Motorcycle Repair: Problem staying running, seasonal storage, tight budget

Question
Falcon,

First of all, thanks for your time. Now onto my question...I have
an older Suzuki Katana (I think it is a '94) that I bought last year.
At first it ran perfectly, but last Fall while I was riding it it stalled
out while at a stop sign. I tried to get it to restart but it would
not. After it had cooled down it would start up again but would
die out eventually. I can now get it to start, but after it runs for a
bit, the engine starts to rev lower and lower. I can keep it going
for a little while by giving it more and more gas, but it fades
eventually no matter what.
I am o student and on a pretty tight budget, but I am wondering
if there is something that I might be able to do to repair the
bike?
Thanks again fro your time.

- John

Answer
Hi John.

 First thing to do is to spend the money on a repair manual, if you haven't already.  That one book is worth it's weight in gold because it has all of the test proceedures and specs on the bike.

 There are a few things that could be wrong.  They are in order from easiest to fix to hardest and most expensive.

1) Clogged fuel filter.  Cheap and easy fix.  Check to see if there is a fuel filter on the bike and, if so, replace it.

2) Spark plugs.  How old are they?  If you don't know, then replace them with a new set, properly gapped.  Check the old ones and see what they look like.  If they are blackened, then you could have other issues.

3) Wiring issues in the ignition system.  This requires the wiring diagram (found in the repair manual) to chase down the wires and look for shorts.  It is time consuming, but worth it if there are any shorts in the system.

4) Dirty carbs.  If the bike spends or has spent any time in annual or seasonal storage, then the entire fuel system is contaminated.  It requires complete cleaning of the carbs, replacement of the fuel line and resealing of the tank.

5) Bad/failing coils.  These need to be checked in accordance with the repair manual, but test them both when the engine is cold as well as immediately after the bike dies out.  If it is heat related, you will find it then.

6) Mixture problems.  This could be due to dirty carbs, dirty air filter, loose/cracked intake manifolds or even loose exhaust pipe connections at the head.  Check all of the connections from the carbs to the manifolds, manifolds to head, exhaust header pipes to head, as well as for visible cracks in the manifolds.

7) Compression loss.  Normally, this shows up even when the engine is cold, but there could be other issues that could cause it to show up when the engine heats up.

One other thing........DO NOT TOUCH THE MIXTURE SCREWS.  They are set at the factory.  If there is evidence of tampering of the mixture screws, then take it to a shop to have it properly reset.

Let me know what you find.
Good luck and ride safe.
FALCON