95% completed GT550

Specifically for ram-air triple freaks

95% completed GT550

Postby Jeff Kushner » Mon May 04, 2009 1:47 pm

Hi guys,

Remember that Godawlful ugly yellow pos I bought a few months ago....I painted it all myself trying to match the black and gold pattern that I always liked the best. I had a couple of pictures to look at to try and match. I learned a lot about painting and even learned how to pinstripe. I put the pinstripes under the clear to help preserve them over time.

After a few months of "puttering" as my GF calls it, I was finally ready to back my GT out of my basement "shop". Here's a pic of it before I took it outside to start for the first time. I use this 12 x 10 room as my work area with an adjoining room for all my tools and equipment. Under the tarp that you see on the floor is a sheet of plywood that sits on top of yet more "carpet protection". The last thing I want is to ruin my floor since this room also adjoins my basement family room.

Long story short.....it started right up but since I've gone with 3 seperate carbs, I also did away with the unified choke system. I tried to use a perch mounted choke but it didn't last past the first time I tried to move the lever. I ended up having to pull the 3 choke cables by hand...for now...I'll have to get that sorted out.

After manually pulling the cables, it fired right up catching the attention of anyone within 2 blocks<LOL>. Seems that no one has ever heard a two stroke triple where I live. My GF came over to help me get it up the basement stairs and when I started it for her she commented that "it sounds like it just wants to take off!"

I listed it as 95% because I still have the task of rejetting this beast. The carbs presently have 102.5's left there from when I bought them(H2 carbs). I'll probably start with 140's and move up or down. Any suggestions from anyone?

I ended up not taking anything off the intake skirts but took 1mm from the bottom of the port. Other then that, all my plans came to fruition....now we'll see how she goes as I get the jetting sorted out. Any comments or suggestions would be appreciated.

Muzza, I have a ton of pics that I took as I went through this project but I wasn't sure where to post them, or if anyone would even be interested is seeing them.

Completed GT550_320x240.jpg
Completed GT550_320x240.jpg (99.76 KiB) Viewed 1800 times
Front view GT550_320x240.jpg
Front view GT550_320x240.jpg (113.05 KiB) Viewed 1798 times
GT550 front rightside_320x240.jpg
GT550 front rightside_320x240.jpg (110.23 KiB) Viewed 1797 times
Jeff Kushner
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Re: 95% completed GT550

Postby engrevals » Thu May 07, 2009 10:06 pm

8-) very nice bike 8-)
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Re: 95% completed GT550

Postby GT Tim » Sun May 10, 2009 11:34 am

You have come a LONG way! Nice work!

If I understand you correctly and can see properly, you are using the VM carbs instead of the CV's that came stock?

If so, '72-'73 550s used the VM's --VM28SC. They used 95's L& R, and 92.5 on the Center stock.

Since you are using pods, I would richen that up a size or two and use the same size on all three cylinders since you have chambers on it instead of the stock 3 into 4. Maybe even go up one on the needle also to start with and work down from there.

You might not be too far off with the 102.5's. Start there and go up one on the needle and see. Consider the elevation that you will ride at also.

Curious to see what you find out.
Sore-ass grouch...

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GT Tim
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Re: 95% completed GT550

Postby Jeff Kushner » Mon May 11, 2009 5:25 pm

Thanks....my '75 came with 28mm carbs together on a rack. These are separate 30mm carbs off a H2 750 Kaw. I had ordered new stock 40 pilots and 105's along with new 45 pilots and mains from 110 up to 130's or 140's. I had forgot that with the larger carbs, I wouldn't need to go up as far as I would have with the stock carbs. You tend to forget stuff like that after 20 some years since your last build. My plan when I ordered the parts was to install the 45 pilots and 110 mains before taking it out....but I may not need to now.

The needles were in the #4 position and I moved them to the #2 then I bumped the timing up a bit from the very conservative place that I started from. It's running very good now to the ear but I haven't taken it on the street yet. I had wanted to put on the bigger mains to get it "safe" before starting my plug reads. I might not wait till the new hardware comes now that it's getting so close to being right.

I also have a set of intake boots that will put the carbs tight to the spigots and they match perfectly to the opened up spigots but I wanted to again, start conservative then I can always place the shorter boots on later. I never heard a gt550 rev like this one before<LOL>....I don't want to frag the engine which is why I'm being safe with it.

This whole build was an experiment (as far as my measurements in porting and the intakes) since I was unable to find anyone who had built a gt550 but so far, things seem to be working well. I've taken it for a couple short stints on my driveway and I'm happy that it's beginning to make serious power at 3000K and I haven't screwed the powerband into a 6500-to 7000 affair!

Monday nite:...I finally got my jets in the mail. I changed my mains to 110's and the pilots from .35's to ,45's and I left the screw at 3/4 open. of course found that I was out of gas<LOL>. I went out and filled my 5 gallion can, dumped a couple into the tank and started it up. Nice and rich now, just how I had wanted it. It also began to rain so I'll have to put off a proper test till Weds evening.
Jeff Kushner
Posts: 51
Joined: Tue Jan 27, 2009 3:34 pm

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