Reply
 
Thread Tools Search this Thread
 
Old 31 March 2014, 08:48   #31
Member
 
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,194
poss look at the crank sensor.
__________________

__________________
Member of S.A.B.S. West Country Division
matt h is offline   Reply With Quote
Old 31 March 2014, 10:33   #32
Member
 
RIB-Teccie's Avatar
 
Country: UK - England
Town: Leeds
Make: Valiant 450
Length: 4m +
Engine: Yamaha 55HP
Join Date: Jan 2013
Posts: 448
There was not a crank sensor on the 50, at least not on one of this age.

I am going to check resistance on all coils, pulsar, charge and ignition before I fit a spare ecu. Trouble is, how do you know if a spare ecu is ok, usually parts that fail do so with a common problem.

On the USA message boards, these CDI packs are occasionally known to give out, there is quite a big aftermarket scene for these. They wouldn't make them, if none ever failed.

I have tried everything so far and spoken with others who know their stuff. Everyone's stumped. I think it is ignition and will report back if I find it.
__________________

__________________
RIB-Teccie is offline   Reply With Quote
Old 31 March 2014, 14:42   #33
Member
 
samt's Avatar
 
Country: UK - England
Town: Midlands
Make: RNLI Y-Class
Length: 3m +
Engine: Mercury 15hp 2st
Join Date: Jul 2006
Posts: 850
RIBase
Update... This was solved quite easily in the end, I found that by switching open the emergency enrichment valve the engine would keep running. It seems that there is exactly 30 seconds of fuel in the pipe that runs to the inlet manifold, so this is what was throwing me, along with the fact it would start immediately after stalling at first flick of the key. This confirmed it was fuel, cleaning the carbs and adjusting the mixture screws one turn out from the workshop manual spec solved it. I think these may need changing due to being over tightened by a previous owner, judging by a few other 'fixes' on the engine, and the complete lack of gear lube in the gearbox!
__________________
samt is offline   Reply With Quote
Old 31 March 2014, 15:10   #34
Member
 
RIB-Teccie's Avatar
 
Country: UK - England
Town: Leeds
Make: Valiant 450
Length: 4m +
Engine: Yamaha 55HP
Join Date: Jan 2013
Posts: 448
I will give this a try tomorrow.

I would have thought a problem with the enrichment mechanism would only affect the bottom cylinder as it only floods the bottom carb to work.

My carbs are spotless and the mixture screws have not been over tightened.

I will let you know how I get on.
__________________
RIB-Teccie is offline   Reply With Quote
Old 31 March 2014, 15:24   #35
Member
 
samt's Avatar
 
Country: UK - England
Town: Midlands
Make: RNLI Y-Class
Length: 3m +
Engine: Mercury 15hp 2st
Join Date: Jul 2006
Posts: 850
RIBase
Quote:
Originally Posted by RIB-Teccie View Post
I will give this a try tomorrow. I would have thought a problem with the enrichment mechanism would only affect the bottom cylinder as it only floods the bottom carb to work. My carbs are spotless and the mixture screws have not been over tightened. I will let you know how I get on.
This engine is 1988, it has a solenoid operated valve, along with a small pump, that opens then allows fuel to flow through a hose to the top of the inlet manifold. The fuel comes is drawn from the bottom carb. That's how I understand it works anyway.
__________________
samt is offline   Reply With Quote
Old 31 March 2014, 15:32   #36
Member
 
RIB-Teccie's Avatar
 
Country: UK - England
Town: Leeds
Make: Valiant 450
Length: 4m +
Engine: Yamaha 55HP
Join Date: Jan 2013
Posts: 448
I will inspect tomorrow.

I can't understand why a problem with the enrichment valve would cause fuel starvation across a 3 cylinders if the float bowls are full.

Also the needle valves in the uk usually work best at 1.75 to two turns out. Factory spec is 1.25 to 1.5 but they never run well at that.
__________________
RIB-Teccie is offline   Reply With Quote
Old 31 March 2014, 15:37   #37
Member
 
RIB-Teccie's Avatar
 
Country: UK - England
Town: Leeds
Make: Valiant 450
Length: 4m +
Engine: Yamaha 55HP
Join Date: Jan 2013
Posts: 448
I'm looking at the manual. I think the bottom carb supplies the fuel into the enrichment valve. The needle lifts allowing excess fuel to be drawn up the small pipe to the top cylinder.

Mine has had a new solenoid. Other than bad starting, I can't see why it would cause the problem I have.

I still think I have an electrical problem, yours looks like mixture. Weird that the symptoms are the same.
__________________
RIB-Teccie is offline   Reply With Quote
Old 31 March 2014, 15:46   #38
Member
 
samt's Avatar
 
Country: UK - England
Town: Midlands
Make: RNLI Y-Class
Length: 3m +
Engine: Mercury 15hp 2st
Join Date: Jul 2006
Posts: 850
RIBase
Quote:
Originally Posted by RIB-Teccie View Post
I will inspect tomorrow. I can't understand why a problem with the enrichment valve would cause fuel starvation across a 3 cylinders if the float bowls are full. Also the needle valves in the uk usually work best at 1.75 to two turns out. Factory spec is 1.25 to 1.5 but they never run well at that.
The problem wasn't with the enrichment valve, but it caused me to overlook the fuel problem at first. I had them set at 1.5 and it would not run at this, now at 2.5 it runs okay. The fact it was cutting out at exactly 30 seconds and restarting easily at first flick of the key and cutting out at exactly 30 seconds again also threw me to thinking electrical and ecu.
__________________
samt is offline   Reply With Quote
Old 31 March 2014, 15:52   #39
Member
 
RIB-Teccie's Avatar
 
Country: UK - England
Town: Leeds
Make: Valiant 450
Length: 4m +
Engine: Yamaha 55HP
Join Date: Jan 2013
Posts: 448
Have you checked the float heights???
__________________

__________________
RIB-Teccie is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 14:28.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.