Different jetting front/rear on v-twin

[AllanB]

My 400cc v-twin Shadow is liquid cooled, so I figured same front and rear in terms of jet sizing, but heard people say that you still need a larger jet on the rear carb. What do you guys think?

 

Just looking for a start point with the jet kit I bought, bearing in mind my air-box and baffles are non-standard, for want of a better description.

 

Any advice on what can be done with the crankcase breather "recycle the crap" system. The bike is a 1983.

[papa al]

1. experiment with jetting is the way grasshopper.

[plug inspection.]

2. vent the crankcase by tube to chain to about-lube it.

[AllanB]

5 hours ago, papa al said:

1. experiment with jetting is the way grasshopper.

[plug inspection.]

2. vent the crankcase by tube to chain to about-lube it.

1. I guess the tuning companies assume different front and back, as they only give you one main jet of each size. Upon inspection, not much in this kit for the money.

2. Good idea, except the bike is shaft drive, may just put the crap in a bottle and drain once in a while.

 

[VocalNeal]

On air-cooled V twins the rear cylinder runs a bit hotter than the front but on a water cooled motor they should both run the same. So no difference. 

That being said on multi cylinder engines certain cylinders run differently to others because of  water jacket design. 

 

Your Shadow is hardly high tuned and running on the edge. Find a Shadow forum and have a look. 400cc is a Japanese taxation class so may not be hugely popular in other countries? 

 

As has been suggested do plug chops to verify.

 

Happy New Year. I'm off to the pub.

[AllanB]

On 31/12/2017 at 10:05 PM, VocalNeal said:

On air-cooled V twins the rear cylinder runs a bit hotter than the front but on a water cooled motor they should both run the same. So no difference. 

That being said on multi cylinder engines certain cylinders run differently to others because of  water jacket design. 

 

Your Shadow is hardly high tuned and running on the edge. Find a Shadow forum and have a look. 400cc is a Japanese taxation class so may not be hugely popular in other countries? 

 

As has been suggested do plug chops to verify.

 

Happy New Year. I'm off to the pub.

Sobered up yet, trust you had a good time, happy new year to you?

 

My NV400 looks pretty much the same as the VT500 Shadow, sold in the USA and the jet kit I bought is specifically for the NV400, which, as you rightly say, is a Jap home market only bike. The kit contains only one of each jet size on the basis that front and rear are different.

 

I currently have two jets of the same size and there is evidence of it being lean on the rear pot, however, that may be down to poor float chamber levels, now correct. Plus the air-box and baffle bodges over the years.

 

I think I will start on the rich side, one up on front, two up on the rear, as it is easier to read a rich plug (sooty) than a lean one.

 

Been following the Shane Conley practice, including documentation, as everything has been messed around with. Useful guy for the amateur.

[VocalNeal]

43 minutes ago, AllanB said:

Sobered up yet..

 

Almost I'm on my third coffee which i said I would give up in the new year!

[AllanB]

Interesting, the instructions on my jet kit really dramatically fuel levels.

 

First they say lift the needles with two spacers, I could only fit one in and get the clip back on.

Next the front cylinder goes one jet size up and the rear 3 jet sizes up, so 2 sizes difference between front and rear.

 

These are the start points they recommend, we shall see, but it should stop the popping.

 

Curiously they also recommend altering the float levels to weaken/strengthen the mixture, surely that is a fixed level for the bike. I am not going down that road.

 

They also suggest clipping the needle lift springs to get a faster throttle response, again, not for me.