Overheated a3

Francisco Rodriguez /

Hey guys I’ve got an 94 golden bullet tt with an a3 stock setup besides the estoril exhaust jetted with a 65 main. which a 53 was og. Airbox delete with a mesh filter at first I had a stock oem exhaust then upgraded to a biturbo exhaust Then to the current estoril So anygiven past days about two months ago I decided to go for a ride as I would any other day. Well nearly home when I can feel some hesitation in acceleration wen given throttle. But before I could pullover I felt my back tire lock up skid ,kinda fishtailed it like I meant to do this. Not in a million years would I ever do this on a moped unless necessary. Came to a stop and overlooked the bike thinking my bungee cord was entwined in the rear wheel causing it to skid like this when it did. But nothing was there. I was boggled. Upon walking bike home two things occurred to me Overheated , seized engine. Was my only conclusion. Yep. After I hit home I put the bike away then tried to crank to no avail. No movement from piston. Called it a Night. Upon reverifiying my good luck. The piston was no longer stuck. Hmmmmmm. I proceeded to go upon my findings and totally remove stock 38mm die cast head and piston. Cleaned em up New head seal gaskets installed. Completion went well. As so did the following startup and test ride which included installation of a trailtech head temp gauge due to my lucky mishaps which got me in this mess. So after the ride went well Temp was high nearing the four hundreds but before hitting those higher temps I allowed to engine to cool down before returning home. After arriving to the pad I couldn’t get around to examining the thing for the next week or so but I did tear down again thinking overheating due to an airleak in exhaust, intake ‘ or head gasket. So I replaced gaskets again. Cleaned up piston, not the rings , they were removed. with a 3m green scour pad. After replacing gaskets and original piston rings were reinstalled. I then did a compression test. 78psi after gaskets installed. Needs new piston rings due to overheated and once seized piston. Correct ? Now checking my ignition points l, flywheel removed, I found that my points are a little offset looking at them from the side of stator they are mounted looking directly at the points pad onto pad the contact pads should be centered on top of one another as a new set would be. Also I found that on my points where the post that protrudes from the front to the back then eventually fits inside a hole on the stator, the points can move off the post that are acts like a spindle for points to move up n down for spark. I have looked at my other two Tomos a35’s both running and points don’t move like that nor is the compression that low. 128psi or so on the other two working a35’s. Piston rings need to be replaced (does piston need to be replaced) with points & condenser and timing Is my conclusion correct? Hope so. Enlighten me boys can send pics if I didn’t make any sense. Thanks.

Re: Overheated a3

Crankshaft seal behind the stator could be going out which could cause an air leak and your overheating problem.

Re: Overheated a3

i'd definitely use the starterfluid check for finding airleaks. seals are a reasonable concern too. your compression tester seems good if it's reading reasonable numbers on the others so yea sounds like rings and hone are probably worthwhile.

the points thing seems concerning but maybe unrelated. I'd probably replace them tho, sounds like theyre busted somehow but not able to picture exactly what you're describing. B ut even if they work, i wouldnt want to invite an unexpected problem later

Re: Overheating

Probably Fred /

Points ignition bikes seize lot more than electronic ignition bikes due to high timing and timing that isn’t regulated very well so even if your seals and everything are good you could still run hot if using a performance pipe, filter and running higher rpm unless you put the timing very low and you know it stays low at a higher RPM not jumping around.

Points ignition A3 could be any setting depending what the point gap is/points wear but from the factory it is very high around 20 to 22° before top dead center which is OK if you’re going to run around 6000 RPM and use the stock parts but if you go to add a performance pipe which is like a supercharger and run higher RPM then your temperatures are going to go way up hotter spark plug will increase temperature is also

Whereas all my Tomos a55 bikes came with 14° before top dead center timing from the factory, a low temperature #8-9 ngk spark plug and all had these stickers on them

33A0F32F-69B5-47FF-BEE4-20209FD0B57C.jpeg

The head temperatures on every stock unmolested a55 bike I had or have now rarely got or get above 230°F at full throttle around 6,800-7,000 rpm

After adding performance pipes, filter and upjet they go up to around 325-330° @9-10,000 rpm so performance pipe could increase 100° or more head temperatures even with low 14° timing so you need to have low timing at top speed/rpm.

Stock Points ignition bikes time in anywhere from 18-25 degrees and can run 300-350f degrees with stock pipes and filters so if you add a performance pipe you can get in seize Territory even jetted perfect if your timing is not set low and controlled.

If you can have your static timed (no curve) points ignition set low like in this graph you should run cool enough not to seize with a non fan air cooled engine (Fan cooled and water cooled can take higher timing)

340C6930-2CB2-4C91-8EC3-3B177A002988.jpeg

That’s where tuning comes in, if you set timing too low you won’t have any takeoff power that’s why racing electronic ignitions have a curve so they could have the high timing for good takeoff but then it retards so they have cool running at high rpm

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