Newtronic Systems electronic ignition controller

Suzuki GT250 Part 2 – Surprise Surprise!

I took the knackered old battery out of the bike t’other day and discovered why I had such a big fat reliable spark. Behind the battery was a Newtronic Systems electronic ignition controller – hence no points to corrode and hence why it started straight up with a drop of petrol in the carbs. I shall be keeping that – it’s a period conversion and makes a huge difference to the reliability and therefore rideability of the bike. I know it may upset the purists but couldn’t care less, why it wasn’t CDI out of the factory I don’t know – they had the tech back then. I have distant memories of my old KH250 triple needing constant attention to keep the points spot on and get the best performance out of the bike. It will be nice to enjoy this one without similar intervention.

Suzuki GT250 carbsI am still going through the appraisal process and making some progress. I have removed the carbs and given them a good clean inside and out, they were working ok so they should go straight back on and be fine and dandy. They look a lot nicer now.

Another job I did was to open up the tacho to see what was going on with that. It may seem strange to be fiddling with something so trivial when there is so much major stuff to do but it was something I could take indoors and do one evening.

These things are precision instruments and built to very fine tolerances so it didn’t help that somebody had applied force to the cable inlet and bent the internal frame that keeps everything in alignment. It took a fair bit of fiddling to get it spot on but it made a nice change from breaking bikes, which is what I do for a living.

Seeing it now working as it should is very satisfying, the binnacle will be fully cleaned up and the glass for this and the speedo thoroughly cleaned before being put back together. I will stash it somewhere dry and warm before it goes back on the bike after the frame is cleaned and sprayed etc.

Cleaning the frame turned out to be a much bigger task than I had imagined, it’s surprising how many bits are awkward to get at. I want it to look decent but not over restored so I spent a fair time rubbing it down but I didn’t go to the extreme of smearing filler all over it to hide any little rust pits – I think that takes things too far. It got a goodly couple of coats of primer followed by two coats of petrol resistant acrylic, it looks rather nice now. The side stand, centre stand, swing arm and air box all got the same treatment, I am very pleased with the results. I think I shall order some brand new shocks so I can get the frame and swing arm together as one.

It is now just after Christmas and the seat I successfully bid for on line has just turned up, I am very happy with it. The base is good and solid and the cover is in good nick, although it doesn’t have the chrome trim running round it, I will see about taking the one off my old seat. Other arrivals include a new left hand switch pack, a pair of ram air covers, the ignition switch and the service kit for the front brake caliper. Talking of the caliper I had a bit of a nightmare with it. The piston was seriously seized in the caliper body and when trying to undo the bolts that hold it all together one picked up and stripped the thread. As if that wasn’t bad enough when I tried to open the bleed nipple that too was seized solid. I soaked it for a while, applied heat , all the usual stuff but it remained firm. In the end the inevitable happened and it sheared off. I drilled it out as far as I dared and then used an easy out on the remains. That didn’t work either, all it did was burst apart the casting where the nipple went in so that is now scrap ally.

I have just bought a job lot of caliper parts on ebay so I should have 3 replacements, hopefully one can be used. I think before I attempt the next one it will be left to soak in a 50/50 mix of auto transmission fluid and acetone for a few days. That should sort it. I still have the service kit unused, there appear to be at least enough parts for 3 calipers in the job lot so I will make up one for me and then get whatever parts I need to make up the other two. I can then sell them and hopefully get back my money and a bit more. There are also 3 master cylinders so I will do the same trick with them – it should all work out quite nicely.

Suzuki GT250 scrap partsI now have quite a large pile of scrap bits, namely: headlamp bowl, rear shocks, left front footpeg bracket, rear mudguard, front wheel, rear wheel, indicator bodies, tacho cable, clutch cable, left switch pack, handlebars and a few other bits. The cost of replacement is shocking and some people are asking daft money for parts that are not much better than the ones I have discarded. I think I will be trawling the auto jumbles when they start up in the spring. I think it may be April or May before they restart due to the coronavirus situation, we shall have to wait and see.

Suzuki GT250 polished rear drum brakeIn the mean time I had a go at aluminium polishing on the rear brake drum, which was pretty badly seized. A soak in penetrating fluid and a couple of well aimed thumps with a hammer had the actuating cam out and the whole caboodle got a good clean. The shoes are knackered but as a new pair are under 20 quid they would have been replaced anyway. The polishing went better than expected, I am a bit concerned that I have over done it and made it rather too shiney, I expect it will dull back with time and look just right – this is a long project so by the time I am done I think it will be ok. Last time I had to deal with a large brake drum that had been sat for ever I had a bit of a nightmare as the drum had corroded and lost it’s concentricity – it caused the brake to pulse and was an MoT failure. I hope this one is ok as while the back wheel rim and spokes are pretty nasty the hub looks ok. I can get a brand new rim and brand new spokes, which will bring the cost down nicely over a complete new wheel. Fingers crossed.

Suzuki GT250 manky engine coverAs work continues I am finding more and more bits that need replacing, the latest being the clutch side engine cover, which is far worse than I thought, no amount of filing and fettling would bring that back so a better one has to be found. Thirty quid should be enough for that and there are plenty available so it’s no big deal.

The carbs are all cleaned and ready to go back on the engine, which is the next big lump to get the thorough clean up it needs. It’s not the original engine as it turns out, this is made up of a T350 bottom end mated to later 247cc barrels and heads. Not many 2 strokes from this era have all their original bits so it was a bit disappointing but perhaps not too surprising. The carbs are not perfect, both float bowls are dented but the cost of replacement is so high they will have to do as they are. I’m not brave enough to attempt knocking them back in to shape, it’s too easy to break ally when you do that.

That’s about it for now, next episode will be much more of the same sort of thing, I might even get to put a few bits back together.

Article provided by David Powell of Boston Bike Bits.

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