Hi all
A friend has just brought a 750b and has been tinkering with it ,
He said that when he picked it up it was running ok now the centre pots not firing ,
Changed the plug and had a look at the points he said that it’s now sparking but still not firing ,
Tried running on choke still not joy Took the air filter out and sprayed some wd 40 In to the carb still not joy ,
Checked the plug which looked dry but when it’s running there is some smoke coming out of the centre pot exhaust ,
Don’t know where to look next apart from checking the compression,
Any help would be welcome
Thanks
Pin
Spark but not firing
- Alan H
- Posts: 12116
- Joined: Fri Aug 05, 2011 6:38 am
- Location: Wombwell, Republic of South Yorkshire
Re: Spark but not firing
If the centre pot isn't firing, there can't be any smoke coming out of the centre silencers. Is the downpipe warm? Sort out the ignition side.
New plug, cut 1/4" off the ht lead, replace the plug cap for starters. Then get Baz to do your carbs.
Use easy start, not wd40.
New plug, cut 1/4" off the ht lead, replace the plug cap for starters. Then get Baz to do your carbs.
Use easy start, not wd40.
Proof that four strokes are over complicated
- pin
- Posts: 254
- Joined: Sun Oct 16, 2011 3:43 pm
- Location: greenford middx
Re: Spark but not firing
The centre pipe gets warm but not hot enough so you can’t hold the pipe ,
There is smoke coming out of the centre pipe exhaust but not a lot , I did hold my hand Over the end the exhaust , the exhaust gas is cold and has a lot of oil enough to make my hand wet ,
I did put a new plug in which I did check that it sparks but when I looked at the plug after trying to start the bike it was or looked dry ,
I’m probably overlooking something but will put a new plug in and get some easy start
There is smoke coming out of the centre pipe exhaust but not a lot , I did hold my hand Over the end the exhaust , the exhaust gas is cold and has a lot of oil enough to make my hand wet ,
I did put a new plug in which I did check that it sparks but when I looked at the plug after trying to start the bike it was or looked dry ,
I’m probably overlooking something but will put a new plug in and get some easy start
- pin
- Posts: 254
- Joined: Sun Oct 16, 2011 3:43 pm
- Location: greenford middx
Re: Spark but not firing
I can’t work this one out new plug good spark sprayed easy start into the carb still does not fire
- canaletto5
- Posts: 5228
- Joined: Tue Jul 23, 2013 8:43 pm
- Location: Derbyshire
Re: Spark but not firing
Did you have the throttle wide open when you sprayed in ther easy start? It sounds like a pilot circuit problem so you could need to have the carbs properly serviced. Kev
- pin
- Posts: 254
- Joined: Sun Oct 16, 2011 3:43 pm
- Location: greenford middx
Re: Spark but not firing
It all started to play up after he striped and cleaned the carbs he doing them again now ,
I still don’t understand with spark and fuel sprayed into the carb it should fire / back fire or do something but nothing
I still don’t understand with spark and fuel sprayed into the carb it should fire / back fire or do something but nothing
- canaletto5
- Posts: 5228
- Joined: Tue Jul 23, 2013 8:43 pm
- Location: Derbyshire
Re: Spark but not firing
Have you checked that the pipes and baffles aren't clogged with carbon? Kev
-
- Posts: 3120
- Joined: Wed Sep 26, 2012 7:33 pm
- Location: Prestatyn.Wales
Re: Spark but not firing
So check the timing. If the piston pushes all the mixture/easystart out before the spark it wont fire. Would also account for no heat in pipe if no combustion.
NO SMOKE .......NO POKE
- BAZ
- Posts: 3599
- Joined: Thu Jun 18, 2009 7:35 pm
- Location: Dudley west midlands
- Contact:
Re: Spark but not firing
Remove the carbs and check for suction on the intake...
- pin
- Posts: 254
- Joined: Sun Oct 16, 2011 3:43 pm
- Location: greenford middx
Re: Spark but not firing
Carbs removed it is sucking on all pots about the same , pipes and baffles checked and look ok ,going to clean the carbs again to see if anything blocked ,