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

[Balduccimoto]

I read some post while googling a while ago that listed all the oem port timing/duration by degrees of rotation rather than from the top of the deck. Measuring from the top of the deck doesn't say much if it has ever been cut before. Also you can work your number closer to a 61x cylinder so you can get a accurate idea of what kind of powerband you will be obtaining. You can try find it, the name of the threas was port timing and duration. That 760 cylinder works good because its a larger sleeve and stronger casting overall. Cheap big bore

 

[sjetrider]

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.

they sell an adaptor for ADA head for that pipe. You can prolly find all ya need here on x used.
the machining will be tricky on a 760 head may want to use a cheap OEM 61x head and have them open it up to 85mm while recessing the squish area.

 

[sjetrider]

I read some post while googling a while ago that listed all the oem port timing/duration by degrees of rotation rather than from the top of the deck. Measuring from the top of the deck doesn't say much if it has ever been cut before. Also you can work your number closer to a 61x cylinder so you can get a accurate idea of what kind of powerband you will be obtaining. You can try find it, the name of the threas was port timing and duration. That 760 cylinder works good because its a larger sleeve and stronger casting overall. Cheap big bore

You wont be changing the duration of the 760 cylinder unless you open up the boost ports top to bottom. Measuring from the top relates only to the exhaust port hieght. Duration relates to distances between the exhaust and boost ports. Correct me if I am wrong here...
IMO the porting should reshape the tops of the boost ports but not make them taller, it should also clean the cast areas out within the sleaved openings and you can widen them if you see fit but the only port I widened was the exhasust port width to 78% of the bore (I beleive aprox 66mm at widest point being the top of the port).

 

[Sasquachcrap]

Originally posted by nuklear6 in another thread.....

Ok so im tired of seeing all the misinformation when it comes to the different between the 61x 701, 62t 701, and the 64x 760 (which is almost same casting as 62t and even is still stamped 62t).


All three cylinder casting measure 4.680 total height, there for i will use the measurement down from the head deck surface to show there isnt NEARLY 5mm difference


Exhaust port measured down from deck:


61x: 1.565"-1.575" (they vary)
62t 701: 1.535" .5mm difference from 61x
64x 760: 1.485" 1mm difference from 61x


Intake ports measured down from deck


61x: 2.167"-2.175" (again they vary)
62t 701: 2.185" Difference from 61x .2-.4mm
64x 760: 2.185" Difference from 61x .2-.4mm


All these measurements were taken from at least 3 of each type cylinder and are accurate to +/- .002"


The 62t and 64x cylinders are very good, mill the bottom of the casting -.030" or run it with out a base gasket, give it some compression and THEY HIT HARD EVEN ON THE BOTTOM!!!! And the 64x can SAFELY measure up to 781cc (85.5mm pistons)


Chuck Palmucci


PS 62t and 64x cylinders are both stamped 62t but the 64x has thicker sleeve skirts and has two extra gussets on the intake side of the casting.

 

[Balduccimoto]

You wont be changing the duration of the 760 cylinder unless you open up the boost ports top to bottom. Measuring from the top relates only to the exhaust port hieght. Duration relates to distances between the exhaust and boost ports. Correct me if I am wrong here...
IMO the porting should reshape the tops of the boost ports but not make them taller, it should also clean the cast areas out within the sleaved openings and you can widen them if you see fit but the only port I widened was the exhasust port width to 78% of the bore (I beleive aprox 66mm at widest point being the top of the port).

Yes duration is the degrees of rotation that each port is open. It's blow down that refers to distance the exhaust and transfer/boosts open up. After looking at the numbers, I don't think it will be beneficial to raise the roofs of the transfers, but rather reshape the roofs if needed. This was confusion on my part, I could've sworn that after lowering the cylinder, the piston at BDC would partially cover the transfers. Im learning like everyone else haha.

I found the thread that I talked of earlier, http://www.x-h2o.com/threads/21863-Port-Timing-amp-Duration-Specifications idk if it coincides with nuklear6's measurements since it's measured in degrees which made it easier for me to understand rather then measuring from the deck.

 

[Sasquachcrap]

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.

What fuel were you running at 200psi, I wouldn't be against running av gas 100LL?

 

[Sasquachcrap]

I'm reading a lot about cutting this off here and that off there but no mention of port timing. Do you know what port timing you are trying to achieve or even how to measure it? I'm honestly not trying to piss on your fire and I hope your project works well but I can't help thinking you are working with half the information you need. If you have already cut the bottom of the cylinder I would do a dummy build next and measure the port timing. Post the figures up here so we can see if you are in the ballpark.
Chris.

I guess I am working with half the info I need. I am still learning and I don't really know what port timing I am trying to achieve. I am reading none stop and trying to get my brain to soak in all this technical data. I should have named this thread "how did everyone with a 62t 760 make it hit HARD" I want to compile every thing that works for others and put it in one thread and into my motor so I can put an end to the nay sayers.

"do a dummy build next and measure the port timing"

When I get my parts back I will do just that.

 

[kevbo]

I guess I am working with half the info I need. I am still learning and I don't really know what port timing I am trying to achieve. I am reading none stop and trying to get my brain to soak in all this technical data. I should have named this thread "how did everyone with a 62t 760 make it hit HARD" I want to compile every thing that works for others and put it in one thread and into my motor so I can put an end to the nay sayers.

"do a dummy build next and measure the port timing"

When I get my parts back I will do just that.

The only way to make it responsive and have good power is with high compression, high octane, and a programable ignition. Lowering the cylinder will gain response at the expense of power.

 

[Sasquachcrap]

Well this is supposed to be a cheap build but I figure I will want to buy an ignition anyway After the carolina beach freeride I got home to find my ebox full of nice green salty water. :brap:so what would be the best no holes barred option , and then what's the best bang for the buck.

 

[Sasquachcrap]

This is my attempt in laying out the exhaust port, it's easy with the sleeves out. It's laid out on a magnetic strip. It will be kind of like the sport port templet when I get done. I want to change the shape to one similar to the second picture. When I lay it out flat it measures 49.5mm across I want to widen it to 57.5mm. But before I start to make my cut out I want to be sure that I have measured right. Is this the correct way to measure and lay it out or should I measure across the cord and lay it out across the cord if it do it that way the exhaust gets much bigger. I also may raise my transfers .065 since that's what I took off the bottom. What do y'all think?

 

[Sasquachcrap]

Hear are a few more pictures. There was .065 taken off the bottom.

 

[Sasquachcrap]

Popped them back in the oven at 500 for about 30 minutes. And slid the sleeves back in. Then aligned everything. Put the head gasket and head on and tightened it all down. Set it back in the oven for 15 minutes or so. Then when I removed them I just set them on the top of the case half to cool.

I was worried a when I started but it really was easier then I thought. The worse part was stinking up the kitchen.

 

[River Rat]

Cool thread! What pipe are you bolting on this ?

 

[Sasquachcrap]

Riva dry. Same as the factory type 4.

 

[Sasquachcrap]

Well I finished up widening my exhaust ports today. I have a question though. After laying out the stock ports on my magnetic paper I multiplied 84mm x 69% to get my widest point. Then I drew over it to modify the width and shape on the sides. This comes out to 57.96mm. I rounded to 58 ( that's still less then 70%). I cut out the templates and laid it out inside the cylinder then started grinding. After it was all said and done I will say they look nice. But my question is. I measured with a compass from side to side and then measured them with my digital calipers. The measurement is 53.6 mm. I believe thes is called a chord, but it's a big difference from 58 mm I was shooting for. Before I start the grinder back up I would like a little explanation on this. Did I do this right, what would be the proper method?

 

[Sasquachcrap]

Here are a few pictures of the degree dial I made.

I don't know much about the degrees and and duration I need, but this is what I have and I'm hoping you guys on here can advise me on what would be the best combination.

With no base gasket the
exhaust opens at 89.5 and the transfers open at 122.5 degrees

with a .030 gasket thickness The
Exhaust opens at 87.5 and the transfers open 119.5-120 degree

If I raise the transfers a little I can get them to open up around 118 degrees or so. What would be ideal?

Also how do I come up with duration and blow down time?and what should they be?

I know there are a lot of questions here but I'm trying to understand. And hopefully come up with a set of specs that someone else can use and get the bottom end braap from their 760.

 

[River Rat]

How's this going ?

 

[powerhouseperformance]

You wont be changing the duration of the 760 cylinder unless you open up the boost ports top to bottom. Measuring from the top relates only to the exhaust port hieght. Duration relates to distances between the exhaust and boost ports. Correct me if I am wrong here...
IMO the porting should reshape the tops of the boost ports but not make them taller, it should also clean the cast areas out within the sleaved openings and you can widen them if you see fit but the only port I widened was the exhasust port width to 78% of the bore (I beleive aprox 66mm at widest point being the top of the port).

This information is incorrect. If you drop the height of a cylinder -any cylinder- you will decrease the port duration of both the exhaust ports and the transfer ports, even more so the transfer ports. The bottom of the port is dictated by the top of the piston. when you drop the cylinder not only does it take longer before the piston uncovers the port, but it also closes it off that much sooner on the way back up. Total duration is the amount of degrees down+that same amount of degrees back up. Like Chuck said a 62t can be made to work great by simply deleting the base gasket, correctly porting the cylinder, cutting the new relief in the domes, and adding a bit of compression...and when your all done you will have a cylinder that has a stronger casing than a 61x to boot.

 

[Nuklear6]

With no base gasket the
exhaust opens at 89.5 and the transfers open at 122.5 degrees

with a .030 gasket thickness The
Exhaust opens at 87.5 and the transfers open 119.5-120 degree

If I raise the transfers a little I can get them to open up around 118 degrees or so. What would be ideal?

QUOTE]

You really should check your findings .030 should not change the exhaust a full 2 degrees. And def should not change the intakes 3 whole degrees. The cylinder height change will have a slightly greater effect on the degrees of the intake but not 3 degrees. My calculations say 1.8 degrees on the intake and a bit less change on the exhaust (at your starting 89.5 E and 122.5 I). You are TOTALLY defeating everything you did machining the cylinder if you are going to end your port timing at 87.5 E and 118 I. 89 E and 119 I is a good place to start for a basic port job with out getting into tricks of stepping intake port by port. Duration is easy, port is closed for 2x the degrees atdc it opens. Subtract that number from 360 and that's your duration. Example exhaust port opens at 89 degrees adtc so duration is 89x2=178, 360-178= 182 deg. Blow down is the amount of degrees from exhaust port opening to intake opening. Example exhaust opens 89 deg atdc, intake opens 119 deg atdc. 119-89=30 deg blow down. Really need to stop over thinking this thing with the basic port set up your going with your not gonna have a monster but will have a great cheap engine that out performs a 701 by multiple times...... Hope this helps

 

[Nate_D]

Not sure if this helps the OP, and correct me if I am wrong, but you should very easily be able to find what your port timing is after changing any element (rod length, stroke, cyl height) using the law of cosines.

cos-1((A^2-B^2-C^2)/-2BC)
A = rod length
B = 1/2stroke
C = rod length + 1/2stroke - distance from TDC to port roof

If we don't know the distance from TDC to port roof, we can find that by using the law of sines and the known port timing of a stock, unmolested motor.

Port height = A+B-(A/sin(a))*sin(180-a-sin-1((sin(a)/A)*B))
a = known port timing (degrees ATDC)
A = rod length
B = 1/2stroke

C = A+B-X+N
X = Port height
N = modification to port height (if removing 1mm from cyl base, N is negative)

If there's any errors in that, please correct me. This is just off the top of my head. I have a spreadsheet somewhere setup to compare the differences made to port timing by changing stroke, rod length, cyl height, etc. If anyone would find it useful I can dig it up. If all of this is already known and repitive, just ignore me and move on with the build. I'm interested to hear your results.