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PostPosted: Wed Dec 19, 2018 5:16 pm 
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Joined: Tue May 18, 2010 5:38 pm
Posts: 1431
Location: New Hampshire
Country: USA
Bikes owned: Suz, Yam, Honda, Kaw.
dorT500 wrote:
The first page refers just a bit to the widening (1mm) No?


Yes you are correct, sorry. Some go over 10mm wide in the link I sent if I recall.

Also more here-> http://www.ozebook.com/. Still stuff not yet seen.

And just saw Craig380 post so |i'll check it out

The concern I have when widening and straightening/matching/smooth flow path is how much can I take off inside curve, starting from the exhaust down pipe gasket Al flat surface (still need gasket surface) all the way back to Ex port casting edge once widened.

Right before the exhaust gasket surface the Al bulges in. And, if you look at outside of cylinder where the bulge is, the mold indents. So if I took that bulge off will I see daylight for thin. Are there other areas? The GT 750 outer casting goes in some but maybe not as much. I just need to get some measuring devices and go slow.

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Current Bikes
74 GT250 (T350 upgrade),
76 GT250 (T350 upgrade),
71 T350,
70 T350,
74 GT380,
75 T500,
73 GT550,
75 GT750,
72 Yamaha DS7 (R5 upgrade),
77 Yamaha RD400 (Daytona Cyls),


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PostPosted: Thu Dec 20, 2018 5:38 am 
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Moto GP
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Joined: Mon Dec 13, 2010 4:32 pm
Posts: 3311
Location: southwestern Pennsylvania
Country: USA
Bikes owned: 69 T350 thru 75 GT750
If you are after a small hp gain, then it might be worth looking into the differences between early & late cylinders.

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BAS (Bike Acquisition Syndrome) - too many bikes but have room for more

Suzuki:
GT750 2x75
GT550 72 project & 75
GT380 72
T500 73 project
T350 69, 71 & 72 project
T250 72
Honda 85 CB650SC & 86 CB700SC
09 Triumph Bonneville SE


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PostPosted: Thu Dec 20, 2018 8:38 am 
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Joined: Tue May 18, 2010 5:38 pm
Posts: 1431
Location: New Hampshire
Country: USA
Bikes owned: Suz, Yam, Honda, Kaw.
jabcb wrote:
If you are after a small hp gain, then it might be worth looking into the differences between early & late cylinders.


Yes, I did this maybe 2-3 years back and have a post here on this. What I found was the intake port is lowered 2.5mm in the earlier vs later which I think is the key. I run the early cylinder on my later bike and a noticeable difference :up: . I still run the later intake setup too. I have the early intake (Airbox, carbs, Boots, etc), but given how much gain from early clys alone I left as is. My T500M 1975 looks all original.

During that post others measured a +/- 1mm on Ex height and we were thinking mfg tolerance. The sets I checked I did not see ( I'll check the ones I just got), but my measuring technique is not exact (paper traces, then measure off paper)

I have not added any new bikes lately :( , but I am modifying what I have. Either through exhaust pipes and or conservative porting. I had good luck with power boost widening ports and that doesn't change power curve's general shape. I have learned for ring life compromise to chamfer well and take time to polish the chamfers shiny smooth: have spare rings in your supply if worried. I have extra sets of things so can go back and forth if I fail... don't want to fail.

I would expect a my mild porting goal will get me 10% more power mid RPM and above and not hurt bottom end. Also the key is pipes. Those can be changed quickly too so one day you have low end torque machine or top end machine without changing really anything else.

My new porting stuff is suppose to be in Friday.

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Current Bikes
74 GT250 (T350 upgrade),
76 GT250 (T350 upgrade),
71 T350,
70 T350,
74 GT380,
75 T500,
73 GT550,
75 GT750,
72 Yamaha DS7 (R5 upgrade),
77 Yamaha RD400 (Daytona Cyls),


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PostPosted: Fri Feb 01, 2019 6:53 pm 
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Expert racer

Joined: Tue May 18, 2010 5:38 pm
Posts: 1431
Location: New Hampshire
Country: USA
Bikes owned: Suz, Yam, Honda, Kaw.
This was easy to widen. I was able to take that inside corner off without break through. I need to figure where I can post pics on cloud so I can link pics

_________________
Current Bikes
74 GT250 (T350 upgrade),
76 GT250 (T350 upgrade),
71 T350,
70 T350,
74 GT380,
75 T500,
73 GT550,
75 GT750,
72 Yamaha DS7 (R5 upgrade),
77 Yamaha RD400 (Daytona Cyls),


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