RD125 - Down on speed & power

[SoCal250]

After I recently recommissioned my RD125 after sitting for a few years I've been trying to figure out why it's lacking top speed and power. 

It has a very hard time even pulling 50mph when it used to do 60-65 before it was parked for a long period of time.  And if I hit a small hill or rise in the road it starts to slow down quite a bit. And it does the same thing into the wind, it just starts slowing down. It just has no power any more (not that a 125 twin is a high powered beast).

Timing is 1.8mm (stock)
New points
New UNI drop-in filters in the stock airbox (no performance change from the old foam ones that were in there)
Running premium fuel (91 octane)
All new fuel lines
New Visu-filters
Pump is intact and running Motul 710
Jetting is stock
Pipes are stock

Today I checked compression.
Right: 122psi cold
Left:   116psi cold

It runs great otherwise. I'm starting to think it may be caused by a rich condition, although it doesn't four-stroke.  I've noticed that it hardly needs the choke to start. Plugs are dark but not sooty or fouled.

[RDFL]

I assume you confirmed baffles aren't clogged.

[SoCal250]

I assume you confirmed baffles aren't clogged.

Yep, pipes are NOS with about 100-125 miles on them. Same pipes before and after recommissioning.

[jradnich]

Carb slides opening all the way?

[Striker1423]

NOS points or aftermarket? Could be point float?

[klaird]

Dirty carbs??  My rd almost always needs the carbs soaked if its been sitting for any length of time.  It runs great low end but falls off on the top end.

[1976RD400C]

If it is too rich it would certainly slow down.

[SoCal250]

Carb slides opening all the way?

NOS points or aftermarket?

Dirty carbs??

Carbs slides are opening all the way. That was verified when I synced the slides and adjusted cables.
Points are aftermarket.
Carbs are spotless clean. They were compeletely torn down and run through 2 20-min cycles in my ultrasonic.
Also the enrichener was rebuilt with new viton o-rings and the float height was reset as per the factory manual spec.
Aside from the top speed and top end power issue it runs great. It revs out cleanly, take off is good and throttle is crisp and returns to idle quickly.

If it is too rich it would certainly slow down.

I'm starting to think that it has to be jetting. Just a little too rich, but enough to cause power loss without causing four-stroking. However the loss in power is quite dramatic, much more than I would expect. For example, a slight rise in a flat road or a 5-10mph headwind causes it to slow down to 40mph and requires a down shift. It never did that before.

Unfortunately, TeiKei jets are unobtanium. And I'm not really too eager to try to rejet with Keihin brass, which can be substituted, as it's not a straight correlation for the mains (and I don't believe there is any pilot jet cross ref).

[m in sc]

see if its better with headlight off. 

[SoCal250]

see if its better with headlight off. 

This is with the headlight off. I've been running with Ignition switch in #1 position (headlight and tail light off)

[m in sc]

see if its worse with headlight on. 

[SoCal250]

see if its worse with headlight on. 

Roger that. Next time I'm out on it I'll run a few comparison tests on the small hill near me

[RDFL]

Related to that check for voltage drop to coils.

[John Ritter]

Any sign that the clutch is slipping?

[SoCal250]

Any sign that the clutch is slipping?

Don't think the clutch is slipping. It's more of a loss of oomph. Revs drop into a very light breeze or a tiny hill.