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Post by divvyjoe on Mar 25, 2009 10:47:45 GMT
Righty, I have had this problem for a few weeks now and il try to explain as best I can.
When I pull hard on the throttle (in or out of gear) from idle I get a massive drop of power with the revs dropping down and when not fully warmed up, this leads to the bike stalling. The engine revs lovely when up in the higher revs, I only get this problem when revving from idle.
If I am gentle with the throttle there are no problems atall - this leads me to belive it might be a fuel/air intake problem?
I regularly clean out the 2 breather hose's and cleaned the air filter a few months ago in white spirit (thoroughly washed out afterwards).
Now before anyone says "you shouldn't be hammering the bike" - I do not ride like I stole it, its just slightly concerning when I try to pull out of a junction quickly and all power dies causing me to lose my balance and confidence! As I say, it runs sweet while trundling along, its just from idle where I have the problem.
Any ideas much appreciated!
Cheers
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Post by cam7777 on Mar 25, 2009 13:11:13 GMT
Has the bike been stood for a while, say more than a few months?
Could be dodgy fuel of blocked jets due to old fuel.
More info needed on when it last ran ok, what has happened in the mean time.
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Post by CD on Mar 25, 2009 13:29:13 GMT
I could be a dodgy coil or plugs but usually that's likely to cause a missfire.
You don't mention any missfires so I'm guessing its a carb flatspot. Take off the float bowls and clean out all of the jets including the choke systems. Then while at it check the float heights are all correct.
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Post by divvyjoe on Mar 25, 2009 15:26:14 GMT
The bike has been left to stand for about a week while waiting for a replacement T-piece for the breather pipes. Hard to tell when it last ran well, as its my first bike so I was paying more attention to staying alive than the flat spot.
Nah, theres no missfiring, but I will whip out the Haynes and (attempt) to clean out the bits you've mentioned. If its a carb flatspot, would this not be noticeable when driven normally?
Cheers
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Post by teejayexc on Mar 25, 2009 16:51:28 GMT
Sounds like fuel starvation to me, sticking carb slides would give those symptons, when you whip the throttle open there is a momentary lapse before they open properly.
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Post by darren on Mar 25, 2009 17:38:43 GMT
have you checked the inline fuel filter? see if its full of carp, if its the original, i would change that as a matter of course, it sounds carb related and stated above,yav got some carp in the somewhere as you are going from idle to main jets,even one can cause it to dramaticly loose throttle,electrical misfires will cause a lot of popping and banging,backfiring, spluttering etc as its trying to pick up spark,so strip carbs and clean, DONT USE REDEX, if you are going to put an additive in the fuel, then use FORTE injection cleaner,as mentioned above check float heights etc while you have the carbs off
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Post by divvyjoe on Mar 25, 2009 18:10:54 GMT
Cheers for the replies, im still a n00bie and its gonna take me a while to work out what im doing so will probably wait till the weekend to have a play and get funky with mr haynes.
Will post when iv had a ganders
Ta
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Post by divvyjoe on Mar 25, 2009 18:13:30 GMT
Sounds like fuel starvation to me, sticking carb slides would give those symptons, when you whip the throttle open there is a momentary lapse before they open properly. This is definately a possibility as I left the carbs uncovered while the airbox was off (a lesson learnt), so some dust and general crap could of found its way in. |
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Post by CD on Mar 25, 2009 18:40:41 GMT
Grannies and eggs time...
Leaving the carbs uncovered isn't a good idea, but a few hours won't hurt - unless there's a sand storm.
If you take your time and do one carb at a time (so the parts dont get mixed up) its not hard to do.
Take off the float covers. One at a time, unscrew the fixed jets and blow through with WD40 and then compressed air or a cycle tyre pump with a flexi connector and replace. One culprit for funny power delivery is the cold start system. Make sure the plungers are all moving properly.
If you strip the carbs get a new type 2 posi screwdriver - anything else is likely to slip and chew a screw cross head. Same goes for the fixed jets inside - always use a sharp well fitting screwdriver.
If possible don't mess with the mixture adjusting screws - once taken out it can be a real struggle to get them back to the correct setting.
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Post by divvyjoe on Mar 25, 2009 19:46:21 GMT
Brilliant! Thanks for the advice  |
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Post by amorti on Mar 25, 2009 23:45:32 GMT
Try this: coax it above 6k, then rev it wide open. If that works, your main jets are OK, and it points to a blocked pilot jet. You can still coax it up to the main jet, as the slow running circuit will provide enough fuel if just trickling up to x revs (don't know where the crossover is on the divvy).
I had this on my fireblade, due to a split fuel filter. Symptoms were, it would run OK at lowest revs, and then cut to three pots if opening the throttle, then catch on all four above about 6k (out of 11). Interesting effect on a bike that powerful.
I cleaned the carbs twice, then figured out the filter was broken, put an auxillary one in (the original is a silly little thing inside the tank), cleaned the carbs again, and touch wood, it's been OK since.
The pilot jets will have very small holes through them, it takes next to nothing to block them, one single piece of sand would do it. Depending how long you left the carbs uncovered, that could be the cause. No amount of redex or anything else will clear the blockage if it doesn't fit through the jet.
Top tip - get to Maplin and buy a can of air. It's not cheap, but the nozzle tube was perfect for the jets on the blade, much easier than messing about with a footpump. Also, WD40 is not the puppy, really you want a tin of carb cleaner. It is a very strong solvent that in short time dissolves dried on petrol deposits. Again the spray tube (which yes you get with WD too) is perfect for a bit more accuracy.
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