does a nexxus exhaust affect the jetting

[muffy]

hi i have just brought a gs500e its been running bad hesitates on take off and holds back if its at about 5k rpm and i open it up quickly
and if i dont give it loads of revs off the lights it bogs down for ages then after a 20/30 yrd wait it picks up and flys off
it has a motad nexxus pipe on it but im wondering if there are things that need changing like jets or mixture after fitting as i recon it was probably slapped on by the last owner
ive fitted inline fuel filters a new air filter and plugs had the carbs off and cleaned the jets bowls etc and still not sorted it
it was popping like mad too so i turned up mixture half a turn on both sides which stopped the pop but didnt make any reel difference to its main prob im also thinking it could be float height but its a plastic type and i dont know if i can adjust it ?

thanx

[Kickstart]

Hi

Think that Motad claimed that they did not need rejetting (they claimed that with the GPZ500 we had), but need and could do with are different.

However that said the behavior your bike is showing sounds far worse than I would expect from the carbs needing minor changes for the pipe.

Floats probably use a metal tag to act on the needle valves and you probably bend these tag a tiny amount to set the float height. Also worth checking the needle valves are in good condition while you are there.
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[muffy]

ive looked at the needles and they look ok to but im no mechanic there clean and set the same as each other and i thought the pipe would change the mixture but how leaner or richer ?
i dont have much knowledge on diagnosing faults but im not scared to get my hands dirty and try fix it myself just dont know how lol
but i have learnt you can chase a carb problem for ages if your trying to eyeball it but any reliable info would be helpful

thanx

[Kickstart]

Hi

Not certain if the idle mixture adjustment on the GS carbs is an air screw or a mixture screw, so undoing it could make the mixture richer or leaner!

Needle valves tend to wear and needle little wear to leak.

I would be inclined to check the carb rubbers are not cracked and that the needle jets are OK, and that the diaphragms are not perished.

If the carbs still appear OK then it is probably easiest to lob it on a dyno and have a look at the mixture trace.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[muffy]

thanx keith

one more thing do you think im best buying a clean second hand set of carbs or buying repair kits and new jets for the ones i got and have them balanced and the valve clearences doing i dont want to spend a fortune on it i would like to do some work myslef to cut costs budget about £250 max

[Kickstart]

Hi

Difficult one really. 2nd hand carbs could be in a similar state and quite often they are not that cheap. But assuming they are OK it makes life easier and gives you spares.

I would check things over more (especially the slides and diaphragms) before deciding.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[WetSparks]

One question, what are your plugs looking like ?

Black would suggest your running too rich.
Dark brown OK.
Very light brown to white is too lean.

Its a very rough guide, but at least a start in the hunt for the problem.

[muffy]

your right wetspark but there really new plugs so would it be a true reading they been in for about 50 miles if that i have looked at them but the electrode is still really gold in colour and only just starting to soot up

[Kickstart]

Hi

Plug colour isn't that useful, as you could be hideously rich in some areas and hideously lean in others.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[el_oso]

may be worth just getting the manual and resetting the mixture screw and then tweaking it from there.
____________________
Duke 390
Previous: '05 XR125L | '96 XJ600S Diversion |'05 Suzuki GSXR1000 | '05 Honda CBR125-R | '97 YZF 600R Thundercat | '11 Honda CBR250
Car: Jeep Wrangler 4.0L