Misfiring/backfiring - any thoughts?

[croddman]

Hello all,

I wonder if anyone can view this and think what could be making my bike backfire

its had new clutch, new sparks etc

but its running very bad and backfiring a lot,

My freind thinks that the exhust has clappsted (sorry for spelling lol)

I took it down to my local garage before it got bad and they could not find a problem and as normal it did not play up down there

any views ??????

Thanks

[Alpinestarhero]

Had the carbs balanced recently? Has it got an aftermarket exhaust on it?

Backfiring could be due to the bike running rich...

Have you had the spark-plugs changed recently?

Matt

[yorkie_chris]

Well what does it smell like?

If it smells of fuel, then I'd start with the choke plungers, bit of a faff to do but not really that hard. If you do them then when you put them back fill the cable, splitter and spring recess with grease.

If it smells wierd then check for air leaks, it could also be seriously in need of balancing.

Could be backfiring due to air leak (lean) or due to stuck choke (rich) or badly out of balance (one running hot, other running rich), changing spark plugs will probably not cure this.

[Scoobs]

Have you been riding it in the wet? If so, my money is on wet front plug. Do a search. This is a really common problem, but really easy (if a little fiddly) to rectify.

[croddman]

I have had someone check the new plugs that I put in and there fine

it has a nasty smell coming from it when it gets warm / a mile down the road

then the backfiring comes in

[yorkie_chris]

What you mean check them?

What colour were they?

My money's on choke plunger, probably front one, and probably a right bugger to get out.

[Alpinestarhero]

What sort of smell? Burning oil smell? Petrol smell? That horrible smell that happens when rain water is falling onto a hot engine?

The water in spark plug idea seems like a thing, but then you would be complaining of lack of power?

Matt

[yorkie_chris]

then you would be complaining of lack of power?

Matt

Too right, a twin turning into a single is a very pronounced thing, also does it at random, not just when engine gets up to temp.

[Scoobs]

There's so much it could be, but without seeing the bike it is really difficult to diagnose. There are a few common issues with the curvies. Water in the front plug. HT leads break down. When they get hot they start arcing to the engine block rather than directing the spark to the spark plug. This would cause the bike to drop onto one cylinder and run pretty rough. Leads are pretty expensive though because the ignition coil is part of the lead.

[yorkie_chris]

Leads are pretty expensive though because the ignition coil is part of the lead.

I'm not sure about that one.

[Scoobs]

I'm not sure about that one.

99% sure.

[croddman]

I am putting her in the shead tonight up on the stand ready to have a good old look at her on sunday

I'll keep you updated

thanks for your input into what it could be

[HopefullySoon]

99% sure.

Hi

Nahh the spark plug caps aren't part of the HT lead , they just unscrew out for you to change them , I know this because i have just changed one of mine .

Hopefully Soon

[Scoobs]

Misunderstanding mate. I'm not on about the caps. If the leads need changing, the coil is moulded onto the lead so you have to buy the whole lot.

[yorkie_chris]

Just had a look at my spare one, its the same fitting as in the plug cap in the side of the coil.