Topic: Yanked ground to kill screaming two stroke

[Greaser Greg]

So the old $100 R5 started first kick but revs went way to high for my liking. I pulled  the ground connection to kill it and now it won't start. Thinking one or both condensers went out from the sudden change of current. Is this possible? It hadn't been started in years. Can they be tested on the plate with both points closed? Nuts are rusty.

[Bodi]

With the points open you just have the condensor between the wire and ground.

[Robbo]

Do you have any power/lights on with the keyswitch in the on position?

If not, first thing I would check is the fuse.

Then check your wiring and connections, especially around where you “pulled the ground”.  You may have accidentally unhooked or damaged the surrounding wiring.

Next I would remove each plug, put the plug cap back on it and hold it against the cylinder head fins.  With the keyswitch on, kick the bike over a few times and check for spark.  If no spark, then look to the condensers.

What work have you done on the bike prior to starting it?


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[Greaser Greg]

Thanks for the responses.
The fuse and tail light work.
Compression is 110 on each side.
Full power at the plate.
Didn't test the coils cuz spark looks good.
I used some too short cables that kept the slides too high, and scared myself when it started.  So I took those off and backed out the idle screw, checked all the gaps, cleaned the carbs, (they looked pretty good already), primed the oil pump, sprayed the ignition plate with brakleen, and charged the battery.
P.o. said he had the jugs off and put in a new piston and cleaned the other one and the pipes, which, by the looks of things through the intakes seems true.
I was getting different readings from the individual caps, with the points open or closed, so ordered some. Open they start out at zero ohms, then go to around 68. Is this a good value? If I spin the mechanism they go from zero to eight while open and closed. I think that second one was with the key on. Spark is blue and bright at 8mm from ground.
The ground is just an alligator clip at this point.
Got it to start again today and it ran for about ten seconds again.  Plugs are oily and wet. I'm thinking there's too much oil in the case because of my overly cautious mix before I primed the pump.  Cleaned them off, but no more starting, just a couple of small puffs out the carbs.

[Robbo]

One thing about the RD is you need a strong healthy battery.

When you get a chance, put a multimeter across the battery terminals and watch the voltage while it’s running.

It’s possible to foul the plugs if the voltage drops too low and the bike will not run.

If you suspect that there is too much oil in the oil/fuel mix because you have premixed in the fuel tank and are running the oil pump, you could try pulling the oil lines off the carbs if you are confident the premix will provide sufficient lubrication.

I always have to choke my RD250 when cold starting and it usually starts first or 2nd kick.


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[Greaser Greg]

Found a broken contact breaker point, and have been doing leak tests.
Intakes are pretty tough, leaky, and after a temp gasket, still loosing pressure and vacuum. Bike had 11,000 miles at an unknown point in time, and one of the pipes was clogged with carbon, and a piston has been replaced by the guy I bought it from. Don't know why for the new piston, probably burnt.

[Greaser Greg]

Split the cases for new seals as they were leaking air, and bearings, one of which had seized with rust, and looking for recommendations on new Pistons and rings; any suggestions? Going .5 over on the cylinders as one was oval shaped and already at .25.

[Robbo]

Split the cases for new seals as they were leaking air, and bearings, one of which had seized with rust, and looking for recommendations on new Pistons and rings; any suggestions? Going .5 over on the cylinders as one was oval shaped and already at .25.

Yamaha stock pistons and rings if you can source them.


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[Greaser Greg]

Found some NOS at a decent price on eBay, hooray!