Honda-SOHC
SOHC.co.uk Forums => Other Bikes => Topic started by: mike the bike on November 29, 2015, 09:28:09 PM
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Hi chaps, I'm having bother with my 650 and could do with suggestions.
I've only done 4 trips (75 miles) since it's back on the road. Firstly, it's always a pig to start - usually needing to be jumped off the van battery.
Once started it'll run OK.
Trip 1: ran great for 40 miles
Trip 2: after 5 miles, after starting again it went on 2 pots. 1 and 2. 3 and 4 were stone cold.
Trip 3: ran OK, took ages to start though
Trip 4; same as trip 2 - went on 2 pots. Limped home being overtaken by mopeds.
I've eliminated poor compression because it runs OK sometimes, not ignition either because 3 and 4 not working (instead of 1,4 or 2,3)
Thinking there may be blockages in the carbs, I stripped them, blasted all the channels with compressed air and fitted new jets etc.
Yesterday it refused to start. 15 mins or so of cranking with the occasional DUF as the engine overtook the starter motor. I didn't even get a DUF DUF or DUF DUF DUF. Sparking OK, air filter not blocked.
The petrol hasn't gone off bacause the 400four started 1st prod with older petrol but it is a Honda so no surprise there.
I'm thinking it may be the carbs need to be ultrasonically cleaned but I've run out of ideas really.
Where do I go from here?
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I recently had issues,
it was a coil failing as it got warm,
or
it could be plug caps. are they old? what is the resistance?
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I'll borrow the ones off the 400 just to eliminate them, thanks John. I'll let you know if it makes a difference.
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Maybe an air leak at the carb mounting rubbers. That always leans the mixture and makes it a pig to start. No evidence, just a thought.
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They were on tight the engine side but not so tight at the air filter side.
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I had similar problems with my oil cooled gsxr750. I replaces the coil leads (you have to rip/cut them out and bond in new ones).
Whenever I have had these issues with old vars its always leads breaking down or arcing. There not supposed to be replacable but you can.
Also, a major problem that was tricky to find was the little tiny o rings on the carb mixture screws.
I dont know how similar yours is to the old gsxrs but these 2 things transformed my bike.
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I'll borrow the Dyna coils off the 400four, see if that makes a difference. Meanwhile, I've just bought a 2 litre ultrasonic cleaner from eBay so I'll give the carbs another swizzle. People pay loads to get their carbs cleaned. I can do mine every week now whether they need it or not.
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I stripped and cleaned my carbs at least 4 times trying to find the problem before I replaced the little o rings on the adjustment screws.
they looked ok but werent sealing properly. They need to be exactly the right size to seal and if they dont it draws too much air at idle.
If your carbs have them, replace them :)
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Are you referring to the air screws?
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Probably, book calls them pilot screws.