Thursday, 24 April 2008
Since our outing at Snetterton, some things have happened...
1) My missus finally hit the roof with the prolonged head-build on the dining room table. Much cooking and grovelling to be done this evening.
2) I have dremelled the inlet manifolds such that they line up with the (enlarged?) inlet tracts in the head
3) I received from Rog (you lovely, lovely man!) some shims of 1.6 - 2.0mm to sit under the lower cups under the valve springs. These allow the installed height to be as per the R/D spec. Effectively this preloads the valve springs. I'd think that failure to appreciate/rectify this would result in valve float at high revs.
4) Ordered some spangly new oil lines.
So last night (having promised that the head would be off the table and atop the motor that evening) I got my shims on, and just before putting the springs & collets etc together, I thought I'd make sure that at full lift the collets & top spring retainer don't foul the valve guide seal.
Guess what?? There's contact... I can still turn the cam, but I wanted about 1mm clearance. The spec sheet recommends 50 thou, but I reckon 40 would do. Anyway, its a no go.
I tried tapping the seals on, taking them off, grease on the guide, etc etc. No f'cking joy. This would surely be asking to drop a valve...
The seals are pattern parts. I have now ordered genuine Yamaha parts, so we'll see if these are any neater... Failing that, it will mean (god no!) machining the already shortened guides.
Its a puzzle, as the motor ran with this cam. Although not these springs collets and retainers... I tell you what, building this motor is fast becoming a pain!
Thursday, 17 April 2008
Friday practice was the low point of an otherwise brilliant weekend. Having been fairly confident that Steve Lakes bike, TZR250 chassis and SRX640 engine, would be reliable for the whole weekend Andy promptly dumped it at Russell’s chicane. I think he had a genuine excuse as the tyres were not brilliant (road-biased), it was on the first lap (cold tyres) and although not actually raining, it was damp. Andy suffered minor, but I expect painful, injuries – hip and hands bearing the brunt of the impact. Unfortunately his long serving Arai splat-hat also took quite a battering as he slid face down along the track.
The race on Sunday, by comparison to the previous days disaster, was slightly anti-climactic as everything worked more or less as it should - no crashes, no breakdowns. Andy finished, albeit in a foul mood. The borrowed bike was still rather underpowered compared to the rest of the field (sixteenth out of twenty six starters is OK, isn’t it?). Perhaps our rather poor showing could also be attributed to a lack of confidence after a fairly fraught weekend. However, we are supremely grateful to Steve for his loaning us the bike. Thanks, you're a gent!
Tuesday, 8 April 2008
To get it race legal, we needed only number boards, a bit of lockwiring, some attention to the fairing, a kill switch, and that's about it. We've changed the sprocket for Snetterton's long straights.