Problem with force not starting after running fine

[P10 WRC]

Hello,

I have a 1991 Force 90. Took it to the lake yesterday and it ran great, up until about 1/2 way through the day. I was at about 4500 rpms and throttled down rather fast to pick up a tube rider. as soon as i throttled down the motor died and would not start. i had to put it in neutral at full throttle in order to get it started, but it would not start with the throttle at zero. I had to basically rev it up, then put it into gear to get it going.

Any idea's what this may be? The carbs were rebuilt in January by the previous owner.

 

[Frank Acampora]

Re: Problem with force not starting after running fine

First remove and clean the sparkplugs. Your stalling and starting only at fast idle is a classic symptom of fouled plugs.

 

[P10 WRC]

Re: Problem with force not starting after running fine

thanks for the reply, i will check that out when i get home from work today. Do i just clean them off with some carb cleaner? If they look really bad, i will probably just replace them. Any advice on which plugs i should buy? are they pre-gapped or do i need to gap them?

 

[Frank Acampora]

Re: Problem with force not starting after running fine

They are surface gap plugs. To clean them use your fingernail and a green Skotchbrite pad. No cleaner or gapping is necessary.

Champion L20V, L76V (mercury plug) NGK BUHX or BUHW

 

[P10 WRC]

Re: Problem with force not starting after running fine

No go still. i replaced the spark plugs with new ones and it still dies when the throttle is at zero. what is next, carbs? the previous owner had them serviced in January. can they already be an issue after only three short trips to the lake?

 

[Jiggz]

Re: Problem with force not starting after running fine

I would start by verifying the idle setting and also the idle air-gas mixture screw setting first. I understand that it used to work great but the idle screw setting could have changed for no reason known to you. So run it under muffs and check idle settings, it should be idling around 1100-1200 in neutral. Read the sticky post for setting proper idling and air-gas mixture screw.

 

[P10 WRC]

Re: Problem with force not starting after running fine

i checked the screws and they seem fine. i cant check idle though as it won't start at idle and dies when i drop the throttle down

 

[Jiggz]

Re: Problem with force not starting after running fine

i checked the screws and they seem fine. i cant check idle though as it won't start at idle and dies when i drop the throttle down

Marked the idle setting just in case you have to reset it back. For now adjust the idle setting one whole turn (clockwise direction) at a time until the engine stays on. This could be high RPM but it will allow you to start troubleshooting. When you said you checked the "air screw" and it seems fine did you mean the setting of the screw is correct base on the manual. If then mark it also and and open it half a turn "counter clockwise" (open direction). After making one whole turn adjustment on the idle screw (this is the screw on the control tower which adjusts the position of the "butterfly" or throttle valve in the carb and a half turn on the air screw (this is the idle air gas mixture adjustment screw which adjusts your idle mixture setting; go ahead and start the engine and use the throttle if need to to get it started. After starting slowly come down on the throttle until it idles or dies. If it dies, do another whole turn on the idle screw. You should see the throttle position move while adjusting. Try starting again and slowly come down. After three whole turn on the idle and the engine would still not idle, then it's time to unscrew the air-gas mixture screw and check the idle port for blockage. Clean the port using low pressure air and then with a carb cleaner although some recommend using brake cleaner instead. After cleaning the idle port, instead screw tip and replace if required. Re-install and set it. To set it turn it in until lightly seated (do not force or overtighten it will damage the tip). Then back it out (counterclockwise) 1 1/4 turns. This is just the initial setting and to set it properly you will have to have the engine idling. Start the engine again and try to idle it. If it dies at below 2000 RPM, backout the air screw 1/4 turn at a time until you can get it to idle. we will pick it up from here on your next post.

 

[P10 WRC]

Re: Problem with force not starting after running fine

Just to be sure i am doing this correctly


1. Adjust the idle screw one turn clockwise and the idle air mixture screws (one on each carb) one half turn counter clockwise
2. Start the motor with throttle if needed and drop it down until it dies or runs. if it dies, go another whole turn clockwise on the idle screw
3. Start again and drop down the throttle until it runs at idle, or dies
4. If after three whole turns on the idle screw, it still won't run at idle, remove the air-gas mixture screws and check the idle port for blockage. clean it with air and carb cleaner.
5. reinstall screws and set to 1 1/4 turn counterclockwise from lightly seated.
6. start motor and try to idle. if nothing, back the air-gas mixture screws out 1/4 turn at a time until it idles

 

[Jiggz]

Re: Problem with force not starting after running fine

Just to be sure i am doing this correctly


1. Adjust the idle screw one turn clockwise and the idle air mixture screws (one on each carb) one half turn counter clockwise
2. Start the motor with throttle if needed and drop it down until it dies or runs. if it dies, go another whole turn clockwise on the idle screw
3. Start again and drop down the throttle until it runs at idle, or dies
4. If after three whole turns on the idle screw, it still won't run at idle, remove the air-gas mixture screws and check the idle port for blockage. clean it with air and carb cleaner.
5. reinstall screws and set to 1 1/4 turn counterclockwise from lightly seated.
6. start motor and try to idle. if nothing, back the air-gas mixture screws out 1/4 turn at a time until it idles

That is correct. Just make sure you mark the original setting of both screws just in case you needed to reset them. While adjusting the idle screw watch the throttle valve on each of the carb, they should move. If they don't check the tower for freeplay or loose connections which can be the source of your problem.

 

[P10 WRC]

Re: Problem with force not starting after running fine

thanks for the instructions. I am able to get it to idle at 1100 rpm's on the muffs now after adjusting the idle screw 2.5 turns clockwise and cleaning out the idle port and resetting the idle air mixture screws. here is a pic of where it is at now. does this look normal. by adjusting that screw for the idle, did i change anything else that i would notice on the water or is this just for idle? Now that I know this proceedure, i will take my tools with me to the lake this weekend for some fine tuning on the water. thanks again

 

[Jiggz]

Re: Problem with force not starting after running fine

Congratulations! Now you can start fine tuning it. First things first, 1100 RPM on the muffs is about normal. Now you can fine tune your air screw. To do this you need to warm up the engine for about 10 minutes and then start turning the air screw out (CCW, one carb at a time) slowly while listening for the engine or watching the rpm gauge. Usually, you can also tell by listening to the engine sound. Anyways, keep slowly turning the air screw CCW until the engine starts to cough or starts to have rough idling (due to rich mixture) and then stop. Mark this position and now go back and screw in the same air screw CW while listening for the engine sound. Continue slowly until the engine starts to cough or have rough idling (due to lean mixture) and then stop. Mark this position. Now set this specific air screw midpoint of the two mark points. After setting the first carb air screw check the idle rpm and if it went higher or lower re-set the idle screw (NOT THE AIR SCREW) and set it again to approx 1100 RPM. And then do the same for the other air screw on the other carb. And then again check the idle RPM and re-set to approx 1100 RPM. Now you should be good to go in the water. While in the water, the idle RPM with the engine idling and gear engaged, should be around 750-850 RPM. If you need to, conduct fine adjustment on both air-screws and idle screw as required.
In the pic you are showing the elliptical screw where the line on the cam and the slot on the screw should be lined up if the idle screw is set all the way in. As it shows, it indicates the throttle valve is slightly opened as adjusted by the idle screw. Good work!