oil and break -in before racing 250

[Kthomas]

Any thoughts on oil weights and break-in times before racing ?
I've always used a good quality non detergent 40w (Castrol). I've always steered clear of synthetics on these old engines but I'm not too old to change.
It has been raining here since Thursday and I hope to put enough hrs on it before Barber. I just cranked the reworked engine two days ago. They are calling for rain into next week. I rode it today in the rain and with leaves starting to cover the roads it was more exciting than being on a track.

[Dave450]

If you're breaking in the engine, I would avoid synthetic oil because it will inhibit the piston rings bedding in. Also, I would avoid synthetic if you have a wet clutch because it could cause it to slip. If you have a dry clutch, no problem - once the engine has bedded in. A good quality 40 wt should be fine. I assume you're taking about mineral oil. Castor oil is very good but obviously you can't mix the two. Nigel Lacey on this forum recommended Silkolene Comp 4 20/50 even over castor oil and he has worked on a lot of these singles. I would try to get as many hours on the engine before the race as you can. This way, you have time to sort out any glitches, re-tighten fasteners, make adjustments and change the oil. I have a magnetic canister filter on a G50 and it showed that after running the engine for about an hour on track following a complete rebuild, there was quite a lot of swarf, which reduced dramatically after the first oil change.

[Kthomas]

I always use mineral oil whenever I'm breaking in an engine. I'm just curious as to whether people put a lot of miles on their engines before switching over to synthetic ( race bike ) as it seems to me that would completely stop the break-in process.
I don't know if I've ever seen Silkolene Comp 4 here in the US but I'm sure they sell it somewhere.

[ElmrPhD]

I always use mineral oil whenever I'm breaking in an engine. I'm just curious as to whether people put a lot of miles on their engines before switching over to synthetic ( race bike ) as it seems to me that would completely stop the break-in process.
I don't know if I've ever seen Silkolene Comp 4 here in the US but I'm sure they sell it somewhere.

Silkolene seems to have been taken over by Fuchs. See if you can find a Fuchs dealer.
Make sure you break-in the engine with high-ish revs with the initial runs being only long enough to reach increasingly higher temperature, but making sure to avoid any over-heating. Change the oil (and obviously clean the filter) as often as you can afford to in the break-in period. That method allows you to use cheaper oil that doesn't need to hold up to hours of gear-grinding, especially if you don't actually spend time on the road. This is what I've done on my '66 350 racer and it's worked out perfectly. Now, she's on Nigel's (and Eldert's and...) suggestion of Fuchs/Silkolene Comp 4 (20W50) for eternity.
Good luck,
Steve, in the NLs