Taper bored 38's on a 845cc Big Bore?
- Thread starter OCD Solutions
- Start date
LBE
Eddie Would Go.
- Location
- Charlotte, NC
Hard to say the diff. I would say they are pretty close.
I'll try to post pics of the barrel of my 38's. They look to have quite a bit of machine work, as well as removing the bomb site.
X2Addict, I hear ya. Art starts expalining why he does this and that and it sounds good, but over my head.
Bottom line, I have never known Art to steer anyone wrong. He said, "this is what I reccomend", and I said: "ok, do it".
masterblaster
X-H2
below is copy and paste of some other relavent info
I had a Riva 46mm single carb manifold "kit" on one of my 62T motors and had a fun time trying to get it dialed in. It seemed to have about the same performance as the dual 44's that were on a R&D manifold (from 1/3 throttle and up), but the low speed (idle to 1/3 throttle) was the area of operation that I never got right. One of the issues was that the pop-off ended to be about 12psi, and with that low pop, the motor vibration (more or less,and frequency) at different RPM's would shake the needle from the seat and mess with my settings. The extra fuel consumption was probably because of this. The AM carbs some of you guys are running with higher pops might be less prone to this issue.
I sold the manifold, and bought another 46mm and made a set that (so far) meters more precise (higher pop-off) and offers better fuel economy. I really wanted to run a single for simplicity, but I couldn't get it to work right. For now I'm dealing with them (the duals).
Here it is from Art himself:
The 44mm Blackjack will flow more air than the unmodified 46 Mikunis. If you are not dealing with very big engines and not using total loss and race fuel compression then I question the need to go bigger than the 44's. For freestyle the 44's are more forgiving than the 46's when you don't have the big ccs, compression or building a full-on radical engine. If you had a properly set up normal big bore and your main concern was bottom end response then the advantage of the 46's would only be at midrange and higher rpms and you might not need that depending on your riding style.
If I build an engine that is say for example an 85 mm stock stroke engine and the customer wants the best bottom end possible with no concern about top speed I would do the 44 Blackjacks. You must remember that just because it is a 44 mm does not mean that it is not a high flowing set up. The difference between a set of stock 44's and a set of Blackjack 44's is night and day. This becomes more apparent the more modified the engine is. We do build engines using our 48.3 mm Blackjacks but the whole combo has to be perfect for the type of riding and the type of modifications for the end result to be the best. Even for most aftermarket cylinders running total loss and mag pumps and race fuel the 46 mm Blackjacks are hard to beat. The nice thing about the 44mm Blackjacks are that they are priced right. Just to let you know we have done stock ported 701s with pipe and impeller running 185 psi and the 44mm Blackjacks worked perfect with out loading up and offered great response even after idling for more than 30 seconds.
Thank you
Art
__________________
I had a Riva 46mm single carb manifold "kit" on one of my 62T motors and had a fun time trying to get it dialed in. It seemed to have about the same performance as the dual 44's that were on a R&D manifold (from 1/3 throttle and up), but the low speed (idle to 1/3 throttle) was the area of operation that I never got right. One of the issues was that the pop-off ended to be about 12psi, and with that low pop, the motor vibration (more or less,and frequency) at different RPM's would shake the needle from the seat and mess with my settings. The extra fuel consumption was probably because of this. The AM carbs some of you guys are running with higher pops might be less prone to this issue.
I sold the manifold, and bought another 46mm and made a set that (so far) meters more precise (higher pop-off) and offers better fuel economy. I really wanted to run a single for simplicity, but I couldn't get it to work right. For now I'm dealing with them (the duals).
Here it is from Art himself:
The 44mm Blackjack will flow more air than the unmodified 46 Mikunis. If you are not dealing with very big engines and not using total loss and race fuel compression then I question the need to go bigger than the 44's. For freestyle the 44's are more forgiving than the 46's when you don't have the big ccs, compression or building a full-on radical engine. If you had a properly set up normal big bore and your main concern was bottom end response then the advantage of the 46's would only be at midrange and higher rpms and you might not need that depending on your riding style.
If I build an engine that is say for example an 85 mm stock stroke engine and the customer wants the best bottom end possible with no concern about top speed I would do the 44 Blackjacks. You must remember that just because it is a 44 mm does not mean that it is not a high flowing set up. The difference between a set of stock 44's and a set of Blackjack 44's is night and day. This becomes more apparent the more modified the engine is. We do build engines using our 48.3 mm Blackjacks but the whole combo has to be perfect for the type of riding and the type of modifications for the end result to be the best. Even for most aftermarket cylinders running total loss and mag pumps and race fuel the 46 mm Blackjacks are hard to beat. The nice thing about the 44mm Blackjacks are that they are priced right. Just to let you know we have done stock ported 701s with pipe and impeller running 185 psi and the 44mm Blackjacks worked perfect with out loading up and offered great response even after idling for more than 30 seconds.
Thank you
Art
__________________
Polish jet pilot
4aces4aces4aces4aces4aces
- Location
- Warsaw, Poland
Bringing the thread back to life: what you guys think would give me more overall power: taper bored oem 38's or single 48mm BJ (I need to get ATP manifold). My motor/pump setup:
- 62T case
- ported 61X cyl with 82.5mm sudco piston
- EPIC
- Modded Bpipe LTD(enlarged)
- increased compression
- oem 2008 prop cutback by 2,5mm
- bored nozzle to 84mm + FS cone
- carbon tech LT reeds + angled manifold spacer
All info greatly appreciated
- 62T case
- ported 61X cyl with 82.5mm sudco piston
- EPIC
- Modded Bpipe LTD(enlarged)
- increased compression
- oem 2008 prop cutback by 2,5mm
- bored nozzle to 84mm + FS cone
- carbon tech LT reeds + angled manifold spacer
All info greatly appreciated
Last edited:
Cannibal
Tasty Human
- Location
- Summit Lake, WA
After talking with Art, he says his taper bore 38s are great up to and including a 760 ported and modified big bore. He says the low end punch is great. I'd almost think a BJ 48 would be too much carb for your engine. I don't have any direct experience with it though.
Bigfish
Bigfish
- Location
- North Carolina
I'm running a set of Jetworks mod 38s on Erica's 701 and they work great ,.One of the guys that ride with us has the same setup but he is running 44sbns and the 38s hit harder and seam to make more power on the 701.Both skis have the same prop ,portwork by Art ,bpipe,same compression , and msd enhancer.I have not tried a 48bj on her ski but i have tried one on my sxr and i went back to the dual bj 46s.I think the mod 38s would be my choice over the single 48bj just my 2 cents ,give Art a call and ask him.
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Freakrider
X247
- Location
- Tampa Bay area
Does anyone know if Blackjack carbs can be ordered/work well without the velocity stacks so you can bolt the stock airbox on ?
chriselmore_1
high on resin
- Location
- san jose ca
those carbs were designed to run those adapters. I have some xscream modded 38s on a on a 84mm 61x cylinder and this motor rips! Pulls waaaay harder than stock 38s
Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
gonna say no. The annular discharge portion of the carbs is part of the bell housing.
Freakrider
X247
- Location
- Tampa Bay area
Called him, he said he can not make blackjacks without the velocity stacks, it's part of the design...he knows his stuff...prolly 50 min phone call of info... Wow ! He said BJ 44's will flow better than reg Mikuni 46's !
Matt you still running blk-jacks ?
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Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
- Location
- St.catharines, Ontario
I'm just curious if money was no object who's carbs are the best?
Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
Mark Erickson builds the best motors..........
WILKEY
SO FAR CHANGE SUCKS!!!!!!
wbwbwhhahahahahha