750 Combat top speed problem (2015)

If the cam is 15 degrees retarded, you have likely found the problem!

Just wondering, did you check the cam differently than you did at the time of your original post? I ask that because you stated in that post that the cam checked out OK and it seems unlikely to me that the camshaft managed to retard itself 15 degrees since then.

Yup, in New England we call that “wickid retahdid!”

Who knows after two years. This time I just checked the intake opening and closing with tappet set at .015”. I put a .002” feeler gauge in the tappet gap and as soon as it could not be removed checked the degree wheel. Not terribly accurate, but gave an indication. As soon as I advanced counterclockwise one tooth on the intermediate I rechecked timing. It was within a degree or two of what it’s supposed to be opening at 59 degrees before top dead center.
Norton double S combat cam. Now just waiting for a JS Motorsport neoprene timing cover gasket and a new oil pump seal to button it back up.

dynodave said:

I've never run anything other than 220 in my combat...and that is with Armours stainless peashooters, They are absolutely empty cans. Lucas Rita of course...
I can almost hit 95 at the drags in third. Shifting to 4th slows the time down for the 1/4.
My floats are higher than when you adjust them for a triumph.
As mentioned cam chains stretch. Make sure the cam is a little advanced and not retarded at all.
I still have to admit it seemed to run stronger with the standard 28.5mm port head.
I'm at sea level.

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Hi Dave

Got the problem not accelerating resolved. It was cam timing retarded. Seems the timing dot in the cam was off.

New question, is there a way to test a Lucas RITA amplifier to know it’s good? I’m running a Trispark now and frankly don’t trust it although the replacement amplifier (first one died at 800 miles) has not given any problems in the last two years. Keeping the previous RITA in reserve.

illf8ed said:

timing dot in the cam was off

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? The spocket dot should be inline with the sprocket keyway.
? The cam keyway is exactically in line with in/exh lobe cross over.
Both of these items are at 11 oclock (actually 12 degrees from up) with pistons at TDC
10 rollers between the dimple marks. (back to the intermediate sprocket dimple) again piston still @ TDC

I'll bet you know this now!!
I don't need any marks and I guarantee my engine will run as well as can be expected unless adding a dial indicator and degree wheel

RITA
You can verify a bad one with an ohm meter but hard to tell if good without running it. Also depends if an "A" or "B" box since they have different out put stage circuitry.
PM me

Amplifier has black on silver label. AB11 electronic ignition amplifier, Y with circle around then 47270 B

Spent some time this afternoon switching back to the Lucas RITA ignition to see if it really doesn’t work. A waste of time.
The bike fires but the advance goes all over. Cannot time it. Switched back to the TriSpark and it runs great. Just hope this second TRiSpark amplifier doesn’t leave me in the backroads some time later this year.