Motoplat timing

[Marc Biro]

Who can tell me the timing specs on a 1973 125 Six days with motoplat? Also, fork and gearbox oil capacities

Thank s

Marc Biro

 

[Gavin Housh]

Marc, I have had good luck with the timing set at 2.8mm BTDC. Late manuals say 2.6-3.2, and early ones say 3.0-3.5 . Advance out to 3.2 or more and the motor will run very fast on the top end, but the motor won't idle and is harder to start. Retard down to 2.6 and the motor will idle and start more easily. Be carefull of over advancing this will cause the motor to run hot and you may run the risk of holing a piston. Listen for pinging under hard acceleration, and be aware of any funny smells. Funny smells are a shure sign that things are heating up. Take plug readings. To check the plug warm the motor up then take some laps. Find a place where you can realy open it up. Run like that untill you know the motor is good and hot. (Remember any smells or pinging shut it off!) Hit the kill button and coast to a stop. Don't come idling up to the truck, shut the engine down while your'e still moving. This will tell you how the engine is running at the moment you kill the engine. let the engine cool some and then pull the spark plug. The porcelain (aluminum oxide) insulator should be a tan to milk chocolate color. If it's lighter or whitish your advanced(3.5) to much, or your jetting is to lean. If it's darker or black you may be retarded(2.6) to much, or your jetting is to rich. Try this combination 2.8 BTDC, NGK B8HS plug, 140-145 main jet with stock bing 27.5mm carb and stock porting. When ever changing timming or jetting go a little at a time and then test for results. Don't ever change the spark plug heat range to a hotter plug to fix some problem with jetting , timming, leaking crank seals, or to much oil in your pre mix. The Penton manual used to list two spark plugs. one was for general riding and the other was a colder plug for prolonged riding like an enduro. The NGK B9HS is the colder plug. In the old days we used Bosch W260T1 for general riding and the Bosch W290T16 was listed for cross country riding. Fork oil capacity is 135cc for 32mm fork, and 180-200cc for 35mm fork. Gear box capacity is 600cc. I'm going to try Kips suggestion of 700cc. (read lack of gear box oil)

 

[Marc Biro]

Gavin,

Thanks for the info. I will give it a go this weekend. I hope to have the bike ready for the "Vintage Iron" meet at Glen Helen in June!

Marc