Suzuki bandit gsf 650 won’t rev

[Texpis]

Hi All bit of a problem with my project it’s a Bandit 650gsf k5 arb model.
When you ride the bike it behaves perfectly in al gears until you tray to go above 8/9k then it coughs and splutters come below that and it’s fine again.
I’ve had the carbs of and cleaned and set them up float heights and pilot screw out. Plugs look good on 2 turns out bit blacker on 2.5.
I’ve changed the coils thinking it’s ignition related (Everything but the boots do these Fail?)
I’ve ran it with the vacuum pet valve removed so it’s a straight flow and with the petrol cap off in case of blocked breathers.
I did replace the pulse generator with a second hand unit because the original was open circuit can this be fitted wrong (timing out.)
I’m guessing if it’s the carbs it would be the main jet I tried pulling the choke when it happens to see if it, Helped it didn’t.
The carbs when removed looked pristine if a PO had overhauled them and use dodgy Chinese jets would I be able to tell?
Bike doesn’t owe me a lot bought it as a project but would like to sort it before getting rid

Thanks and apologies for the long post

[jaffa90]

Sounds like the main jets need to be bigger with the intake / exhaust set up you have. Also i would check for unwanted air going in somewhere.
Any jet size marks ? The inner two cylinders should have bigger jets than the outer two being air cooled.

[Texpis]

Hi Jaffa thanks for the reply. When I got the bike it had cheap K@N type filters and it has a carbon can stainless exhaust, I have put the original filter back but kept the can . I’ll pull the carbs again and have a look

[Texpis]

Okay according to to the Hanes manual my jets should be 102 & 105
The jets in the carbs are all 147.5 if the numbers Ayre the hole size I guess mine are bigger than standard which would make sense with the K@N and the can. But that would make mine run rich so cand be the problem right?

[sickpup]

[Texpis]

Hi and thanks for the reply I did think that was a possibility so I left the air filter out for a run see what happens and it was no different.
Just abit of info I bought the bike with a lot of it missing it came with the filters I believe are they are the cheap Amazon ones but could be wrong. I don’t think the bike has been ran with these filters so it may have been rejeted too much anyway. I would expect the plugs to be black if I was running too rich and they aren’t.


Very much like these
https://www.amazon.co.uk/Motoforti-Universal-Motorbike-Cleaner-Tapered/dp/B09G2S8XRG/ref=sr_1_4?crid=19QSRU9TGD73D&dib=eyJ2IjoiMSJ9.u10Qm1GGKrwdDjaHV0ZIjz8-cBlEI9_OBGsZTd5omPbk8UbW2c0WFCd8ZoCE-eLdhWJIpkk2Xu-9IU1Dp944ZMVuAD-MdOWMbMauR-BpkaLTnhbX1nJrDnQ794EdNdJAqB4GV83dUPpEikfqVKoZnjG10UIV1-J4F3JcWK-pI3ulIHJyuPGa6zkVACz3LtmrwqUTECLRk4WAL_3gv-ms4t8yaLEd40Ev5F1zn9ETQEV-RsFeReU2tCRazaX15eRV4CI0qRCUC83A3reQTwqfzzVYwdUYdADVpgijrdU8U_8.wMWUlhOyRWy24CDnc7QwrM6DRtT3le7zwaW2RyKPwb4&dib_tag=se&keywords=Free%2Bflow%2Bmotorbike%2Bfilters&qid=1777822131&sprefix=free%2Bflow%2Bmotorbike%2Bfilters%2Caps%2C183&sr=8-4&th=1

[sickpup]

You are running rich and potentially have stage 3 kit fitted.

You are running so rich that the bike bogs so rather than burn the fuel richly the excess fuel simply drowns the spark, then when you drop down the revs it burns off the excess fuel. That's why the plugs aren't black.

[A100man]

[Texpis]

Well done guys installed the standard jets and now revs it’s little bollocks of chuffed to bits.
One slight problem when moving a way in first there is a shake after that it’s fine could it be clutch adjustment