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Old 20 May 2014, 15:52   #1
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88ish yam 50 2s autolube starting problems

having problems with my serviced yam so plugs are new etc

it starts no problem lasts bang on 30 seconds then dies carbs are clean and set correctly
now i`m thinking this could be a sticking overchoke issue as it has ran like a badger on the m5 then planed great 5 minutes later. it is currently set in badger mode!
i actually broke down in the southampton shipping lane but teased the engine back into port at about 2 kts using an excessive amount of fuel which stunk of petrol
on googling i have found that a choke solenoid could be to fault, i wonder what the forum views are
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Old 20 May 2014, 17:37   #2
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To follow up what Richard has said, the engine has been fully serviced, carb cleaned, new fuel filters plugs etc. Ignition and timing all correct. New fuel line, fuel pump working fine.

Engine will start and run okay, if i set the mixture screws +1 turn from factory settings. But this is not satisfactory. Initially this issue was put down to worn mixture screws.

But at the settings in the book it runs for pretty much exactly 30 seconds and cuts out... I believe this is how much fuel the enrichment valve lets in when started. There is no choke solenoid as such. Due to the excessive fuel consumption at such a low speed I am thinking this valve stuck open when the problem occurred in the solent.. This fuel passage is essentially open to pressurised fuel from the fuel pump and feeds directly into the intake manifold.

Ribteccie had almost the same problem, and after a lot of investigation found a tiny o-ring on the enrichment valve to be at fault. So once i've got spare time to look at the carbs again, we are hoping for a similar simple result.

Unfortunately the history of the engine is unknown and some of the previous owners work is eye watering! Richard is on a tight budget so if anyone has any other idea's then it will be appreciated as it will keep my workshop time down to a minimum.
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Old 20 May 2014, 18:20   #3
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yep i am on a tight budget some of us are leaders of industry whilst others are site chippys with 2.4 children , but anyone who has seen my kids on the water will tell you this inner city kids heart is coastal
any help or suggestions kindly taken on board ,sam is a more than capable engineer with a heart of gold who unfortunately has a boss who likes to charge me for the privelege of fixing me boat !
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Old 23 May 2014, 11:20   #4
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bump for the weekend
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Old 23 May 2014, 15:30   #5
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Did you have the carbs off?? There are two o rings which seal the auto choke to the carb body and if one drops off when you take the choke body off it sucks air and does exactly what you say. I spent ages and even stripped one down before I found it. Luckily the engine needed it. If your stuck PM me.

The 30 second thing is a red herring, they are auto choke and give 30 secs at 1100rpm then drop to 750 at idle. Trouble is a slight fault will drop it too low to keep running.

Use a spark checker when running the engine, if it sparks on all 3, do not suspect the electrics.

The only thing left will be the fuel pump.
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Old 23 May 2014, 15:32   #6
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Ha ha, just re read the forum. Someone beat me to it. PM me, I'll get it running.
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Old 23 May 2014, 15:59   #7
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Lots of fuel use could be fuel pump diaphragm. This would do the same.
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Old 24 May 2014, 05:17   #8
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Small update,

In order to eliminate anything else, i've swapped for another set of carbs off a manual start motor. The engine runs perfectly.

I've had the carbs apart twice. They are clean, and set up properly. I've had the primer apart, all o-rings are in place.

The prime start solenoid clicks if it's attached to the carb, but doesn't click if its loose and plugged into the blue wire and earthed?.. Going to replace the o-rings with new ones.
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