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| Mikuni running good, until 2/3 throttle + http://mudmotortalk.com/mmt_v2/viewtopic.php?f=3&t=30443 |
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| Author: | bbb [ Sun Jul 01, 2012 10:44 pm ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
I saw a few threads about this, but no final solution. Runs fine til 2900-3000rpms and then it starts skipping/missing. When it first happened, a few weeks ago, I could feather the throttle and get it up to 4000rpms. Yesterday with 2 adults and 2 kids, it ran good out of the gate and then started missing after 2 miles. I have opened up and cleaned out the carb. I've checked valve lash. And I'm just not sure what to do next. I have noticed the primer bulb is very tight and the filter is full of gas. When I disconnect the fuel line from the carb and turn the motor over, the fuel pump is working fine. Thinking its in the carb. Not sure I need to buy a rebuild kit after 75-100 hrs, or keep tinkering. Whatcha say? |
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| Author: | Team Camo [ Mon Jul 02, 2012 12:07 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
If you have a rev limiter, disconnect the green wire & try it again. Might have a bad rev box |
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| Author: | deadbird8 [ Mon Jul 02, 2012 4:39 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
IF its a CDI, probably no external limiter on it. When it starts happening if you pump the primer bulb does it gain RPM? |
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| Author: | Will [ Mon Jul 02, 2012 4:44 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Will the rpms go up out of the water? If so, not a rev limiter issue. Have you checked the condition of your plug wires? This maybe something other than the carb. |
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| Author: | bbb [ Mon Jul 02, 2012 5:54 am ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
| Author: | dguidry [ Mon Jul 02, 2012 7:45 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Check your valve lash now!!! Check your push rods to make sure they are straight.... Pull them out and roll them on a flat surface like you would a pool stick. If this checks out ok your problem will be fuel delivery or water in gas or something else. The more info you can provide the better your diagnostic feedback on this forum will be. |
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| Author: | Team Camo [ Mon Jul 02, 2012 8:10 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Does it have the external rev limiter that came in the bps kit hooked up? |
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| Author: | OwenDickeson [ Mon Jul 02, 2012 8:55 am ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
Mine was doing this with my CDI motor and I had to add a fuel atomizer to the carb. |
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| Author: | bbb [ Mon Jul 02, 2012 8:58 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
| Author: | dfou [ Mon Jul 02, 2012 9:07 am ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
Had a motor doing pretty much te same thing just last week. Check the diodes and wires from the diode. Where the black wore is zip tied to the intake can get damages and ground out |
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| Author: | OwenDickeson [ Mon Jul 02, 2012 11:20 am ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
| Author: | pnazworth [ Mon Jul 02, 2012 12:27 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Had this same problem with my stock carb so this may not be relevant. Checked everything and i mean everything! Ended up being ethanol slime in the carb and the main issue was the rod attached to the float in the carb was real rough and would not slide properly. Had to clean the carb and sand down the float rod. It was catching and dumping too much fuel inside the carb, especially under a load. Ran great out of the water like you said |
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| Author: | Will [ Mon Jul 02, 2012 1:33 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Plug wire |
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| Author: | bbb [ Mon Jul 02, 2012 2:17 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Wow, 10 responses and 12 possible solutions. Typical of a Vanguard problem. Could be one of 50 things, and most likely will be the 49th thing you check. Gonna double check the float pin. Appeared to be in great shape. But a stuck float would make sense as its saying send fuel, but there's no place for it to go, so it makes the fuel bulb tight and fills up the fuel filter. The float bowl had good fuel color and no particles. Gonna double check the jet. I unscrewed the jet, and it was clear. Not sure what else I can do on that end. Gonna check the plug and plug wires when I get the cowling off tonight. I know its something small. I will say if I launch the boat and take off running, it will run fine for a couple miles. So may be a situation where a wire is heating up and then starts losing a good connection. Saturday night I cleaned the carb out with some SeaFoam spray and when I ran the boat the next morning, at first, I thought the problem was gone. But low and behold after 5 minutes of run time, it started doing it again. |
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| Author: | Team Camo [ Mon Jul 02, 2012 3:14 pm ] |
| Post subject: | Re: Re: Mikuni running good, until 2/3 throttle + |
| Author: | txmudcutter [ Mon Jul 02, 2012 3:28 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Maybe you have a vent clogged and its getting vapor locked that might be causing your bulb to be so tight |
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| Author: | txmudcutter [ Mon Jul 02, 2012 3:29 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Might be the vent on your gas tank |
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| Author: | Will [ Mon Jul 02, 2012 4:34 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
plug wire or cracked ceramic on the spark plug |
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| Author: | bbb [ Mon Jul 02, 2012 5:51 pm ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
Kinda rusty on the sides. Does that matter? Can you not replace the spark plug cable without replacing the whole coil? I'm gonna leave it apart, clean everything up, put it back together later thus week, then cross my fingers. |
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| Author: | dfou [ Mon Jul 02, 2012 6:03 pm ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
I don't believe rust is your problem. Either tape or heat shrink ur plug wires. Did you check your diodes and wires? |
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| Author: | bbb [ Tue Jul 03, 2012 6:11 am ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
What is this? It is split and I can see the metal inside. |
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| Author: | take'emgator [ Tue Jul 03, 2012 6:27 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
That is your mercury switch which allows your motor to start only in level position. could be the problem...... |
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| Author: | deadbird8 [ Wed Jul 04, 2012 5:52 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
| Author: | BoatDR [ Wed Jul 04, 2012 7:54 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
| Author: | OwenDickeson [ Wed Jul 04, 2012 8:02 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
I HAVE a set of coils boxed up that I can send you. Let me know, I can send them out tomorrow. |
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| Author: | bbb [ Wed Jul 04, 2012 8:42 am ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
Thanks guys. Took some guys frog gigging last night so had to put the motor back together before we left. Seemed to run a little better than last time. But did notice that later into the night, it sounded like the motor would go to one cylinder. When I would throttle up, it would clear up after a few seconds. It did this several times. That's got me thinking carb again. I think i'll change the plugs, and coils. If that doesn't work I'll dive back into the carb. Let me know about the coils and how much I need to send you. I have a paypal acct. Dale Tyre 158 turtle pond rd Bainbridge, ga 39819 |
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| Author: | OwenDickeson [ Wed Jul 04, 2012 9:07 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Me or BoatDr? |
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| Author: | bbb [ Wed Jul 04, 2012 1:10 pm ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
I'm gonna borrow a buddy's mikuni this weekend and see if that solves my problem. If not, I'll be interested in trying the coils. Thanks. |
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| Author: | Will [ Wed Jul 04, 2012 7:44 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
$20 says its not the carb. |
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| Author: | duckduckboom [ Wed Jul 04, 2012 7:53 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
i think you friend has to poo. that is the face i make when i have my butt cheeks clinched and i'm running to the shitter |
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| Author: | bbb [ Wed Jul 04, 2012 8:41 pm ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
| Author: | Jamie B. [ Thu Jul 05, 2012 7:46 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
I really think that you have an Intake leak of some sort, if it sounds like it runs on one cylinder then when gave a little bit of throttle it goes to running fine. |
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| Author: | Will [ Thu Jul 05, 2012 7:53 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
| Author: | bbb [ Thu Jul 05, 2012 9:10 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
| Author: | cb5331 [ Thu Jul 05, 2012 9:21 am ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
If oil level is going up, may have a stuck float and be dumping fuel into the case...though it could still be a coil not firing and the gas that isn't getting fire is making its way in the case. Who knows?  Either way, change the oil. Gas does not make a very good lubricant. |
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| Author: | bbb [ Sat Jul 07, 2012 8:23 am ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
Well I changed the oil and spark plugs last night. Boat ran perfect. Could a plug have been my issue? Both plugs were black, but I figured they would be after 4 hours of idling. |
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| Author: | Will [ Sat Jul 07, 2012 12:12 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
The ceramic can get a hairline crack in it and cause issues. Since it was only doing it after you got it warm led me to believe it was a firing issue of some kind....see post from a week ago saying spark plug . I will get the $20 from you on the Seminole run coming up. |
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| Author: | coonass381 [ Sat Jul 07, 2012 5:14 pm ] |
| Post subject: | Re: Mikuni running good, until 2/3 throttle + |
Mine was doing same thing about a month ago then yesterday was hard to start and was running bad when it would idle and die when I gave it gas messed with everything still was doing it then this morning I disconnected the rev limiter and ran like it was supposed to so might be your rev limiter like it was in my case |
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| Author: | bbb [ Sat Jul 07, 2012 5:59 pm ] |
| Post subject: | Mikuni running good, until 2/3 throttle + |
I'm gonna run it hard tomorrow and see if I can get it to repeat the symptoms. Would love if it was just a $4 fix. That's why I love and hate these motors. Hard to diagnose, unless your the knowledgable Will, but usually an easy and relatively inexpensive fix. |
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| Author: | coonass381 [ Sat Jul 07, 2012 10:58 pm ] |
| Post subject: | Re: Re: Mikuni running good, until 2/3 throttle + |
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