Michel Higuet Posted November 6, 2023 Report Share Posted November 6, 2023 It started with the flash gun, the engine started like clockwork, the color of the spark plugs was good, I was satisfied... No timing flash on cylinder 1... erratic lights on 2 and 3 on the contrary lots on cyl 4 I decided that the problem was the trigger of the flash gun finally timing flash on cyl 1 (was it the trigger?) So I put my oscilloscope on the primary of the coil (current probe) I synchronize but big wobbling shifting of the signal, seems the trigger from the distributor cam is erratic, I buy and place a vacuum gauge 14-15 inHg (compression > 160) not terrific! Ignition is electronic but after 25 years I will buy a new the distributor cap, HT wires and rotor. It is for today. I let you know... Quote Link to post Share on other sites
stuart Posted November 6, 2023 Report Share Posted November 6, 2023 Sounds more like the distributor is in need of a rebuild, bearing wear in the shaft. Stuart. Quote Link to post Share on other sites
Michel Higuet Posted November 8, 2023 Author Report Share Posted November 8, 2023 (edited) So I placed new cap distributor rotor and ignition Ht cables no change... The motor start directly, seems running well carbs are balanced without problem colour of sparkplugs is OK. I ride around the corner and could be happy until... I connect the vacuum gauge... 15 is a maximum ( in Idle and the needle is not very stable ) I recheck the manifolds etc... no problem If I made a static ignition adjustment ( At this moment I realise that I made 4° ATDC but in reality is BTDC! ) Gauge gave 10-11 turning the distributor, more advance and it jump to the maximum of 15. Motor warm I have self-ignition. Following the signal on the scope i removed the electronic ignition and placed my old contact set, just to compare, no real change. OK I shall remade the static ignition adjustment but not I expect changes. I have never understood here sometimes the pic come upside down and what you do sometime it stay so???? Edited November 8, 2023 by Michel Higuet Quote Link to post Share on other sites
Michel Higuet Posted November 9, 2023 Author Report Share Posted November 9, 2023 Ok one of the two problems is solved. Not solved the two degree oscillations, I order an HT probe to check the secondary side of the ignition. to be follow... Solved the low vacuum in the intake manifold. In fact no problem at all. It was the first time I used a vacuum gauge and had no reference of the values, Why didn't I have the 18-24 iHG? The motor started at the second, running well with power in the driving test, 90% of people would say It run very good and still... 18-24 iHG is a value for stock engine, OEM Cam not hot cam ( I have a Piper fast-road ) It is not the high lift the problem of that cam but the Overlap of the cam. The rule is Hotter cam lesser vacuum. 30 years ago I restored the TR, camshaft was shot, I exchanged for that camshaft, error I didn't know that for street riding the OEM camshaft was OK (or maybe a high-torque camshaft) better idle too. so in case lower vacuum for the brake booster ( except that I don't have :-). Still vacuum gauge a useful tools! Quote Link to post Share on other sites
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