How does the Hot Weather affect your bike? (Fuel System)

[Craggles]

Hiya,

Recently I've had a couple of problems with the bike.

It started a few days ago - as I pull the clutch in, the revs just die away. This is completley random - happened about 3 times so far though so it's not just me stalling it (I fail to believe I've lost all sense of clutch control in a matter of a few days, yet am still able to change gear smooth as ever!).

I've also noticed, whilst travelling at speeds which require constant power (80 - 90mph) the power seems to drop off and come back. A little like if I was running low on fuel, just less so.

Yesterday, following a lorry, the bike started to seriously splutter and jump as if the tank was empty. "Odd" I thought - I would not usually even think of filling up for another 10 miles. Anyway, I pull into a layby and the engine just dies as soon as I pull in the clutch.

Switch to reserve, try starting again. No Luck. "Bugger" I think. So faf around for a few minutes, switch fuel off, on, reserve. Leave it etc... Checked the tank - it was low but still had fuel! Try again... No luck. By this time, a friend had stopped - he suggested I open the tank and then try starting. So I do, and as if by magic, it starts!

So we head home. Speaking to some friends, they also seem to be having problems like this with their cars - they put it down to the hot weather and fuel evaporation...

Could this cause problems like this, or should I be looking deeper?

I'm wondering if the air filter could have become gummed up with flies - considering the state my headlamp and helmet after weds! Cleaned the bike on friday too!

Craig[/code]
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If this signature is blue, you're riding too fast

[king756]

Not sure why it should loose revs pulling the clutch in, if anything shouldn't it be easier to rev with the clutch held in as theres less force required. Does your bike have a swithch on the lever so it starts only if the clutch is held in? Could be a electrical problem.

The traveling at speed/opening the petrol tank problem might be the breather hose on the tank. Might be blocked, come loose ect ect, so it's strugling to create a vacume thrus stoping the bike getting petrol fast enough.

[paulthewitt]

hiya,

could be the carbs getting dirty. i'm no expert but its a possibility. unless its fuel injected.

Paul

[craigs23]

Fuel Vapourisation?

My mate's CB1 suffers from poor starting when the weather/bike's hot. My bike does it a little when running hot at low engine/road speeds aswell.

[Craggles]

[Dom_]

Yep. Mine runs shit in the hot weather, then at night it runs a bit better.

[Kickstart]

Hi

Hot weather can cause fuel vapourisation issues. Normally this would cause a problem with warm starts (unless you are unlucky enough to get a vapour lock in a fuel line), basically because there will be a load of fuel vapour in the carbs / airbox / etc causing it to be very rich.

However the heat also causes issues with the mixture. You are getting far less mass of air into the engine for the same volume which should richen the mixture up. If the bike is already fairly rich then this might well cause problems.

Also you noticeably loose power in hot weather. Last years Big CC dyno day was a very hot day. Everyone seemed to be about 5% down on the expected levels of power (eg, my Bandit made 145hp, where it had made 153 only about a month before at the same place). Now 5% is not likely to be noticeable in normal riding (quite noticeable if you have measuring equipment, or try a top speed run), but might well cause the idle speed to drop enough to cause problems.

A fuel injected car really should not suffer problems like this though (the fuel is under serious pressure and flowing rapidly so should not vapourise, plus the car can adjust the mixture with the readings from the lambda probe, plus most fuel injection systems will measure the mass of air, rather than a CV carb that will meter the fuel based on the volume of air).

All the best

Keith
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[danclarkie]

i suffer exactly the same problems on my TW spluttering along sometimes and after i was riding it full throttle in 5th for about 10 mins it started splutterng as if out of fuel so i pulled over dropped the clutch and the engine just cut out. que 10 minutes of faffing around with spark plug fuel tap ect, being about 6 miles from home without my mobile on a fast A road with no hard shoulder or pavement, i had to hike my bike off the road onto the field next to it, started after i changed the plug at the roadside. only time its occoured recently is when im high up in the revs the bike will sometimes sort of judder as if its not sparking, then i change up the gears and its fine
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Bah Humbug

[Kram]

i don't normally get a problem (always takes a few seconds to start) but whenit gets hot, and i'm off to the petrol station... open the fuel tank, it always goes ... "TTTTIIISSSHHHH"
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FS1E -> SR125 -> CB400N -> CB650 -> FZR600 Genises -> VFR400 NC21 -> CBR900RR Fireblade -> Renault Clio 1.4

[Method]

[craigs23]

So is the soloution to fuel vapouration to run a slightly leaner engine with smaller sized jets? (or a free'er flowing can? )

[Courageous T]

the hot weather warms my bike up so i can blast straight away!

[Kickstart]