T350-GT250. Do you want to add Expansion Chambers?

[Vintageman]

Hello,

I always ask crazy questions so let me see if I can add some value to someone. I hope its value not pain

I Have 1974 GT250. I have a parts bike that is 72 T350 later style. I think the same frame as early T350, T305 or T250, but not sure if what follws applies

I put a T350 top end onto the GT250 motor (really a T305, 1mm over… I have true T350 jugs as well… why I chose the T305 is another post someday).

You know the upgrade, Jugs, Heads, different head gasket, pistons (actually longer wrist pin too to be perfect), And I changed the oil pump for I believe the t350 needs more oil if that’s the difference, air box, air box boot to carbs and mufflers.

I must brag and say the T350/305 is fast for a 315cc.

How much better could it be with chambers?

No one makes them anymore... that I could see. None show up on ebay

I have D&G chambers for both an Rd350 and Rd400. First, I can say the chamber cone design is very near the same. Maybe the small difference is only to make it fit the two bikes.

The RD400 due to mounting bracket position looked like the best chance to fit or the least cobbling. The RD350 D&G should work too. So I bought a set of D&Gs for Rd400

How to mount to those threaded cylinders exhaust ports?

Easy if you have a set of GT380 exhaust: at least two of the threaded mounting flanges. That thread is just right for T305/350 jugs exhaust. If you had a GT250, Maybe a GT185 would work ( I can check this?).

The Rd jug to pipe couplings you get from D&G will line up pretty well the GT380 flanges two holes (a little drill hogging is needed). The T350 gasket donut can be used too if you don’t thread all the way down. No leaks.

Have to screw gt380 flanges with cooling fins towards jugs so you have the flat surface or rd mounting flange. Need to grind GT flange cooling fins down some to be able to screw on far enough without hitting jug fins too soon.

On the RD400 there is a 2-3 inch or so outer section of pipe right at the jug side of each chamber (not on the RD350 version). This allows the flange to pipe mount to seal better. The inner pipe goes into the RD400 mounting flange ID and the outer pipe goes over the mounting flanges OD. I had to cut the pipes a bit shorter to fit frame. Cut right at the end of the Outer pipe sections.

It was a perfect fit! I only had to weld a 1 inch tab at 90 degree to existing mounting tab hole and drill another hole. Easy for my stick welding skills, Now it bolts right to rear of foot pegs nicely and looks neat. I did save the outer pipe and had some one weld it on the end of the pipe again so I have a nice seal. Had to remove center stand and di cut tab off frame. Not sure latter was really required. I’ll try to get some picks.

enjoy

[Vintageman]

Here is a couple pictures.

http://i266.photobucket.com/albums/ii25 ... /001-2.jpg" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;"
http://i266.photobucket.com/albums/ii25 ... /004-1.jpg" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;"

[alanr]

with the t350 parts bike do you have baffles you dont want.

[Craig380]

Wow, she looks SWEET with those chambers. Very nice looking machine. How does she go with them on?

[Vintageman]

alanr,

I keep stock exhausts for if I ever sell my bikes, I'll put it back on for resale value. There was a rough set of pipes on ebay USA in CA. I think he/she would sell just the baffles and that would reduce shipping cost quite a bit which was high for I am on other side of USA. You are in Europe?

Craig380,

Thanks, yes it does run better. I see no problem any place in the RPM range. I did not change any jetting (maybe should raise needle one clip). I still have good bottom and midrange... the same if not a touch better. Above 6000 RPM there is a slight power boost or hit that was not there before. The bike revs/pulls comfortably to 9500 RPM. This is maybe only 500-750 RPM more than with the stock exhaust. I think porting is needed to rev out more. This bikes porting is stock.

It sounds close to my RD400 or R5 with D&Gs. I'll make a youtube post soon. IMO the sound alone is much better than OEM pipes, for me making it very enjoyable to ride. There may have been a better chamber design, but this works well and there is some gain in performance not just sound.

[tz375]

No. He's in England......

That's an old view of the world from centuries of wars and bad blood that still has relevance in currency for example.

[alanr]

no sorry.you are both wrong.Im in New Zealand

[tz375]

Oops, I looked at the wrong profile and came up with Craig 's address/county.

So much for humo(u)r...

[Vintageman]

Here is a youtube of it running

http://www.youtube.com/watch?v=n9XVfI2y8Zk" onclick="window.open(this.href);return false;

[Craig380]

Oh yes, she sounds sharp Nice deeper tone to the sound, too