MC21R throttle valve marks

**Wed Nov 11, 2020 4:22 pm » Post: #1 » Download Post**

Hi all,

Having completed a bottom and top end rebuild, I’m trying to set up the oil pump. I have read all the information on setting up but can’t find any throttle valve marks on my carburettor slides. Are these marks on all mC21’s ?

I have a 90 year MC21 and my bike is smoking somewhat more than it did before the rebuild.

Any info appreciated.

**Wed Nov 11, 2020 6:57 pm » Post: #2 » Download Post**

No, the marks aren't on all carbs.

Where there are no marks, use the crest of the cutaway on the slide to provisionally balance them.

This is generally enough, but for ultimate accuracy setup should be completed with vacuum gauges.
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**Thu Nov 12, 2020 10:40 am » Post: #3 » Download Post**

If you lubricated everything on assembly, ie piston, rings and bore you would expect it to smoke a bit extra on start up.
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**Thu Nov 12, 2020 5:02 pm » Post: #4 » Download Post**

Sorry, I skimmed that post a bit, and thought it was more to do with balancing the carbs.

To be fair, the oil pump setting really isn't that critical. Shocked

I know, shock horror! But it's rather "safe" as standard, and getting it near the mark is always going to be close enough!

To set the pump gently turn the throttle just to take up the free play. The oil pump pulley should just be touching the cast stop on the pump body. The pump pulley should move as soon as the slides start to lift. At WOT (wide open throttle) the marks on the oil pump pulley should line up with the index mark cast into the pump body. Adjust the cable if necessary.

If the pump is way off the mark at WOT, and and cannot be brought into range, you need to replace the oil pump control cable.
_________________
Andy.
NSR-WORLD.COM

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