GT550 -75

[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:


After lots of work and a bit of investment I got something like this:


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

[Alan H]

Very nice. I've just done a 550 and starting on another in the next few weeks. Love them.

[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.

[motorpsycho]

That looks great!
More pics please!

[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






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







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








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





Locking tab must be expensive...




Some pictures of the wheels, dirty and rusty and bent

[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

Coil was replaced and new cables




New rubbers and I welded the cracked arms




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




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




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




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




New lock washer and chain.




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




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







New custom made lamp holder with "retro style" flasher




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




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.






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:

[Roos]

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

Newtronic ignition






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




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.






New piston ring (for nikaseal) and needle bearings




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




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)

[Roos]

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






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








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)






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










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.








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.




Here is the control box mounted.

[Roos]

The seat was modified and flashers was moved a bit








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




Some dismount has been done






New swing and steering bearings




Steering was repainted and had new bearing:





The rear swing also had new paint and bearings










Some other detail also got new paint and protective film.






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








Seat spacer lighten




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

[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




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








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






Holder for the EGT LED Bar



Tachometer and LED bar test mounted.










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








Controls repainted and text filled with orange paint






New slim instrument cluster

[Roos]

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




Tank sand blaster together with side pods.




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








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






Ready to be painted






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.






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

[Roos]

So this is how the bikes looks for now








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

[Alan H]

Superb attention to detail.

[ConnerVT]

Thanks for the photos, and the detailed commentary. I love seeing how something goes from start to finish.

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

Must be something we don't do in the USA. Never heard of taking pictures with a potato before...

[Alan H]

That's the point.

Lovely bike though, potato or no potato.