Dear Groupies,
I thought I would bring you up to date with my problem of breathlessness with my newly installed Arnott Blower (yes, on an MPJG!) on snap acceleration, and indeed in double-declutching. And take the opportunity to thank those who responded to my plea for advice.
Graeme in Oz and Joe in the US put me on the right track (thank you both especially ain t this group wonderful), by pointing out the need for more damping on the carb piston, not less as I was trying to figure out. After a long discussion with Burlen I discovered my H4 carb was in fact a pre-war intermediate version, with a tall top, very heavy piston and no spring (no room for one either) unlike the post-war H4 carb. Having got to that point we discussed damper piston dimensions and damper oil to use. The only damper piston length (brass tube) at the lower end that Burlen could supply for my H4 was 0.3 which is what I have. As I had previously tried 20/50 engine oil, then 3-in-1 as thinner, then no damper at all, these tests only made things worse. So Burlen suggested SAE40. Once it arrived (I only need 5.3cc but had to order a litre of course) everything worked as it should. Obvious really, I suppose.
So again, thank you guys, another T-type problem solved.
Kind regards,
Ian Linton TA3120
Lewes, East Sussex, UK