How much weight/metal to remove from the steel caps

Hi just posted this on the CRMCC site as well.

Does anyone have any photographs & advise on how much weight/metal to remove from the steel caps on commando con rods?

I am starting work on my engine for next season & this is one area that I have been advised to look at.

Its a 750 engine 7S cam polished crank flowed head Mk11 carbs reangled inlet valves (still need to cut out the pockets in the pistons) I also need to shape & lighten my rocker arms.

Any advise gratefully recieved.

all the best Chris
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I only removed enough to get them in balance, which wasn't much.

Chris
This shows how much you can remove from rod caps! Seriously, my bike came with lightened rockers and rods. Basic recommendation is to grind the excess cap metal where it meets the rod and blend in. I would not remove too much of the ribs except to match the rods for weight. With the caps blended to the rods mine were about 18gr lighter than stock caps.
Sorry pics are scanned prints and not that clear. The rockers had lots of metal removed around the adjuster end, similar to Dunstall's work. Do you have his book?

http://links.pictures.aol.com/pic/eba0C ... MO4=_l.jpg

http://links.pictures.aol.com/pic/eba0C ... 2Pc=_l.jpg
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Ouch

John
Thanks for your reply, keep in contact.
We have traced the leak by the crank pulley. We changed the seal 3 times & came to the conclusion that the cases are pourous where they have been strengthened by weld around the boss. I have got stuck in to my Commando engine because I know I will leave it then be chasing like mad 3 weeks before Mallory practise in March. Its just how it is. John Conroy told me just to blend the steel caps in to the alloy rod. My friend Rob thinks there is far to much mass rotating there & a lot more can safely be removed!!!

Looking at your motor Kieth I will start with the blending in only.
Strangly Rob has never broken a Commando rod. One crank through the journal & another through the front pulley both times with no damage to the rest of the engine.

Keep up the advise

A little bit of follow up to the gearing advise. I changed the front pulley to a 36 from a 32 the gearbox sprocket from a 19 to a 21 & the rear from a 40 to a 44. Still runs beautifully drives well but on fitting my Scitsu from my Antig Daytona I found that where it stops reving was at 4,500 revs. Ie thats were it felt right to change up! Well I found out that you could drive through this & the bike picked up its skirts & went again. Nothing dramatic, ie no big step just drive, so a small platue was holding me back a lot.

I will be changing the carbs to MK2's next year & the PD3 cam will be staying in the Atlas & a 7s will be in my engine. I am going to get a daylight ticket as I have a log book for the Caffrey frame. I cant wait to get out there again.
all the best Chris

Chris
Theory is that the rear rod bolt broke. It was only 3000m old but I also had been having oiling problems with tank emptying into the sump at high sustained revs and pressure could have gone to zero occasionally. (front oil pickup on those infamous Combat cases with no lower case breather to help return oil). The bolt is in the pic and broke just on the radius of the waisted portion. Dunstall's notes recommend polishing that area and when I installed brand new rods the finish was much nicer. Rods usually break at the top end and all the damage you see was a consequence of the bolt going so I wouldn't worry unecessarily!