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PostPosted: Sat Dec 15, 2018 11:38 am 
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Expert racer

Joined: Tue May 18, 2010 5:38 pm
Posts: 1471
Location: New Hampshire
Country: USA
Suzuki 2-Strokes: Suz, Yam, Honda, Kaw.
Hello,

I am interested in widening the Ex port on a T500. As you may know the Ex opens at the liner and takes a 45 degree turn as it exists the cylinder a ways to the muffler downpipe. The Aluminum of cylinder, inside corner sid , near muffler downpipe is where my question lies for advice.

I can tell the flow is low here since I see carbon build up. I feel I would like to take a few mm off the Al casting near muffler to improve flow and so I can widen that side of the cast liner with Burr porting tool and achieve a better flow though cylinder.

My concern is this Al may very thin near/just behind the downpipe exhaust donut and can't take too much off before breaking through. How much can I remove if that makes sense?

What have people done improve flow and especially widen the EX port and can shed somes advice (pic would be amazing).

I will do the same to intake port, but the Al material to remove is more near the cast liner and looks fairly thick.

Thanks

_________________
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 Jun 21, 2019 4:46 pm 
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Around the block

Joined: Tue Jul 03, 2018 4:32 pm
Posts: 84
Country: Usa
Suzuki 2-Strokes: '74 GT250
I haven't done a 500 engine but if you can tig weld or take it to someone who can and you can get to the outside where its thin and build up the material that would enable you to take more out when porting. If thats not possible I would try to leave at least 3mm of material. me and many engine builders I know have also used epoxy to build up and strengthen ports but I don't know if there is an epoxy that would hold up to the heat of the area around the exhaust. I hope this is of some help to you and good luck with your project.


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PostPosted: Mon Jul 08, 2019 8:01 pm 
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Joined: Tue May 18, 2010 5:38 pm
Posts: 1471
Location: New Hampshire
Country: USA
Suzuki 2-Strokes: Suz, Yam, Honda, Kaw.
It had no problem removing the aluminum material I was concerned about . I did not break through anywhere on either side (not sure how thin it got but so far so good). The Exhaust passage has more of a straight shot and not such a sharp bend /corner as it was stock I only widened the EX not raised so no concern there about breaking through at the top.

I opened up the passage to match the cast port widening I did all the way out to the pipes best I could. I was not too concerned for spare set of cycl, but it took some time to do this handy work.

Per my butt dyno significant improvement :up: and still have perfect street manners as was my goal. I quickly cleaned up intake port but really did not change any dimension. The transfers were pretty decent from factory. Stock later style cast piston and rings.

What is clearly different is the bike now revs and pulls hard for several hundred RPM more now and the stock tach needle will show up to 8K quickly. I back off throttle as not to blow it up so soon. It does not run out of breadth :up:

My bike is a 1975M and when I first got it stock it was out of breadth too soon and as we all know it was de-tuned after 1972 model. The early cylinders and now the EX port widening, makes the bike more frisky for sure. Dare I saw it is now fast for what it is. It is exciting to drive. Fresh crank. All else is stock for 1975, except the Jemco chambers (loud but seams to work well with my changes, they don't hold back RPMs that I can see). Will try to get video of before (on youtube now) and after soon.

Thanks

_________________
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: Sat Nov 16, 2019 3:23 pm 
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Expert racer

Joined: Tue May 18, 2010 5:38 pm
Posts: 1471
Location: New Hampshire
Country: USA
Suzuki 2-Strokes: Suz, Yam, Honda, Kaw.
Now that I know how to post pics on a free site again (use to use PhotoBucket) this is what I meant about widening the Ex port outlet, "taking off the corner", first pic shows cast aluminum stock and the second i removed it and blended so you can see straight back into exhaust port without a sharp bend. As stated I did not breakthrough anywhere and overall widening Ex Port as stated and matching flow out to pipe did help top end noticeably and very street capable mild tune IMO. This is also the early T500 Cyls. These two changes made the 1975 breath much better top end. Stock Airbox, Jemco 3 into 3s.

Before ->
https://ibb.co/HXXQX5n


After (different side pic maybe but both were the same)

https://ibb.co/FgfNRvQ

_________________
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: Sat Nov 16, 2019 3:25 pm 
Offline
Expert racer

Joined: Tue May 18, 2010 5:38 pm
Posts: 1471
Location: New Hampshire
Country: USA
Suzuki 2-Strokes: Suz, Yam, Honda, Kaw.
Now that I know how to post pics on a free site again (use to use PhotoBucket) this is what I meant about widening the Ex port outlet, "taking off the corner", first pic shows cast aluminum stock and the second i removed it and blended so you can see straight back into exhaust port without a sharp bend. As stated I did not breakthrough anywhere and overall widening Ex Port and matching its flow out to pipe. It did help top end noticeably and still very street capable mild tune IMO. This is also the early T500 Cyls on a 1975 which helps all on it s own. These two changes made the 1975 T500 breath much better top end and bike more fun. Stock Airbox, Jemco 3 into 3s.

Before ->
https://ibb.co/HXXQX5n


After (different side pic maybe but both were the same)

https://ibb.co/FgfNRvQ

_________________
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),


Top
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