Hi guys, haven't posted for a while on the Pantha project. the bike is done (more or less) entire rebuilt wiring, carbs have been cleaned, vapor blasted and rebuilt with new seals, new slides. everything seems to work except it wont start i checked for spark and i got spark on both cylinders, i also think fuel is getting to the carbs (the bowl nuts were not tight so they leaked first time i run fuel into them) the engine turns fine on starter but wont start. spraying a little carb cleaner in the carb seems to have some kind of affect but still not starting. i run my battery flat (new battery) and don't have a charger yet - waiting for a noco5 from amazon to arrive in couple of days. what else should i look for in debugging this problem, I'm really frustrated that it happened. Eran
Hi Eran. I well understand your frustration, having put in a lot of work to reach this point and now find the bike will not start is a real downer and we have all be there at some point. Having had many issues with hard starting bikes over the years, I can tell you there is no substitute for being methodical in your troubleshooting; remember you only need compression, sparks and gas to make a motor run. First check that you have compression and that your valve timing is correct. If you are sucking gas into the cylinders and then pumping it out again, before you have a chance to ignite it, then the engine will never run. Check your timing marks on the cams and crank as you wind the engine over. Check that your ignition timing is correct too; that you are sparking the correct cylinder, at the correct time. It is very hard to tell if the sparks you are seeing at the plug are happening at the correct time in the engine cycle, remember a fat healthy spark at Bottom Dead Center is not going to start the engine. Check that your wiring from the ignition pick ups is correct and the wiring did not get mixed up at the plastic four-way plug under the tank. Put in a fresh set of spark plugs, fill the tank with fresh gas. Check that your carb jets are clean and clear, set the float height carefully, and sync the slides by eye, drop the carb bowls and check if there is any debris from the tank or small pools of water, lying under the gasoline. You should be able to smell gas on the plugs after you have tried cranking it for 30 seconds or so. If you don't smell gas suspect that you are not getting fuel into the cylinders and investigate. Make sure that you don't have a plugged up air filter. I am sure that I am stating the obvious but if you work through the list you should be able to solve the problem. By tackling one potential issue at a time you should be able to identify exactly what is wrong. Post an update if you have some new evidence to share. Good luck and please let us know what you find and how you solved it!
Thanks for the encouraging words. the carbs have been completely stripped, ultrasonically cleaned, all seals are new as well as new slides,new choke pistons and new float needle valves, i think i adjusted the float level ok (per the manual). i tried to be as metodacial as possible when replacing the pickup wires, i marked the old wires with numbers and replaced them one by one to avoid mistakes, also with the ignition timing i checked and rechecked and everything seems to be aligned per the advice i got here. plugs are brand new, i also replaced the spark plug caps with new ones. i'm using an external fuel tank for the starting attempts, not the bike tank. so i think it's unlikely there's dirt or gunk in the system. how can i test the ignition timing to see if i'm sparking the right plug at the right time? i don't recall seeing a procedure for that in the manual?
Try swapping the plugs leads front to back. You say it's got sparks and by very nature of the pickup arrangement it's not possible to get the timing far out, but it is possible in the re-wiring that you have swapped the wires for horizontal and vertical round somewhere. If the plug lead lengths won't allow swapping between cylinders you could swap over the connectors to the Bosch ignition units
Simple way to check timing and compression VERY roughly. Take both plugs out and put them back in the caps, resting on the heads. Put your thumb over the spark plug hole on one cylinder and turn the engine on the starter. If your thumb is pushed away on the compression stroke then there is enough compression to at least start the engine, and at the low cranking speed you should be able to get an idea if the spark occurs at about the same time your thumb is pushed away by the compression. Pantah has a wasted spark I think so should be a spark at every tdc approximately. A can of easy start is sometimes better to get a recalcitrant engine to show at least some signs of life.
Eran, what Derek says, my brother did a full strip on a 500 Pantah in 1982 and spent nearly 3 months checking, rechecking and double checking everything. The thing that worked (after the first suggestion from a trained bike mechanic) was to check it was firing each cylinder when it should have done as we knew the timing was correct but had not checked the pick up leads were connected correctly, it was running sweet as a nut in two minutes.
A Small update, The bike starts on choke, but if i'm not holding the throttle at least 1/4 turn open, it wont hold. also, without the choke opend it wont start. Carbs have been cleaned and rebuilt so i tend to rule out clogged pilots. throttle response seem not bad for an untuned motor. what should be my next move? pilot screws are ~2.5 turns out
Eran: Have you read this thread?: https://www.ducatiforum.co.uk/threads/pantah-starting-issues.79233/
been long since i updated, bike starts and I still didn't get it dialed to idle good, but there is progress, so i feel im almost there, unfortunately i have very little time to work on it, but i did mange to get a complete silentium system in a very very good condition and good price too.
