Mail me to talk
about your GT, or ask me a question, even send me a pic!
How do you tell whether you've got Chrome (Nikasil) bores, or Cast liners? - it's easy says Mike Buckby - "Thanks guys, finally got it sorted. The cast barrels mount on short rear studs which are the same length as the front. The chrome barrels have long rear studs and short front." My thanks too, to Mark Tinley (aka funnymachine) for taking the time to photograph some and upload the pictures!
Chrome bore on the left,
cast on the right...
See that the chrome bore has a long casting for the stud....
whereas, the cast liners are finned and will use a shorter stud.... 
You'll also see, Nikasil liners don't
necessarily have a chrome look to them!
I've posted this on Sundial's (Eric Kalamaja's Suzuki Twins 7 triples Message Board) but
maybe some of your regulars don't visit it. So for you restorationists out there.....
For the "GT" portion of your side cover badges to get that original
"glitter" look, try some of this stuff:
Auto-Air Colors of East Granby, Connecticut, USA
Color #4548 Orange Flake
www.autoaircolors.com
1-800-509-6563 which only works in North America but if you visit their website I'm sure
they can point you in the direction of one of their local dealers.
A friend of mine manages a body/paint supply shop and I took one of my good emblems in
after noticing this stuff in a paint chip sample brochure. It's an exact match...or as
close as my tired old eyes can determine. So for all you restorers out there who don't
want to put up with the later emblems as supplied by Suzuki with that lame red paint
instead of the true glitter look....give this stuff a try. It can't be any worse that what
you have now if your emblems are knackered or you bought a replacement set with the red
paint.....right??
Kind regards,
H2RICK
Hello,
I am in USA and I thought you should know that there is a guy Here who does custom
exhausts for the GT's including the GT550.
He can be found here: http://omarsdtr.com
I am restoring a 1977 GT550L. I had this bike in college and I never got over it. :-)
Roy R Justus
Hi Clivey;
Pictured please find attached my GT380 sporting modified 3 into 1 exhaust as well as my
blueprint :-) for the design.
My original GT380 (back in the early eighties) also had a 3 into 1 which worked well and
pulled the bike well over 100 MPH and I was sure that I could re-create that moment so I
have been experimenting...In the hope that it may help others (particularly Zakk, who I
sold your pipe to in the US who is copied on this mail) - please include the information
on GT550.com
ie: please use the body of this email as a brief article and explanation of how/why it
works at least as well as the standard 3 into 3 system.
I have been out on the bike today and it pulls hard in all gears and revs out quite
nicely. It is no longer choking at around 80 MPH and wants to sing!!! :-) It has not been
rejetted - though I have
modified the air box by removing the rubber dam at the back, but only because I wanted to
get really resonant induction noise.
My thinking (and it has proved to be correct) is that the standard system is none too
efficient - so any system that works as well as that should give as much power. I can't
understand where Piper were
coming from back in the day. Their pipes don't follow any of the rules - I think they were
just meant to look like expansion chambers maybe?
Anyway, the rest of my now revised thinking is as follows:
That a 3 into 3 expansion chamber style system which uses negative pressure pulses to
increase performance works well but will require rejetting.
That a 3 into 1 expansion chamber style system which uses negative
pressure pulses to increase performance chokes the engine in the Piper style format (too
long) and while a system with very short
header such as those on Mercury V6 outboard motors which uses the pressure pulse from one
cylinder to help another works extremely well, the header pipes are just too long on a
GT380/550/750 (mainly
due to the twin downtube frame) to make the pressure pulses work at any useable RPM. The
system also provides too little overall back pressure and is horribly inefficient at
higher revs.
That the 3 into 3 system uses the megaphone shape of the exhaust to
spread the tuned length of the exhaust over a more useable power range.
That a 3 into 3 system with no tapers (open headers) would still work but would have a
more pronounced peak power output.
That a 3 into 1 system with no tapers would still work as well as the standard system but
would have a more pronounced peak power output and would need similar back pressure to the
standard system to keep the charge from escaping from the engine (loss of power).
That the Piper system does not maintain enough back pressure because it is relying on the
negative pressure pulse travelling back up the pipe to plug the charge - it simply lets
too much gas escape and the
engine loses power at high revs. My solution was to obtain a car silencer and to cut the
silencer box off leaving a nice long diffuser tube attached to a curved piece of regular
pipe.
I crushed the end of the diffuser tube into the shape of an X.
I then cut off the end of the 3 into 1 until I could slide the diffuser pipe into it
(roughly 44mm) all the way down to the clean part of the pipe.
I moved the pipe around until I found a place where I was able to attach a silencer and
welded it in place.
Initially I has a straight through megaphone - which was insanely loud and the bike would
not rev above 8000 RPM - much the same as when I fitted the 3 into 1 - flat response
throughout rev range -
loss of top end revs and power.
I had thought that the 3 into 1 was not letting gas out fast enough and this is why it
would not rev - but in fact the exact opposite has been true - the pipe was not creating
enough pressure and the fuel charge was escaping before the ports closed and the badly
timed pulses were also screwing things up.
So I scavenged the garage for a way to increase back pressure and decided to try one of my
(slightly modified) Ducati Monster silencers.
The upshot is that it works at least as well as the standard system, with good low end
torque but some loss of smoothness associated with the megaphone shape of the standard
silencer. There also seems to be a distinct point between where it pulls with low end
grunt and screams like a regular two stroke. In other-words, it is lightly more peaky.
It's quite good fun actually and now quiet enough to ride past a Police car without trying
to keep the revs down!!!
It is also starting to look like a very big TS185 - I am considering a high mudguard -
long shocks and flat track tyres next :-)
Hope this helps
Best
Mark
Hey Clivey;
A foot note to tack onto the end of my article / email. This is a manifold from a 3
cylinder two stroke snow mobile...
It is a 3 into 1 that works (improves power at a set RPM)
Note the very short headers (before the pipes merge/join) This pipe uses the tuned length
between the cylinders to provide a negative pressure wave from one cylinder to plug the
charge in
another - as opposed to the length of the expansion chamber to provided a timed negative
pulse per cylinder on a 3 into 3 system.
On a GT series 3 cylinder bike the frame would need to be modified to accommodate it.
Cheers
Mail me to talk
about your GT, or ask me a question, even send me a pic!
I do have more web pages...