That could've been bad!
Glad it wasn't.
I think the bracket is the way to go for testing.

 

I took the quicker way and just dropped off the unlightened stock flywheel with the local welder for him to add 3mm. He'll do a good job and it won't cost much at all.

 

The other flywheel has been lightened? Another variable into the mix then?

 

Ya the one without the added timing piece had been lightened. You never know how lightening the flywheel on a single cylinder is going to affect it. It could rev quicker in the lower gears, but with less flywheel effect to carry the engine through the other 3 cycles it could be slower in the taller gears?


I'll get the stocker lightened after the welding is done on it.

 

"5 grams at 7400 g's is almost 90 pounds of force. Use good glue - lol! "

If I had to guess, it probably came off the first time you blipped the throttle.

I figured that's what would happen - glad it didn't cause you any problems. I'm really enjoying reading about all of your experiments - good on you for getting your hands dirty and playing with all this stuff.

 

I had a feeling I didn't want to leave it on any longer than necessary. The idle was noticeably higher each time I went out and returned -except maybe for the last time I rode it. So I think that added piece was still on during the first couple tests at least.

I'll bet it turns out initial tests were valid, especially regarding Bernie's assertion that this change in timing allowing higher rpm and more power as the revolutions climbed. But to better match his test I'll put the 34 CVK back on when I retest the timing mod after I get my welded flywheel back.

 

Please take some good pics of the modded flywheel - I'm likely to get mine done up..

 

I think the difference between the 36 & 40mm carbs at 250cc has more or less proven to be negligible. 0-60 times and trap speeds over my course are near identical. At least it's now known the 40mm will work very well and could be something to use with bigger bores.

I still have a BB 331 kit here waiting its turn to go on, so I can try the 40mm again after I'm at 331cc.

I'm getting the itch to save doing any more minor comparos for later, and do the cam mod next. I can still try all the little changes later after the cam mod. I'll want to put the 34 CVK back on to check a/f ratios just before and immediately after the mod to try and identify any jetting changes the cam mod requires.

I probably want to change my course set up one more time first though because the bike is just droning along/tapped out at 8200rpm the last few seconds making it hard for the change a mod may make to show up in measured speed.

 

The timing mod just adds a 3mm long piece at the front of the nose. Which is very tiny. Evidently width (side to side across the flywheel) doesn't have to match the rotor's nose width because Bernie was taking 15mm IIRC.

I'll take a Dremel to the welding he's done to get it looking perfect, and I might as well take the flywheel to a machine shop and have them match the OD to the lightened one I have. If I need to skim any weld off the top they can do it while it's there. Or I can wear it down with a sanding drum.

I'll probably get the flywheel back today so I'll have to pull that cover to measure the light flywheel OD.


Look into buying another $3 bracket that holds the pick up coil to either elongate its' holes or slice it/move one half 3mm, and get it welded back together.

 

What is the timing mod?