GT550 -75

Retro, Wild, Cafe, etc. The stuff only your imagination can come up with.

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Roos
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Joined: Wed Jan 22, 2014 2:47 pm
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

GT550 -75

Post by Roos »

Hi everyone,

I have been working on my GT550 from 75 that I bought 1,5 year ago. It was out the
MOT registry and not been used for 30 years when I got the opportunity to buy it

When I found it looked like this (and had lots of "unique" solutions), sorry only foto:
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After lots of work and a bit of investment I got something like this:
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I know I enjoy to read about others progress and adventures so this post is to
force me to share my journey, more post will follow so keep looking :D
Bring back the smokers!
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Alan H
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Suzuki 2-Strokes: 4 x GT550s - J, M, A, B.
Location: The Republic of South Yorkshire

Re: GT550 -75

Post by Alan H »

Very nice. I've just done a 550 and starting on another in the next few weeks. Love them.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
pearljam724
AMA Superbike
Posts: 1681
Joined: Tue Jul 24, 2012 11:45 pm
Country: U.S.
Suzuki 2-Strokes: 75- GT 550 / 76- GT 750
Location: SW PA

Re: GT550 -75

Post by pearljam724 »

I'm not a café racer fan. But, I do like that tail. I like how it integrates with the original fender. Another big 550 fan here. They're fantastic motorcycles that aren't served proper justice. Nice, pipes. :up:
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motorpsycho
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Suzuki 2-Strokes: Suzuki GT550, Kawasaki ZRX1200,YamahaR5,

Re: GT550 -75

Post by motorpsycho »

That looks great!
More pics please!
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Roos
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

Re: GT550 -75

Post by Roos »

Here are some pictures how it looked at when I got it:

It wasn't so shiny and the exhaust was ok but the two main pipes had no inserts

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The carbs was a mess up, protective rubbers was gone, arms cracked.
(clutch is new, mounted by me)

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One coil was replaced with something else and electrical was also full of inovations...

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Main cylinder and brakes was filled with old rusty jam, I actually got it working
but later on got it renovated.

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Locking tab must be expensive...

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Some pictures of the wheels, dirty and rusty and bent

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Bring back the smokers!
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Roos
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

Re: GT550 -75

Post by Roos »

I did this as an two stage project, first I did the main things that had to be done last summer
and then drove it around 1300km. Next winter I did the the rest.

There as some photos taken with a potato and they are also taken during stage 2 but you get the point :D

Coil was replaced and new cables

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New rubbers and I welded the cracked arms

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New 18x2.15" alu rim with 4mm stainless steel spokes

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Get a left hand disc and caliper on ebay, the where modified and mounted and right hand side

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First mounted new Progressive Suspension shocks, cc 292mm (little bit shorter than stock)

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New 18x2.5" alu rim with 4mm stainles spokes

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New lock washer and chain.

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Braided brake lines, main caliper is standard GT550 size, works very well!

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Most of the alu parts was clean and polished, some new stickers. New toolset.

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New custom made lamp holder with "retro style" flasher

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Electrial was cleaned up, the alternator worked fine with new coal and restored cabling.

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Bought a custom seat from U.S at ebay and modified it a bit to fit the GT550,
the flip up and locking is still working for easy access.

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Replaced all wires and many gasket and rubber details, new tires of course.
There are some modification not mention above and also mounted a new
higgspeed exhaust. After that I run the bike for what was left of the summer
something looking like this:

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Last edited by Roos on Sat Aug 23, 2014 11:44 am, edited 1 time in total.
Bring back the smokers!
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Roos
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

Re: GT550 -75

Post by Roos »

During the winter/spring 2013-2014 I started to complete the job on the bike

Newtronic ignition

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The cable was glued in the coil and I also got new non resistor caps and iridium spark plugs

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Got a spare head and the other one was milled something like 0.3mm or so.
The plan was 0.2mm but the workshop actually manage to make it wrong the
first time so the had make another round (seen on picture).
Final compression on milled head is 7.2:1.

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New piston ring (for nikaseal) and needle bearings

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Plan is here to make some minor performance work on the engine, in theory
the peak power is raised approximate 1000rpm. Made a extension for my porting tool

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Cylinder ports was mostly just made a bit more smooth and equal.
Exhaust port rised 0.5 or 1mm and piston shirt shorten and port was
matched to cylinder head (do not remember but it was checked with angular wheel)

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Roos
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

Re: GT550 -75

Post by Roos »

The Higgspeed connector was far from perfect, made a new ring with perfect
match to the cylinder head.

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Since I mostly think its fun I wanted to mount EGT sensors. welded M5 connector
on the exhaust pipes.

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To read the EGT I use a extension board that outputs analog 0-5V.
The board was re calibrated to 0-800C by replacing some small SMD's
(this is an extension board for the MegaSquirt EFI)

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Using an prototyp board and an Arduino CPU made it possible to read the analog input.
(the small LED boards are for testing)

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Main display is going to be a LED bar, during warm up it show the biggest difference
in tempeture between EGT1-3. I have made some diffrent display mode the can be
changed by pressing the button.

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LED bar display unit, I also have LED number display to be able to read the actual
values. It is done but can't find the picture.

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Here is the control box mounted.

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Last edited by Roos on Sat Aug 23, 2014 11:52 am, edited 1 time in total.
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Roos
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

Re: GT550 -75

Post by Roos »

The seat was modified and flashers was moved a bit

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New shocks (again), with chrome springs and these was a little longer thand standard

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Some dismount has been done

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New swing and steering bearings

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Steering was repainted and had new bearing:
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The rear swing also had new paint and bearings

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Some other detail also got new paint and protective film.

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New front tubes, old one bent and had pitting (new gasket din't last). Also
made a small spacer for some more preload.

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Seat spacer lighten

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Steering crown was milled and later on welded for permanent clip on installation.

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Last edited by Roos on Sat Aug 23, 2014 11:59 am, edited 1 time in total.
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Roos
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

Re: GT550 -75

Post by Roos »

For instrument I wanted something smaller than the original cluster but also
wanted to keep the mechanical drive also an RPM range close to what was used.

I bought this 3-9000rpm ducati replica at ebay and an custom specified
speedo from an firm in germany

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Tachometer had an M16 connector so I made an small modification and an
adapter to still use the original wire with connectors.

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Made a new cluster from aluminum with 3 indicator (required for MOT)
Neutral, flasher and high beam

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Holder for the EGT LED Bar

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Tachometer and LED bar test mounted.

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For indicator I use a small prototype board with LED lights, they are later
on fastened with 2 component glue (same as on LED bar

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Controls repainted and text filled with orange paint

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New slim instrument cluster

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Roos
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

Re: GT550 -75

Post by Roos »

Cylinder, piston and head mounted. New intake rubbers for carburator. One size up for the
carb jets to 105 (if I remember correct)

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Tank sand blaster together with side pods.

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Installation of the newtronic box and some connector to rear light and flashers

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Made an fiberglass seat base to be used to make an new seat later on.

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Ready to be painted

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Made an adapter to used for ignition timing, was set 0.01mm lower than specified.
Thought is to be a bit safe due to higher compression.

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Parts back from painter :) Everything is painted black on the inside.

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Bring back the smokers!
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Roos
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Suzuki 2-Strokes: GT550-75 XN85-83 GSX-R-88

Re: GT550 -75

Post by Roos »

So this is how the bikes looks for now

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Have not been so much opportunity to drive the bike only like 400 km but some short notes:

Engine responds well, hard to tell if it actually gain anything but the goal is to have it
measured later on (there are some occasions here when you can do it for like $70).
After 7200rpm you can feel it drops of but have not invested if its going lean or peak
power has passed. Spark plugs looks ok but next step is to make a focus test on upper
rpm range.

If left unstarted for a while it smokes a bit in the beginning (noticed oil was left in the crank
house when it was dismounted) so guessing the one way valves is leaking. Planing on buy these
(http://www.ebay.com/itm/171387687512?ss ... 1423.l2648" onclick="window.open(this.href);return false;)
and replace them during the winter. When use for daily riding it doesn't smoke much.

Some rear sets would be nice, will see if I try to buy some pre made or do some myself.

The temporary seat is ok, but maybe have it done during winter as well.


That's all for now, I hope doing some short video later on so we can enjoy the sound 8)
Bring back the smokers!
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Alan H
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Suzuki 2-Strokes: 4 x GT550s - J, M, A, B.
Location: The Republic of South Yorkshire

Re: GT550 -75

Post by Alan H »

Superb attention to detail.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
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ConnerVT
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Suzuki 2-Strokes: T500R (now), T500M (40 yrs ago)
Location: North of Albany, NY

Re: GT550 -75

Post by ConnerVT »

Thanks for the photos, and the detailed commentary. I love seeing how something goes from start to finish.
Roos wrote: There as some photos taken with a potato and they are also taken during stage 2 but you get the point :D
Must be something we don't do in the USA. Never heard of taking pictures with a potato before...
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Alan H
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Suzuki 2-Strokes: 4 x GT550s - J, M, A, B.
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Re: GT550 -75

Post by Alan H »

That's the point.

Lovely bike though, potato or no potato.
Think of how stupid the average person is, then realise that half of them are more stupid than that.
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