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Discussion Starter #1


Hi, I have a CBR 250 R, i am in the UK

When i start my bike from cold, no choke. Then take it for a run i seem to lose power. For example the other day i was on the bypass doing about 100mph for about half mile in top gear with throttle fully open and they bike started to slow to about 8000rpm and when i tried to go down a couple of gears. they just seems to be no power and it just didn't sound right, like it was running on 3 cylinders

Problem disappears if i go to a mates, turn bike off, wait 30 mins and then reappears when we go out for a run.

I gave it to a mate to have a run on and give me his diagnose as its a electrial issue.

The bike got new oil, oil filter, air filter, new plugs and new HT leads last year. i have only done a couple of hundred of miles as they bike gets stored for the winter.

So i took the spark plugs out they were dry, wired brushed them and cleaned the
coil pack contacts
and the little bar they sit on
and the earth wire near the bar.

Took it for a small run and i think the problems gone. Weathers been rubbish to go for a longer run.

My question is are my coil pack on their way out? or is it something else?

Link to you tube of me starting my bike

http://www.youtube.com/watch?v=XLqgMbY0Qh0
 

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That's a light saber in the background isn't it?

Justin.
 

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100mph at full throttle... I would have expected a good 115mph. Unless your a big guy blocking a lot of wind. Not really sure about this problem, but I'd possibly wonder if the fuel pump was the problem. I'd be most suspicious about the carb boots leaking (rubber collars attaching carbs to engine), which perhaps is only occurring when they warm up. I'd check if they collars are tight, but also pull the carbs off and inspect for damage. As they get old, they get brittle and can tear/damage.
 

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Discussion Starter #5
No light saber, just my jacket.

Yeah you are right. its 115mph. im build like a stickman, but i ran out of road, also it doesn't help when cars pull out in front of you.

I thought there might be a fueling issue. I have got a fuel filter ordered
Ill double check tomorrow that the boots are tight. Also is there a filter in the fuel tap or does it just need stripped and cleaned?

No, what should i be checking? the resistance between the 2 spade connection on the coils?
 

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I think thats its a dirty fuel filter or a fuel pump thats giving you trouble. Start with replacing the fuel filter first
 

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i had a similar problem, lost all power riding about 110kmh. turned out the vibrations from the bike were rattling the grounding wires loose that attaches to the frame. this completely stuffed the electrical system up. Wouldn't start, Lose power, Temp gauge went crazy, indicators messed up.

take the tank and air filter box off, and follow the main cable. An offshoot should connect a wire to the frame, make sure that the nut holding it in place is SUPER TIGHT!

might not be the problem, but worth checking anyways.
 

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Discussion Starter #8
I put a new fuel filter in and filled her up. Also cleaned all my earths and battery connections.

I took her for a run the other day and she seems to be running even better than before.

Also noticed when crusing in town, 30mph or less for more than 30 seconds. When you crack the throttle open there is a slight delay before you get any power. I asked a mate who has a cbr 400 and he gets the same problem. But you it doesn't happen when you rev the nuts out of the bike. So im guessing its a CBR250/400 thing?
 

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i think you might just be in a gear higher than you should be
generally i've found that theres lag when im in say 4th gear at 4k rpm, but if i shift down to 3rd, the lag is gone
 

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i have the lag problem too, but i assumed it was just my riding style coz i cleaned carbs/fuel/plugs etc..

because im so used to driving a car around 2.5krpm. Im not used to a bike that does 18krpm, so i used to just keep it around 3-6krpm and hardly have any power. but then someone said i should be cruising all the time between 7-9krpm.

tried it and have never looked back. although it chews the fuel much quicker :(
 
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