1990 force 120 wont start 10 min after running

[dariel17]

Hello like the title says my motor wont start after it runs for a while... heres what I have done to it changed the diagram thing on fuel pump. Set sync and timing to 28 deg at WOT. Also to start if I have to choke it everytime no matter if its cold or hot I have to putt my hand in front of the top carb to start it and give it gas manually untill it clears out and idles perfect and revs perfect at WOT when running.. also when idle timing has to be at TDC?.any help would be great this motor is driving me nuts thanks guys

 

[MickLovin]

Re: 1990 force 120 wont start 10 min after running

Firstly, do you have a manual, if you have set the timing at 28, your timing should be right if idle has been adjusted properly, I have a Chrysler and the Force look similiar, so have you made sure your choke comes in properly, you have 2 carbies I take it, in the manual you can set your choke, I found mine to be not working properly one time when I first got the motor, it didn't close the shuuters fully, they only went half way closed and were jamming due to the plunger not being lubricated and having oxidisation on it. I put some light machine oil and worked it in and out a few times and my choke closed properly. Have you checked your float levels in your carbies? and have you cleaned or checked the bowl of your carbies for junk and or filter.

I put reinforced clear fuel line on mine so I could see if there was any air or junk in the fuel. Good Luck with it, there are plenty of others on here who will help a lot more than me.

 

[dariel17]

Re: 1990 force 120 wont start 10 min after running

Thanks alot. And yes I cleaned the carbs and adjusted the floats on both I do not have the manual but I did my timing and sync thru the sticky thread thats on here. Also I forgot to mention when I try to crank and it's turning over flames come out of the exhaust..??? Thanks once again

 

[jpwilly]

Re: 1990 force 120 wont start 10 min after running

Some common causes for exhaust backfire are spark plugs wires are mixed up and a sheared flywheel key (will allow the flywheel to slip out of time that it will fire when the exhaust port is open).

 

[dariel17]

Re: 1990 force 120 wont start 10 min after running

I mean i putt the timing light on it when i crank it over to start and timing is at 30 when start up and at wot is at 28 degress when running do i dont know if flywheel key is bad. Thanks

 

[jpwilly]

Re: 1990 force 120 wont start 10 min after running

Sounds like your choke doesn't work when cold and you have too much gas flodding it when warm. Seem that way to you?

When you synced the carbs per this sticky are your mixture adjustment screws within the specified range?

Is there excess fuel running out of the carbs when you are trying to restart when hot?

What's your starting procedure when it's hot vs cold? (are you using the neutral throttle to warm up when cold and / start when hot?)

Does your primer bulb stay firm after you prime the carbs?

 

[Jiggz]

Re: 1990 force 120 wont start 10 min after running

I mean i putt the timing light on it when i crank it over to start and timing is at 30 when start up and at wot is at 28 degress when running do i dont know if flywheel key is bad. Thanks

This is very confusing. The timing is set with the throttle position at maximum opening, meaning the throttle lever should be all the way forward with both throttles in horizontal position. If set properly depending on the idle screw setting the timing at idle could be at least 3~5 degrees BTDC, AGAIN DEPENDING ON THE IDLE SCREW SETTING. The backfiring is a very good indication timing is absolutely way off.

Try doing the Link and Synch again but before doing so, make sure the throttle lever, idle screw, timing tower and linkages are all zero'ed in with the carb throttles. This means with the throttle lever at neutral position, idle screw just off or not pushing against the engine block, the timing tower at zero degree with the #1 cylinder at TDC both carb throttles should be fully closed or in vertical. Note do not confuse the carb throttles with the carb choke butterflies. The throttles are the one in the "throat" while the chokes are the one in the opening or "mouth" of each carb. There is a mention of a "line" on each carbs cam that should be aligned with the slot of the eccentric screw roller, this should be perfectly aligned with everything be zero'ed.

However,after setting the timing, obviously you will need to set the idle speed, by then the "line" and "slot screw" alignment WILL NOT BE PERFECT ANYMORE since the throttles are now partially opened to maintain idle speed, so does the timing which will advance a little bit.

On the topic of choke, there is a built in choke which you an activate by pushing in the ignition switch and kept pushed in while starting. As soon as you release the ignition switch the choke will disengage. Do not overchoke otherwise you will flood the carbs making it even harder to start. In choke condition, try holding the starter no more than 10 seconds each time and no more than two consecutive chokes. Thereafter you can keep starting without the choke. If after three tries and it still won't start, you can give it another choke but thereafter is should start, if not you have more than just a choke problem.

 

[jpwilly]

Re: 1990 force 120 wont start 10 min after running

I mean i putt the timing light on it when i crank it over to start and timing is at 30 when start up and at wot is at 28 degress when running do i dont know if flywheel key is bad. Thanks

Sorry I didn't see this post. So you set the timing but your getting strange readings. +1 Do what Jiggz said. If that's not working I'd Pull the flywheel and see if the key is missing or damaged.

 

[MickLovin]

Re: 1990 force 120 wont start 10 min after running

I would be asking if you have checked your TDC to see if it is correct. to your flywheel. Hard to find the tool to do it with, but you can do with a screwdriver paying close attention to where your top cylinder is locating. And as the others are saying check your flywheel key to make sure there is no damage, you said you have to put your hand over the top carb, yet if the choke butterfly was closing you shouldn't/wouldn't have to do this. Just for your info
2 stroke terms - Honda 2-Stroke - ThumperTalk

 

[dariel17]

Re: 1990 force 120 wont start 10 min after running

I did that already tdc is right on cyl 1 on the block mark also today I was working on it and Now the bulb pump thing fir the gas stays empty like sucked in and the little gas filter stays empty and then shuts off no idea whats going on maybe new pump?

 

[dariel17]

Re: 1990 force 120 wont start 10 min after running

To start it I have to choke it manually because my choke solenoid is broken the I tries to start but I have to putt my hand in front of top carb and kinda choke it more and give it gas then it clears out and runs perfect... then if I turn it on right away it will start but if I let it sit for more than 5 min I have to do the same thing over like choke it again... very frustrating thats guys for all your inputs.

 

[roscoe]

Re: 1990 force 120 wont start 10 min after running

The primer bulb in the gas line from the tank is going flat?

Then either the tank vent is closed/clogged, or the fuel pickup in the tank is clogged.

 

[fisheymikey]

Re: 1990 force 120 wont start 10 min after running

+1 on previous post..

I would buy a small pressured tank for outboards and check what happens if all is good check fuel lines and vent clogged

 

[dariel17]

Re: 1990 force 120 wont start 10 min after running

I will try that next weekend I blew thru the tank breather hose and it seem fine to me could it be the fuel pump maybe bad?

 

[dariel17]

Re: 1990 force 120 wont start 10 min after running

It stays on until the little filter runs out of gas the boom shuts off it started doing that today because yesturday it ran fine without that problem that is not sucking fuel into the system

 

[roscoe]

Re: 1990 force 120 wont start 10 min after running

If the bulb is getting sucked in or flattened, it is because the fuel pump is sucking well.

Sounds like the fuel pickup in the tank is clogged with debris.

 

[Jiggz]

Re: 1990 force 120 wont start 10 min after running

Before trying an external tank, crack open the internal tank cap. Prime the system until the fuel filter is full. With the primer bulb getting flat, is a good indication the fuel pump is working properly. If problem is solved, it means you have a clogged vent on your fuel tank. If the problem persists, you have a clogged pick up tube. The next step is to empty the fuel tank, open the access hole and inspect the tank internal and pick up tube. Simply blowing back into the pick tube is only a temporary repair until the debris gets suck back in.

 

[dariel17]

Re: 1990 force 120 wont start 10 min after running

Ok w I will try that thanks guys

 

[dariel17]

Re: 1990 force 120 wont start 10 min after running

Well I worked on it and it is sucking fuel but im just having trouble with the sync adjustment. Question on the adjustment cam there is a screw with a lock nut when im adjusting it does the screw have to be all the way off of the block? And the little adjustment bar thing that connects from the cam rod to the carbs how far close are they suppoused to be? Please help me with this and the timing can I adjust it while on idle and if I do adjust it will it change cranking timing? Sorry for all these dumb questins but I dont know much bout these motors thanks...

 

[Jiggz]

Re: 1990 force 120 wont start 10 min after running

This video just about explains it all on how to set the static timing. One thing he did not mention is that when idle is set, the idle timing also advances. This was explained in the link and synch tutorial by Frank A. In fact, the cam with the eccentric screw should have the line on the cam aligned with the slot on the screw with the idle screw back off and not pushing against the engine block and carb throttles fully closed. After setting the timing, you need to make sure you set the idle back again. Here's the video tutorial.

Timing Tutorial Video