occasional lack of power
 

evening all,

i've just had to replace the reg/rec as that broke and i am now having an intermittent power problem. when i first get the engine up above 5k revs on a ride there is no more power coming and the engine sounds as if it is struggling with a regular misfire from the exhaust.

if i keep the revs low i can nurse the bike along ok.

three times this has happened to me, i've put new fuel in the tank so not thinking it is water in the tank now.

all three times it has happened it seems to have been corrected by low revs riding for a period of time followed by a large downshift from 2nd gear to 1st. i get the engine to engage in 1st at 7 or 8k revs and let it run down. this may well be just co-incidence but it has *seemed* to have worked each time.

bike feels healthier after doing this and then power delivery is back to what it should be.

what could be causing this?

stuck choke? (i'm not getting a strong smell of fuel though)
carbs problem?
residual electrical problem from reg/rec blow up?
throttle problem (feels the same as it always has)

any views greatly received

Re: occasional lack of power
 

I have had similar problems and it was a plug breaking down. Try replacing the plugs ... won't do any harm if it doesn't do any good ;)

Re: occasional lack of power
 

Does sound like one cylinder not firing properly. Could be ignition, damp, HT lead, LT supply, coil or plug. Wasn't wet was it?

Re: occasional lack of power
 

I had a very similar problem on the Monster last weekend. Last Friday I decided to clean the K&N filter but got a bit to keen when reapplying the oil which effectively blocked the flow of air when the throttle was cranked open. I fitted a standard filter and it solved everything so make sure your filter is clean/in good nick.

HTH

Cheers,

Paul

Re: occasional lack of power
 

thanks for the replies folks,

probably not the wet front cylinder problem, i've had that before (about two weeks after getting the sv :eek:) and dealt with it by fender extender and grease round the lead cap.

today it was ok apart from the problem occurring right at the end of the journey in (after 35-40 mins on the A40) and right at the start of the commute back home. i had to ride slowly anyway through heavy trafiic straight out of work and when i got back on the A40 it was fine.

guess i'll replace plugs & leads and the filter and see if that sorts it out.

the brake and front fork upgrades get bumped back once more.....:(

Re: occasional lack of power
 

It's completely free to:

1) Unplug all your leccy block connections that you may have disturbed fitting the new reg/rec, clean them up and re-plug them. Check the batetry terminals are tight.

2) Drain some fuel out of the carb float bowls to check for water and other junk.

I might start there because I'm tight :)

Re: occasional lack of power
 

Think of those pennies worth of fuel being wasted if it's not that though! :D

Re: occasional lack of power
 

Here's a rank outsider... Carb needle issue, you might have a damaged slide, diaphragm, or loose carb needle. I had that once, I rushed a refit and didn't seat it right, but it could come loose over time I imagine. This has basically no effect at idle and a minimal effect below 4000, then at 5-6 it all goes off- the needle controls the flow of fuel in the midrange circuit, if it comes loose then you get unrestricted flow as it pops out of the jet. Alternatively, if the slide isn't working properly, the needle can simply sit in teh jet or not move enough, starving that piston of fuel. Having a look down the barrel of the carb is one way to check, although I suppose that could lead to you getting a faceful of petrol, possibly exploding petrol. But still, that's what I'd do.

Easier option- the foam may have fallen off the top of the tank and choked the filter. More common than you'd think, that, and it's a total nightmare to diagnose.

Re: occasional lack of power
 

mmmm...carbs. not got a clue about them really. time to look at the haynes manual.

bike had absolutely no problems today. well, apart from being royally cut up by a senior citizen cage driver this morning. i've got a 120 mile round trip tomorrow so fingers crossed for no probs tomorrow. sunday is the next day that i'll get time & light to do the work.

Re: occasional lack of power
 

well, round trip to near chelmsford went without a hitch. cracking country roads out there, will need to return on pleasure rather than on business.

i'll still go through the checks suggested on sunday though