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Aft high compression kit.

94K views 658 replies 48 participants last post by  Greg Riddle 
#1 ·
ive been thinking about getting the kit. anyone have info on it. i know jojostang put one in. has anyone else
 
#427 ·
Make since to me. I can't see needing more unless you turn the timing up which I don't think can happen.

it can but too much involved. instead of advancing the timing would running a lower octane do similar
 
#428 ·
what would it do? you can never stay away.


i am putting the 62 slow back in. i am getting some decel popping and coming out of a turn and rolling on the throttle just aint the same. feels sluggish. the 60 slow made it drop some bottom end torque. i cant have that

I'm puzzled a bit here in the theoretical science of carburetion. I am, assuming, much closer to sea level. Which in turn means that my air is denser then yours. You see my a/f ratio on the before posted dyno charts. My a/f doesn't go lean until 4k rpm or so. I'm running a 58 slow, 4th notch, and I think a 230 main. Yet you are running a 62 slow and said you think you went lean when you dropped to a 60. This doesn't make sense to me. I believe your real world results. But the theory of it all just doesn't seem to add up to me. If I have denser air down here then wouldn't I be able to run more fuel then you since I am getting more charged air?

What have you done to your air cleaner? I am running a BAK.
 
#429 ·
I'm puzzled a bit here in the theoretical science of carburetion. I am, assuming, much closer to sea level. Which in turn means that my air is denser then yours. You see my a/f ratio on the before posted dyno charts. My a/f doesn't go lean until 4k rpm or so. I'm running a 58 slow, 4th notch, and I think a 230 main. Yet you are running a 62 slow and said you think you went lean when you dropped to a 60. This doesn't make sense to me. I believe your real world results. But the theory of it all just doesn't seem to add up to me. If I have denser air down here then wouldn't I be able to run more fuel then you since I am getting more charged air?

What have you done to your air cleaner? I am running a BAK.

i just looked at you dyno sheet again. you could easily use a bigger slow jet. your a/f mixture in the slow jet range is 18:1 way to lean.

some of the jetting difference is probably the air box. i have the stock box decapitated and the back cut out. here is what it looks like




i also have the cover cut. i will post a pic of it when its done. running a k&n filter. with this air box setup i believe it is the best flowing setup i have came across. with the bike stock the jetting was 225 main 5th clip 62 slow and 1 1/18 a/f. no the jetting is 245 main 5 1/2 clip 62 slow fuzz under 1 turn a/f. the main maybe too much but it is very close within 1 size i would guess. the needle may have to go up again but i need to ride it to find out and its too cold. should be 53° not 28°
 
#431 ·
That peak and valley I was told was due to sudden WOT and the air ingested suddenly followed by the accelerator pump kicking in to offset the lean condition with it finally leveling out. It certainly can't hurt to try a bigger slow.

i would have to call bs on that. the fuel from the acc. pump will only be there for a few short revolutions. not enough to effect the chart. if what he said was true then my a/f ratio would have done the same
 
#432 ·
i would have to call bs on that. the fuel from the acc. pump will only be there for a few short revolutions. not enough to effect the chart. if what he said was true then my a/f ratio would have done the same
Good deal. I was wondering and had doubts myself. Too many service techs down here want to pass of a shrug and an excuse to avoid having to actually earn the money they charge by doing actual work. I'll be getting a 62 soon.
 
#433 ·
what would it do? you can never stay away.


i am putting the 62 slow back in. i am getting some decel popping and coming out of a turn and rolling on the throttle just aint the same. feels sluggish. the 60 slow made it drop some bottom end torque. i cant have that

I had this kit in my 400EX ( 11:1, web cam,etc), night and day how it ran, but I only ran it on weekends. Not cheap!
 
#435 ·
Greg, have you tried a after market intake. I had some here with the stock cover/box cut and just could not get it completely running right. Something about the way the air flows. I'm thinking if you went with an after market, some of your issues would clear up??????????

no i havent tried an aftermarket kit. but i dont think i have issues. anything that is going on with my jetting now is just me retuning for the aft kit
 
#436 ·
no i havent tried an aftermarket kit. but i dont think i have issues. anything that is going on with my jetting now is just me retuning for the aft kit
K, I was just asking. Just because I have the Hurricane intake, and if I change the filter to one that is one inch thicker depth wise it runs like chit unless I change the slow jet( bigger) and jump to a 220-225 main, better but still will not run perfect.
 
#437 ·
K, I was just asking. Just because I have the Hurricane intake, and if I change the filter to one that is one inch thicker depth wise it runs like chit unless I change the slow jet( bigger) and jump to a 220-225 main, better but still will not run perfect.

if you want the bigger filter is there a reason you dont want to tune the bike for it
 
#438 ·
if you want the bigger filter is there a reason you dont want to tune the bike for it
I think my carb has been pulled a zillion times playing with different tunes. I'm getting old and tired of playing with it. She runs good and I got 53.2 miles to the gallon (speedo indicated) last weekend. Just gonna ride her for awhile. Who knows, I may put the Aft kit in one day????????????
 
#439 ·
I think my carb has been pulled a zillion times playing with different tunes. I'm getting old and tired of playing with it. She runs good and I got 53.2 miles to the gallon (speedo indicated) last weekend. Just gonna ride her for awhile. Who knows, I may put the Aft kit in one day????????????

i understand that. i think im done with tuning but will have to wait to see what the dyno says
 
#442 ·
I'm puzzled a bit here in the theoretical science of carburetion. I am, assuming, much closer to sea level. Which in turn means that my air is denser then yours. You see my a/f ratio on the before posted dyno charts. My a/f doesn't go lean until 4k rpm or so. I'm running a 58 slow, 4th notch, and I think a 230 main. Yet you are running a 62 slow and said you think you went lean when you dropped to a 60. This doesn't make sense to me. I believe your real world results. But the theory of it all just doesn't seem to add up to me. If I have denser air down here then wouldn't I be able to run more fuel then you since I am getting more charged air?

What have you done to your air cleaner? I am running a BAK.

here is the cover i made

 
#443 ·
did a valve adjustment today and topped of the coolant. after 800 miles of the carb cooling line leaking i only had to put in about 2 cap fulls of coolant. all the valves but 1 needed adjusted. valves are completely quiet now
 
#445 ·
Are you worried at all about the valves being quiet? I would think you'd want to slightly hear them like we normally do with an adjustment.
nope. the only time i ever heard valve noise was while the engine was idling and it was only once in a while. i adjusted the valves to the web cam specs so im not worried at all
 
#449 ·
some of the jetting difference is probably the air box.
i have the stock box decapitated and the back cut out. here is what it looks like
i also have the cover cut.

One thing concerns me a little - Air Density - Are you aware what happens to HP,
if the incoming air gets even slightly pre-heated on the way in?

That's one huge air heater behind the airbox.

Great View, by the way.

Just wanted to share the same concerns learned by many years of drag racing a few moons ago.
It's one of the reasons turbo / super-charging advanced to inter-coolers.
The concept fooled many for years before it was fully understood - about air density.

It really came full circle restoring WWII bombers with 4 radials stacked back to back behind one prop,
with built in superchargers to fly above 10,000 feet - the one main reason we won.

Maybe air diversion can be fabricated behind the box - to only grab cool air -
The cut outs look nicely done.
 
#450 ·
When do we sign you up for it? :mrgreen:
if it ever stops snowing it will be very soon

You haven't got it done yet, seems like an okay way to go.
. seems like it. from what i was told these guys bought a dyno for tuning there race bikes and run other bikes to help pay for the dyno
 
#451 ·
One thing concerns me a little - Air Density - Are you aware what happens to HP,
if the incoming air gets even slightly pre-heated on the way in?

That's one huge air heater behind the airbox.

Great View, by the way.

Just wanted to share the same concerns learned by many years of drag racing a few moons ago.
It's one of the reasons turbo / super-charging advanced to inter-coolers.
The concept fooled many for years before it was fully understood - about air density.

It really came full circle restoring WWII bombers with 4 radials stacked back to back behind one prop,
with built in superchargers to fly above 10,000 feet - the one main reason we won.

Maybe air diversion can be fabricated behind the box - to only grab cool air -
The cut outs look nicely done.
i have thought about that. the good thing about the 1300 is the top hald of the engine has fake heat sinks on it. the are rubber insulated from the engine and actually shield the air box from the heat. the only part that i have a question about are the bottom 2 holes. they are next to heat sinks for the cylinders. and they. the front one does get hot but the rear is shielded by the timing chain and does get hot. i may end up plugging the front bottom hole while its on the dyno but idk.
 
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