole > I I < Is now lodged in the main jet at an angle I / I. If you answered #1 correctly, what is the fuel proportion out of that [partially] clogged main jet, 25% ~ 50% ~ 75%... Yes or no it is so and so percentage. No, your percentages are off, they are... Fill in the #.
3. If I say the same vacuum is going to pull out an equal proportion of fuel out of those two holes, what is the overall percentage of the low speed to the main jet, main jet to low speed.
4. If I say the low has a proportion along with the high speed, what is the fuel signal doing to the low speed... Is it pulling fuel out of the main jet, yes or no?
5. If I open the fish market, who is going to stand in front of that market and change the absolutes to their thinking? Sorta like reading an abstract that will replace cupcakes for chum. Change [pick any 3 amigo] and now change one of those variables to cupcake-fuel-compression or fuel-spark-cupcake. Like there is a different pressure over both holes in the same room sorta, slowly I turned, step bye step.


but when the motor is running the head lifts and it will leak. Agree. Peak pressure to push off the head would be peak TDC or a 1/2 a degree before if we are splitting hairs.

Torch
11-10-2010, 12:01 AM
what the hell are you on? where is this fish market and who gives a shit about that.
we are not talking about vacuum being clogged it is the gas that gets clogged off. the pilot circuit has a fuel passage that goes from the bottom of the bowl and is drawn up through a .025 brass jet that is located inside the back of the base behind an aluminum plug. it is that jet that gets plugged up with dried up gas and there is still plenty of vacuum at the pilot holes but no fuel. those 2 holes are always in a vacuum especially when the slide is closed, those 2 holes sometimes clog up but most of the time it is the pilot jet that clogs... if you thread the screw in it closes off the air flow from the front of the carb and causes the 2 little holes to emit a high ratio of fuel through the pilot jet thus enriching the idle mixture, if you open up that screw it increases the air ratio into the mixture thus leaning out the idle mixture.
you can pull the metering screw out and feel vacuum there and all will tell you is you have suction there not fuel. the pilot or low speed circuit is always working even when the main jet is fully open. it still represents about 25% of the 14/1 air to fuel ratio needed to run correctly.
go ahead and drill out that 1/4" plug on the other side of the mixture screw and you will see a little brass jet. that is the pilot circuit fuel jet, ..that is what clogs up!... I'm not just making this shit up.
an Amal carb only has 2 fuel circuits, unlike the Mikuni's and Keihn's they all have 3 fuel circuits, (idle jets, intermediate jets, and main jets)
Listen I don't really know what your level of experience is and don't want to belittle you at all. but here is my story. I own and operate a Triumph repair shop, on any given day there is about 35 bikes in there in being repaired, my 3 employees and I go thought this same thing at least 5 times a week, most of the time we clean out the pilot circuits and the bike runs fine. we rebuild about 4 motors a month and see a lot of blown head gaskets.
Now.. you can assume I'm total bullshit, and you don't have to believe a word I've said,...and you can research all this on the Amal carburetor home page here...http://www.amalcarb.co.uk/TechnicalDetail.aspx?id=11
anyway good luck with your fish market thing, I hope you do well.

cntrhub
11-10-2010, 9:12 AM
Torch, no disrespect. We are in a diagnostic mode here. So we have to think both main and low as a fuel lean problem. We know the carb floats on that compressed o-ring spigot and now someone barks down a flat gasket that is hard, has loss of memory not to push the leak or keep the seal from leaking... Then there goes the amal body with a twist to the distortion, the slide hangs up... All that damage over an old o-ring needing replacing ~~~~ <<< So it floats off the head = No Metal to Metal Contact! Look MA! no hangup!

I've listened to Ivan, Brock, rodracingworld's tech and now; send me to Lucas and read that fish report? I am new fuel injection self taught learning curve-here. I do not need a new bike press kit in hand and hey, not my fault the 1Atmo; tell me about some guy that worked on carbs; telling me I would have to throw the bike over a cliff to draw fuel out the main [with the slide closed] < That is right... To pull fuel at idle with 9 pea yes I said he may have his cliff-notes LOL. NOt in my world, sir.

I am sure you have a lot of years like me in the field. Well, I am self trained from the word go and tell me to modify my bike, my wordage, my theory if you do not get theory fished out and cleaned for eating; I express your 25% as 50% at the low-main. Then, the main is at WOT and what may I guess might be a 50% constant, as in 9 lbs of constant at idle and then the same constant no matter how you see it: 100% equal flow says either side is the, "Linear."

50% low-mid [low-main-jets =14.1]- Then at [mid-WOT] = WOT number is also that constant 14.1 must be also that 60Mz signal; [mid to WOT and now [main-low = 14.1] at wide open throttle.

Therefore, the bottom line, you have to check the main or you have to check the low being a 50% chance of 20/20 hindsight you do not get it right the firstime> !S


:killerjob: THE 1ATMO

Fish market says I have zip of 25% of anything for ya, guy... Dis ain't no jj come hither. Go back to camp. I ain't got nut inn 4-stroke ya four teen point seven come eleven you miss a step come place the fish on the scale 1ATMO = ALL EVEN UP is fueled by both sides in the middle 50.

Ask the eyes connected to the cranium to ask the Q?

Does theory hold water 25% ~ YES
Does Fish Theory hold water in the gills is the accel pump... But, getting back to the variable of the 1Atmo fill... Are we drawn to a vacuum [like a bug flying around a lampost] sort of 50% out of one draw is closed 'in proportion =14.1. So, will WOT be in a 50% proportion not WOT with 25% drawn out of a hole that has as constant 9lbs no matter the pulse say for argument sake; @ Idle, hello? Yes or NO?

:cheersmate: For being swamped at work.

englishbob
11-10-2010, 7:14 PM
Need help my triumph is back firing and popping and seems to have lost a bit of power. Seems like maybe a intake leak but I tightened every thing up but still back fires. Any suggestions

The joe hunt mag . Everyone ive known that has ran one of these has had trouble sooner or later.

KT
11-10-2010, 9:19 PM
anyone that has had to deal with 2 tits or 2 wheels has had trouble sooner or later :clap for you::cool:

Torch
11-10-2010, 10:42 PM
The joe hunt mag . Everyone ive known that has ran one of these has had trouble sooner or later.

that's a fact, we have gone of the Hunt probs on this forum and the other. good luck.