Motorcycle Repair/cams


hi Wayne
i am in the process of building my 81 gs 1100 i am planning on putting the following into it

1166 block & pistons ( 10-25-1)
33mm smoth bores
stage 2 ported heads
engerearing race headers
andrew coils
dyna tek ignition system
the cams i got are as follows
intake g9  410 lift 258 duration
exhaust g21 380 lift 250 duration
are theses cams to big for the bike as i still want the bike as a daily driver ????? if they are what would you recomend ???
thank you for youre time
steve kettles

The cams you plan to use are just on the edge of being
a full race cam. They will not be too good for low speed
driving as they are better at mid to high speed performance.

A safe bet is stay with cams in the "3" range as anything with
a "4" like the 410 lift is better for the race track.

For very hot street/strip  use these specs would suffice:
G21/G5   .380"   lift    250   duration  
         .360"   lift   266   duration

The milder cam will give you more street performance
and the wilder cams will only be better for high speed
or longer distance performance.
You might be surprised when a street cam equipped bike
passes you due to their greater low end torque around town.

If you plan to go nitrous or full race then the other cams may be a benefit
however they often require shortened valve guides and
extended rocker arms and other extensive modifications.
Also, the crankshafts will twist on these 81's if things get
too wild as they are not welded.

Just be sure to use ample clearances as you set things up
to prevent any mechanical interference problems.

There is always a tendency to choose wilder cam specs
but it can be self defeating depending on what you plan
to do with the added power.
If you just want a fast street machine then looking
for a balance between low end torque and mid range
might be best. If you want a bike that has a stronger
mid to high speed then the full race camshafts will
be your choice.
The race cams may require a carburetor change as well
so things can add up.

Whatever you choose the process will still be fun
and interesting, that's the real point anyway
isn't it? Have fun!


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Wayne S.


Licensed Motorcycle Mechanic, Knowledge of motorcycles from 1960 up, Japanese, British and most other brand motorcycle repairs.


Worked for Yamaha, Honda, Suzuki, Kawasaki British: Triumph, Norton, BSA Other: Most Scooters and Mo-Peds

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