SRAD running like crap

[SMOKEU]

Over the past 1000km or so my GSXR has sometimes started to run really rough at low revs, usually when I'm cruising along at 100kmh in 6th gear. It will randomly start running rough and being way down on power, and trying to accelerate away becomes very difficult. If I drop it down a few gears and go hard on the throttle then it's fine until I slow down again. It only sometimes happens, and it's fine 90% of the time.

Yesterday I made the dumb n00b mistake of dropping it in my driveway. It was only a very gentle drop as the mirror didn't even bend in at all and there isn't a single new scratch on the bike at all. Ever since I dropped it the bike has been hard to start and it's been running rough pretty much all the time. I took it out for a decent ride on the open road and I can't get it running smoothly unless it's at very high revs. It still revs out nicely but it doesn't want to be kept below about 10,000RPM. It still idles very well. Where should I start looking?

[whowhatwhere]

Maybe disturbed any sediments in the bottom of the tank, which have now made it to the carbs blocking up the pilot jets. Also check for air leaks - mine was running crap at gentle throttle but seemed fine at full - one of the caps on a carb hole for used for balancing wasn't sealing correctly.

You're having a few probs lately. If you can have your bike off the road for a bit a full strip down, check and cleanup would be what I'd do.

[SMOKEU]

You're having a few probs lately. If you can have your bike off the road for a bit a full strip down, check and cleanup would be what I'd do.

That's exactly what I'm planning on doing. I'll start by taking the fuel tank off and checking the fuel filter. I can't find anything obviously wrong with it like damaged hoses, so I'll have to take it to a mechanic to look at it as it seems like a carby issue.

The spark plugs are slightly fouled and I've checked the gaps on all of them to make sure they're within factory spec.

[tigertim20]

That's exactly what I'm planning on doing. I'll start by taking the fuel tank off and checking the fuel filter. I can't find anything obviously wrong with it like damaged hoses, so I'll have to take it to a mechanic to look at it as it seems like a carby issue.

The spark plugs are slightly fouled and I've checked the gaps on all of them to make sure they're within factory spec.

ok a few things.
next time it happens while riding, pull over and take your helmet off. lean over and undo the gas cap, and see if you can hear a quiet 'whooosh' when you open the cap. If you do, then you have a blocked breather which will be your problem.

next step, check your filter.

Next step whip your carbs off and give them a clean. go the whole hog and set the float ehights too while youre at it, and if you can find one, borow a manometer to balance the carbs - the last few things are unlikely to help, you just might as well do them while you have th carbs out.

Whop your pugs out and take a look. are they oily and yuck? with the pulgs out, turn the bike over, holding your hand over the holes, to see if any traces of oil are coming out, you mightt have a slight leak into the cylinders

[Fast Eddie]

told ya to bring it out to the workshop where the sidecars at tday homie ;)

coulda pulled everything apart and blown compressed air thru shit etc.

good luck finding the gremlin munching on your power.

fix that throttle too haha getback out on the track

[Grumph]

Classic water in the fuel symptoms, aggravated by the tip over bringing more shit through the lines...

ChCh servos are bad through winter for the amount of water in the tanks - buy only from busy outlets to ensure fresh fuel.

Pull tank and carbs, strip and clean. New filter.

[Matt Bleck]

Have you had the airbox out recentley? could be a hose not connected to it properly.

[SMOKEU]

Whop your pugs out and take a look. are they oily and yuck? with the pulgs out, turn the bike over, holding your hand over the holes, to see if any traces of oil are coming out, you mightt have a slight leak into the cylinders

The plugs look a little on the dark side IMO, but they're far from being black.


told ya to bring it out to the workshop where the sidecars at tday homie ;)

coulda pulled everything apart and blown compressed air thru shit etc.

good luck finding the gremlin munching on your power.

fix that throttle too haha getback out on the track

I thought I'd give it a go myself first, but cheers anyway.


Have you had the airbox out recentley? could be a hose not connected to it properly.

I haven't taken the airbox off before this started happening.

[SMOKEU]

I've just shaken up the fuel tank and poured some of the fuel into a clean jar. There are a lot of contaminants in the fuel like pieces of dirt. Should I throw the fuel out and fill the tank with fresh fuel after I replace the filter?

[FJRider]

I've just shaken up the fuel tank and poured some of the fuel into a clean jar. There are a lot of contaminants in the fuel like pieces of dirt. Should I throw the fuel out and fill the tank with fresh fuel after I replace the filter?

Pour ALL the contents out. Remove the fuel tap, then place a few handfulls of washed pea gravel (stones not sand) in the tank, Swirl the gravel back and forwards along the bottom of the tank to dislodge any other "contaminants" and remove any rust there. Empty out the stones and put a few litres of petrol in. Swirl that around and tip it out.

A inline filter in the fuel line stops some fuel "issues" later too.

[FJRider]

The plugs look a little on the dark side IMO, but they're far from being black.

I haven't taken the airbox off before this started happening.

A piece of flattened wire down the sides of the plug electrodes to scrape out carbon there. The carbon can short out the spark (even partially)
To eliminate a possible problem ... fit new plugs.

The air filter could need a clean.

[SMOKEU]

A inline filter in the fuel line stops some fuel "issues" later too.

Something like these (as long as the hose fitting sizes are OK)?

http://www.trademe.co.nz/motors/motorbikes/parts-for-sale/fuel-tanks/auction-508203291.htm

http://www.trademe.co.nz/motors/motorbikes/parts-for-sale/fuel-tanks/auction-508968123.htm

Would I need a reasonably big filter on that bike?

[bogan]

Classic water in the fuel symptoms, aggravated by the tip over bringing more shit through the lines...

ChCh servos are bad through winter for the amount of water in the tanks - buy only from busy outlets to ensure fresh fuel.

Pull tank and carbs, strip and clean. New filter.

I agree with this guy.

Also, has the tank started to rust much? there are coatings you can jam in there to suss that out, and stop it happening again. An added benefit is it'll stop it rusting through the lower tank seams and pissing fuel out...
Actually, just pay Doug to make you a CF tank, no rust issues there :D

[FJRider]

Something like these (as long as the hose fitting sizes are OK)?

Would I need a reasonably big filter on that bike?

Nah ... too expensive. A small plastic one from supercheap or similar. You replace rather than clean. Cheap but effective.

http://www.forbesanddavies.co.nz/products/141-fuel_filters/2467-fuel_filters_inline.aspx

Some people I know have removed the filter from inside the tank, and rely on the inline filter. The clear plastic ones make what appears in it ... easily seen ...

[SMOKEU]

Those small ones should have enough flow for my bike as well won't they?

[Madness]

Those small ones should have enough flow for my bike as well won't they?

A Holley fuel regulator only has a 5/16" bore and it flows enough for most 350 Chevs. You'll be fine with the filter FJ linked.

[sinfull]

Stop looking at ya dirty plugs thinking they look ok ! If petrol is flowing it will be spark that's the issue at low revs or bad fuel but you've obviously gassed up lately !

Start with them plugs (new ones)

Clean ya air filter or replace it if it aint washable !

Inline fuel filter aint silly !

then think about carbs if it's still rough, or valve timing even if that aint been looked at for a long time

[FJRider]

Those small ones should have enough flow for my bike as well won't they?

I have one on my FJ ... but I can only get to 220 km/hr indicated (before I chicken out). I doubt if you will have any issues with fuel flow though.