Poor Acceleration

[tomscotland]

I just bought my '95 M600 and had it fully serviced. It seems to have a flat spot and doesn't respond well or pull all that well and it can last for a while. Then it seems to clear and jumps foward the way you'd expect and runs much better until it does it all again.
Is it likely to be a carb problem and has anybody else had this happen to their bike ? Any ideas would be great before I take it back to my local bike shop for them to look at it.
Tom

[rac3r]

I just bought my '95 M600 and had it fully serviced. It seems to have a flat spot and doesn't respond well or pull all that well and it can last for a while. Then it seems to clear and jumps foward the way you'd expect and runs much better until it does it all again.
Is it likely to be a carb problem and has anybody else had this happen to their bike ? Any ideas would be great before I take it back to my local bike shop for them to look at it.
Tom

Where is the flat spot in the rev range?

Maybe it might have a restrictor fitted? :mand:

(someone who knows what they are talking about will be along soon!)

[tomscotland]

No - it hasn't been fitted with a restrictor or anything like that, it seems slow generally until it seems to clear and then it responds really well until after a few minutes it does it again and so on. It runs but runs with poor performance. I suppose I'd call it that really. When it decides to clear itself, or whatever it does, it really goes much better and just pulls away really suddenly and is impressive. It's as if there's a fuel prob or something.

[Ducmon]

were the plugs changed when it was serviced? Mine did the same until I changed the plugs from the iridium plugs (they were not getting hot enough to clean them) to the standard plugs. I would clean the plugs first before I started to play with the fuel system. Check that the air bleed pipe and that the water drainage pipe is also clear. They are under the fuel cap which you may to remove to clear the air intake properly.

[Gilps]

Could possibly be the igniter/cdi units. they are the two black boxes behind the battery next to the coils. They do break down sometimes causing intermittent firing. perhaps you could find someone local to you to temporarily swap over. its a five minute job to swap them.

[Liz]

No - it hasn't been fitted with a restrictor or anything like that, it seems slow generally until it seems to clear and then it responds really well until after a few minutes it does it again and so on. It runs but runs with poor performance. I suppose I'd call it that really. When it decides to clear itself, or whatever it does, it really goes much better and just pulls away really suddenly and is impressive. It's as if there's a fuel prob or something.

The M600 does seem to have a 'flat spot'. I find now, having had mine for a while, that you just need to change down a gear or even 2 sometimes to get the acceleration (if you change down 2, you need to change up again quickly to get the range right otherwise it's revving too much.) It's not really so much of a 'flat spot' but that it is a relatively small engine which we are asking a lot of? I still love mine though!!

[tomscotland]

Hi Liz - thanks for replying. I think it's more than that as the bike responds well some times and then it appears to sit back and it doesn't seem to matter what gear it's in, if you know what I mean. It will suddenly jump forward as if a blockage has cleared and it just flies away. I've tried changing down and to be honest once or twice I had to anyway as it was sitting back too much and I needed it to move on faster. Is this what your bike does ? I'm annoyed as I've just bought it but I'll get it fixed it there's something wrong with it as I like it now and it looks great !

[Oily Fingers]

mine does this, and i have got a restrictor kit fitted. exactly does what you say, sort of a flat spot/juddering when trying to say get round a car, when you accelerate, then it surges forward and its fine. mines a m750 carbed engine.

[BluprintZ]

Sounds fuel related to me, the fact that it plays up, then runs ok for a while makes me think there is a blockage somewhere, fuel lines, or possible the pump is playing up!
Check the vacuum pipe from the tank to inlet manifold isn't split.
Sorry, that is what i would be checking first before the electrics...although i could be wrong.

G : )

[tomscotland]

As far as I know there's no restrictor fitted to my bike but I'll check ? Hope you're having more luck with yours than I am haha.

[Black Bob]

Where is the flat spot in the rev range?

It's an M600, so presumably between 0 and 9,000 rpm ? :chuckle:

Oh sorry, I see Liz_62 already used that gag...... I'll get me coat.

[uksurfer]

might be worth emptying the fuel tank and a bit of carb cleaner, my bike ran like a pig after it had stood over the winter?

[tomscotland]

I put in a Lucas cleaner two days ago and it's sounding worse since. It missfired and backfired and won't start now. My local bike garage reckon it was a mistake to have put this Lucas cleaner in it and said to drain my tank and carbs.