Building my motor i'm looking for advise again please, I have read that a duplex chain is favourite, although due to the relative low state of tune is this really necessary? As long as I can dial the cam with a new chain gears and vernier surely that would be enough?

er which engine? is it a high lift cam?

sorry, locost xflow with control cam

Ah ok I'm not sure about the x-flow but as a general principle I would say that the duplex chain is for durability - the simplex chain will stretch and affect the can timing - particularly if driven enthusiastically (and why have a Locost if you aren't going to drive enthusiastically?)

I would fit the duplex chain and then it can be forgotten about.

I'm pretty sure my Randall engine has a simplex chain, part no is TC 1346. It gets replaced at each rebuild.

BTW for 750MC racing you can't use vernier gears, but offset dowels are ok for the camshaft timing

[Edited on 25/3/12 by Richard Jenkins]

Realy i just assumed as i didnt read it the specs.ive not completely researched this off set dowling yet any info would greatfully be received. I have dialed in dohc race engines before so im hopeful that i can get my head around it

In section 5.7.1 of the regs it says offset dowels are permiited and in 5.7.2 vernier timing is prohibited. But that is as far as my knowledge on this subject goes, hence why I get Brian Randall to build my engine!!

Found this on the Burton Power website which may help?
http://www.burtonpower.com/tuning-guides/tuning-guide-pages/camshaft-fitting-timing.html

I dont know why but i like to understand as much as race, i've been refreshing re-building bike engines for some time more down to money than anything my last bike was 400miles between refresh's! The valve timing thing the first time drives you crazy but once you got it its easy enough. Off set dowls are very new on me and the burton's info you sent(thank you) only just touches on it. for all at Silverstone have a belter!!

I'm now familia with off set dowels