Super Jet Bottom end opinions?

[CRJ]

This winter i'm putting together a big bore motor, and have some questions as this is my first go at this. The top end is a ATP head, with 35cc domes (also have 40cc), 61x cylinders, resleeved and ported, bored to 84.5mm (762cc) with wiseco pistons. I want to stick to a 44mm mikuni, but its the bottom end that has me up in the air (pardon the pun). Regardless i need to bore the cases, to fit the sleeves. I currently have a 61x bottom end. I was considering trading some parts for a 62T bottom end with dual 46mm intake. both need reeds regardless, and i want to settle on something before i order a gasket kit.

the motor is going in a basically stock mint square nose hull, till i can afford an AM hull. I will have a solas 12 vane, and hooker 11/17 prop behind the motor. If i went 62t, i would have to get the new bar to run dual 44's off single machines, if i went 61x my current carb is highly jetted enough to handle the requirements of the big bore (i think) 160M 120P. ski is mainly to learn on and grow with, and i have no problem going to 62t next year.

So, what do you think? if i went 62t, it comes with a 61x top end that i would bolt to my 61x bottom end and drop into my sit down that has a 650 in it now.

Thanks for any advice!

 

[FlightPlanDan]

Sorry if I'm not understanding completely, but I'm having trouble finding the actual question in your post.

The debate will likely go on forever when it comes to 61X vs. 62T and low end hit. The truth is..... get ready......
They are both pretty darn good when dialed in right. Lots of folks forget the pump when defending the single or dual carb issue. "My buddie has a 61X that smokes my 62T" but the buddie has a mag pump and is leaned out to the point of destruction.

Sounds like you've got a really good start on things. Just ride as much as you can. The ski will tell you what it needs.

 

[CRJ]

yea i over complicated that one. What i want to know is, will a 62t bottom end be a large step above the 61x, or its is it similar?

am i better staying with 61x bottom and single carb or going to 62t bottom end and dual 44's?

 

[FlightPlanDan]

here's an old thread that might help.

http://www.x-h2o.com/threads/45410-61x-VS-62-T

 

[CRJ]

so what im picking up is theres no advantage or point to go with a 62t case, correct?

 

[waxhead]

Why do you think Yamaha went to the 62t cases. Why do you think they used to cut the intake of the 61x cases and fit Kwai style intakes. It's because it was/ better

 

[Quinc]

How much more power can you get out of a big bore 61x vs a standard bore 61x?

 

[wanderer1]

How much better on just a rec boat? None IMO. Are you gonna take existing setup and switch cases to create an arm yanker, no. I did the swap a few years ago on my B1's. Is it better yes, was it worth the dough for bayou cruisers no. I you are eventually take the motor farther than yes the 62T cases will better support future upgrades. Wax- when they port the intake area of a 62T they still make them into a Kawi lol. I also think that Wax and I will agree that the true case upgrade from the 61X is the 66E case. As for the cylinder, did you install bigbore sleeves? If not you are on your last bore/leg anyway on those sleeves. I guess what I'm getting at is a 61X61x ported with a single 46/48 and a Type4 is a great all around motor that won't break the bank and if I had it to do over I would've stayed 61X for the recreation application that I did the swap for.

 

[wanderer1]

How much more power can you get out of a big bore 61x vs a standard bore 61x?

Been discussed a lot. Search or new thread maybe. Quick answer is like 4-6hp per 1mm bore average (if I remember what some guy said lol). Problem is loss of transfer port area on stock cylinders so is the gain really there, idk. Worth it? Opinions vary. EDIT- I'd get cc's from a crank before big bore sleeves for sure.

 

[kevbo]

so what im picking up is theres no advantage or point to go with a 62t case, correct?

There is an advantage, but with smaller displacements, it is expensive for what you get. Basically the 62T case with 44s will hit a little harder than a 61X case. The difference becomes more noticeable with higher port cyls and/or larger displacements.

 

[McDog]

If you can trade parts to get it then yes, it is worth it.

 

[High Speed Industries]

Just find a set of 760 cases with carbs. The cases are bored to fit bigger sleeves and they would come with dual 44s. Just spend a little time tuning and it will hit really hard.

 

[powerhouseperformance]

There is not a ton of difference on engines 760 or smaller guys. If we were talking about a high rpm race motor I wouldnt be saying this, but unless you are racing a 61x bottom makes a pretty killer setup. A 61x case that has been ported correctly with a dual carb setup will be almost identical to a 62t with good aftermarket reeds on the cages. We've built a ton of them with almost the same mod setup besides the cases. If you go with a single 44 intake you are really going to limit the achievable top rpm because of the intake reverb. The R&D dual intake for the 61x works really well.

 

[wanderer1]

Glad you came on and said it Zack.

 

[waxhead]

Its shame they dont make v-force reeds for the 61x as these are a great gain. Each to there own but I dont encourage anyway to use 61x cases.
However different horses for courses

 

[CRJ]

How much better on just a rec boat? None IMO. Are you gonna take existing setup and switch cases to create an arm yanker, no. I did the swap a few years ago on my B1's. Is it better yes, was it worth the dough for bayou cruisers no. I you are eventually take the motor farther than yes the 62T cases will better support future upgrades. Wax- when they port the intake area of a 62T they still make them into a Kawi lol. I also think that Wax and I will agree that the true case upgrade from the 61X is the 66E case. As for the cylinder, did you install bigbore sleeves? If not you are on your last bore/leg anyway on those sleeves. I guess what I'm getting at is a 61X61x ported with a single 46/48 and a Type4 is a great all around motor that won't break the bank and if I had it to do over I would've stayed 61X for the recreation application that I did the swap for.

There is not a ton of difference on engines 760 or smaller guys. If we were talking about a high rpm race motor I wouldnt be saying this, but unless you are racing a 61x bottom makes a pretty killer setup. A 61x case that has been ported correctly with a dual carb setup will be almost identical to a 62t with good aftermarket reeds on the cages. We've built a ton of them with almost the same mod setup besides the cases. If you go with a single 44 intake you are really going to limit the achievable top rpm because of the intake reverb. The R&D dual intake for the 61x works really well.

Thats what im looking for.

Thank you for the advise! the motor is pure freeride, in a stock SN. The 61x cylinders have been resleeved, so i can bore to 86mm. it was also ported by one of the guys at cold fusion from what im told.

so i will see limitations at high rpm, with the single 44 on a 61x case. if thats so, i dont mind, it will very rarely see top rpm.

 

[oside-tanner]

I know my advise isn't as creditable as zack from powerhouse factory, but Last year I stepped up from a 61x cylinder and 61x cases with a taperbored a 44 carb to 62t cases on dual 38 carbs, both setups were 701cc, same pipe, same impeller, same intake, same pump. both setups make very similar power overall, but power on the dual setup is much more linear and I believe it has a stronger mid section. If you have your eyes set on a much larger setup down the road I would say upgrade, but with your current setup it's not going to make that much difference

 

[powerhouseperformance]

Its shame they dont make v-force reeds for the 61x as these are a great gain. Each to there own but I dont encourage anyway to use 61x cases.
However different horses for courses

I totally hear where you are are coming from wax, back in the day we would swap a whole sxr ignition system back to an 03' or sxi analog system just because we felt it made a small difference in how well a "stock" class race boat went. If we are splitting hairs or confined to rules t cases will make for a faster boat, but for a guy who would spend the swap money on porting vs. converting it is a way better return on investment. I agree - it would be pretty killer if they made a vforce 3 for a 61x!

 

[powerhouseperformance]

I know my advise isn't as creditable as zack from powerhouse factory, but Last year I stepped up from a 61x cylinder and 61x cases with a taperbored a 44 carb to 62t cases on dual 38 carbs, both setups were 701cc, same pipe, same impeller, same intake, same pump. both setups make very similar power overall, but power on the dual setup is much more linear and I believe it has a stronger mid section. If you have your eyes set on a much larger setup down the road I would say upgrade, but with your current setup it's not going to make that much difference

More than likely Tanner, the stronger mid to top that your feeling is coming from isolating the cylinders from one another on the intake. If you would have dropped a set of dual 38's on an R&D manifold and kept the 61x chances are it would have felt pretty close. Singles seriously limit your upper mid to top end potential. A set of well tuned dual stock 44's will crush a single 48mm novi on the same engine for high rpm pull...been there done that, tested till the point of exhaustion

 

[CRJ]

exactly the info i need! Thanks PHP!