Thorspark electronic ignition

Hi Anna, I had my mag "reconditioned" a few years ago, since then, the bike has not done more than 2,000 miles (it was stored in a dry garage for 6 years). I am still experimenting, with timing & fuel mixture, but have no "top end" power. The engine starts with the first kick from cold, and, after increasing the valve clearances (alloy pushrods with iron head), it also restarts easily when hot. However, it runs out of steam at about 70 m.p.h. I owned a '53 88 in the 50's which, in bog standard trim, would reach 90 m.p.h. on the flat. Although I do not want to drive long distances at this speed, I do want it available for overtaking (Spanish drivers, like most motorists, tend to accelerate when you catch them up!). I have not got the equipment to rebuild a mag, and, it is a pig to remove & refit anyway. The Thorspark system looks like an easy solution, and retains the original "look". Regards, John.

Hi Gordon, you may well be right, and it is not a magneto problem. The timing was set up "by the book", only on one cylinder. However, the exhaust "beat" sounds identical, on both sides, and, with one set of points how can you adjust each cylinder? The carburettor needle has been up and down like a yo yo, and, I've tried up to a 270 main jet (which should be far too large for a 500 cc.). The plugs are still coming out white. My latest thought is; maybe the float level is too low, and there is fuel starvation at full throttle. Any thoughts on this? Also, a previous owner has fitted a 1-1/16" monoblock carb, and may have modified the inlet manifold. The manifold to carb bore is 1-1/16", but the manifold to inlet 1". Would this be a 99 manifold, or has it been reamed out to match the carb? I have a good head of hair, for my age, but it is rapidly being torn out! John.

Well, it WAS the mag, it packed up completely, with no spark at all. I have ordered a Thorspark unit, which will be the quickest, and probably cheapest, way to get back on the road. Once fitted & tested, I will post details, of how well it works, and any problems that arise. The web sites says it takes "one to two hours to fit, and re-time". I HOPE this is true! John.

Previously wrote:

Hi again Phil, your comments are, as usual, well reasoned and helpful. However, I am not at all interested in achieving Dommiracer speeds! All I am trying to get is the same performance as the"bog standard" '53 Dominator 88 I owned in my youth. The engine in, my '54 model, has been totally rebuilt, as far as I know, to original spec , including a new auto advance unit (although I did not check what cam was fitted, and I know the carb is incorrect). The electronic unit arrived, today, but has not even been unpacked yet as I have family visitors from the U.K. Your previous post, regarding the alloy pushrods & iron head, helped a lot. Thanks again for that. John.

Well folks, after a bit of delay, the Thorspark unit is fitted to my Dommi 88. Works perfectly, and, without close inspection you can't tell the original mag is no longer working. The ignition switch has been fitted where the old cut-out button was, and the twin coils sit in the under seat toolbox. The old H.T. lead are now taped up under the tank, and the new leads look as if they are an extension of the originals. The "Bumpff" (fitting instructions!) says it takes about two hours to install, but reckon on double this to make a neat job. When you consider the cost, and time, it would take to have a mag serviced, or replaced, this unit is excellent value for the money (£150 + p&p). Plus, you still have the old mag in place if you ever want to be a purist and restore it. Hopefully, this information will help someone else who has "run out of sparks", and wants to get back on the road quickly. John.

Previously wrote:

Previously wrote:

Hi Anna, I had my mag "reconditioned" a few years ago, since then, the bike has not done more than 2,000 miles (it was stored in a dry garage for 6 years). I am still experimenting, with timing & fuel mixture, but have no "top end" power. The engine starts with the first kick from cold, and, after increasing the valve clearances (alloy pushrods with iron head), it also restarts easily when hot. However, it runs out of steam at about 70 m.p.h. I owned a '53 88 in the 50's which, in bog standard trim, would reach 90 m.p.h. on the flat. Although I do not want to drive long distances at this speed, I do want it available for overtaking (Spanish drivers, like most motorists, tend to accelerate when you catch them up!). I have not got the equipment to rebuild a mag, and, it is a pig to remove & refit anyway. The Thorspark system looks like an easy solution, and retains the original "look". Regards, John.

John Your Problem of have no top speed is down too the alloy push rod as they expand more than the steel ones it should have in there , And Magnetos do not like standing unused for a long time span like 6 years , for my money I would rebuild the mag as there is nothing to them ,There easy to do , if you know what your doing like ,I do ,I have stripped and rebuilt many of them over the years , too make a simple test on one all you need is a length of wire a 6volt bulb a 9volt battery take the wire a bear one end so it goes round the slip ring and rap the other end to the battery + side and have a length for the side attached to the negative side then that goes to the bulb the bulb goes to the earth pick up and if the bulb lights up your mag is OK , if not your mag is dead hope this may help

Well Anna, you have obviously not read the previous posts on this subject. I KNOW my mag was dead, and there was no way to get it quickly repaired (I am living in Spain). I have already fitted the Thorspark unit, and, if you had read my earlier post today, you would know it works perfectly. The alloy push-rods are no longer problem, now the valve clearances have been increased. The carburettor still needs a little adjustment, but the bike reached over 80 M.P.H. today (almost fast enough for a 75 year old!). Regards, John.