Hey Taxonomy, what elevation you at with those jets?

 

I am pretty much at sea level. 190 feet.

I think I could even do $120ish to Canada. I could check if you want. PM me if interested.

Great you got that carb, it's going to rip! Totally different bike.

 

Dash8 (The Plane?) I installed the 351 and Pumper modified by Bill this spring and it completely transforms the bike. Thinking exhaust next year...Where are you in the Great White North? If you were nearby I would help with the install.

 

Ya, the plane. Flew for Jazz years ago and the name stuck. Moved up to bigger stuff now lol

I'm just west of Toronto, in Milton. What do I need to bribe you with to come over??? I'm thinking of doing it first half of Nov.

 

Milton's a long way from Ottawa, maybe a couple of buddy passes (brother worked for AC for 35 years) No problem walking ya thru it. Lots of good info & photos on here. Make sure you have good torque wrenches, ring compressor (or zip tie method), and feeler gauge for checking valves before you start. Lots of cleaning ahead of time, scraping base and keeping debris out of crank area is the most difficult. Make sure your at TDC before taking cams out and a manual is very helpful (or online freebie). Keep us informed, Frank,

 

Just to chime in, I'm not sure if you've had a chance to get an AFR gauge on your Bike Taxonomy, but on my stock bore 250 running a very similar set up (smaller pilot jet), I'm a touch lean on full throttle with a 130 main jet. 13.5 - 13.8 AFR. Mid range is good with the 50 needle in the P4, but the top needs more fuel.

I'm not sure how the dynamics of the carb fueling changes with a big bore kit in though, the added flow may pull more fuel than the smaller bore. Could be worth putting in a bigger main to see how it runs for you. I'll be doing mine in the spring and updating my thread.

 

Lots of people are running a 127.5 with basically my setup.

I believe conventional wisdom states that a BB kit usually reduces jet size as the stronger signal pulls fuel up more readily.

As it sits the bike starts perfect, needs choke when cold, will idle all day and has what I consider to be strong snap in the middle. I rarely run on the main as I like the torque curve down low and mid.

The bike pulls hard enough and I don't really road ride it so I rarely see WOT. In New England, in the woods I am rarely over 25 MPH.

I have no idea where I would even get a AFR and if I had one I would have no idea how to use it!

I am happy with it the way it is, so no dyno runs for me.

 

Nice!

Yea, the different bore size probably has a huge effect on that. Looking forward to doing mine!

 

This "pulling more fuel with a stronger signal" stuff really fascinates me.. On the surface, it makes sense - but lets go deep.. Main jets have a max flow rate. Once flowing at that rate, would a linear increase in vacuum signaling produce a linear increase in flow ? Would MEANINGFUL additional flow be possible at all ?

I submit another theory: Bigger engines need bigger jets..

It would be terrible if the "popular" TM setups for the 351 actually kills/ages engines due to a lean top end..

 

In truth I haven't dealt with this stuff much, but when twice (one bike was stolen) setting the BB up I had the same carb and the same jetting and it ran fine on both. So, within reason, I'd say jetting stays roughly the same.

Read down to what Motocross Action says, bigger bore, smaller jet.

You can suck through a straw (main jet) and the cross section of the straw can be totally filled, but if you suck through that straw with greater pressure more fluid will come though because it will move faster.

In my mind bore size doesn't matter so much as does intake and exhaust changes where jetting is concerned. A bigger bore will benefit from a bigger carb but if it was running well on an given carb and you changed nothing else then the same jet setup should work. If it doesn't I would look at leaner before richer.

Many of the stock bore TM setups look a lot like the BB TM setups. Many of the BB CVK setups look a lot like the stock bore CVK setups. PWJM's TM setup looks a lot like mine and I am BB and he's stock.

I admit in all of this that I am a seat of the pants jetter.

Anyhow, I use WOT about 1% of the time.