- Joined
- Aug 20, 2014
- Messages
- 151
Correct, cams are the same apart from rev counter worm.
It's the inlet that was retarded. The "emissions" viewpoint is, in doing this, the overlap was reduced which reduces exhaust emissions. You are also correct that correcting this tends to fill the mid-range more than top end. I've never seen a before and after dyno but people do swear it's very noticable. I'm guessing top end might be reduced slightly, but probably net result is a much sweeter engine. Here's a quote from Richard Darby (3D motorcycles) from the Triples Online forum, but the whole cam timing optimisation started within the factory race shop. The methodology I mentioned in the previous reply for setting cam timing revolves around getting a specific lift figure at TDC, hence Richard's quote.
"I find that # 4 throttle slide is preferable as it is slightly leaner and gives a much crisper throttle response. As regards cam timing, I said that the T160 inlet tended to be 1/3 tooth retarded compared to the standard factory figure (approx 0.135" @ TDC) or 2/3 tooth compared with the optimum setting of 0.150" @ TDC. Hope this helps".
I also understand that Jack Shemans and/or Les Williams used to recommend setting tappet clearances a couple of thou wider which would achieve a similar thing (with even more valve train noise!)? Search tool on Triples Online is your friend!
It's the inlet that was retarded. The "emissions" viewpoint is, in doing this, the overlap was reduced which reduces exhaust emissions. You are also correct that correcting this tends to fill the mid-range more than top end. I've never seen a before and after dyno but people do swear it's very noticable. I'm guessing top end might be reduced slightly, but probably net result is a much sweeter engine. Here's a quote from Richard Darby (3D motorcycles) from the Triples Online forum, but the whole cam timing optimisation started within the factory race shop. The methodology I mentioned in the previous reply for setting cam timing revolves around getting a specific lift figure at TDC, hence Richard's quote.
"I find that # 4 throttle slide is preferable as it is slightly leaner and gives a much crisper throttle response. As regards cam timing, I said that the T160 inlet tended to be 1/3 tooth retarded compared to the standard factory figure (approx 0.135" @ TDC) or 2/3 tooth compared with the optimum setting of 0.150" @ TDC. Hope this helps".
I also understand that Jack Shemans and/or Les Williams used to recommend setting tappet clearances a couple of thou wider which would achieve a similar thing (with even more valve train noise!)? Search tool on Triples Online is your friend!
Apologies for the off-topic. Carry on!