- Sat Dec 27, 2014 5:57 pm
#4533
Hi all, and particularly TimB (NZ). Thanks again for the advice a few years back on twin-plugging – a great success. I’ve been carrying out all sorts of tests on cam and pinion settings, both OEM indian and Mr H’s Performance cams, different silencers (OEM torpedo, shorty english, dunstall copy and short rev-cone megga) and found little difference in the reversion. The best cam timing is that equivalent to the Redditch cams (see attached image and available in ChrisD200 in Bullet Cams folder in Photobucket) – but it is still not right as reversion occurs. The images show the zones of overlap too – very interesting (please note I measured pushrod lift at 15degree intervals but for this plot have extrapolated to every 3degrees and the grid is at 9 degree spacing. Please note too the Redditch plots are based on the reported open/close degrees at 12 thou and the symmetry – I assumed straightline lift between max and min values, all the others are measured. If anyone has real data for the Redditch cams, I’d love to get a copy.
Its not just a slight puff of reversion (known to be exhaust gas because the carb gets sooty), it’s a cloud the size of the air filter box itself! Now, after all these tests, I can only assume it is, as you say, due to the speed of the exhaust gases – there’s nowt else to check. I know the head is badly coked up with oil – suspect either leaky valve guide or dirt on metal-to-metal head joint, so I guess the gas flow rate is somewhat reduced anyway, however the 43mm ID downpipe is not blocked as a ball will roll through OK.
BTW, whatever the state of the bike, from new until now, and despite all this work, I’ve NEVER managed to get it to go faster on full throttle than it does on half throttle. But in the meantime, can you please advise on which 350cc 1½†pipe. Is it PN 200088 or 91006/5 (which are both far too expensive for me at GBP165 complete) or is it the indian one (PN 14055)? Is that an ID or an OD?
I’m also puzzled. Every source I’ve seen, both our hosts and other sites, say to fit a larger down pipe if you tune the bike as I have (8.5:1, 32mm carb, larger exhaust valve, performance cams etc) so there must be hundreds of others who did the same upgrades and found the similar problem? Or is there something else it could be?
Cheers, ChrisD
Its not just a slight puff of reversion (known to be exhaust gas because the carb gets sooty), it’s a cloud the size of the air filter box itself! Now, after all these tests, I can only assume it is, as you say, due to the speed of the exhaust gases – there’s nowt else to check. I know the head is badly coked up with oil – suspect either leaky valve guide or dirt on metal-to-metal head joint, so I guess the gas flow rate is somewhat reduced anyway, however the 43mm ID downpipe is not blocked as a ball will roll through OK.
BTW, whatever the state of the bike, from new until now, and despite all this work, I’ve NEVER managed to get it to go faster on full throttle than it does on half throttle. But in the meantime, can you please advise on which 350cc 1½†pipe. Is it PN 200088 or 91006/5 (which are both far too expensive for me at GBP165 complete) or is it the indian one (PN 14055)? Is that an ID or an OD?
I’m also puzzled. Every source I’ve seen, both our hosts and other sites, say to fit a larger down pipe if you tune the bike as I have (8.5:1, 32mm carb, larger exhaust valve, performance cams etc) so there must be hundreds of others who did the same upgrades and found the similar problem? Or is there something else it could be?
Cheers, ChrisD