Sendyourqueriesto:[email protected], CMM,PO Box99,Horncastle,LincsLN 96 LZ
YAMAHA SR250
Q:
All of myprevious
bikeshave haddisc brakesfitted,
bu the donor for my latest project
(Yamaha SR250)has atwin lead ing shoe
drum on thefront. I’d like to retain this,
but am unsure as tohow t oadjust the
linkage so that both shoes bite at the
same time for best braking performance.
Do youhaveany ti ps to share?
RobNealA:
Youagain, Rob?Well,this n ever
seems to be adequately explained in
manuals andIhave touched on this topic in
my Honda CL350 restoration series. Check
this month’sentry on pages 126-127 and
future issues!SUZUKI GS850GG
Q:
Ihave been trying to getaSuzuki
GS850GG back on the road. It had
an accident on the M25 due to black ice
and came down on the points cover
(electronic ignition side). The owner of the
bike at the time (who thankfully was unhurt)
had areplacement signal generator unit
fitted byadealer.Ibelieve it was from a
GS1000. He was told that it would be ‘good
enough to get it started’. That is exactly
whereIam. It starts first time, ticks overgreat, but has no power.Itisunable to top
35mph!Iwould like to check the timing,
but have no marks at all left, due to the
accident.Ihave had two-strokes all my life,
so am used to setting ignition timing with a
dial gauge and multimeter.The manual
states that the timing is 17 degrees BTDC
below 1500rpm and 37 degrees above
2350 rpm. Could you please inform me of
the measurement in mm, soIcan make my
own timing marks, using the dial gauge.
Next problem would be, there is no method
of moving the base plate, as there is only a
hole and notaslot. Ihave filed the slots on
two-strokes before to enable the timing to be
correct, and wondered if the timing is out. I
could file the hole and turn it intoaslot.
What do you think?
PeterWellsA:
In theory,the GS1000signal
generator should work ok because
the ignition timing specification is the same
as you quote. Clearly there is something
wrong somewhere though, andIthink it
would be an idea to check the timing in
case it is radically out as this will cause
damage to the engine. The timing marks are
on the rotor so if you cannot see them then
it must be quite badly damaged.Iam
wondering if the parts you have are
incompatible with each other as on the
GS1000 to design progression was: (1)
conventional system with mechanical auto
advance and points, (2) halfway house with
mechanical auto advance and electronic
firing, (3) fully electronic system with auto
advance provided by ignitor unit. So mixing
and matching parts is likely to beabit
fraught. The reason why the stator plate
does not have slots is that you are meant to
check that the timing is correct with yourOurvery own wizeneedsages,
MessrsMarkHaayycockand
SteveCooppeer,are here to
answerraalllofy our woes,be
tthhey mechanical or sstrobe rather than adjusting it, if you see
what Imean.
Youare right that it is possible to
calculate advance as piston position rather
than crank degrees from TDC, but you need
to know the effective length of the con-rods
to do this.Youwould be better off using a
degree disk withastrobe, but the best
course is just to get the known correct parts
for your bike.YAMAHA XJ650 TURBO
Q:
IamFrench and have subscribed to
CMM and it's great! I'm involved with
manyYamaha restorations, including the
likes of the RD200, RD350LC, RD500LC,
FJ, FZ and XJ models. I’m just trying to get
a650 Turbo on the road again and my
question is: is thereaturbo specialist in
England able to renew this Mitsubishi turbo?
Here in France, all the said ‘specialists’ can
only replace it withanew one that doesn’t
exist any more! Inabid to getaworking
one, I’ve got three turbos: mine plus two
from the internet, but all are rusty andIam
unable to dismantle one!
Jean-LucBernardA:
As th is is amagazine for restorers of
old bikes,Ialways recommend that
readers should carry out work themselves as
far as possible, but this is one area where it
is notapracticable proposition.Turbos spin
at incredible speeds andaslight error in
preparation or assembly could result in a
real disaster.Withthatinmind, one
company over here which will be able to
help is UniversalTurbos, who can be
contacted at [email protected]. I
am sure they will be able to help, butIam
afraid the cost is likely to be high.58 / classic motorcyclemechanics
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