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BF 50 Rumble

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shart777

New member
Late 90's 50 hp honda with carbs - Starts and idles fine. Wont quite accelerate all the way before it stumbles. I pulled the carbs, cleaned and reinstalled. It got better and almost acts like the prop hub is spun, but it isn't. Thoughts?
 
3 way manometer I connected it to each of the three vacuum test ports, carb three is the lower carb. The adjusting screw on that carb actually adjusts the linkage (all three carbs). It's there that you set the engine idle speed (950rpm +/-50 rpm). Once that is done the middle and upper carbs are synced to the lower carb. I dialed in enough balance in the linkage to allow me to idle with the manometer connected. Once I had it idling I was able to dial the carbs to a very fine balance following the procedure outlined in the manual. The goal is to get the fluid levels balanced in all three tubes and you are done. I got this from the forum. Question: What is the procedure outlined in the manual?
 
you set idle
which always is bottom carb
then you need to flick the throttle and check
then do carb 2 the middle
then flick the throttle
then 3
flick the throttle

i bet that you did not clean the carbs good enough or you have a fuel problem
 
Thanks for the information - What points to the fuel system as the problem, why with your experience do you feel it is the carbs or fuel?
 
because i know that 100% of backyard mechanics always never clean carbs the right way

you need an ultra-sonic cleaner
 
Well it sounds as if the carbs might be the problem. However, I never attempt to fix a problem with out first doing a compression check. A leakdown test. A spark test. A check of the fuel (old? contaminated?) You must definately know the overall health of the engine. Then when you clean the carbs, pay careful attention to putting compressed air through all passages. In a Honda 50, the passages and orifices are very very small, they can hold dirt in parts of the passages. You must know the carbs very well and carb theory and construction very well. Synching four stroke carbs is a must.
 
I work on "neglected" Honda carbs all the time and sometimes I find that it is easier and less costly in terms of time spent (I don't work for free so labor charges add up) to just replace the fuel bowl and "jet set" tube as they can be difficult to get thoroughly clean at times. Those tubes can get a small, hard particle in them that you can barely see at all and it won't come out UNLESS you have a sonic cleaner. I just toss it.

I've even got a brand new fuel chamber, that I personally unwrapped, with crap PACKED TIGHT in the vacuum passages. Now THERE'S one that will burn you! It sure got me! I chased my tail over that one because I really thought "it can't be the carb, I just cleaned it". I flush all new parts now because of that one!

I don't have access to a sonic cleaner but I have very good success cleaning and servicing carburetors. As hondamech stated, if you are VERY familiar with the carburetor and all it's passages and what they are for then you will see the need for COMPLETE dis-assembly as well as new seals and gaskets, along with needed hard parts, to get them properly squared away.

Many of my calls are for "I cleaned the carb so that must not be the problem". However, it often is.

The "jet set" cracks occasionally too and the upper, tiny little oring that seals the tube in the top of the throttle bore is very easy to damage going back in so extreme care needs to be taken there.

I have posted several times on this forum my method for cleaning and checking the flow of the three and/or four feed circuits in the Honda carburetor so I won't rehash that here. I will reiterate though how important proper storage is to keep from having problems. I don't want any of my carburetors sitting for more than a few days with any fuel left in them. So, when you get your outboard running right, do yourself a favor and drain the carbs each and every time you put the boat to bed.

Good luck.
 
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