nc30 jet swop?

[vfrgav]

Hello all, 1st post on the forum. Straight in and looking to pick the experienced vfr400 riders brains for jetting specs. I posted the same question in another forum but have got no response so here it is again.

In the middle of rebuilding a project vfr400. Stripped the carbs today and found 110 main jets all round. Its jap import K model so that works out correct according to Mr Haynes manual. The previous owner said there had been a flat spot about 8000rpm. I havnt rode the bike yet to decide what i think. should i think about upping the main jet size to closer to Uk spec, especially with the colder weather here in UK?
thoughts please.

In addition to the original question, i will be having the carbs balanced just to be sure they the bike will run as well as possible

thanks

[Cammo]

Good move to up the K model jets, they're too small in standard form, the bike can run very badly at the top end with exhaust changes and these small jets. You can see just how undersized they are by looking at what the UK models ran (virtually the same setup) 122's, more than 10% increase.

Does it have the standard muffler/exhaust?

118 front and 120 rear main jets are a good size with an aftermarket muffler, even without it will be a safer tune than what you currently have.

To help the midrange flat spot it's common practice to put an extra 0.5mm washer under the needles (should aready have 1 as standard). This richens up the midrange slightly, and has worked for me in the past.

While the carbs are off, it's a good idea to set the pilot screws also, 2.25 turns out will do it with this setup.

[Cammo]

I posted the same question in another forum but have got no response so here it is again.

I think you'll find most nc30/35 experts frequent this forum mate! The level of combined knowledge on here is amazing, there's not many questions you won't get (correct) answers to.

Oh welcome!

[vfrgav]

Good move to up the K model jets, they're too small in standard form, the bike can run very badly at the top end with exhaust changes and these small jets. You can see just how undersized they are by looking at what the UK models ran (virtually the same setup) 122's, more than 10% increase.

Does it have the standard muffler/exhaust?

118 front and 120 rear main jets are a good size with an aftermarket muffler, even without it will be a safer tune than what you currently have.

To help the midrange flat spot it's common practice to put an extra 0.5mm washer under the needles (should aready have 1 as standard). This richens up the midrange slightly, and has worked for me in the past.

While the carbs are off, it's a good idea to set the pilot screws also, 2.25 turns out will do it with this setup.

it has an ART silencer but ill be putting the std silencer on for the mean time as i have to MOT it before i can ride it on the road. I think ill order up some jets then and have that done before i build er for the final time. so 118 front and 120 you reckon? or would 115 118 be a big enough increase? Might even do the washer mod too on the needles. Thanks for the input

[vfrgav]

I posted the same question in another forum but have got no response so here it is again.

I think you'll find most nc30/35 experts frequent this forum mate! The level of combined knowledge on here is amazing, there's not many questions you won't get (correct) answers to.

Oh welcome!

just found this forum tonight. good to have a wide variety of knowledge on hand

thanks

[Cammo]

it has an ART silencer but ill be putting the std silencer on for the mean time as i have to MOT it before i can ride it on the road. I think ill order up some jets then and have that done before i build er for the final time. so 118 front and 120 you reckon? or would 115 118 be a big enough increase? Might even do the washer mod too on the needles. Thanks for the input

Nah mate go for 118/120, its a better tune than using L & N model sized jets with an aftermarket pipe (especially a loud one like yours!).

The washer mod works well, cheap as chips to do.

[CMSMJ1]

it has an ART silencer but ill be putting the std silencer on for the mean time as i have to MOT it before i can ride it on the road. I think ill order up some jets then and have that done before i build er for the final time. so 118 front and 120 you reckon? or would 115 118 be a big enough increase? Might even do the washer mod too on the needles. Thanks for the input

Nah mate go for 118/120, its a better tune than using L & N model sized jets with an aftermarket pipe (especially a loud one like yours!).

The washer mod works well, cheap as chips to do.

What he said!

Welcome too..