The specs are there for a reason - too tight and they’ll seize, too loose and you’ll get oil flowing into your combustion chamber. And other problems which are just not worth it if you are rebuilding the engine. The best advice is to take it to a shop. If you can’t or don’t want to, then if you have...

Here are the specs for all singles. Measure your parts to see if your valve to guide clearance is ok. If still under, buy a hand reamer and ream the guides to proper bore.

The seats are hardened, the guides are a much softer metal - cast iron or bronze. So the abrasive will not imbed in the seats.

There should be a clearance spec for your model. Do you have a manual?

I’m afraid that was not a good idea. The abrasive particles of the compound are now imbedded on the surface of your guides and will keep wearing your guides and valves away. You should have used a hand reamer and then lap the valves, or better yet have the seats recut. Now it’s done, so if you don’t...

I think it is just a convention that the flat side of the distributor faces the back. On the Sq4 magdyno the flat side of the distributor must face to the left of the machine, n'est-ce pas? Actually it doesn’t have to. On mine for some reason, if I do it that way I wasn’t able to get enough movemen...

Mine also does not have an air filter.

... the location of the open end of the breather in the timing case as a possible cause of this. , Hi Roger, There is indeed some problems with the location - do a search here and you‘ll find a topic on it. Oil does seem to „blob“ around the dynamo sprocket and run down the walls straight into the ...

Could be anything really. I also had some vibrations on mine after the rebuild, as well on another bike I restored early this year. One source of vibration was the head lamp, and I was convinced it was the engine. On another it was the speedo cable touching somewhere. Now when I have a vibration, I ...

Hello everyone,

Looking for a cylinder barrel for my 1951 MkI Square 4 in usable condition.

I‘m located in Germany.

Cheers,
Gui

Perhaps reducing the oil pressure will help lower the overall amount splashing about. Nev But how could this be done on a Sq4? There‘s nothing one can adjust other than maybe putting a weaker spring on the oil pressure release valve. When idling, I can only see a puff of oil vapor coming out of the...