Honda 90 low rpm stumble

[Chaps]

'98 BF90, 615 hours, usually purrs like a kitten while trolling at low RPM's but lately sputtering & stumbling and occasionally dies at idle. Recent plugs & valves adjusted but no improvement . . . ideas?<br /><br />BTW, runs like a raped ape above 2000 rpm

 

[Jim@KSC]

Re: Honda 90 low rpm stumble

Carb rebuild sounds appropriate.<br /><br />If it starts right back up again, pay particular attention to the low-speed jets. If it's flooding and hard to start after it dies, it may be the floats or needle valves.<br /><br />I saw a good clue on this board about running the disassembled carb body parts through the dishwasher. Wish I had seen it before a can of carb cleaner!<br /><br />Good luck.

 

[Chaps]

Re: Honda 90 low rpm stumble

dishwasher?? oh yeah, my wife would be thrilled!<br /><br />Thanks for the input. I've heard these carbs need to be "balanced" - I wonder if that is similar to a tune-up on the old english SU's?

 

[Chaps]

Re: Honda 90 low rpm stumble

bump to top . . . hoping to get additional comments?<br /><br />maybe I need an attention getter . . .

 

[radsrh]

Re: Honda 90 low rpm stumble

Chaps let me know what you find out on your motor, other than the current problem what do you think of the Honda BF90? What rig are you running it on and what kind of hole shot do you get? If you are wondering about all of the questions I just purchased a 99 BF90 to replace a old Force 85. and hey this will keep you back on top for awhile.

 

[Chaps]

Re: Honda 90 low rpm stumble

radsrh - its actually been a fabulous engine. I've got it on a rather heavy welded aluminum workboat style craft, 21'. The key is propping it correctly for the load. I put on a 15" pitch wheel and the boat pops out of the water quick. Great mileage and easy to maintain . . . always starts and goes and is so quiet I forget it's running. I've got a couple of other props for lighter boats so let me know if you need to change something - what do you have?

 

[hondon]

Re: Honda 90 low rpm stumble

You've got some time on this one ,so a leak down test might be a good idea. That will give you a good idea as to the overall health of the top end of this engine.If that is all good ,the valves are all properly adjusted,and the carbs are in sync,and remember that that last bit is way important,then I would certainly remove that manifold and have a look inside those carbs.Not a small job so make sure all the regular stuff is done first.

 

[radsrh]

Re: Honda 90 low rpm stumble

Chaps I have a 87 17' Bayliner runabout comes in right around 1220Lb's with out the new motor.

 

[Chaps]

Re: Honda 90 low rpm stumble

thanks Hondon . . . do you know if "sync'd" and "balanced" are the same thing?<br /><br />Radsrh, on a 1200 lb, 17' Bayliner you might want to compare engine weights. Figure the differance and add that much to your engine well and check your boats attitude at rest and underway. The Honda weighs about 380 lbs.

 

[hondon]

Re: Honda 90 low rpm stumble

I'dd say the same.What you are after is equal vaccume in all the carbs as the air enters them.You have a multi carb engine and if one of those gets out of sync for whatever reason it will affect your performance and it will generally be first apparant at idle.

 

[Boatist]

Re: Honda 90 low rpm stumble

Chaps<br />I do not have much to add but suggest you do a compression check before working on carbs. A bad valve or valve adjusted too tight will always show up as a low speed miss. So do the compression check first. Also is the rpm at idel the right speed or could it be a little slow.<br />Good Luck and please reprot back.