Freestyle Looking for 62t 760 freestyle specifics 64x Decking Porting

[Sasquachcrap]

I've been reading for 3 weeks now and have accumulated a ton of info. Most every one said build a 61x if you want bottom end, we have got that covered. But I have a FREE 760 so that is what I want to build. I would like to document this motor build and post plenty of pictures and let every one know how it turns out. Maybe it will be good enough to be a how to. It will be done on the CHEAP. I've read Matt_E's home porting thread and also A. Graham Bells' two stroke theory. Tons of other threads all saying similar things. I heated the cylinders and dropped the sleves out and am about to drop my cases off at the machine shop to have the bottom decked and i want to know just how much to tell him to take off. The plans are to deck the cases re-cut the squish band in the head and bump the compression, port the cylinders and cases. Wow doesn't seem like that much when I write it out....HAHA I have thought about using the sport port templates but if all i need to do is open the exhaust up to 68% to 70% I feel like I can lay that out myself. And if I do which ones should i get is there any difference in the 701's and the 760's. Again I would like to hear from people who have done this and can/want to give up some info. I read where someone posted the port measurements of the 61x and the 760 and now I cant find it. But I did take notes when I read it and know that there were .080 difference to the top of the exhaust port. Is 2 mm the magic number I also read where nuklear6 said that was a bit to much, he recommended 1.5 mm. If there is any one out there that can/will inform me I would be very great-full. And I do realize that i have to run the right prop for this setup. In my notes I have either a 10/16 or 9/15 hoping some one can steer me to the best one it will be in my sn until i scrape together the funds for a bob g3. I know I am forgetting some info but I cant type as fast as my brain thinks.:Banane25:

Oh yea I about forgot do I need to grind the transfers back up after lowering the cylinders and if so how much?



So the only thing I'm sure of is my squish band. .045-.050

 

[weston]

If you popped the sleeves out you can just deck the bottom of the cylinder 1.5mm. No need to machine the cases. Have domes cut for piston stick out and desired compression. After the cylinder is machined, install sleeves check for square clean up the ports and assemble the motor. I can't help much on exhaust porting other than you want to widen it about 1/8" per side don't quote me on that.
i run a 11/17 hooker in a Solas 144 on a similar motor.

you will want to swap the electronics over to 62t

 

[Sasquachcrap]

Thanks if I said cases I meant cylinders. Did you build your motor yourself or have it done for you? Is it ported? Hows it hit off the bottom? I will be running a Stock pump for now?

 

[Half flip95]

don't do it bro!

 

[Sasquachcrap]

Have you done it?

 

[Sasquachcrap]

I though I would load some pictures of the cylinder tare down and I scribed a few lines on the top or the cylinders to be sure I get the sleeves back in just the right spot. They will be decked later to slick them up.

 

[Sasquachcrap]

 

[Sasquachcrap]

The cookies are fresh out of the oven.

 

[loictahiti]

Subscribed right now ;-))

 

[Sasquachcrap]

Oh yea I measured my squish band pre tare down using a ball of solder the pto was 2.75 mm and the stator side was 2.20. Those numbers seem like a lot even for sloppy factory assembly. But I checked them several times. Is the ball of solder a viable way to measure or do I need a softer media? I thought it would be a good idea to know my squish before I started cutting the domes even though I know I will need to measure it again.

 

[Balduccimoto]

I have been thinking of doing this to a SXR motor. I was thinking to raise the roofs of the transfers now since cylinder is dropped, the piston should cover a little bit of the transfers? Definately pay close attention to the roofs of the transfer if you do decide to do this. Im subscribed, I really dont have any experience in this, im just speculating so take my advice as a grain of salt. I had a 62t/62t this was done to and it made some good power. If you cant cut the domes good with a nice squish band; ada racing makes custom domes just tell them how much negative cut.

 

[d_moss]

http://www.x-h2o.com/threads/105915-Le-RN-big-bore-850-color-change-build&highlight=color+change

more info for you. idk if it will help

 

[weston]

I had the machine work done. The motor runs well.
TBM wheel,msd enhancer,62t electronics,stock 44mm carbs,190psi,85.5mm bore, "POS" Solas 144,hooker 11/17.
very good off idle. Just as snappy as my T motor.

 

[madness maker]

Few months back I did a 760 cyl setup on a 62t bottom/electronics, decked the base 2mm, recut the ada domes,185psi, used sport port templates, 85mm bore, ported cases,filled in the fingers in reed area of cases(epoxy) made some reed stuffers from some kawi 750 stuffers. stock 38's with a power factor pipe. 9/17 impeller on solas mag, 85mm nozzle w/short cone,stock cdi w raised rev limit. Prob could have def benefited from a cdi. Setup is In my old(now my friends) -2 glass freak. Runs good, hits pretty quick. Kinda on/off power band, I fig that's due to pf pipe.

Sent from my Blackberry 9650 using Tapatalk

 

[Sasquachcrap]

Well I dropped off the cylinders this morning. I decided to cut .065 off the bottom, I guess if I want to go lower I can Change my base gasket or run with out one and just use 1211. As for cutting the squish in the head does anyone have any do it yourself ideas or should I just send it off to have it done. I have 2 64x heads so I might sacrifice one to see if I can make a tool to chuck up in the drill press and sand or grind the squish deeper. This thread will either be a "how to" or a "how to not".
I was hoping to hear from matt_e or some one with experience with porting. Still wandering what I should do with the transfer ports and the boost port. Widen them or raise them back up or both?

 

[yamanube]

The stock 760 head has slightly different dome shapes to reduce engine heat in the rear cylinder due to (I believe) crank twist. An aftermarket head might be a better place to start.

 

[sjetrider]

I have done it and it worked well.
Actually that motor is for sale on here not I built it 2 years or more ago and I loved it in my carbon Rok hull.
I decked the cylinder 1.5mm and went into the dome 1.25mm decreasing the squish to aprox 1.27mm ran it at 200 compression
Its simple really your exhaust port ends up somewhere around 38mm hieght if I remember correctly. You gain bottom end but keep the nice port duration for mid range hit as well.
To prove to myself it was my work that showed the results and not compresion overcoming porting I ran it at 180comp and it hit realy nice there as well but me wanting more I put it back to 200 to maximize performance.
Its not powervalve power but definately more power than a ported regualar T or U cylinder offers on bottom end.
its cheap so why not do it IMO, decking $30 cutting domes $60 and the rest is time in porting, no brainer you spend that on freaking flame arrestors.

I personally would go with ADA head and domes, it can be done with stock head for sure but more difficult and you will need to pay attantion to squish angle a little more.
Or use an OEM 61X head where compression is set the same in front and rear from factory.
It is much more difficult to do the machine work on an oem head and hell gaskets are expensive, find a used or new ADA where the domes can be cut in a simple lathe.

 

[Sasquachcrap]

Well for now I want have to run the factory head because I am running a riva dry pipe and my lord mounts bracket mount to the top of the head.

 

[yamanube]

It has been broken down somewhere, I'm sure MattE can dig it up.

 

[Sasquachcrap]

I recall the measurements being posted some where in the past. But can't find then now. The exhaust port in the 61x was 2 mm or .080 lower then the 64x 760.