What is happening to my bike??? - Update Pics on pg2-

[rojer386]

I was out for a good ride out on Sunday but my bike - CBR400 NC29 - wasn't running right. At times it was very sluggish. It could be cleared by dropping a gear and giving it some but other times it wouldn't bother then all of a sudden it would be back to normal.

One of the guys I was out with suggested it could be running rich (tip of end can quite black and at one point made an awesome bang on over run). It is intermittent but the closer I got to home the more the bike felt restricted. It would rev happily but just wasn't as smooth as it should be. I have changed nothing on the bike apart from fork seals and a new tyre recently but that will have nothing to do with it.

It really just happened all of a sudden and is really puzzling me as to why!

Any help would be great. Thanks

[wullvfr]

it sounds like its a fuelling problem,nxt time it happens try putting the choke on and see if it makes it worse or even clears it.
if its running rich then putting the choke on will make it even worse where if its lean then putting the choke on should clear it.
i had a similar problem where the bike felt sluggish every now and then,not all of the time and i could only describe it as if it was running out of fuel and it turned out to be running lean and a quick set up and now is fine!!!!!

never rule out a possible electrical fault,plugs etc but i would do a few checks just to be sure.

[rojer386]

That's exactly the same as mine, could almost be running out of fuel feeling. I will try the choke and see if that helps. If not I will change all filters and plugs to rule that out too!

How much did it cost to have yours set up? Don't suppose you know of anywhere in Central Scotland area that could do it?

Thanks, Brian

[tanuki]

the fact that you are getting intermittant banging on overrun makes me think that its dropping off a cylinder either caused by a dodgy plug or plug cap or possibly just a loose cap..

the trouble with it being intermitant is you cant just whip the plugs out and check for a spark. for what it will cost on top of replacing your plugs it will be well worth replacing the plug caps and HT leads while you are at it.

[rojer386]

Thanks for the replies. I may just do airfilter, plugs etc and see if that helps fix it. Fingers crossed!

[rojer386]

Finally got round to stripping the fairing off and have a look. The allen bolt that secures the raditor has been rounded by a previous owner so I had to just get my hands in best I could with the raditor in place.

I pushed firmly on the plug caps/HT leads and when I started it it was back to normal. I took the bike out for a blast and all was well......almost. Only once did it run as before, sluggish etc.

Is this a sign of ht leads and plugs needing changed?

Brian

[rojer386]

Anyone?

Thanks

[leopard_pagan]

avoid the haynes route of changing plugs via the radiator...

tank off
air box off
coils off
duct tape the rubber skirt out the way.. full access to plugs/HT leads.

if you have a GF, borrow 4 colours of nail polish and mark each HT lead/coil so you know how they go back on...

[rojer386]

Thanks LP. Is it an easy enough job to change the HT leads?

[superlite]

I'd start with the plugs, if no improvement, then got the HT leads. Try giving the plug cap that came off a quick crimp before re-fitting. They shouldn't come off unless someone has been messing with them.