- Thu May 24, 2012 6:36 pm
#522
Just thought I'd look in and say how I've been getting on with the Hitchcocks tuned head I fitted to my 350 bullet classic to replace the original one that dropped its valve seat.
All in all, it's made a big difference to the bike. In combination with the tuned samrat rockers it must have wiped a couple of ounces off the moving parts in the valvegear. The bike is noticeably quicker off the throttle and will pull through to higher revs. This has the major upside of allowing the bike to pull fairly well up to maybe 50mph in third making it not so much of an uphill struggle to hook fourth and get it purring along nicely at road speeds. The whole experience seems smoother.
To put some figures on it, I went along to the drag racing again at Kirkbride drag strip. My previous best had been 22.68s @ 58mph over a 1/4 mile sprint. This time round I managed 19.86s @ 63mph. The speedo was showing just under 60mph in third before the valves started to float and I had to hook fourth. My 30yd times were very similar to the last time out so it's all top-end gain.
Interestingly, I also noticed the pressure bypass valve working for the first time. By the time I'd done a few runs the oil was getting pretty thin and hot and I reckon the overrevving and abrupt gear changes meant the scavenge pump was working overtime as I finished each run and wound off. I could see a little oil seeping round the banjo on the bypass valve each time I came back down the strip. I've kept the o-rings in the samrat rockers so they are properly pressure-fed so it's nice to see the bypass valve is doing its job.
It's tempting to try a bigger carb on it to take full advantage of the tuned head but equally, it's running really sweetly on the standard mikcarb. I may try one of the several CV carbs I have lying about off various defunct Japanese machines, more to see what happens than anything (I suspect an almighty backfire and a torn diaphragm).
All in all, it's made a big difference to the bike. In combination with the tuned samrat rockers it must have wiped a couple of ounces off the moving parts in the valvegear. The bike is noticeably quicker off the throttle and will pull through to higher revs. This has the major upside of allowing the bike to pull fairly well up to maybe 50mph in third making it not so much of an uphill struggle to hook fourth and get it purring along nicely at road speeds. The whole experience seems smoother.
To put some figures on it, I went along to the drag racing again at Kirkbride drag strip. My previous best had been 22.68s @ 58mph over a 1/4 mile sprint. This time round I managed 19.86s @ 63mph. The speedo was showing just under 60mph in third before the valves started to float and I had to hook fourth. My 30yd times were very similar to the last time out so it's all top-end gain.
Interestingly, I also noticed the pressure bypass valve working for the first time. By the time I'd done a few runs the oil was getting pretty thin and hot and I reckon the overrevving and abrupt gear changes meant the scavenge pump was working overtime as I finished each run and wound off. I could see a little oil seeping round the banjo on the bypass valve each time I came back down the strip. I've kept the o-rings in the samrat rockers so they are properly pressure-fed so it's nice to see the bypass valve is doing its job.
It's tempting to try a bigger carb on it to take full advantage of the tuned head but equally, it's running really sweetly on the standard mikcarb. I may try one of the several CV carbs I have lying about off various defunct Japanese machines, more to see what happens than anything (I suspect an almighty backfire and a torn diaphragm).