Reed valves for the GT550

Getting your blazingly fast Suzuki powerplant to perform even better!

Moderators: oldjapanesebikes, H2RICK, diamondj, Suzsmokeyallan

Post Reply
User avatar
gsx1400dave
Still in the Driveway
Posts: 9
Joined: Mon Jun 04, 2012 5:34 pm
Country: UK
Suzuki 2-Strokes: GT550 x3, GSX1400, CR250
Location: Southampton UK

Reed valves for the GT550

Post by gsx1400dave »

Hi,
I have been looking into fitting the reed valve block and carb from an Aprilia RS125 to the GT550.

At this time work has only been done on scrap cylinders so nothing has been lost.

Please follow this link and download the PDF document.

https://www.dropbox.com/s/liz6v1n6q81e6 ... 0.pdf?dl=0" onclick="window.open(this.href);return false;

Any comments please.

Dave
Southampton UK
Dave.
GSX1400 K4
GT550 x 3
CR250


"You need only two tools: WD-40 and duct tape. If it doesn't move and it should, use WD-40. If it moves and shouldn't, use the tape. " - Dave Barry, columnist
User avatar
tz375
Moto GP
Posts: 6204
Joined: Mon Nov 03, 2008 10:47 am
Location: Illinois

Re: Reed valves for the GT550

Post by tz375 »

Dave,
I have but one question: why are you wasting time here when you could be welding up those reed blocks? :wink:

OK, so I lied, I have couple of others. What advantage do you expect to gain from just the reed block or do you anticipate porting the cylinders at the same time? 33HP from an RS125 at whatever revs requires a pipe that works with those ports and an ignition timing curve that works too. In addition, the heads are probably a little different in shape and effectiveness.

On a 181cc long stroke motor you will be looking at very different port areas and timing to achieve the correct port-time area. There are two primary advantages of reed valves. The first is what Yamaha exploited on the RD twins, namely that wild inlet timing required to make good top end, no longer hurt low RPM torque. That implies using longer inlet port duration to take advantage of the reeds.

The second advantage is the extra transfer port area. In the RS125 that boost port can work either way - to flow into the crankcase or into the cylinder from the reeds or from the crankcase up to the cylinder through that small boost port. So that means adding a boost port into each cylinder.

Access from the reed cage to the transfers is a neat touch on the Rotax cylinder. Those are generally known as Boysen ports and generally seem to work well if a cylinder can't access enough flow from the crankcase straight up to the transfers and work well with a great pipe design. GT550's don't have much crankcase volume and I suspect that the extra (Boysen) ports will help.

Of course the transfer ports and exhaust port dimensions need to match the power target but calculations we have done suggest that you new motor with the right ports and pipes could be incredibly powerful, to the point that engine cooling and other mechanical issues may be the limiting factor.

Good luck and keep us posted.
ja-moo
Yeah Man, the Interstate
Posts: 554
Joined: Wed Apr 01, 2009 11:47 pm
Location: NM USA
Contact:

Re: Reed valves for the GT550

Post by ja-moo »

Go for it! :up: I have been doing reed conversions on the triple Kawi's since 1995. Makes a world of difference!
Visiting from the "K" camp...........
User avatar
Suzukidave
Moto GP
Posts: 3980
Joined: Fri Oct 24, 2008 5:55 pm
Country: US
Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
Location: Lancaster Pa.

Re: Reed valves for the GT550

Post by Suzukidave »

Dave , any updates ?
the older i get the faster i was
User avatar
Alan H
Moto GP
Posts: 3160
Joined: Thu Feb 16, 2012 11:50 am
Country: England
Suzuki 2-Strokes: 4 x GT550s - J, M, A, B.
Location: The Republic of South Yorkshire

Re: Reed valves for the GT550

Post by Alan H »

Very interesting ideas there.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
Vintageman
Expert racer
Posts: 1483
Joined: Tue May 18, 2010 5:38 pm
Country: USA
Suzuki 2-Strokes: Suz, Yam, Honda, Kaw.
Location: New Hampshire

Re: Reed valves for the GT550

Post by Vintageman »

I don't think adding reed valves will make any more peak hp as desired?

If goal is more HP a change of port timimg and or area is needed.

Now if you change intake timing reeds should give you back bottom end which is very nice.

Work is impressive :up: .
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),
User avatar
gsx1400dave
Still in the Driveway
Posts: 9
Joined: Mon Jun 04, 2012 5:34 pm
Country: UK
Suzuki 2-Strokes: GT550 x3, GSX1400, CR250
Location: Southampton UK

Re: Reed valves for the GT550

Post by gsx1400dave »

Hi,

I have not been around for some time due to work projects.
It must be noted that this work is intended for the Euro Nykasil cylinders with the extra boost ports as standard (7 ports).
This cylinder (Jug) was never available in the USA.
Further work so far is to start to enlarge the inlet port for the reed valve as per:

https://www.dropbox.com/s/r3biba0rco6jm ... 8.jpg?dl=0" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;

I am still within my scribed lines (just about visible) and now I need a finer burr.
Inlet port size has not been changed so far.
As you can see the inlet will be much improved.

I also state again that this work so far is on a scrap cylinder that I have that was part of a GT550 engine that I purchased some years ago.
Engine advertised as fully working but with only 2.5 con rods and 2 pistons.

Dave
Dave.
GSX1400 K4
GT550 x 3
CR250


"You need only two tools: WD-40 and duct tape. If it doesn't move and it should, use WD-40. If it moves and shouldn't, use the tape. " - Dave Barry, columnist
User avatar
Suzukidave
Moto GP
Posts: 3980
Joined: Fri Oct 24, 2008 5:55 pm
Country: US
Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
Location: Lancaster Pa.

Re: Reed valves for the GT550

Post by Suzukidave »

Dave , did you get any further on your 550 reed intake idea ?
the older i get the faster i was
User avatar
Suzukidave
Moto GP
Posts: 3980
Joined: Fri Oct 24, 2008 5:55 pm
Country: US
Suzuki 2-Strokes: GT750 x2 97 -1200 Bandit 86 GSXR1100
Location: Lancaster Pa.

Re: Reed valves for the GT550

Post by Suzukidave »

bump
the older i get the faster i was
Post Reply