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Hi, as the title says - a 1983 GS 850 (bought 2011) with 9000 km that won't fire, even though it got spark, fuel and compression.
Short background: 2013 it started to run badly, mostly on 3 cyl, so with the help of two handbooks I managed to replace cylinder rings, gaskets, adjust valves, clean carbs etc. After reassebling it started on first try and ran smooth on all cylinders.
Last autumn I noticed it wouldn't run on cyl #3, but I let it be. This spring it - from time to time - neither would run on cyl #1. In addition to this it would'nt idle and was impossible to start within 10 minutes after stop. Of course this could be caused by up to two cylinders not fireing. I then discovered an oil leak btw top and block, which i guessed came from broken cyl head gasket.
I recently performed these tasks:
When trying to start after the above the only result, every five seconds or so (when running on starter), is bangs from the exhaust. That's it. Not even a "cough" from any cylinder.
I've done this:
Of course there are one or several reasons of the bike not fireing, but what am I missing? Any ideas are more than welcome.
Short background: 2013 it started to run badly, mostly on 3 cyl, so with the help of two handbooks I managed to replace cylinder rings, gaskets, adjust valves, clean carbs etc. After reassebling it started on first try and ran smooth on all cylinders.
Last autumn I noticed it wouldn't run on cyl #3, but I let it be. This spring it - from time to time - neither would run on cyl #1. In addition to this it would'nt idle and was impossible to start within 10 minutes after stop. Of course this could be caused by up to two cylinders not fireing. I then discovered an oil leak btw top and block, which i guessed came from broken cyl head gasket.
I recently performed these tasks:
- replaced the head gasket (was broken)
- cleaned the carbs (checked float height)
- checked valve clearance (all good)
- replaced the r/r (which i discovered had a missing cable, probably since long before I bought it)
- replaced spark plugs/caps
- replaced ignition coils (had read that this could be the reason the bike is hard to start after running, though my old seemed to be good according to ohm-test)
- replaced battery
- removed the pre-muffler since it was to rusty to repair (had leaked a lot of exhaust smoke), I instead attached exhaust pipe from cyl #2 and #3 directly to exhaust pipe #1 resp #4
When trying to start after the above the only result, every five seconds or so (when running on starter), is bangs from the exhaust. That's it. Not even a "cough" from any cylinder.
I've done this:
- (Double)checked ignition timing (eg cam shaft position in correlation to timing mark)
- Sprayed starter fluid directly through carbs and start within 5 secs (no reaction what so ever)
- Checked that spark plugs has a spark
- Checked compression: cyl #1 120, #2 120, #3 90 (know this is too low, but the PSI is the same as before the maintenance ), #4 120 PSI
- Can see that fuel (fresh 95 oct) reach all cylinders, spark plugs smell gas and I can see that cylinder head get moist/wet
- Changed back to old ignition coils (which has been working)
- Switched coil leads 1->4 (and then 2->3) just to...I don't know...
- Changed back to old spark plugs
Of course there are one or several reasons of the bike not fireing, but what am I missing? Any ideas are more than welcome.
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