New project '73 Yamaha RD250

[Czakky]

I've definitely done the same with the roll pin...

[Arrow]

For maximum security I fit the roll pin with the tapered end, but it ends up full diameter all the way through the hole/top casting with no tapered end, works well.

Sent from my SM-G973F using Tapatalk

[so-cal-sdr200]

I am at a complete loss to figure out why I am not getting spark to my left side cylinder.

SoCal250 came over and we set the point gap(s) and set the ignition timing as close
to 1.8 BTDC on each point set as possible. He used the dial gage to set the piston height.
and a little 12VDC light to turn on when the point gap opened.

New Yausa battery fully charged. Added gas and gave it a kick, or two and the RD started
on the Right side cylinder only.
Things I've tried so far.:
1. Changed spark plug to another new one.
2. Checked orange wire continuity from the point plate to the coil = Okay.
3. swapped the left and right coil set, including plug wire and plug cap.
4. just for the heck of it, I added grounding wires from the studs that mount the
      coils to the frame. My frame has been powder coated and the coils would not
      see ground if they needed it. Which I don't think they do.
[Edit:]
5. changed condenser with a new one from Economy.

Still only runs on the Right side cylinder.
Only thing I can think of is there is a problem with the left side point plate itself.

[Edit:] I have a new set of points, but, would have to re-gap and re-time with gage tool.

Visually left set appears to be in great shape and looks no different than the other point set.

  OR!! The carbon brush(s) are failing.

I do not fully understand how this system works and if the brushes could cause
my problem.

Does the Rectifier / Regulator system have any effect on the Ignition system?
Also, I do not think it does. I believe they are independent.

Before I drop the $$ on an electronic ignition system I would like to figure out my problem.

Thanks, Jeff

[dgorms]

Gas? Is the left plug wet?

[so-cal-sdr200]

Yes, gas.
Pull plug, grounded to head... no spark.
Thanks, Jeff

[Striker1423]

Yes, gas.
Pull plug, grounded to head... no spark.
Thanks, Jeff

First, try running a file or fine sandpaper over the points itself. Burnt points means no spark.

Next, make sure that the left side set of points aren't grounding out. If you have spark on one side your brushes are fine.

Points like to ground between the points spring and the pivot pin. The plastic insulators gets brittle over time and can crack. They can also be misaligned, allowing the spark to jump to ground.

[so-cal-sdr200]

Thank you for the suggestions. I used 800 grt paper and matchbook paper to clean the points.
They look fine to my eye. The plastic / fiberglass followers that ride on the cam lobe also looks
to be in good condition. I can take a pic and post it up here if anyone might see something that
(me), Captain Obvious, might have missed.
I will inspect the left side points even closer for any possible grounding.

And as a last resort replace the point sets with the new ones I have. Will have to invite my
friend So-Cal-250 back with his dial indicator kit to re-time the ignition.

Thanks for the tip in the carbon brushes. I was hoping they were not the problem.

  Hopefully I will have a positive update soon.
Cheers, Jeff

[so-cal-sdr200]

Update:
Not sure what I did, and not sure it is a permanent fix, but, I got spark. Might be intermittent.

See pickture:

I removed the two screws holding on the carbon brushes, green wire and the brown insulated
cover for the green and orange wires being held by the clamp on the right side of the
brush assembly. The clamp looked to be binding the insulated cover before this pic was taken.

I cleaned the copper rotor and the carbon brushes with a paper towel and reinstalled everything.
 
Turn on the key and I get spark in the left cylinder. First couple kicks seemed to be intermittent,
but, now it seems to be consistent.

I'll need to check again, but that clamp might have cut through the insulation on the orange wire
from the left side points.
Will have to re-install the tank etc... and see if it will start.
Wish me luck.
Jeff

[SoCal250]

Turn on the key and I get spark in the left cylinder.

[Striker1423]

Turn on the key and I get spark in the left cylinder.

Agreed! Nice work.

[so-cal-sdr200]

Seems to be running on both cyl's. Both pipes getting warm, (hot).

Taking off from an idle the bike boggs giving it throttle till the R's get to maybe
2K and then it takes off. Around 4K RPM the clutch slips and the motor rips to
6-7K before I can pull the clutch lever in. 

Guessing I have a jetting issue. Both mains and pilots are brand new and carbs
cleaned and rebuilt. Think the pilot is #35 and mains are #150. running larger
than stock sizes on the recommendation of my engine builder. So far maybe 5 min
of run time on the new motor in two thermal cycles. And 1 mile of 1, 2nd and one 3rd
gear run up the street.

So seems I have a new problem... Using fresh Motul TechnoSynt gear oil.

More to follow... Thanks.
Jeff

[Striker1423]

What are your air screws turned out to?

35 pilot is what I have in my 350 setup on a Dave F mod. My air screws are at 1 turn out basically. But, that's what felt ok on my off the line throttle. May even need bigger myself.

But. You're air screws will determine off the line performance.

[so-cal-sdr200]

 My air screws are set at 1.5 turns out. Next time I start the bike I will try adjusting them in
and out in 1/2 turn increments.
One possible issue.... The other day when I was not getting spark and trying to start the bike.
I let it sit over night and the carbs started weeping around the float bowl gaskets and had a
little gas in the overflow hose's.
So I bent the float tabs to reduce the float height and may have gone too far. Maybe I am having
a lean condition at the pilot jets? Although it does idle fine and starts with 1/2 a kick through.
Wish all my bikes started this easy.

As a side note. I am running the rebuilt stock injector pump, Honda GN2 injector oil, and initially
mixing Motul 800 @ 40:1 till I am sure the pump is working correctly.

Still think I need the replace the points and re-time, just to eliminate that possible problem.

The clutch slipping is going to be a bigger issue that I need to discuss with my engine builder.
He installed a whole new basket, pressure plate, clutch plates / springs etc...

  Thanks for following my journey.

[Striker1423]

Sitting on the sidestand overnight a little gas weeping out of the lower carb is normal. A pool of gas under the bike on the center stand or side stand isn't.

Setting FUEL height is more important than float height. Evans Ward sells a kit to aid in adjusting the actual fuel height. It's not that hard and works well.  Setting the float height is the standard method but not the preferred way. In either case, the measurements should come close to matching and not be eye-balled if you can help it.

[so-cal-sdr200]

I guess it is time for an update...
The RD250 is more or less finished. I have put around 100+ miles on
it so far.
Seems tweeking the orange point wire and replacing the points and condenser
has fixed the spark on the left cyl issue.

With the 35 pilot / 150 main with the needle in the middle clip. The bike had a very
pronounced bog from low RPM into mid-range. I dropped the clip, raised the needle to
this richest level and the bog mostly disappeared. But the bike would not pull above 5K RPM
in 5th / 6th gear.

I figured that the Needle jet was too lean. Stock it is a O-8. So I ordered two new sizes.
A P-0 and a P-2. Installed the P-2. Figuring I might be too rich with the needle clip in the
bottom groove, I moved it to the 2nd from the top. Thinking the 35 was also too rich as adjusting
the air screw seemed to make no RPM difference I dropped in a pair of 32.5 pilots.
  ( I know... never change more that one thing at a time!) I'm not done. Since stock was 120 main
I had a 150 in there. Thinking it was too rich to pull above 5K RPM I dropped the main to 145.

So?  The mid-bog was back, but it pulled well into 6-7K RPM once it got beyond the stumble...

Put the clip in the middle position and the bog was reduced, but, not as crisp as I think it should.
And with the 32.5 I do not get a pronounced rpm shift moving the air screw from 1-1/2 turns either.

Confused... Through all of this the plug colors have remained a fairly nice tan to a slight lean look.

Kind of chasing my tail, but yesterday was warmer, (82F) and the bike seemed to pull stronger
than the last test ride in the mid 60F's.
Guess I will drop the needle clip one more groove, 2nd from bottom, and see if it improves more.
Suggestions are always welcome BTW....
P.S. Was looking for the torque spec for the head bolts / stud nuts and could not find it in the manual.
Can some one let me know? Thinking it is around 18-20 FT/LB, but, don't want to screw up.
Thanks, Jeff