I need some knowledgeable opinions on 61x versus 62T -64X cylinders

[E350]

@WFO Speedracer This fits within your title of "I need some knowledgeable opinions on 61x versus 62T -64X cylinders"

While @waxhead is thinking about how to organize his thoughts on how to write his treatise on modding the 62t couch engine for freestyle power, here is a little tech article I found on his waxracingproducts.com website about cylinder squish:

Unlock Free Horsepower: Why Squish Clearance Is the Most Overlooked Po

Squish: The Simple Secret to Power, Cooling, and Reliability in Two-Stroke Engines If you’re building or tuning a two-stroke engine, there’s one thing you absolutely need to get right: squish. It sounds weird, but it’s one of the most important parts of how your engine makes power, stays cool...

www.waxracingproducts.com

And hopefully this will push wax to get his toroidal shaped domes to market quicker:

Wax Racing Billet Head kit

Upgrade your jet ski with a high-performance billet head from Wax Racing—designed for durability, performance, and ease of use by riders who wrench on their own skis. Available as a Complete Kit or Individual Parts Whether you're doing a full top-end build or just replacing a component, the Wax...

www.waxracingproducts.com

And dude, where's the bolt-on larger pump for the FX-1? (Just pushing, because I am not getting any younger . . .)

 

[subnsxr]

Hey Watcon, I've been running stock 44's, Art at Jetworks changed the angle of the throttle plates and that's it, they run on a 61X/62T big bore setup 771, what aftermarket carbs would you recommend? Motor has ported cyl and ported case, Bpipe, MSD enhanser and Solas BH 12/18. prop. thnx!

 

[WFO Speedracer]

Everyone has their preference in carbs , me I like Blackjacks , someone else will say OEM 44'S , someone else will say Full Sprectrums and so on and so forth , what really matters is if you can get the carbs you have properly set up to get the most out of your setup.

 

[kevbo]

Kevbo while I appreciate your response it's always the same, pump load , pump load , pump load , sorry but there are way more variables to consider than just the pump load , I am just saying it's time to get some new material.

I would talk about carburetors, if it made as much an improvement. Do you know your port heights? How far will your pipe rev before it goes rich? What RPM are you turning? The last question is answered by the impeller. It’s the one item that is relatively easy to change. Yet nobody wants to do it

What is your definition of a flat impeller and what is considered high port?

A flatter impeller is one that needs to be bent that way, because nearly everything available is too steep. This includes ALL Solas 144 impellers. You could get a Skat or Hooker that was shallow enough for more unusual applications. High port means anything over a stock 61x cyl. Once the cylinder and pipe are installed, all that’s left is adjusting the load to match. There’s not much difference in high speed performance if the impeller is too steep. The difference in power response is much more pronounced. The best race impeller will be noticeably slower to respond at low speeds. I have ridden a couple of Superjets that were so bad you could light a cigarette waiting for the pipe . All they needed was some blade bending, then they were screamers.

 

[fastgtfairlane]

The 62t in my opinion is the best of the 61x and 64x cylinders. It still has decent port timing stock, the casting and sleeves are thicker as well. Im running a 62t setup in my superfreak that lpw did the port work on.. im running a stock 44 manifold that I filled the crossover tube. Tried the oem 760 carbs but didn't like them once I had the engine work done. You can also get a .010 base gasket which will slightly increase the compression and lower the port timing. I have the a/m 44s that mikuni sells that have an extra bleed hole and flow more fuel in the low speed circuit. If I were to do it again, id just go with 46s because they work on everything from a 701 to 1000cc dasa.

I know kevbo always goes back to pump load but hes exactly right. Especially with a mag pump and these current big hub impellers. They load the engine super hard at lower rpms so getting the pump right is critical to optimal performance.

 

[waxhead]

my carb choice goes like this and its worked out of your budget. 1 being no budget 4 being best budget 38s oem44s 46 mikuni and lastly novi. If you have 38s and they dont need any work then run them. If they need to come off for a rejet then sell them to some one who likes them. from then on its the 760 carbs and these are great setup for some one with limited budget. from there its to the unsung hero which is the 46mm mikuni. when you have a heap of money then its straight to 48 novis. now on the that story

 

[WFO Speedracer]

My choices are defiantly dictated by a budget of zero dollars and I have OEM dual 44's so you know what I am going with.

 

[waxhead]

How to Turn Your 701 62T Into a Real Mini Weapon​

Start with a stock Yamaha 701 62T. First job: remove the stock head and throw it away. Next, pull off the twin 38 mm Mikunis — they’re only really useful for a lites-class rider, so sell them.

Step 1: Cylinder Head & Squish​

Buy yourself an aftermarket head. When you measure squish, you’ll probably find Yamaha has it around 1.4 mm. That’s too wide — you want it in the 0.8–0.9 mm range. To get there, you’ll need to machine the cylinder.

Step 2: Port Work​

Go to the Wax Racing website and download one of the printable port-map guides. If you want to keep the stock exhaust timing, that’s fine — I can even provide a stock-timing map with just the wider exhaust port. But I recommend raising the timing; the blow-down timing on this cylinder is not up to speed unless you widen the exhaust port.

Step 3: Carbs & Intake​

Choose your carbs carefully:

• My pick is 46 mm Mikunis on a Wax Racing velocity manifold.
• OEM 44 mm carbs also work great. ( just not as great)
• Aftermarket 44s aren’t worth it — for the same cost, go 46.
  If you can stretch to V-Force reeds, do it.

Step 4: Reassembly & Compression​

Once the cylinder is milled and ported, put it all back together and re-check your squish. Aim for 190–200 psi cranking compression — it might sound high, but with squish set correctly it’s safe on pump fuel. Just don’t try pulling a really tall prop everywhere, and you’ll be fine (I agree with Kevbo on this).
When you rebuid your engine then dont bother trying to bore it to its max bore. you only increase the heat path from the centre of the piston to the outer and are making more unreliable with very little gain. This is a budget build remember

Step 5: Ignition​

Buy a Zeel ignition and run the Wax Racing V3 curve.

Step 6: Exhaust​

Yes, we make pipes — so I’ll say grab a Wax Racing Thruster pipe (and yes, I can already hear the “made in China” comments). For all-out ballistic performance, fit the SXR chamber, though you’ll need to massage it a little to fit in a SuperJet. On the header screws, run the top and mid closed, and the bottom open about half a turn.

Step 7: Propeller​

Run the lowest-pitch Solas prop you can find. You’ll lose 2–3 mph up top, but you won’t care once you feel the holeshot and bottom-end punch. Im with Kevbo on this one !!

---

This isn’t a full-on freeride engine, but it’s a solid performer. It’ll run with plenty of builds that have had far more work (and often been tuned by people with no real idea). This is the kind of engine that has everyone on the beach calling it a “freak motor” — and no one quite knows why it goes as hard as it does.

 

[waxhead]

The 62t in my opinion is the best of the 61x and 64x cylinders. It still has decent port timing stock, the casting and sleeves are thicker as well. Im running a 62t setup in my superfreak that lpw did the port work on.. im running a stock 44 manifold that I filled the crossover tube. Tried the oem 760 carbs but didn't like them once I had the engine work done. You can also get a .010 base gasket which will slightly increase the compression and lower the port timing. I have the a/m 44s that mikuni sells that have an extra bleed hole and flow more fuel in the low speed circuit. If I were to do it again, id just go with 46s because they work on everything from a 701 to 1000cc dasa.

I know kevbo always goes back to pump load but hes exactly right. Especially with a mag pump and these current big hub impellers. They load the engine super hard at lower rpms so getting the pump right is critical to optimal performance.

46 mikuni are the unsung hero. i used them on my 550 i raced at the worlds. The ski was fast and responded well. The rider not so much haha

 

[waxhead]

I would talk about carburetors, if it made as much an improvement. Do you know your port heights? How far will your pipe rev before it goes rich? What RPM are you turning? The last question is answered by the impeller. It’s the one item that is relatively easy to change. Yet nobody wants to do it

A flatter impeller is one that needs to be bent that way, because nearly everything available is too steep. This includes ALL Solas 144 impellers. You could get a Skat or Hooker that was shallow enough for more unusual applications. High port means anything over a stock 61x cyl. Once the cylinder and pipe are installed, all that’s left is adjusting the load to match. There’s not much difference in high speed performance if the impeller is too steep. The difference in power response is much more pronounced. The best race impeller will be noticeably slower to respond at low speeds. I have ridden a couple of Superjets that were so bad you could light a cigarette waiting for the pipe . All they needed was some blade bending, then they were screamers.

Best way i know to blow up an engine is to over prop and make it build huge heat. Then you get to blame everything else as to why it blew up when in reality you were just trying to driver everywhere in top gear.

 

[fastgtfairlane]

46 mikuni are the unsung hero. i used them on my 550 i raced at the worlds. The ski was fast and responded well. The rider not so much haha

i agree and wish i wouldve gotten the 46s instead of the 44s when i bought them. im also very curious of how your manifold compares to the stock manifold with the crossover filled. im sure the increase will be more noticeable the bigger engine you go but also curious to see how it will change on a 701.

do you know what the squish clearance is with the ada 35cc domes? my compression was 195 per hole with 35cc domes and a .010 base gasket. i never measured the squish on my engine.

 

[waxhead]

i agree and wish i wouldve gotten the 46s instead of the 44s when i bought them. im also very curious of how your manifold compares to the stock manifold with the crossover filled. im sure the increase will be more noticeable the bigger engine you go but also curious to see how it will change on a 701.

do you know what the squish clearance is with the ada 35cc domes? my compression was 195 per hole with 35cc domes and a .010 base gasket. i never measured the squish on my engine.

If you’re running OEM 44s, the stock manifold will be fine. In fact, I’d rate it as the second-best manifold out there. All the work I used to put into modifying the OEM 44 manifold has already been built into our design—plus we’ve added a few extra improvements on top.

I also prefer to machine the cylinder, since a 0.010" gasket isn’t always easy to find, while the stock base gasket is practically indestructible.

And if you haven’t already, check out the article I wrote on squish—it’s one of the most important factors to get right.

 

[E350]

Do you prefer oem Mikuni SBN 46 carbs or aftermarket Mikuni SBN 46 carbs?

How do you measure squish.? It is not in your Tech article.

Can you avoid shaving the cylinder by buying your aftermarket head with 35cc domes and then installing your toroidal-shaped domes when you release them?

 

[waxhead]

Do you prefer oem Mikuni SBN 46 carbs or aftermarket Mikuni SBN 46 carbs?

How do you measure squish.? It is not in your Tech article.

Can you avoid shaving the cylinder by buying your aftermarket head with 35cc domes and then installing your toroidal-shaped domes when you release them?

You’re talking about I-body carbs there—they’re really just emission carbs and best avoided unless you’re in the alloy scrap business.

The main issue with the 701 is that the cylinder is too tall to get the squish right using domes alone. A 0.010" gasket might get it there, but I’ve never tried it myself. I prefer to stick with the OEM base gasket, as it’s reliable and easy. The simple way to check is to pull the base gasket out and test fit it. I usually do this without the piston rings installed (if they’re new) since it makes sliding the cylinder on and off much easier.

Squish is measured with a piece of solder, and there are plenty of good videos out there showing the process step by step.

 

[E350]

So, checking for understanding. Just to be clear, for 46mm carbs, you prefer aftermarket Mikuni 46 SBN carbs, correct?

 

[waxhead]

So, checking for understanding. Just to be clear, for 46mm carbs, you prefer aftermarket Mikuni 46 SBN carbs, correct?

Mikuni Dual Carburetors 46mm Performance Package

Mikuni Dual Carburetors 46mm Performance Package Modified in house dual set of Mikuni 46mm carburetors. These can be set up to the specifications of a Yamaha Superjet 701-900cc. These carbs are ideal for a mild set up motor with a pipe and ignition upgrade or an up to 900cc aftermarket engine...

showtimefreestyle.com

 

[WFO Speedracer]

Or you can use the old Kawi 650 trick and just 1211 the cylinder to the cases , no gasket, I have been running my 650's that way for years with zero failures , you get a slight bump in compression , tighter squish and slightly lower the exhaust timing that way .

 

[waxhead]

Or you can use the old Kawi 650 trick and just 1211 the cylinder to the cases , no gasket, I have been running my 650's that way for years with zero failures , you get a slight bump in compression , tighter squish and slightly lower the exhaust timing that way .

Yup i have done that before, on stroker motors when you need to get the timing lower, bascally pretty much any stroker motor using an oem yamaha cylinder

 

[E350]

Mikuni Dual Carburetors 46mm Performance Package

Mikuni Dual Carburetors 46mm Performance Package Modified in house dual set of Mikuni 46mm carburetors. These can be set up to the specifications of a Yamaha Superjet 701-900cc. These carbs are ideal for a mild set up motor with a pipe and ignition upgrade or an up to 900cc aftermarket engine...

showtimefreestyle.com

@waxhead HST will put whatever jets in at whatever popoff settings I request.

So, if I buy your Thruster Exhaust for a 62t, and your intake manifold for the 62t and your manifold plate adapters for 46mm dual carbs,

What jets and what popoff settings (etc?) should I request from HST?

 

[MarkWalker]

Did anybody check with SUPERJET-113 to see if makes the 0.010 base gaskets?