Firestorm feels weird at 3500rpm

[DSDAN]

Hi, I have a questions I would love to get an answer to as this is the first bike I ever owned and I'm not too familiar with the Firestorm yet.

for good measure its a 1997 model, with stock everything and has 86000km in the clock.

When I cruise at about 3500rpm in 2nd or 3rd the bike feels like it wants to go but the decides not to, gives a strange noise (from chain and sprockets?) and its like im fiddling with the gas ever so slightly even when I hold it perfectly still, so it kinda goes a tiny bit faster then a tiny bit slower, then a tiny bit faster then a tiny bit slower and so on.
This behaviour is almost gone under heavy load but still noticeable.
Its especially annoying when cornering as I get the feeling the bike is losing grip as if you were to pull and release the throttle while cornering (which I obviously don't do).

I have replaced the back disk brake as it was down to 3.1 mm , the break pads, and also replaced the rear wheel bearings and cushioning rubbers. (the previous owner wasn't to concerned about maintenance)

So I'm trying to figure out what to do next, should I replace the chain and sprockets as the chain has some tightspots in it so that might be it? or should I balance the carbs or both?
Or is there anything I haven's thought of that might cause this problem (or maybe its normal for a firestorm)

Please help.

[tony.mon]

Sounds like an overtight chain, when adjusting you need someone of your weight to sit on the bike, otherwise the chain gets too tight once you're aboard.

Better sorted sooner than later, or you'll snap the chain or bugger the output shaft bearing.

[AMCQ46]

if not the chain, it sounds a bit like bad fueling at that throttle opening.

worth checking the air filter and then perhaps balance the carbs or even try to change the air screw or needle position

[benny hedges]

when did you last replace the plugs?

[DSDAN]

I have cleaned out the airfilterbox, but haven't changed the plugs, so I might give that a try.

Also I haven't tightened the chain with someone on it as the manual states:

Turn the ignition switch Off, place the motorcycle
on its side stand and shift the transmission into neutral

Check the slack in the drive chain lower run midway
between the sprockets

so I did that, but you guys reckon someone needs to be on it then?

I read about the TPS mod could that make a difference?

[DSDAN]

I could ask my girlfriend to sit on the bike when adjusting chain slack, but I'd have to wait a few months for her to gain the extra 30kg to come up to my weight
Not sure if I like the trade-off : fat GF for proper chain slack

[benny hedges]

mine also had a very annoying misfire at 3500.
have you fitted a different air filter at all????

if its same as mine was it's most likely caused by maladjusted mixture screw causing a weakness at very small throttle openings.
you need a special tool to adjust it while the engine is running... google mixture screw tool

mine felt like a misfire and was causing snatching and lurching at low rpm

also worth changing the plugs as imo the iridium type are only at their best for 8k miles or so and you cant clean them.
well, you can but it ruins them!

but yeh, as the lads have suggested, make sure the chain is adjusted proper too though this wouldnt be directly related to a misfire at particular revs.

[Eclectic]

Haha! Bike will bring a bigger smile in a few more years

Though what you describe is what mine does on a steady throttle. Kinda stutters... Fine on an open throttle though.

I've cleaned air filter, changed plugs, adjusted tps and had carbs balanced. Whilst I'm glad those jobs are sorted it didn't solve the issue.

The idle jet was pointed out by a gent on here, and as my bike was laid up for 2 years I reckon it probably is a gummed up idle jet at this point. Problem is I'm too wimpy to go that far in :/

Posted using me thumb on ma dog and bone.

[DSDAN]

Air filter is stock, but clean

woke up early this morning and did the TPS mod, its now at 433 Ohm, and going to get new sparkplugs now, hope this helps.

[DSDAN]

OK, so I adjusted the chain with my GF holding a big stone and a bag of sand on the bike to simulate my weight.
installed new sparkplugs and adjusted the TPS to the magical 430 Ohm.

I just tried the bike and its still feels like I'm stepping on the brakes a tiny bit and then releasing.
Cant hear to much noise form the chain as my helmet is noisy, but at low speed and rpm I can hear it go chggnng chgggnnng, and also a little "knack" sometimes (if that makes any sense)

the strange thing is when I release the throttle and engage the clutch the sound is almost completely gone it also runs/glides smooth.

So is it the chain or could it be something worse like my gearbox? it does shift a bit rough.

[Jazzscot]

I thing the chain would be a good call. I had a similar thing going on with my bike last year. Fitted a new chain and it was fine. Turned out to be a couple of tight spots causing the uneven feeling at constant revs.

Jazz