Increasing size of rear main jet

[Traumahawk]

Edited for content

 

[dannymax]

I can't recall ever seeing that either altho the Haynes manual does say '85 - '87 bikes run the larger mains in the rear cylinders.

I would expect the rear cylinders to be hotter just by virtue of their location ....the rear cylinders are more enclosed than the fronts and sit directly above the exhaust pipes. That's at rest, once the bike is in motion the dynamics would change somewhat but the rears would probly remain warmer.

Wouldn't altering A/F or main jet fuel flow to achieve even temps actually be creating an imbalance in lean/richness?

 

[one2dmax]

The water cooled bikes aren't as affected as an air cooled bike that almost always has different jetting front/rear. Some inline 4's use the same jetting technique for the middle cylinders since they don't get as consistent a flow but again this is mostly air cooled stuff we're talking about.

You can try it but not sure if it needs it.

The only way to truly know would be a reading from each pipe which would be 4 sensors.

 

[Itgoes]

As Sean said you really need a afr reading from each cylinder to get it completely right.

I know for a fact the late model Ventures have different jets front and rear.

The Gen 2s are not completely right from the factory and do benefit from individual cylinder mapping.

 

[Traumahawk]

I can't recall ever seeing that either altho the Haynes manual does say '85 - '87 bikes run the larger mains in the rear cylinders.


Wouldn't altering A/F or main jet fuel flow to achieve even temps actually be creating an imbalance in lean/richness?

I dont think so....your just tuning the temps for the individual cylinders. I was always taught that instead of looking at the engine as a whole...you look at it as individual cylinders that are tied together. In this case.....4.

 

[Traumahawk]

The water cooled bikes aren't as affected as an air cooled bike that almost always has different jetting front/rear. Some inline 4's use the same jetting technique for the middle cylinders since they don't get as consistent a flow but again this is mostly air cooled stuff we're talking about.

You can try it but not sure if it needs it.

The only way to truly know would be a reading from each pipe which would be 4 sensors.

LOL....I have thought of that.

 

[Traumahawk]

As Sean said you really need a afr reading from each cylinder to get it completely right.

I know for a fact the late model Ventures have different jets front and rear.

The Gen 2s are not completely right from the factory and do benefit from individual cylinder mapping.

I'm glad that you brought that up....I had read that on a venture thread.....and even some people for the early ventures (same as a Vmax) seem to benefit from the different jets....although the evidence is strictly anecdotal.

LOL....cylinder mapping seems to SO much easier with fuel injection.

 

[falling]

I know in my dad's V65, after trying hundreds of different jetting combos, I ended up with one size larger jets in the rear cylinders. To this day, it's the only V65 I've seen pull clean from idle to WFO. Not a Max, but about as close as you can get.


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[Itgoes]

I'm glad that you brought that up....I had read that on a venture thread.....and even some people for the early ventures (same as a Vmax) seem to benefit from the different jets....although the evidence is strictly anecdotal.

LOL....cylinder mapping seems to SO much easier with fuel injection.

Yes....tuning a carburetor can be more difficult.......definitely more time consuming. It takes much more trial and error and also skill on the part of the tuner.

With FI and a fuel management controller like a Power Commander you can adjust the fuel a 250 rpm increments at 10 different throttle positions. You can also tune each cylinder individually as well as each gear.