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Old 15 May 2012, 18:13   #1
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Country: UK - Scotland
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Honda Engine Woes

Hi guys,

I've got a 2006 Honda BF50 ( A4 Carbed Generation ) on the back of my rib. Recently it's been causing me some headaches with intermittent rough and lumpy running and I was wondering if anyone could share some knowledge with me.

Symptoms In A Normal Day Of Running:

•The engine takes a good bit of cranking to he going in the morning but once it's started it seems to idle ok.

•Leaving the marina in the morning the engine runs just fine, idling nice and smoothly.

•Upon acceleration out of the marina there is a bit of reluctancy/bogging down as I throttle up to get on the plane, and there is a good bit of vibration/roughness until I'm going at speed.

•Once the boat is on the plane the engine runs really sweetly, above about 2,200rpm throttle response is great and the engine is very smooth. Even in the highest reaches of the rev range the engine doesn't miss a beat.

•However, when bringing the boat back down to idle / general pottering about speed after being thrashed for a bit it runs rough as a dog, idling very slowly (around 400rpm rather than the usual 800-900rpm). The engine will stall frequently when idling/going between gears and can be a real pain to get going again.

•If i try to get the boat on the plane again the engine is very reluctant to accelerate, sounding very rough and vibrating a lot. But once I've reached about 2,200rpm everything is fine, and as before, responsiveness and smoothness return at higher revs.

•The boat will continue to run rough for the rest of the day at slow speeds.

•Another peculiar thing I've noticed is that when the engine is running rough and I raise the warm up lever, the revs are all over the place. If I raise the lever about half way, the revs can vary erratically between 1200rpm and 2,500rpm.




I know it's quite a long description but hopefully someone could maybe shed some light on what might be up. The engine is serviced regularly and has always been run on premium fuel from new so I don't think it's anything I've done to the boat.

Any help that could be offered would be greatly appreciated.



Cheers Guys, Alex.
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Old 15 May 2012, 18:51   #2
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Try cleaning the jets especially the slow speed running jet.
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Old 15 May 2012, 18:54   #3
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Hi there,

I've tried cleaning the carbs out with brake cleaner to no avail. Might see if there's any mileage in sending them away to be professionally cleaned and then have them
rebalanced. Do you think that would help at all?
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Old 16 May 2012, 00:40   #4
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Was it sitting for a while? Or did you fill the tank at a less than reputable station? Sounds like the carbs need a good cleaning, though whether from debris or varnishing, I have no idea.

jky
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Old 16 May 2012, 02:49   #5
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Hi

you are just down the road from us so do you want us to look at it for you.

Dave
ps will be in the workshop at 9.15 if you want to call and get it booked in and it costs nothing for us to look. 01475 635 700
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Old 16 May 2012, 08:15   #6
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Sounds a lot like my old Suz when I got it.

If when you accelerate and it gets "lethargic" - blip the choke - does it solve the problem? (I know you probably won't be able to answer that instantly!)

If your idle screws are set too lean, when you open the throttle it leans out even more = less grunt. once past about 1800/2000 rpm (ballpark numbers) the main jets have kicked in so you are running at an appropriate mix.

It was a simple 1/8 turn of the idle mix screws on the Suz.....


Other things:

- All spark plugs sparking the way they should? for the cost, it's probably worth replacing them & checking all the HT connections are intact.
- Is your thermostat working? My old Yam used to do some crazy stuff when coming off the plane to idle when it jammed open (thankfully open!)
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Old 16 May 2012, 08:43   #7
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Country: UK - Scotland
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The engine has been run pretty Frequently over winter but I've filled up with marina fuel a few times recently, which can be a bit dodgy at times...

Dave, I've booked the carbs into Yampower for ultrasonic cleaning but I don't think Phil has vacuum gauges for Honda engines, I'll probably need to get you to balance them next time you're in Largs if that's ok?

9D280, thanks for the advice, I'll need to get the idle screws looked at by a pro as I don't yet have a service manual for the engine. The sparks have been changed recently but I'll have a look over the leads to make sure all is well. The thermostat was replaced at the tail end of last season and the engine is always flushed thoroughly with fresh water so i'd hope it's not got gummed up that quickly.
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Old 16 May 2012, 09:19   #8
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Hi

we are down most weeks as we do a lot in largs so just let us know when. Oh and just so you know we have an ultrasonic bath here. we use it as standard as part of the service on all engines.

Dave
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Old 16 May 2012, 11:51   #9
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Quote:
Originally Posted by alexmcrobbie View Post
The engine has been run pretty Frequently over winter but I've filled up with marina fuel a few times recently, which can be a bit dodgy at times...
Do you have an external fuel filter? If not, you should think about getting one. A filter cartridge is a lot cheaper than a carb teardown and rebuild.

That said, it sounds you've got a lot of help offers, and should get things sorted shortly.

Luck;

jky
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Old 16 May 2012, 12:13   #10
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Nearly bought a boat with a BF50 on it and in my research found a quite a few folks had issues with them if they left fuel sitting in the carbs for any length of time i.e over winter. If it is the same fault and it sounds it a thorough carb clean will hopefully sort it out but the conclusion of the stuff I read was that best to run it out of petrol before laying it up or run it every few weeks on muffs to stop it gumming up. think it has very small jets or something.
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