Author Topic: A starting question regarding my Mk-V  (Read 2706 times)

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Offline Jeffbo1

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A starting question regarding my Mk-V
« on: 16 Dec 2012 at 04:40 »
Well now that I have had my Douglas Mk-V for a couple of weeks now, I am finding that it is pretty hard to start....I have adjusted the valves and installed new sparking plugs, but even still I find that it takes about 15-20 kicks to get it to start, using carb cleaner as a starting fluid it only takes about 5 kicks and she's off and running well....I know it is colder now where I live but am wondering if there is something with regard to tuning that I am missing....I would sure hate to have to bear the embarrassment of breaking out the starting fluid when I am at a meet etc...the plugs are B7HS heat range...and am running unleaded fuel.....I may switch to 100 octane aviation gas as it has a long shelf life and great flash point...my 47' BSA 350 starts easily on this fuel......so what might I be missing? Jeff

Offline shrinker

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Re: A starting question regarding my Mk-V
« Reply #1 on: 16 Dec 2012 at 10:13 »
I see your in Washington state, that gets really cold there doesn't it? If your engine is in good condition with its correct compression pressure and the valve timings all correct etc and the spark energy is good then you may be experiencing a lack of vaporization due to the low compression of the original engine design and the high distillation temperatures of modern fuel designed for high compression engines. AV-gas would be a suitable solution as it evaporates much easier. Even though AV-gas has technically a higher initial boiling fraction than street unleaded it actually has a high evaporation rate compared to street unleaded. I would suggest using Av-gas and trying this technique. You could even try this on street unleaded if you wish. Go through the appropriate choking technique, or fuel level raising with the tickler, and perform a couple of kick starts with the idea of drawing fuel into the cylinders, then let it sit for 15 to 20 seconds without kicking it. This will allow the fuel thats in the cylinders to evaporate into gas form. Then kick it again with the intention of starting the engine. It may start with that first kick if your lucky.  If your really good on the kick starter you may be able to master the technique so that the fuel is drawn into the cylinder and the intake valve is still left open, that way the next motion after resting will be compression and firing.

Other reasons (two of many)for hard starting is ignition timing too retarded, and carburetor fuel level too low. Best of luck.
Bruce Robertson
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Offline eddie

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Re: A starting question regarding my Mk-V
« Reply #2 on: 16 Dec 2012 at 16:52 »
Jeff,
       I have found that with the modern unleaded fuel some adjustments to the original carb settings may be needed. On my bikes I use 4/4 slides and 90 main jets - the smaller cutaways on the slides improves the pickup from idle, and the larger main jets help to keep the temperature down on full throttle. To compensate I run with the needles lowered one notch. To obtain reliable starting, set the tickover slightly on the rich side (air screws about 1 turns off the stop). With these settings, you should get first kick starting with a warm engine - for cold starts, tickle up the carbs first. I have found the original choke slides to be more trouble than they are worth, so only have them for originality.
   Regards,
                Eddie.

Offline Jeffbo1

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Re: A starting question regarding my Mk-V
« Reply #3 on: 16 Dec 2012 at 19:19 »
Thank you both for the tips...I find that in this cold climate, about 37F, the bike does seem to like a bit of a rest between kicking, as do I. But given a rest of about 20-30 seconds it invariably will always pop over a few strokes and if i am lucky I can open the throttle and it will catch....once warm it starts easily on the first kick....I think I will do as you both say, first by switching to 100 octane aviation gas which still has the benefit of some lead in it, and also adjust my air mixture screw as you suggest Eddie, maybe then i can get away from using a starting fluid....I am like you in that the choke slides are a pain, one works well and the other jams a bit....after that I may play with jetting since I don't know what the environment was like where the bike came from and now that it is at sea level it may need some adjusting.....many thanks again fellows!  Jeff

 

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