95 - 6 HP that will not idle

[motwerf]

I have a 1995 +- 6 hp that has low compression , 75 PSI on both cylinders. I am unable to get a constant or smooth idle on this engine under load. I have tried all the set up procedures in the book and am unable to get a smooth idle below 900 - 1000 rpm. Under no load it will idle fine<br /><br />I started by re/re the pump, no effect.<br /><br />I had it down to the bearings this spring as it had 60 PSI at that time and would not idle under load for more than 5 minutes, mostly less. Now, under load, I get any where from 5 seconds to half an hour. the longest times are generally when the engine is cool or cold, I use an electric motor to troll most of the time but need the gas motor for windy times. <br /><br />just had the cab apart lst night after talking to a small engine mechanis and still the same performance. <br /><br />Suggestions?<br /><br /> <br /><br />On the advice of a couple of mechanics we did not replace the rings, just buffed the cylinder walls. (there was no obivious glazing and the rings and pistons were all above minimum specs.) this gave us the 15 PSI increase. <br /><br />I saw a previous posting about using water sprayed into the carb to remove carbon, will this little trick work in this situation.

 

[Xcusme]

Re: 95 - 6 HP that will not idle

What did you do to the carb when you had it off?? Rough idle can be a dirty low speed idle circuit or mis adjusted idle mixture screw. Dis-assemble carb, remove needles and spray with carb cleaner. Blow out passages with compressed air.<br />You didn't mention anything about cooling. Is the motor running hot?? Low compression from a motor that new could be a result from an overheat at some time . You said that "the longest times are generally when the engine is cool or cold" , this can be temperatured related. Heat related power pack failure is a consideration too.<br /><br />Since you said that you had the power head "down to the bearings ", that's when you would have cleaned the exhaust ports, so there shouldn't be that much carbon build-up. Spraying water into the carb throat will shock the carbon deposits causing them to crack and be blown out the exhaust. It's unlikely that you have that much carbon build-up unless you're running way to rich.

 

[motwerf]

Re: 95 - 6 HP that will not idle

thanks for the comments. Here is a bit more info.<br /><br />I bought the motor used, 3 years ago, and was not completely happy with the low end idling, a bit too fast in my opinion. The motor would die in 2 ways : suddenly without notice while at idle; and slowly as if starving for gas. <br /><br />I have always had to pull out the choke to get it restarted. This indicated to me that there was a fuel delivery problem.<br />So I replaced the pump. NO change.<br />Logic lead me to the carb next.....as <br /><br />I have had the carb apart so many times over the last 2 seasons, I think I could do the job blinfolded, each time looking for something stuck in the low speed cicuit. <br /><br />after soaking the disassembled carb overnight in carb cleaner and using compressed air, I installed a complete carb kit last year. <br /><br />This spring I discovered that the top cover plate had been upgraded. I replaced this about a week ago. and last night I took it apart completly again to make sure I had not missed someting as there was a posting elsewhere about looking for vacuum leaks etc so I did all those things. the article also suggested running a piece of denim string through the main jet but I did not do this, as yet as the jet was clear. used a small wire probe to make sure there was no 'invisible' hair or something. <br /><br />I was told by our local J/Ev shop, while getting the new cover plate, that there had been a recall on some 6 hp engines and the solution was to change the carbs, using the 8 hp carb. <br /><br />I have the shop manual and the parts # book and the only difference is the main jet size. #33 = 5 Hp # 38 = 6 Hp and #50 = 8 Hp.<br /><br />My next step will be to change the jet size.<br /><br />I have had a suspicion that I have been dealing with an ignition system fault as well as the low cicuit proble due to the sudden 'cough' like sound it makes when dieing suddenly<br /><br />hopw this helps explain hwere I am at.

 

[Xcusme]

Re: 95 - 6 HP that will not idle

Changing the high speed jet won't do too much for your low end idle. Since you've gone over the carb issue, you may try looking for an ignition problem as you suspect. Look for solid ground wire connections as a start. High resistance ground connections can cause all sorts of weird symptoms. Failing that, power pack overheats and other ignition part intermittence could be the source of the problem too. <br />You didn't mention anything about engine temps. Are they OK too??

 

[motwerf]

Re: 95 - 6 HP that will not idle

the reason I am thinking a larger jet is it just seems to get slower and slower when it dies now. I tried the water spray and I, for now, am not getting the misfire/ cough/ die symptom. I must have had some carbon bits causing a misfire. also the starter cord resistance indicates slightly higher compression now. I am able to get a slightly longer idle than over the last few hours before the spray tresatment but not in excess of a couple of minutes of idle. <br /><br />also I tied applying the choke at about 50% on and can get a continuous idle but dies when I push the choke off, dies off ever so slowly firing to the end...like it is starving for fuel.<br /><br />re temp: how do I check this? the manual wants a 5 minute @3000 rpm then 5 min at 900 (idle) when I can not get it to idle for that long when warm..<br /><br /> manual states 100F for idle add 163F for high speed<br /> the water coming out of the spit valve hose is warm to hot, but not too hot to the touch. I am tank testing it right now and the water is warmer than lake temps around here. It has always felt slightly warm when in the lake.<br />Manual is rated at an inlet temp of 60 - 80 F and the tank is in that range, warm but not hot.<br /><br />re ground: I tightened the ground strap on the coil that comes from the harness and thightened the one that grounds the module. No change.<br /> <br />am I missing anything else?<br /><br />How does one go about testing the module for low speed problems?

 

[Xcusme]

Re: 95 - 6 HP that will not idle

You're temps seem fine. You say now that you can get it to idle if you half choke, right?? Will it continue to idle , without choking if you squeeze the primer bulb?<br />Have you checked the fuel tank vent? Disconnect the fuel line from the carb, put it in a small container and pull the rope a couple of times. Do you have good fuel delivery to the carb?

 

[motwerf]

Re: 95 - 6 HP that will not idle

Disater struck last night. I am doing the testing in a tank at home and we had a wind storm. some leaf matter got into the tank and I didnt see it. plugged the water screen and I got steam. now I have 75 PSI & 0 PSI. will have to go down to the bearings again. <br /><br />thnaks for your assistance so far.<br /><br />in answer to to your last questions, I had done some of the tests and it would still die if I pumped the ball. <br /><br />tanks vent is OK as I found out when I forgot to open it one time in this series... that problem disappeared upon opening...<br /><br />will return in about 3 weeks, will be on holidays for 2 weeks as of saturday.<br /><br />thanks for your help

 

[Xcusme]

Re: 95 - 6 HP that will not idle

Motwerf, Gees, if it wasn't for bad luck, you'd have no luck at all. Before you go on holiday, email me at xcusme123@hotmail.com (omit the 123 from the address when you reply). I had a similiar situation when the water intake was blocked by cottonwood fluff. It was enough to partially block the water flow but I caught it in time before any damage was done.