I'm interested in buying an A10 which has been described as being a bit noisy in the top end. The seller has explained that engines with alloy heads are noisier than the older iron versions. Has anyone got an opinion on this? I only have had experience with A10's with iron heads.
Hi mate,
here's a link from the other side > https://www.a7a10.net/forum/index.php?topic=3383.msg23214#msg23214
Other threads are available. HTH.
Hi,
The aluminium heads can be a bit noisier as I think the iron heads muffle the valve noise a bit better.
With iron heads the valve clearance is 10thou and 16thou whereas the ally heads has 8thou and 10thou specified. Initially the iron head can sound a bit noisy but will quieten down as it heats up. I think it is the other way with the ally head as the it will expand a bit more.
The ally head is meant to help with heat dissipation from what were intended as more sporty models. They also have a slight 'downdraught' angle on the inlet manifold. This would be very hard to replicate on an iron head.
Larger valves can be fitted to iron heads and some porting can be done but in the end it will not have the potential of the ally head.
A slight increase in compression will help but higher compression will result in more heat especially when used in anger.
If you have to change then valves fit the Road Rocket type and Eddie Dow type springs and caps and collets from Ebor Bikes. Proper control of the valves helps at higher rpm.
Another tuning tip is to lower the gearing with a 20t engine sprocket rather than a 21t as this allows the engine rev more freely and gives better acceleration. Sidecar gearing using and 18t engine sprocket will result in phenomenal acceleration but 85mph may be as fast as you will be happy go as the engine will be singing at a this point.
However, before doing anything drastic go back to basics and check everything. Timing, valve clearance, compression and the carb setup. Also, when it is running try to determine if any of the valve guides are slack as they make a noticeable noise when sliding up and down.
This answer may also be relevant to another post.
Dave.
Thank you Dave for such a valuable and lengthy reply, it's much appreciated .
In the end there's no substitute for taking it apart and checking for wear on the push rods, rockers and adjusters and setting the clearances right. I think the ally vs iron is a distraction, having had both I don't recall much difference.
Hi,
The closer you can get to the exact design specs. the better so yes, check every thing for wear and spend a bit of time getting the adjustments spot on.
If you have an iron head work with that but at the end of the day it depends on how you want to use your bike. Personally I would rather have low to mid-range performance which takes you well above the speed limit if you really need to. Going for top end may be tempting but possibly at the risk of less flexibility and little increase in top speed.
Not that I would try it today but when new a Golden Flash was allegedly good for 105mph. The better flowing ally head will allow more and easier revs and acceleration but top speed will not change that much unless you up the gearing at the expense of ride-ability on todays roads.
To get the most out of the engine a Spitfire cam and higher compression would also be needed.
Dave.
Hi espeas, both head types are reasonably quiet if little or no wear. Only way to find that out is to strip and examine. I have 2 S/Rockets, '59 and '61, and both heads having been rebuilt with new guides etc are really quiet. The Flash is excellect for what it is, so i would suggest if you want something a bit "sportier" then go for a R/R or S/R .