Still Hard Starting

steveyacht · Aug 1, 2011

This thing is driving me mad(er). Seems like every time I get on this 1973 750 she is getting harder to start. Took me who knows how many kicks to get it started yesterday morning. I even resorted to some starting fluid which to my surprize, had absolutely NO affect on starting. Only when I kicked her with the throttle WFO and choke engaged did it FINALLY start.

Even after riding nearly 75 miles non stop I pull into a watering hole to get a cold one and shoot the breeze with other motorcycle enthusiasts, ONE beer later, started easy on one kick, as soon as I let the clutch in, stalls. have to put choke on and kick at least half dozen times to get it started.

Currently running with single Mikuni (put that on based upon recommendations from here and ellsewhere). Boyer ignition, only about 1500 miles since complete restoration and rebuild. Totally frustrated, sore, and tired...... May just get mad enough to have amals or keihins or some other wonder carbs installed..........

any help will be greatly appreciated.

Steve

rx7171 · Aug 1, 2011

Steve
Me and a hear a lot of others with Mikunis find them easy to start so if it's the carb it will be in its setup.
With the symptoms getting worse over time doesn't sound like carb setup either unless the idle screw is backing out by itself.
With the Boyer the timing shouldn't be sliding out of adjustment either.

Do the plugs show clean burning? Possible fouling.
Any chance you are gettin a manifold air leak?
Since it didn't start even with starter fluid I wonder if an intermittant loss of spark. Maybe you need to check all connections to the Boyer for loosness.
Even if hard to start the vibration of a running bike may make the connection work.

Good luck
Bob

rx7171 · Aug 1, 2011

>>Only when I kicked her with the throttle WFO and choke engaged did it FINALLY start.<<

Since the Mikuni enricher circuit only works with a fully closed throttle that is not a factor, however with full throttle after unsuccessful kicking with enricher only it sounds like flooded engine starting procedure.

Brly · Aug 1, 2011

Steve,

I have a single mikuni on my '74 850. If the bike is cold (meaning it has been allowed to cool down from running to outside air temp), I free the clutch plates with a couple kicks, turn on fuel, put the choke on (lever all the way down at carb), ignition OFF, kick twice, take choke off (lever all the way up at carb), snap the throttle a couple times, turn engine over to compression, ignition ON, throttle CLOSED and in one kick it fires off. I have my hand on the throttle so that the instant it starts I can give it enough to stay alive. Once it starts, I keep it alive with the throttle. I find I only have to leave the choke on while starting when its quite cold, and I take it off as soon as I can.

When the bike is warm or hot, all I have to do is turn it over to compression, turn the fuel on, turn the ignition on and one kick it will idle without help from the throttle.

If you leave the choke on (lever down) while kicking, you CANNOT open the throttle at all. Not even a little bit.

Hope this helps. I don't know how your clutch is, but if its sticky, make sure to free the clutch plates before starting. Just pull the clutch in and kick a couple times till they free. I say this because you mentioned something about it stalling when letting the clutch out?

Hope you figure it out.
Ben

swooshdave · Aug 1, 2011

Brly said:
Steve,

I have a single mikuni on my '74 850. If the bike is cold (meaning it has been allowed to cool down from running to outside air temp), I free the clutch plates with a couple kicks, turn on fuel, put the choke on (lever all the way down at carb), ignition OFF, kick twice, take choke off (lever all the way up at carb), snap the throttle a couple times, turn engine over to compression, ignition ON, throttle CLOSED and in one kick it fires off. I have my hand on the throttle so that the instant it starts I can give it enough to stay alive. Once it starts, I keep it alive with the throttle. I find I only have to leave the choke on while starting when its quite cold, and I take it off as soon as I can.

When the bike is warm or hot, all I have to do is turn it over to compression, turn the fuel on, turn the ignition on and one kick it will idle without help from the throttle.

If you leave the choke on (lever down) while kicking, you CANNOT open the throttle at all. Not even a little bit.

Hope this helps. I don't know how your clutch is, but if its sticky, make sure to free the clutch plates before starting. Just pull the clutch in and kick a couple times till they free. I say this because you mentioned something about it stalling when letting the clutch out?

Hope you figure it out.
Ben

Good stuff here.

Josh Cox · Aug 1, 2011

Steve,

With the Boyer, what coils do you have fitted ?, two 12 volt or two 6 volt ?, two 6 volt makes it a lot easier to start.

Leads, what type, copper, carbon, recommend the copper without suppression.

Plugs, BP7ES is the norm, recommend the BPR7EIX Iridiums.

Whilst I am running the twin Amals, with Boyer MKIII, copper leads with NGK non suppressed leads, BPR7EIX plugs, my bike is a first, some times second kick starter everytime.

Normal start, hot or cold, is flood the shit out of it, choke for cold starting.

Hard starting is usually one of two things, fuel or spark, from my experience they like a reasonable amount of fuel and good spark to start.

My bike was a very hard starter before the rebuild, changed the coils plugs and leads, and its a different bike ( even went back to the original carbs from a single Amal ).

rdleeart · Aug 2, 2011

Steve-I recently fell victim to the broken Boyer wire experience. Mine is 16 yrs on my 75 850 and the black/yellow parted about 1/4" from the pickcup. The wire looked fine on the outside but showed intermittent continuity when I checked with the ohmmeter. Don't know how old your Boyer is but it might be worth checking.

I run a single 34 Mikuni and a Boyer MK3. It always started fine but the bike would act like it was slightly out of tune when it warmed up-increased idle and a little hesitancy, sometimes a hiccough or pop.

Never had much problem with the Mikuni getting out of tune. I've found it to be pretty stable and always starts with a strong battery. I kick the plates loose and start with the choke lever down. I use the E start and it turns right over. The lever can come off early but I have to stay on the throttle for a minute or two.

I've spent too many hours trying to find a carburation problem only to find the problem to be timing or spark.

Good luck

Still Hard Starting

steveyacht

rx7171

rx7171

Brly

swooshdave

Josh Cox

rdleeart

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