Postby blethermaskite » Tue Mar 20, 2018 7:47 pm
Hi All,
Thanks to everyone for your input on this, all advice has been greatly appreciated, thanks Eldert for your contact info on John Witman, Great to report that through the help of fellow contributors to this forum I now have all I need to build a standard spec 250 desmo head and am looking forward getting the little desmo back on the road after nearly 27 years hidden away in a bedroom.
By way of explanation ref. my desire to build a standard set up head with hairpin valve springs.....it is obviously proven to be perfectly ok to convert from hairpin springs to bevel v type springs while at the same time reducing the overall loading on the valve train, and if I had been unsuccessful in finding the parts I needed this is exactly the path I would have followed, I have in the past run (single) desmo heads in a number of different specs.
1.....as suggested without any springs......result......ran perfectly for several thousand miles, but eventually clearances became out of tolerance due to the split ring collets getting hammered as a result of running the predictable wide closer clearance ( I only do nil closing clearance at the tightest spot on camshaft rotation not at tdc).
2.....for curiosity (when desmo's were not so valuable) ran a 250 without any closing rockers........result...... ran perfectly even at fairly high rpm, however I was scared to run it up to 10k plus just in case????
3.....set up as completely std. spec. with hairpin springs and nil closer clearance at the tight spot on cam rotation........result.......ran perfectly for over 6000 miles......( when inspected all clearances as when first built).
If I was building a competition engine I would happily run with out any springs or maybe very light versions of the v type springs, but for a completely standard road bike rightly or wrongly I am going for the standard head set up again. ( photo's to follow in due course)
Cheers,
George