Studdering Suzuki

[keepa]

I have a 92 40 hp that shifts it's rpm's on it's own. When rpm's are at 3000 or higher it will raise 200 for a few seconds and fall back to where it was. this happens about every 60 seconds or more. It feels like it belongs at the higher rpm when it kicks in. The electrical system checked out good, new carb. kit, fuel lines renewed and filters too. I replaced spark plugs 1st thing. Now I am begining to studder. Any words of mechanical advise may sooth the pain. Thanks for your time. keepa

 

[12Footer]

Re: Studdering Suzuki

You didn't mention fuel pump. Gas with alchohol in it eats rubber. The fuel pump has a rubber diaphram. To check it,remove the plugs.Take the fuel delivery line off of the carb,stick it in a jar,and turn the engine over.Carefull that it gets nowhere near plugs or open spark. It should "pulse"fuel out at a high rate..Say, 16oz pepsi bottle in 10 seconds. But dont turn it over longer than 10 seconds (so as not to damage impeller).<br />It will pump some, as the engine ran (albeit poorly). But My first guess is the diaphram is desolving.<br />Fuel pump ok? then;<br />Change-out the pump ball. I know you allready did this, but there has been a run of bad ones,and they have been giving boaters grief for over a year. There is some sorta "anti-syphon" valve built -into them.Anyhoo, this valve is the culprit.<br />It is a fuel problem,( am 90% sure anyway).<br /><br /><br /><br />------------------<br />I'm no expert, but I DID sleep at a Holiday Inn last night!

 

[12Footer]

Re: Studdering Suzuki

Ooopps. Dont remove the plugs....Remove the plug WIRES. If you remove the pulgs, you will not have compression (the fuel pump works on compression).<br />Sorry.<br /><br />------------------<br />I'm no expert, but I DID sleep at a Holiday Inn last night!

 

[keepa]

Re: Studdering Suzuki

Thanks for the info 12footer. I went right out and tested it. Only about 2 ounces was pumped. I had installed a pump kit and I looked it over again today but no signs of failer to my eye ball. I had replaced the primer ball and am on my 3rd now. I am debating a new kit or a new pump. With your help I think the end is near.

 

[12Footer]

Re: Studdering Suzuki

You rebuilt the fuel pump? Do a compression test. They operate off of compression,and it sounds like the fuel pump is doing it's part, just not being operated as it should.<br />2oz in ten seconds is low. <br /><br /><br />------------------<br />I'm no expert, but I DID sleep at a Holiday Inn last night!

 

[kevlar3000]

Re: Studdering Suzuki

What condition is your fuel hose in? I changed mine and couldn't believe the difference it made. I also agree that those fuel pumps are real finnicky.<br /><br />Good luck

 

[keepa]

Re: Studdering Suzuki

Well, I have changed every inch of fuel line, some even twice. I was hoping for that easy inexpensive repair but it keeps heading the other way. I sure do like the looks of those new 4 stroke yamaha's, but old suzy has been a great engine and I sure would like to figure her out. I am going to do a compression test and see were that leads. Fingers are crossed here. <br /> Any rooms left at the INN?

 

[JB]

Re: Studdering Suzuki

Check out your ignition system wiring and timing linkage, too, keepa. My intuitiuon keeps telling me that something is loose in Suzy.<br /><br />A note on fuel pumps: They are operated by the alternating pressure and vacuum in the crankcase, not by cylinder compression. Their performance can be degraded by failing crankcase seals, reeds, and diaphrams and valves in the pump itself. Rebuilding a fuel pump does not guarantee good fuel delivery. The symptoms you describe do not suggest fuel delivery problems to me. They suggest a loose electrical connection or something moving that shouldn't.<br /><br />Good luck.<br />JB

 

[keepa]

Re: Studdering Suzuki

Well after extensive mechanicing with my fishing partner, we have determined that it is an intermitting electrical problem. We opened the manual and went thru all of the settings for timing and linkage. They both were off but not by much. Our test run studdered 3 seperate times with in the first 5 minutes and then ran smooth from idle to wot. We think maybe a coil is breaking down for just a fraction of time but they check out fine for resistance. Gonna run her till she stops then I'll know for sure. I may look under the fly wheel for suspicious wires that may ground out when the magneto rotates. Well time to go fish, thanks for the help fella's. Keepa