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Engine just cuts out! Any suggestions please?

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bobajob
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Engine just cuts out! Any suggestions please?

#1 PostAuthor: bobajob » Sat Jan 18, 2020 1:24 pm

I am somewhat a layman fixing bikes but I am sufficiently frustrated enough to trade looking even dumber than I already am to solve the issue now! I managed to get the bike running , hadn't run for over 9 years,, but since I started it, had never ran it for any length of time until now! It will start no fuss right off the button from cold, run up and come off choke and still run fine and rev freely for about 5 minutes (does vary) then just die as if someone has hit the kill switch and refuses to restart, leave it 5 to 10 minutes and same again away she goes. It as had new plugs, new battery, new ignition coils (both secondary coils where open circuit). Has boyer electronic ignition fitted. Checked/cleaned all connections- the ones I can see and all seemed good. Checked for good fuel flow, and does appear to be a decent spark even when problem is there but not 100% on that one. Had it running with tank off and good voltage to the coils, but is it too good, getting up to 14 to 15V revving the engine. The fact that it will run reasonably well for a period of time makes me assume without confidence it is not a carb or fuel problem, more something electrical breaking down when it warms up! Anyone else had similar problem or ideas or suggestions of what else I can check/ or something blindingly obvious I may have missed? Also, just an aside, I have some old nippon denso plug caps on the bike and just found out they are 9k resistance - tried with 5k ngk caps made no difference to the cutting out but still intrigued by the difference in resistance rating?? Cheers Mike.
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Re: Engine just cuts out! Any suggestions please?

#2 PostAuthor: weaver » Sat Jan 18, 2020 1:48 pm

sounds like fuel starvation,is the fuel tank vent clear?restrictive fuel filter?

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Re: Engine just cuts out! Any suggestions please?

#3 PostAuthor: bobajob » Sat Jan 18, 2020 3:55 pm

Thanks for the reply, I have had the fuel tap off and apart, everything seems clear and get a reasonable flow out of both outlets, the fuel hoses where tired so replaced them. Just tried again, 5 minutes fine then stops abruptly. Not even sure if it fuel flow or ignition now, back on it tomorrow methinks!

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Re: Engine just cuts out! Any suggestions please?

#4 PostAuthor: z1bman » Sat Jan 18, 2020 4:45 pm

i would have thought if it was fuel it would die steadily & not die as it is doing

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Re: Engine just cuts out! Any suggestions please?

#5 PostAuthor: Philippe » Sat Jan 18, 2020 4:53 pm

Hi bobajob
I think it's just like z1bman says: fuel starvation due to a clogging of the fuel cap ventilation...
Take the cap apart and check the ventilation, it's only a little hole and very fine channels. Make sure these are clear. On the inside of the fuel cap is a little hole. When you take the cap apart you'll see some sort of channel starting at the hole and running around, ending in another hole.
Before you take the cap apart try to run the engine with the fuel cap open, if it keeps running you found your problem, if it dies you should look for another reason.
Good luck!
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Re: Engine just cuts out! Any suggestions please?

#6 PostAuthor: z1bman » Sat Jan 18, 2020 7:33 pm

the next time it cuts out turn the fuel tap off straight away & drain one of the float bowls & see how much fuel is left in the carb

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Re: Engine just cuts out! Any suggestions please?

#7 PostAuthor: warren3200gt » Sat Jan 18, 2020 8:46 pm

If it was fuel or carb related it would start to run rough and get steadily worse untill it died. To stop abrupty as you say it has to be electrical. I think your on the right lines with something making a higher resistance as it warms until its too hot to have contnuity. The most likely suspects and my first port of call would be the pick ups in the boyer. If you have a points plate to hand I would swop out so you can rule in or out the ignition system.
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Re: Engine just cuts out! Any suggestions please?

#8 PostAuthor: Pigford » Sun Jan 19, 2020 7:56 am

Sudden stopping (as said) more likely electrical, fuel starvation will be slower & more ragged stall.
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Re: Engine just cuts out! Any suggestions please?

#9 PostAuthor: Ultim8pc » Sun Jan 19, 2020 10:06 am

Bobajob,

Can you please provide more info about how the bike dies?
Does it do it regardless, or only do it when revved etc?
Thanks
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Re: Engine just cuts out! Any suggestions please?

#10 PostAuthor: z1bman » Sun Jan 19, 2020 10:35 am

chuck the boyer ignition in the bin & fit dyna s

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Re: Engine just cuts out! Any suggestions please?

#11 PostAuthor: Garry.L » Sun Jan 19, 2020 10:58 am

Pigford wrote:Sudden stopping (as said) more likely electrical, fuel starvation will be slower & more ragged stall.



What He said.

Something electrical breaking down when warm. Cools down and contact remakes thus all Ok again.

Check Spark as soon it cuts out to prove.
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Re: Engine just cuts out! Any suggestions please?

#12 PostAuthor: zed1015 » Sun Jan 19, 2020 11:22 am

If it's electrical and dies on all four you can rule out everything from the actual ign pick-ups to the plugs.
So you are looking at everything back from the ign pick-ups.
Is it just the ign or the whole bike lights etc.
If the whole bike then main power to the ign.
If just the ign then it's power and wiring from the fuse box ,ign, kill switch and boyer.
I'd punt for the Boyer box as a likely suspect..
Had them fail like this before and wouldn't touch one again.
Try with your old points back in if you have them and then get a Dyna 'S' .

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Re: Engine just cuts out! Any suggestions please?

#13 PostAuthor: bobajob » Sun Jan 19, 2020 1:10 pm

Hi, thanks for all the advice, all greatly appreciated! Sadly not time to do anything today, tasks for next weekend now. Simply the engine will run fine on all four starting from cold, even off choke and revs freely and ticks over for about 5 minutes (does vary) then abruptly stops and refuses to restart -revving the bike doesn't cause it to cut out. Once cut out all electrics remain on and strong, starter engages and turns engine over freely. Tested with fuel cap open -no difference, not had chance to drain float bowl. It still sparked but not confident how strong it is. Admit I am starting to eye the Boyer ignition now! Bike came with this ignition on so have non of the old parts to put back on and test. Plenty of tasks for next weekend, thanks again. Mike

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Re: Engine just cuts out! Any suggestions please?

#14 PostAuthor: Ultim8pc » Mon Jan 20, 2020 11:23 am

bobajob wrote:Hi, thanks for all the advice, all greatly appreciated! Sadly not time to do anything today, tasks for next weekend now. Simply the engine will run fine on all four starting from cold, even off choke and revs freely and ticks over for about 5 minutes (does vary) then abruptly stops and refuses to restart -revving the bike doesn't cause it to cut out. Once cut out all electrics remain on and strong, starter engages and turns engine over freely. Tested with fuel cap open -no difference, not had chance to drain float bowl. It still sparked but not confident how strong it is. Admit I am starting to eye the Boyer ignition now! Bike came with this ignition on so have non of the old parts to put back on and test. Plenty of tasks for next weekend, thanks again. Mike

It is sounding more like an electrical issue and I have also encountered troublesome Boyer ignitions so that may well be something to check or remove.
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Re: Engine just cuts out! Any suggestions please?

#15 PostAuthor: TimH » Tue Jan 21, 2020 1:23 am

My son had the same problem with his Harley, it would run OK then stop instantly then not start till it had cooled down. Everyone told him it was fuel but they will generally die slowly if its fuel related as it burns the weakening fuel mixture, stopping instantly is usually electrical. You need to check the plugs are firing after it cuts out, I have some of the spark testers that go between the plug and plug cap, watch for the spark before and after it cuts out. If it doesn't fire after it cuts out its probably the ignition circuit.
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