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I believe this is an early 90's commercial engine. I have had this engine for about a year but it never seemed to run right. Its fine but idles rough warm or cold. Runs up to 5500 or more RPM but then looses power and will only run at about 2500-3000 rpm or will stall. Shutting of and waiting ten or fif**** minutes will cure the problem. Seems to be lots of water out the pee-hole. Problem was worse until I replaced fuel lines and primer bulb and switched to poratble tank from built in. Would this be an overheating problem or possibly coil/power pack? Started engine last weekend in the driveway- pee trail ran cold then warm then cold.Are coil/power pack problems easy detect? Are these parts expensive? Thanks in advance.
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vicman2,
Problem could be with the power pack ignition - but I would first do the following since they need to be done anyway:
1. Pull carbs and clean and install kits.
2. Clean/replace fuel filter.
3. Check thermo switches for proper continuity at rated themp.
4. Make sure grounding out a thermo switch sounds an overheat alarm.
5. If it has been at least four years since last water pump repair - do it.
6. Check thermostat for proper operation - if any question, replace.
7. Get yourself a Yamaha shop manual to perform the above.
If all of this doesn't fix your problem, then I would suspect ignition power pack, and, yes, it is quite expensive to replace.
Good luck,
Ken K -
sounds to me like you are losing your fuel prime....start at the tank pickup/screen,is there debris in the tank? eliminate any unnessary fuel line connections/junctins,including the quick disconnect at motor and run the line straight to the motor filter. fuel pumps? take them off,dry them off you should be able to blow thru one way only, and none the opposite way,if any air bleeds thru , its bad. and finally clean them carbs,very simple after you do them once,break them down as far as possible and soak overnight in a good cleaner then blow carb cleaner thru all orifices and replace all worn carb parts/washers/gaskets.Comment
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Thanks for the quick replies. A few more questions if you don't mind. Is there a rev limiter that kicks in if the engine over heats? Will a Cylmer type manual contain all the info I need or will I need the Yamaha manual? I've tried squeezing the primer bulb when it looses power with no change. I have the primer bulb installed between the spin on fuel filter and the engine. All hoses are new and double clamped. Thanks again.Comment
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vicman2,
I believe your motor will drop in rpm when the temp sensor signals the ignition power pac that an overheat condition exists - it does on my 2000 C115. You need the Yamaha manual to be sure.
The temp sensor (thermo switch) closes at around 180 degrees to indicate overheat condition. You can remove and test it fairly easily. But I don't think this is your problem at low rpm.
Good luck,
Ken KComment
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