Backfire in L/H Cyl on 1150 Adv

[Adventure before dementia]

Hi

Looking for some help with a problem on my 1150 Adv. I'm getting an intermittent backfire from the lefthand cylinder which is producing a whisp of smoke out of where the intake attaches. It runs well however is lumpy on tickover when hot.
One last thing - I have noticed that the LH downpipe glows a lot brighter in the dark than the RH.
Any ideas?

Thanks a lot

 

[MattW]

OK - I'll start you off - I'm sure others will contribute.

Could be an airleak somewhere in the left hand intake - this can cause backfires and it'll be running lean and hence hot which could account for the hotter L/H downpipe.

Check the security of all the fastenings / rubber bits in the intake system. Check for cracks in any rubber bits (with the bike running try spraying something like WD40 onto the rubbers - if the engine speeds up, you've found an air leak.

Missing vacuum balance point bung?

Edit: Air leaks in the exhaust system can cause backfires, but this shouldn't make it run lean / rough.

If it's running very lean / hot on that side, I'd try to isolate and fix the problem sooner rather than later - lasting damage can occur.

just my 2p

Welcome to the site by the way

 

[Adventure before dementia]

Thanks a lot - will check it out tomorrow.

 

[Steptoe]

While the engine is running spray wd40 in the area where the throttle body attaches to the inlet. Does it effect the idle ?

The hose clip is often over tightend which causes an airleak.
The opposite of what people expect so they then tighten it up somemore

 

[ExpatinIstanbul]

Take it to Borusan, they're brilliant.

 

[Adventure before dementia]

Thanks Steptoe. Just got back from business travels so just looked at the bike again. It seems that there are gasses escaping from the manifold where it joins the head - see pic. Does this just mean I need to change the rubber mount or is it something more serious?

Thanks a lot

 

[MattW]

Whoa - you need to resize that image! (like this - just grab the properties of the preview image in Windows live and use that as your image URL)

Others will no doubt have some ideas, but the first thing I'd do is check the security of the fastenings between the rubber manifold and the head? If they appear tight, remove the manifold and check for flatness.

 

[Adventure before dementia]

Thanks for that!

It is all really tight - so will have a go at removing and checking for flatness at the weekend. Is this a common problem then - do they warp with the heat?

Cheers

 

[MattW]

Thanks for that!
Is this a common problem then - do they warp with the heat?

That I can't tell you - only had my GS for a few months

You could possibly try a small smear off gasket sealant on the face of the rubber manifold - however, I'm not sure if this is a 'no-no' - better wait for others to offer opinions first.

cheers
Matt

 

[Adventure before dementia]

The saga continues!

I found a rip in the manifold so I changed the manifold today - great I thought, all sorted - wrong

I just fired up the bike and although there are no leaks now it is still not running right. Every now and then it misfires and stops the engine, it fires up straight away and runs fine for about a minute then does it again. Also noticed the downpipe is running a lot hotter than the R/H (glowing red whilst the choke is on) then seems to cool down off the choke.

Any ideas anyone?

Thanks a lot

 

[Carl]

The saga continues!

I found a rip in the manifold so I changed the manifold today - great I thought, all sorted - wrong

I just fired up the bike and although there are no leaks now it is still not running right. Every now and then it misfires and stops the engine, it fires up straight away and runs fine for about a minute then does it again. Also noticed the downpipe is running a lot hotter than the R/H (glowing red whilst the choke is on) then seems to cool down off the choke.

Any ideas anyone?

Thanks a lot

coil? try switching them round, or pull off the bottom plug caps and see if it still runs.

 

[MikeP]

"Choke" is only a fast-idle on these things.

Does this misfire happen when warm and the choke is closed?

Do both throttles open when the choke is opened or just the one that's getting too hot?

When it's cold, start without the choke, just hold the throttle open a bit. If it starts okay and doesn't overheat that one cylinder, there's something gone wrong in the splitter box.

 

[ExpatinIstanbul]

I reckon it's the HT lead.

 

[Adventure before dementia]

Spooky that you should say that - I think you are in thre wrong job!

Discovered that the L/H HT connector at the plug was loose - thus the intermittent backfire.

All sorted now - thanks to everyone for your help.

 

[L]

I think you should always start with the basic checks before posting excessively large photos on a website and hanging around for 2 hours waiting for a bloke to come and look at it.

 

[Adventure before dementia]

At least I didn't set fire to my bike

 

[L]

so I was cold... so what...