Author Topic: Overnight loss of drive power  (Read 395 times)

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Offline Richard Stannard

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Overnight loss of drive power
« on: 31 Jul 2017 at 13:58 »
Hi,
My Mk5 starts , idles & revs, but has no drive power to pull away. Such a dramatic loss of drive cannot be exhaust valve settings. The clutch is operating. Has anybody suffered this problem & can offer advice?

Offline eddie

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Re: Overnight loss of drive power
« Reply #1 on: 31 Jul 2017 at 15:41 »
Richard,
             With the engine stopped, put the bike into gear and first try pushing the bike backwards, and check whether the engine turns. then push it forward, and again check if the engine turns. If pushing the bike forward turns the engine, but doesn't when you push it backwards, I reckon you have sheared the key on the gearbox input shaft. Pushing the bike backwards or having the engine driving the bike will undo the nut on the splined adaptor, but operating the kickstart will tend to tighten the nut - thus you can start the engine on the kickstart, but the engine will not power the bike as it then tries to release the nut.
 Hope that makes sense!
   Regards,
               Eddie.

Offline Richard Stannard

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Re: Overnight loss of drive power
« Reply #2 on: 01 Aug 2017 at 13:57 »
Eddie, Hi. Many thanks for your reply & thoughts. I tried your suggestion & the engine turned pushing it forward & backwards. Regards, Richard.

Offline eddie

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Re: Overnight loss of drive power
« Reply #3 on: 01 Aug 2017 at 14:36 »
Another thought - it could be a problem with the gearbox sprocket or shock absorber - but both of these are usually obvious as they are accompanied by a loud noise as either the chain jumps the sprocket or the shock absorber rides over the top. Sprocket damage is visually obvious. Wear of the shock absorber is only evident on dismantling. On full lift, the sliding member of the shock absorber should lift higher than the end of the splined stub shaft. If it only lifts flush with the end, you will need to insert a spacer washer (about 1/16" thick) to limit it's movement. When reassembling the shock absorber, there should be a spacer about 1/2" thick between the end of the stub shaft and the spring retaining plate. The centre nut should then be fully tightened - it is not intended to be an adjustment for the shock absorber.

  Regards,
                Eddie.

Offline Richard Stannard

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Re: Overnight loss of drive power
« Reply #4 on: 15 Aug 2017 at 15:58 »
Eddie,
The problem seems to be focusing on blockages within one carb. I have always shied clear of carb maintenance but feel that now is a good opportunity to `have a go`. Could you give me some pointers re; any special tools required, error traps, logical methodology. In the meantime, i will trawl through old forum entries to see what is there.
Regards, Richard.

Offline Hampshirebiker

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Re: Overnight loss of drive power
« Reply #5 on: 16 Aug 2017 at 07:07 »
Richard, undo the bottom nut & remove the float chamber from the carb. together with the slide etc. Take the body off the bike & remove the big capnut from the bottom. From the slide end GENTLY tap out the brass jet block. If it's stuck, loosen the capnut a couple of turns & push it out in the vice; using a socket etc.
Soak the block in thinners for a couple of days & blow through every orifice with a C/A nozzle. There is a semi spherical indent in the block, which looks like it's blind. In fact, it has a tiny hole in the centre; which should be clear.
I'd like a pound for every time I've done this, but I got there in the end.
Dave.

Offline Hampshirebiker

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Re: Overnight loss of drive power
« Reply #6 on: Yesterday at 08:06 »
I should have added that the only way(IMO) that a carb. problem can develop "overnight" is for a bit of crap to wash down & obstruct the main jet. Possibly just remove the bottom nut to check this first.

 

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