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Improving Your Mokai

Shop Talk => Engine Performance and Modifications => Topic started by: hotrodelrod on August 01, 2017, 06:56:04 PM

Title: 07 Mokai with EX21 upgrade shutting down
Post by: hotrodelrod on August 01, 2017, 06:56:04 PM
As the title stated my 07 with Toms ex 21 upgrade is giving me trouble.Performance Mods are Toms clutch and exhaust(not water cooled) After a short run (a few minutes) at full throttle the engine sputters and ultimately shuts down. Only after it rests for a spell will it re-start. I disassembled the carb and cleaned as per the video. Did not help the problem. I'm guessing its heat related. Also, i find that while under full throttle I need to "play with" the choke control to find a sweet spot where the motor runs best. Its been a frustrating time as I dont get to run the mokai often and when I do I have these problems. Gas is fresh, carb is clean, plug is good etc. Can someone please tell me what I am missing? My buddy still has the Honda and pull start in his and he runs better and faster. I am 20lbs heavier.
Thanks for any input,
Rick
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 01, 2017, 07:20:09 PM
Sounds like it's starving for fuel. Check your fuel line connector to the tank, it should have an o-ring on the end to seal it. If that is damaged or lost, the fuel pump will suck enough fuel to idle but not enough to run full throttle.
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: happul3 on August 01, 2017, 07:55:05 PM
Can it be running very lean because of pulse line fitting completely loose?
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 01, 2017, 08:00:46 PM
Can it be running very lean because of pulse line fitting completely loose?

This is one of my conversions, my pulse fittings don't come loose. ;)
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: hotrodelrod on August 01, 2017, 09:06:58 PM
Sounds like it's starving for fuel. Check your fuel line connector to the tank, it should have an o-ring on the end to seal it. If that is damaged or lost, the fuel pump will suck enough fuel to idle but not enough to run full throttle.

Thanks for the response Tom. So if both of my fuel tank connections are not sound this could be the issue? I ask because I recently replaced the vent side hose fitting and I could not get it to snap into the tank side fitting completely.I discovered, once back home, that the tip of the old fitting was broken off inside. It appears that the fuel side fitting is sound.

Thanks
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 01, 2017, 09:44:20 PM
Very possible that is the problem. Those connectors are valved, meaning when they are not hooked together the flow is shut off.. on both sides. So if the vent side fitting is broken, the valve wouldn't be opened when connected and the tank wouldn't be able to vent. The fuel pump is drawing against a vacuum, the flow stops, and the engine starves.

http://quickcouplings.net/osc/product_info.php?cPath=21_23&products_id=51

http://quickcouplings.net/osc/product_info.php?cPath=21_23&products_id=82
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: The Man on August 01, 2017, 10:14:54 PM
You could temporarily loosen the gas cap to vent. But I would avoid rough water. You could also empty the fuel to a half tank.  Just a suggestion to see if it is a vent issue, not a fix by any means.
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 01, 2017, 10:17:55 PM
Yes, I should have mentioned that. Thanks Shawn.  \./8
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: hotrodelrod on August 02, 2017, 08:40:03 AM
Thanks guys. I'm going to try to get out this afternoon and will report back. I'm thinking that venting is not the issue as I thought to leave the cap loose previously but maybe not loose enough?

Rick
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 02, 2017, 08:34:25 PM
Did you get a chance to test it again today?
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: hotrodelrod on August 05, 2017, 07:57:23 AM
I wasn't able to get out until yesterday. I did make some more changes/improvements during the week though. I upgraded my starter wiring to 8 gauge wire soldering all connections and installing a disconnect in line copying Tom. Works 10x better, no hot wires! lol I also finally installed my steering swap kit as per the you tube video. Love it! Now to the fuel issue.......While running on the bench I noticed a fuel leak (steady drip) coming from the carb area. I snugged up the bowl and 2 bolts that attach it to the motor and it seemed to go away. Got away from work early yesterday and headed to the river (Shenandoah) Boat fired right up and I headed up river, grin on my face as it was running smooth. Speed checked on gps at 8-9 mph. (I am 210, 3/4 tank, cooler with ice and drinks, bottom beat to hell and back from ledges) so I am happy! 2 minutes later it starts sputtering! I ease off the throttle and it runs better. I now smell gas! I get over to shore to have a look and cant see gas leaking but sure as heck smell it. Now don't judge me here but I make the (stupid) decision to forge forward as I dont get out often. I dump a little water in "bilge" and forge on. This went on the rest entire afternoon. Run well, sputter, stall as it wont idle. Would only start with throttle wide open. I'm sure all due to fuel leak so I plan on removing carb and starting over. At least I got out?
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: hotrodelrod on August 05, 2017, 08:08:41 AM
Forgot to mention that I also removed pull starter from flywheel for better cooling.
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 05, 2017, 08:11:51 AM
Sounds like the float needle is leaking and causing flooding. Hopefully a good cleaning will solve the problem. Fuel pump could be causing problems too, have seen that many times. 10 gauge wire is all that is needed for the battery wiring, if that was getting hot you were cranking too long or something else is wrong.
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: hotrodelrod on August 05, 2017, 08:34:42 AM
as for the wiring I was using 14 gauge and it was wired incorrectly. It worked but struggled. Great now. Can I test the fuel pump?
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 05, 2017, 08:59:32 AM
Ah, ok. That was one of the conversions I did not do the wiring on then. 14 awg was definitely too small, when I said 10 gauge I was remembering what Mokai uses, I use 8 and you were right to use that too; I can imagine how much better that works now!

The only easy way to test the fuel pump, is to swap in a new one and see if there is a difference. Hard to test it when the motor has to be running to supply the pulse signal.
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: hotrodelrod on August 06, 2017, 08:37:18 AM
So I pulled the engine and ran it on the bench yesterday. Same gas tank, fuel lines etc. Ran like a top and no leak whatsoever. Ran it wide open for a few minutes....nothing! We all know things rarely fix themselves, especially a boat. No doubt as soon as I get it in the water it will act up again >:(
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 06, 2017, 09:10:04 AM
You should never never never run a motor full throttle without a load. It tells you nothing either, the engine only requires a fraction of the fuel without a load. How much oil is in it? Too much will cause issues. On a flat surface, the oil should not come past the step that is below the fill plug threads.
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: hotrodelrod on August 06, 2017, 09:45:49 AM
Do you measure oil with the plug screwed in? Where on the stick should it read?
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Hillbilly on August 06, 2017, 10:59:55 AM
Running OK on bench might lead us to believe that heat is a factor.  Don't forget about the coil.
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: happul3 on August 06, 2017, 12:02:47 PM
So the theory is that the carb bowl is overflowing, right? Assuming you have already cleaned needle and polished needle seat as per Tom's recommendation and that was not enough, would it make sense to temporarily install a fuel pressure gauge and use it to reduce fuel pressure by putting restriction and/or leak into pulse line? Something I almost did myself when I had carb gas leak, but polishing did really fix the problem for me...
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: happul3 on August 06, 2017, 12:07:26 PM
Do you measure oil with the plug screwed in? Where on the stick should it read?

If you remove the plug and shine light into the hole, you can see threads. I think the recommended level of oil level is right at the very bottom of threads.
Title: Re: 07 Mokai with EX21 upgrade shutting down
Post by: Painlesstom on August 06, 2017, 06:33:46 PM
Do you measure oil with the plug screwed in? Where on the stick should it read?

You look into the fill plug hole, the oil should not come past the ring below where the threads are, up too the threads is way too much. I don't use the stick so can't say where it should land for sure, the engine sits at an angle in the boat when in the water, so filling till the stick says full is too much.