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Discussion Starter #1
Untill recently my bike was kept in a nice warm garage. It was great, easy winter starting, nice & dry etc. Now its out in the cold & suffering a bit.
On particularly cold mornings it is quite reluctant to start, taking quite a while on the starter button (ie a few seconds rather than instantly). When it does eventually spark up it does so with a massive cracking backfire, accompanied by a nice shot of flame. Whilst I take some pleasure in waking the neighbours, frightening small children (live near a school) & inducing coronary arrest in any elderly folk who happen to be passing (also near a rest home), I cant help but think this is not good.
1. Is this normal?
2. Is is causing any damage? (other than split eardrums)

Cheers
Gibbo
 

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Generalissimo Tea Boy
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Mine gives a little pop/backfire when starting up first thing on a cold morning, I never use the choke unless it's a dire emergency.

A backfire usually means a leak in the exhaust or airbox.
 

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YEN_POWELL said:
I never use the choke unless it's a dire emergency.
Wow, mine does not even start without choke in summer :shock:
How do you manage to do this?
use a rusty choke-cable perhaps...?
:wink:
 

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Discussion Starter #4
YEN_POWELL said:
Mine gives a little pop/backfire when starting up first thing on a cold morning, I never use the choke unless it's a dire emergency.

A backfire usually means a leak in the exhaust or airbox.
I often get a little pop as well but its the really cold mornings that it sounds like a shotgun. I do use a K&N filter & remus GP pipe, I think they seem to create more backfiring for whatever reason.
 

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robelst said:
YEN_POWELL said:
I never use the choke unless it's a dire emergency.
Wow, mine does not even start without choke in summer :shock:
How do you manage to do this?
use a rusty choke-cable perhaps...?
:wink:
I hold the throttle with my right hand, press the button with my left, so that my right hand can work the throttle with more finesse. Then I have to carefully keep the engine running gently and I pull away almost straight away.

If it's very cold, I may keep the bike ticking over for a count of say 15 and then pull away. The only time this doesn't work is when I've left the bike standing for a week and it's cold. Then it's choke time.

Keeps the mpg down, especially as there's less chance for the choke to stick on.
 

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gibbo said:
YEN_POWELL said:
Mine gives a little pop/backfire when starting up first thing on a cold morning, I never use the choke unless it's a dire emergency.

A backfire usually means a leak in the exhaust or airbox.
I often get a little pop as well but its the really cold mornings that it sounds like a shotgun. I do use a K&N filter & remus GP pipe, I think they seem to create more backfiring for whatever reason.
Sounds like symptoms of lean running. Is the bike rejetted to suit?
 
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I used to get some pretty good backfires when starting when I had the BSM exhaust on. That was one of the reasons I put the original back on, as I leave for work at 6:30 on a morning!

Steve
 

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Discussion Starter #8
YEN_POWELL said:
Sounds like symptoms of lean running. Is the bike rejetted to suit?
As far as I know it has not been rejetted. The bike had the pipe & filter when I bought it. How would I know if it had? The guy had a pretty comprehensive service history & reciepts but cant remember seeing anything about jets. From what I have read, rejetting isnt absolutely necessary for a K&N & race pipe.
In normal circumstances it very rarely backfires, only when cold starting.
 

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Check the spark plugs. They will tell you if it goes to lean or to rich. Back firing is a sign of lean mixture. To lean mixture is not good for the engine. Valves and combustion chamber can become torn. Use the choke when you start the bike. You can also check if the engine goes lean by putting on the choke when the engine is hot. If it runs smoother you have lean mixture. If it starts to behave strange it is probably not lean. I tried this and found that the intake rubbers on my bike where leaking air. ..
 

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tjompen said:
You can also check if the engine goes lean by putting on the choke when the engine is hot. If it runs smoother you have lean mixture. If it starts to behave strange it is probably not lean.
I'll definitely try this, since my bike started back firing a lot since I've fitted the Remus. Usually does it when deccelerating. Don't get the loud bang when I'm starting it up though...
 

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kiroh said:
...my bike started back firing a lot since I've fitted the Remus. Usually does it when deccelerating...
Popping on the overrun can be caused by an air leak in the exhaust system. Seeing as you've just changed the exhaust it'd be worth checking that the new end can is sealed to the header pipe completely.

Iain 8)
 

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iswoolley said:
Popping on the overrun can be caused by an air leak in the exhaust system. Seeing as you've just changed the exhaust it'd be worth checking that the new end can is sealed to the header pipe completely.
Iain 8)
Thinking about it - yes, there is an air leak where the exhaust meets the pipe. It's held by two springs with hooks, but I can see a black residue coming from there. Do I need to use some kind of special sealant?
 

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Sometimes mine backfires when I start, I thought it was due to the bike been out of tune at least I now know that it is common to the bike, as for the choke I have not used it since the bike was back on the road earlier this year, it needs adjusting :(
 

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Backfire

The backfire is caused by raw fuel building up in the exhaust - so its not a lean fuelling problem.
If the bike was OK when garaged, then its almost certainly electrical.
I'd check the plugs and plug leads. Take the tank off, and hit the starter in the dark - look for arcing from leads to frame - listen for any ticking. Next whip the plugs out (not easy, clean or replace) check the low voltage leads to the coils, are the spade connectors corroded?
The correct procedure for starting from cold on choke (which most bikes will need especially in winter) - is to use full choke, with the throttle shut and as soon as the engine fires, slightly open the throttle and back off the choke as soon as you can, also ride off as soon as you can.

The exhaust will have nothing to do with the problem.
 

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I find my bike backfires when a pop the throttle on a cold startup with the choke open excessive mixture methinks :D But then again I do it on purpose 8) Remus grand prix
 
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