Honda BF75 4-Stroke - A lot of fuel getting into oil.

[sandiegofisher]

Just got my Honda BF75 (7.5 hp?), 4-stroke with CDI ignition put together. (Serial number above 7100001.) It was given to me in pieces because of a bad lower unit seal. After replacing the seal I got it to start on the first crank. I was busy adjusting the idle speed when I noticed a steady fuel leak comming from the the breather valve body where it connects to the starter case. If anything leaks here it should be oil, right? Upon checking the crankcase oil dipstick I discovered that it was nearly pure fuel. What would cause this problem? I will drain the crankcase tomarrow and replace with fresh 10-40 oil. Then try again. The motor had been taken apart about 4 years ago by a young boy who gave up when it became too difficult. Fortunately he did'nt take apart the power head. It took me about a week to put it back together and another year to figure out the CDI wiring (no manual)! I don't know how many hours the original owner put on it but it looks as though it got regular use. I'm sure it's gone through it's break-in peroid and then some. Do the rings need a chance to re-seat perhaps? If I change the oil regularly and run it, will it be OK and not cause damage to the motor or blow up? This is my first experience with outboard operation and repair. Any help or suggestions on what I should do and what might be causing the problem would be greatly appreciated. Thank You, Chris

 

[hondon]

Re: Honda BF75 4-Stroke - A lot of fuel getting into oil.

Sounds to me like your float is stuck and you are deliveriing fuel right into your oil pan when you prime the engine but with this scenario, there could be alot of possiblities.Have you done a compression test or better even a leakdown test on this unit?Those tests will tell you a great deal.Did you do a carb overhaul before you put this mothballed engine back in service?With the engine cover off and squeezing the primmer bulb ,do you see any fuel spitting out of the carb?

 

[sandiegofisher]

Re: Honda BF75 4-Stroke - A lot of fuel getting into oil.

Thanks for the reply... Update. I drained and replaced the oil and ran it for 5 min, 1 minute at full throttle the rest at idle while adjusting the idle speed. No smoke so rings are apprently OK and the leakage at the breather valve body stopped. I checked the oil again and it seems to be OK no hint of fuel in it now. I'll check it very often for awhile. If it was the float it must of become unstuck. The only problem I have now is that it wants to run away with me when I put it in gear. Can't slow down enough to shift into nuetral so have to use the stop switch. I'll keep making adjustments. I've been adjusting idle speed with the carb jet screw because the lower part of the throttle lever is broken off and the idle adjust screw nor the pilot screw has an effect. That is probably why it wants to run away. I'll get one ordered today. And try again.

 

[granpafish]

Re: Honda BF75 4-Stroke - A lot of fuel getting into oil.

Just for FYI. If you check about a page and a half back (as of this message) there is a question titled "Yamaha 115 four stroke getting fuel in the crankcase" or something similar. There is some discussion on several points that would, at least, be of interest to you. Good luck Granp***

 

[sandiegofisher]

Re: Honda BF75 4-Stroke - A lot of fuel getting into oil.

Update #2.<br /><br />Found the problem.<br /><br />I had removed, cleaned and reinstalled the carb. My manual explains how to measure the float height with the float valve just touching the float tang; 9.85-10.15 mm from top of float to carburator body. It does'nt say how far up the float should travel. Or is this the adjustment I'm making. I think I got it backwards. There is about a 1/4" play before it actually touches the tang. This means the float will actually rise to the top of the carb cavity. Do I need to bend the rear tang down until it holds the float at the measuring position just touching the float valve?<br /><br />The manual also explains how to adjust the PILOT SCREW, if needed, for highest idle speed then adjust the idle adjustment screw for optimum idle speed. But it does'nt explain how to determine if the pilot screw needs adjusting. Any adjustment so far does'nt seem to make a difference.<br /><br />I also repaired the idle screw adjustment lever by glueing a bent crimp-type electrical spade connector to the top of the spring loaded lever which now drops down far enough for the idle adjusment screw to make contact. Works great! Apparently you have to replace the whole carb when that plastic idle adjustment lever is broken. ($109)<br /><br />After changing oil I gave it another test run. Hard to start but got it running and took it out. It got up to speed but then slowed way down very quickly then died at full throttle. After several attempts it finally siezed. Or, I should say, I couldn't pull on the start rope... Just wouldn't budge. Pulled it off the boat and took it home. <br /><br />Removed the plugs and gave it another pull. No longer siezed! Great! Re-installed the plugs and it starts up first try but fuel still getting into oil. Removed the fuel pump and found a bad diaphram. This was probably the culprit the whole time. I know I should have checked all this out before putting it in the water. But it's the height of fishing season darn-it!<br /><br />Am having a hard time finding parts on-line. Can buy locally but everything is closed this time of night and I need to know what to expect for a fair price. Anyone out there have an idea how much a diaphram should run me?<br /><br />Also is there anything else I should do while I have the fuel pump off... besides cleaning? And I'm wondering what caused it to sieze then release after getting it home? Don't have a compression gauge. Is there something I can use instead?<br /><br />I know this is alot of questions all at once. I'm so close! You guys have been great and I truly appreciate the advice given so far.<br /><br />Am looking to boat to work everyday, about a 20 minute trip on San Diego Bay from Shelter Island, past the Coronado Bridge, to National City and then fish my way back home!<br /><br />Thanks again.

 

[Bear]

Re: Honda BF75 4-Stroke - A lot of fuel getting into oil.

Nice success story!<br /><br />Don't know about the Honda prices, but Mercury 15 four diaphram is about 21 bucks.<br /><br />Try this dealer (no prices):<br /> http://www.twimarine.com/7_5hp_thru_8hp.htm <br /><br />Good luck!