"New" problem

I've recently started having a problem while riding. Occasionally the bike will randomly start loosing power and die on me. When this happens it is impossible to restart until it has fully cooled down. My dad informed me that he had also experienced this problem which caused him to put the bike up in '89. He told me that he took it to several repairshops and no one was able to solve the issue. Any ideas?

 

It sounds like it's could be overheating and could be due to a weak fuel mixture.
Check the colour of the plugs to give a bit of an indication, white equals hot (running weak), brown/tan is normal and black/sooty is rich.
Also, long shot here but, are you getting the bike into top gear when riding?
When i was a novice, 30 odd years ago, it happened to me because i didn't get into top and was over revving causing the bike to overheat. JAT.

 

I'm mainly riding on back country roads so I hardly have a chance to shift into fifth. I've wondered about it overheating but my plugs are a tan color though it smells like its rich.

 

Could be many things but you need to start with the basics to narrow down what it happening. The engine needs two basic things to run, fuel and spark. Which one is missing?

 

Classic symptoms of a motor needing a VALVE ADJUSTMENT.

A motor needs compression too; if one or more valves isn't sealing once hot it ain't gonna run.

Check the valve clearances right away; you might get lucky and catch it before you burn a valve.

 

The valves are all in spec. I have good compression in the 145 to 150 range. I have yet to checker compression when hot though.

 

If you have 145+ Compression, ... you're in good shape.

 

Vapor lock?

 

+1 Thrasher
Happened to me twice on 2 bikes.
Check that gas cap

 

I had a similar issue, it turned out that the kill switch contacts had gone a little green and needed cleaning. The heat and cool down period was a red herring.

 

If the Plant and Carbs haven't had Scheduled Maintenance pulled and the Carbs removed and thoroughly cleaned, ... you NEED to do everything listed in a the Maintenance Schedule do to the bikes age, ... not miles.

 

The gas cap has been cleaned and the vent holes can be blown through. Are the only contacts for the kill switch in the switch itself or are there others? I have cleaned all of the relays that are ignition related. Unfortunately when this has occurred I have not checked to see if I have spark.

 

My vent holes could be blown through too.
I took it apart and found gunk inbetween the seal and it wasnt breathing.
Its 2 screws up top, then 4 down low. Check it out. Do the easy free stuff first.

 

I've had it apart to clean it, but ill look again. Any chance it coul possibly be tci related?

 

Anything's possible, of course.

When you did the carbs, did you wet-set the floats, individually and accurately?

Are you running an inline fuel filter?

 

How long before problem starts? Easy to eliminate gas cap, just undo it with spare key when problem starts

 

I have an inline filter and have wet set the floats. I currently have them apart again due to my failure to replace the throttle shaft seals. I had one that was leaking.

 

From the time the problem starts it usually takes about two seconds until it dies. Not really enough time to open up the cap.

 

My bet is on the TCI

dave f

 

Today I had an opportunity to mess around with the seca some more and had it die on me again. I managed to remove the gas cap though it did not alleviate the issue. Being very close to home (in the driveway) when this happened I immediately checked the compression and came up with good numbers along with a good strong spark in each cylinder. After a few minutes I found that If I blew into the gas tank, to pressurize it, the engine would start but die as soon as I stopped.

 

Then try setting the petcock to PRI and see what happens. Sounds circumstantial to me at this point, and I'm gonna stick w/ the tci for now. But try it.....it may turn out to be a bad fuel valve or a collapsing hose, but we'll see.

 

Have you tried it without your inline filter? Maybe it is clogging but doesn't show it.

 

I've removed it and put in a piece of straight fuel line. It does seem to be heating up really quick at idle on the 1st and 2ne cylinders. I recently replaced the idle jets with #40's from power barn. Any adjustment to the pilot screws on these cylinders seem to not make a difference.

 

If there is no discernible changes to the rpm's while making adjustments to Pilot AIR Screws, ... the Bike isn't Tuned to Run on the Pilot Jets.

You should be able to have the Bike IDLE until it runs out-of-gas if the Idle is set right.
(Speaking of which, ... check you aren't low on Fuel)!

Bench Sync to the 3-Carb using 3X5 Card Strips.
With the Butterfly's closed, ... Adjust IDLE.
ColorTuning is a great Time Saving Tool.

Get the Hole to Burn BLUE.
TWEAK the Mixture Screw OUT until the BLUE fades-out to Reddish.

Idle + Supplementary Richness to Fuel "Off-Idle".

 

I replaced the idle jets with #40 Hitachis from powerbarn. Could these jets be the wrong ones despite the being #40s? Is there a way to measure the hole? I have done a bench sync and a running sync but neither of these have helped.

 

I pulled the carbs earlier and found that the main needles were all slightly different. It seems that on each one, the plastic "ring" at the top is pressed on all the way or just partially.

 

It almost sounds to me like you aren't using vacuum hose somewhere from the tank/petcock to the carbs. Or it's very old vac hose. The hose could work fine until it heats up from siting behind the motor with no airflow around it, then it collapses on itself and cuts off vacuum to the petcock, causing low to no fuel flow.

Vac and fuel hose is about 5 bucks at the auto parts, start with that.

 

Open up the TCI unit and make sure that the heat sinks are still attached to the transistors. If they get overheated, thy can cause shutdown issues like you're having.

 

Running it on prime should prove if the vacum hose has a crack or is faulty, but dont leave it on prime if not in use. I had a stopping problem with mine and eventually replaced the TCI unit and now she runs like a dream.

 

5 bucks says it's the coils