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Old 12-13-2017, 02:52 PM   #91
JerryHawk250   JerryHawk250 is offline
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I have the same burrs. You can buy a good Wen Rotary tool for less that $20. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
And these work well for cleaning up. https://www.amazon.com/SE-82331TF-30...2PW5D3RJG1KF1K
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Old 12-13-2017, 04:01 PM   #92
Megadan   Megadan is offline
 
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I may have to snag a set of those diamond burrs. Thats a great price, and I like the selection of shapes.
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Old 12-13-2017, 10:39 PM   #93
Musictrek   Musictrek is offline
 
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Quote:
Originally Posted by JerryHawk250 View Post
I have the same burrs. You can buy a good Wen Rotary tool for less that $20. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
And these work well for cleaning up. https://www.amazon.com/SE-82331TF-30...2PW5D3RJG1KF1K
I ordered that tool. That looks like a dremel copy


 
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Old 12-13-2017, 11:04 PM   #94
Musictrek   Musictrek is offline
 
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Quote:
Originally Posted by Megadan View Post
Just for comparison, a side by side before and after so far. Note that in the after picture you can actually see the end of the valve guide, where the before picture it is hidden. A lot of material got removed around the top of the guide.
I took a valve side shot to show it a little better. I still want to do a bit more work around the sides of the guides, and then blend it all together a little more, but I want to try and remove as little material from the bowl as I can, so a little of that recess around the bottom of the guide will likely stay where it is. We will see though. My main reason for this is to try and maintain some velocity. The port opens up quickly between the seat and into the bowl, and opening it up too far could kill velocity. So my main focus has been to simply remove any flow path restrictions.

You can tell I couldn't help but hit the guide a couple of times. The carbide burrs I am using are even fairly small, but there isn't a lot of wiggle room to work with. This is one of the tightest exhaust ports I have worked with, so I am having some small issues. Already made a couple of marks here or there from the teeth on the chuck of my die grinder. Oops. Ah well, it's all fixable.
looks good. I need to try this.


 
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Old 12-14-2017, 08:30 AM   #95
JerryHawk250   JerryHawk250 is offline
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Quote:
Originally Posted by Musictrek View Post
I ordered that tool. That looks like a dremel copy
I used mine over the weekend. The flex shaft is a nice feature. Lot easier to control. Be sure to grease the shaft. Like most things from China it lacks lubrication.
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Last edited by JerryHawk250; 12-14-2017 at 09:46 AM.
 
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Old 12-14-2017, 10:50 AM   #96
Megadan   Megadan is offline
 
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There, I beat ya!

Now it's my turn to motivate you with a little pressure Jerry

I worked a little bit more around the guide into the bowl. It's still not ideal, but there are no ridges present where the bowl transitions past the guide anymore. I finished up by "gasket" matching the exhaust port and making it round(er). I left a couple MM of a lip inside the gasket to ensure adequate clearance for any gasket "squish" that may happen. I then blended it in with a taper back into the rest of the port. I still want to do a little finish work on the texture of the port to smooth it out some more, but that is more my OCD than a necessity.
Attached Images
File Type: jpg porting5.jpg (36.7 KB, 558 views)
File Type: jpg porting6.jpg (38.5 KB, 562 views)
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Last edited by Megadan; 12-24-2017 at 02:35 AM.
 
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Old 12-14-2017, 11:03 AM   #97
Megadan   Megadan is offline
 
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Intake.

I did remove a lot of material around the valve guide and roof with the intake side, but not as aggressively as the exhaust. I focused a lot more on the shape of the port and blending areas together.

All of the transitions from the valve seat to the bowl and short radius were smoothed out or rounded.

The sides of the port walls were also worked to help promote velocity as well as free flow. You can note on the long side of the curve in the port (right side of port in 4th picture) was favored when removing material from the roof/guide area. This helped me shape it into a much cleaner and more direct line into the bowl and at the valve. The shorter/inside curve (left side of port in 4th picture) was reshaped more in favor of reducing the curve into the valve face and bowl, giving it a more gradual radius to help reduce turbulence.

I also opened up the bowl around the valve guide and blended it with the side channels created around the guide, but I feathered this out to the valve seat to help maintain more velocity.

The whole intake port now has a nice gradual arc straight into the valve and a nice gradual decreasing taper as it heads into the bowl area and valve seat.

A little more involved and aggressive than simply smoothing out the stock ports, but not so aggressive that my powerband shoul be shifted much. Only a dyno run will show if I achieved my goals for sure, but I am fairly confident I achieved what I was after.
Attached Images
File Type: jpg porting1.jpg (37.6 KB, 545 views)
File Type: jpg porting2.jpg (37.0 KB, 545 views)
File Type: jpg porting3.jpg (35.9 KB, 546 views)
File Type: jpg porting4.jpg (32.6 KB, 536 views)
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Last edited by Megadan; 12-14-2017 at 11:52 AM.
 
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Old 12-14-2017, 11:05 AM   #98
JerryHawk250   JerryHawk250 is offline
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LOL, I've been motivated. Like you, it's finding the time to do it. Looking good.
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2023 Venom Evader
2022 Lifan KPX250
2020 Kawasaki Vulcan S
2020 Venom Ghost 250
105main,40pilot,17/36 sprockets,NGK DPR8EIX-9
2016 Black Hawk 250
Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster
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Old 12-14-2017, 11:13 AM   #99
Megadan   Megadan is offline
 
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Quote:
Originally Posted by JerryHawk250 View Post
LOL, I've been motivated. Like you, it's finding the time to do it. Looking good.
I made time. I took the remainder of my vacation time to get a break from work for a couple of days lol. I decided to make use of that time and do the intake side in one go.

I think it turned out alright.
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Old 12-14-2017, 10:37 PM   #100
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I went ahead and ordered a genuine VM30-83 carb to go with my CRF intake. I think it will be the best combination with this head work. I may still try the 32mm flat slide PWK, but I have a feeling it may be a bit too much carburetor without a more aggressive camshaft.

I am curious to try this head with the VM26 clone as well, just to see the difference between the two. While they are both technically a 30mm bore size, the VM26 "30mm" carburetor has a small choke area for its enlarged bore, and will likely hold the bike back at the top of the rev range.
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Old 12-17-2017, 04:26 AM   #101
Megadan   Megadan is offline
 
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Just to keep this thread alive in the meantime, and because I like engine discussions....

I was doing a bit of poking around, and ran across this article from 2012 on Cleveland Cyclewerks land speed racer.

https://rideapart.com/articles/how-t...200-motorcycle

The same article is on their website as well, with the pictures missing from the first one.
http://clevelandcyclewerks.com/ccw-land-speed-racing/

While not a Hawk, it is a CG250 engine. Try as I might, I couldn't find much in terms of specs on the build as a whole.

The cylinder jug being decked 2mm is impressive, all in the name of gaining a quench area in the cylinder.

The headwork section is what had me most interested. I wasn't surprised by the stock valve size being used, or the lack of change in port size. Realistically, the CG250 intake port is plenty big. What caught my attention was the recessed valve seats because of the cam they had made.

Outside of the serdi valve cut, and probably to a slightly more aggressive degree, the port work is very similar to what I pulled off, at least from what I can see of the intake port in the picture from page 2 on he article (check out that piston dome on the picture above it!). They were definitely a bit more aggressive around the valve guide than I was, but I was concerned about velocity and maintaining some low end.

What impressed me the most was the 23 wheel horsepower. This is on their "stage 1" engine, without any of the crank or flywheel lightening. I can only speculate at their compression ratio, but if I had to guess, I wouldn't be surprised if it was around 12 to 13:1.
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Old 12-17-2017, 02:33 PM   #102
ben2go   ben2go is offline
 
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I wonder if using a 20mm machined spacer between the intake and head would help bottom end torque, or just slow down the fuel/air mix? With increase in flow and compression it usually helps with faster intake flow. It may work on a head like you have reworked. I don't think it would work on a stock set up.


 
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Old 12-17-2017, 02:43 PM   #103
Megadan   Megadan is offline
 
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A spacer where you describe could, in theory, alter the powerband. That would actually change the intake harmonics. I wouldn't expect a huge change though, and a lot more complications. The same effect could be had with altering the intake length on the air filter side of things too, which on a single runner intake with no plenum, acts as the anode end of the resonance wave.
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Old 12-18-2017, 09:38 AM   #104
JerryHawk250   JerryHawk250 is offline
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My head gasket is on its way so hopefully I can do it over the holidays. I do have some vacation time I need to use up.
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2022 Lifan KPX250
2020 Kawasaki Vulcan S
2020 Venom Ghost 250
105main,40pilot,17/36 sprockets,NGK DPR8EIX-9
2016 Black Hawk 250
Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster
2016 Cazador180 XL
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Old 12-18-2017, 02:41 PM   #105
Megadan   Megadan is offline
 
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Quote:
Originally Posted by JerryHawk250 View Post
My head gasket is on its way so hopefully I can do it over the holidays. I do have some vacation time I need to use up.
So the real question is how aggressive are you going to be? Just a good cleanup and small amount of material removal like Silva, or a bit more aggressive like what I have done?

I am somewhat contemplating removing the valve guide ends the more I look at my head. I also may go back and trench the sides of the valve guide on the exhaust a bit more. I can never leave well enough alone lol.
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