help please on backfiring


Information and questions on GL1200 Goldwings (1984-1987)
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loopy
Posts: 64
Joined: Mon Nov 22, 2010 5:32 am
Location: Australia
Motorcycle: 1985 1200 interstate

help please on backfiring

Postby loopy » Sat Sep 10, 2016 5:36 pm



My 1984 1200 goldy has an backfiring issue along with misfiring on acceleration.
Backfiring: When decelerating and reaching around 25-30 mph on decelerating more often than not there is a loud backfire thru the exhaust. Quite a loud crack backfire.
If I keep the engine revs high on deceleration ( above 3000 rpm) it doesn't seem to do it. Sometimes I can also hear a slight backfire thru the carbies/airbox.
Misfiring on take off.:
When accelerating from stationary position, the engine misfires almost like its starving on fuel. However if I keep the revs above 3000 rpm when taking off the takeoff is smooth with no misfiring.
On cruising the bike is perfect however when accelerating at higher speed I can still feel a hesitation in the engine.

If I were working on an older car I would say the timing was out. Had that many times with older cars and once timing adjusted runs OK.

Action taken so far: New spark plugs, new spark plug leads, new spark plug lead boots, carbies cleaned and then air balance and also mixture setting adjustment with gauges.



loopy
Posts: 64
Joined: Mon Nov 22, 2010 5:32 am
Location: Australia
Motorcycle: 1985 1200 interstate

Re: help please on backfiring

Postby loopy » Sat Sep 10, 2016 5:39 pm

I forgot to mention that the carbies have been synced several times and appear OK

tbeiler
Posts: 138
Joined: Tue Oct 18, 2011 9:25 pm
Location: Waterloo, Ontario, Canada
Motorcycle: 1986 Goldwing Aspencade,
1985 Goldwing LTD
1983 CX650 Turbo

Re: help please on backfiring

Postby tbeiler » Sat Sep 10, 2016 6:12 pm

When is the last time your timing belts have been changed on your bike?

loopy
Posts: 64
Joined: Mon Nov 22, 2010 5:32 am
Location: Australia
Motorcycle: 1985 1200 interstate

Re: help please on backfiring

Postby loopy » Sat Sep 10, 2016 7:49 pm

hmmm. I have had the bike 7 years and not done the timing belt.
is there a link somewhere explaining how to do it.

tbeiler
Posts: 138
Joined: Tue Oct 18, 2011 9:25 pm
Location: Waterloo, Ontario, Canada
Motorcycle: 1986 Goldwing Aspencade,
1985 Goldwing LTD
1983 CX650 Turbo

Re: help please on backfiring

Postby tbeiler » Sat Sep 10, 2016 8:35 pm

Get yourself a Clymer manual, if you haven't got one.
You can also find on this site in the How To articles or just google in You tube.
Good Luck

loopy
Posts: 64
Joined: Mon Nov 22, 2010 5:32 am
Location: Australia
Motorcycle: 1985 1200 interstate

Re: help please on backfiring

Postby loopy » Sat Sep 10, 2016 8:54 pm

is it common place for a worn belt to jump and upset the timing?
I also watched the process on YouTube which Steve Saunders site

User avatar
geraldm
Posts: 133
Joined: Fri May 15, 2015 12:07 pm
Location: pumphandle Saskatchewan ,Canada
Motorcycle: 86 gl1200 Aspencade

Re: help please on backfiring

Postby geraldm » Sun Sep 11, 2016 9:30 am

I don't believe the belt actually jumps a cog but rather the bit of belt stretch allows the cams to be a bit out of line. In some extreme cases the belt might jump a cog. But likely is just stretched if that is indeed your problem. When doing belts maybe you would want to check belt tensioner for bearing wear. Have a good one.. good luck.

Rusty Bike
Posts: 270
Joined: Sun Feb 28, 2016 1:55 pm
Location: New castle, PA
Motorcycle: 86 GL1200 SEi, 78 Yamaha XS750SE, 86 Honda XL125, 4.5 HP belt drive Minibike my dad built, foot clutch!

Re: help please on backfiring

Postby Rusty Bike » Sun Sep 11, 2016 10:34 am

Two things that may cause backfire are a lean fuel condition and leaky exhaust. If the age and mileage on the timeing belts is unknown, they need replaced. This may not be your problem?? From your description my guess would be one or more carbs is malfunction in the low RPM range, (gunked up carbs) . Very common problem with the ethanol fuel we use these days. Run the bike at low speed, shut off then read the plugs. One or more may show an errant cylinder. This may help narrow down the problem. Buy the manuals and work patently...Good luck...Rusty

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Rednaxs60
Posts: 728
Joined: Wed Nov 18, 2015 12:44 pm
Location: Victoria, British Columbia, Canada
Motorcycle: 1985 GL1200 LTD, 2008 GL1800

Re: help please on backfiring

Postby Rednaxs60 » Sun Sep 11, 2016 4:33 pm

I've the manuals electronically and can send via wetransfer. If you would like some info, send me a PM with your email and I will send you what I have.

Cheers
"When you write the story of your life, don't let anyone else hold the pen"

Ernest

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WingAdmin
Site Admin
Posts: 17050
Joined: Fri Oct 03, 2008 4:16 pm
Location: Strongsville, OH
Motorcycle: 2000 GL1500 SE
1982 GL1100A Aspencade (sold)
1989 PC800 (wife's!)
1998 XV250 Virago (sold)
2007 Aspen Sentry Trailer

Re: help please on backfiring

Postby WingAdmin » Thu Sep 22, 2016 7:45 am

I think your fuel starvation and backfire issue might be one and the same.

Look for a vacuum leak. A vacuum leak will let more air into the mixture than it is designed for, giving you a lean condition, which can cause the crackling noise on deceleration. A vacuum leak can also reduce the air available to draw fuel through the carbs, which means you can end up with a lean fuel condition - not enough fuel to accelerate the bike under load.

loopy
Posts: 64
Joined: Mon Nov 22, 2010 5:32 am
Location: Australia
Motorcycle: 1985 1200 interstate

Re: help please on backfiring

Postby loopy » Tue Sep 27, 2016 10:56 pm

Can anyone assist with the procedure for checking for a vacuum leak as stated by our Wingadmin.

eg How many vacuum hoses are there and where can I find them.

I will persist until I find the cause.

Cheers evryone

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WingAdmin
Site Admin
Posts: 17050
Joined: Fri Oct 03, 2008 4:16 pm
Location: Strongsville, OH
Motorcycle: 2000 GL1500 SE
1982 GL1100A Aspencade (sold)
1989 PC800 (wife's!)
1998 XV250 Virago (sold)
2007 Aspen Sentry Trailer

Re: help please on backfiring

Postby WingAdmin » Thu Sep 29, 2016 7:33 pm

If you have a propane torch, turn it on (don't light it!!! Just let the propane come out) and while the bike is idling, move it in and around the carbs. If you hear the engine suddenly speed up, you may be near a vacuum leak, and the leak is sucking in the propane.

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geraldm
Posts: 133
Joined: Fri May 15, 2015 12:07 pm
Location: pumphandle Saskatchewan ,Canada
Motorcycle: 86 gl1200 Aspencade

Re: help please on backfiring

Postby geraldm » Thu Sep 29, 2016 7:55 pm

I guess we're all afraid to tell someone to do that because someone usually has something to say about it but That's what I do and works great just be careful




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