To rejet my 120 or not????

J

jy118lfd

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My 1989 120 looper runs rough from 800 to about 1300rpm. It previously had run bad to 1900 but a link and sync isolated the problem to the rpm listed above.It will idle 650 all day long but is a little rough. (rich)<br /><br />Is it common to have to rejet the idle air bleeds and/or the intermediate air bleeds.<br />My motor runs rich as pushing the primer even for a split second makes it run worse. :rolleyes: <br /><br /> I see that many on this board have the same problem and mine is livable :mad: BUT I know it did not run like this from the factory and refuse to give in only to live with a motor that runs rough
 
R

rodbolt

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Sep 1, 2003
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Re: To rejet my 120 or not????

actually a lot did that from the factory. the air jetting is an average and is not tailored to each and every motor on each and every application.<br /> make a careful note of jetting on each carb, then you can use a wire drill set and start opening the orifice in .002 or .003 increments.<br /> but if you drill them out do yourself and the rest of us techs a favor and file off the original numbers.<br />if I hit a jet with no numbers I know to check it with a wire drill set.
 
J

jy118lfd

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Re: To rejet my 120 or not????

Rodbolt thanks <br />They are stock for an 89 now 41 idle and 50 intermediate.<br />Do you think I should start with the idle jets as I know it runs off the idle jet into part throttle for a little bit. Once it gets to 1400 it smooths right out and I know this is on only the itermediate jet.<br />Kinda just blubbers just off idle not even a real miss
 
D

Dhadley

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Re: To rejet my 120 or not????

I'd suggest finish playing with your height first. As you go higher you'll have less and less backpressure. That will dramatically affect the idle.
 
S

steelespike

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Apr 26, 2002
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Re: To rejet my 120 or not????

Jon states he feels it is running rich won't drilling the jets make this worse?
 
D

Dhadley

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Re: To rejet my 120 or not????

Those type loopers have air jets for low and mid range. Opening them will allow more air which will lean it out some.
 
J

jy118lfd

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497
Re: To rejet my 120 or not????

I figured I would check the basics all over again and found two check valves that would flow in both directions and one that would not flow at all. I replaced all four as I had cleaned all these before starting the motor this year. I ran the motor and it is 80% better. It is still a little rich from 800 to about 1100 but not as bad as before. :cool: <br /><br />Rodbolt or dhadley do you know when the carbs transfer from idle to the intermediate jet??? I want to lean one out at a time and could narrow down the trial and error if I knew what rpm it was running on what circut???? :cool:
 
B

Brew2

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Re: To rejet my 120 or not????

Hi Jon,<br /><br />Glad you are narrowing down your problem...just for my own info, what "check-valves" are you referring to? Would this be the same as what others refer to as "reeds"?<br /><br />Thanks.
 
J

jy118lfd

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Re: To rejet my 120 or not????

No they are the recirculating valves. They look like a little pipe fitting with a barb on one end. If you follow the hoses that come out of the block (there are four of them) follow them to the intake and youwill see them. They retail for 13.00 each!<br />They are number 46 in the schematic<br /><br /><br />http://www.ishopmarine.com/ishop/jsp/AsplIsmCcatViewBase.jsp?reqFor=29&req4Browse=1&lvlCode=5&pCode=C0307452&path=BMC~A0000022~M0015432~M0015473~M0015475~C0307452&docId=&docName=&i sForSupStore=false&cCatFilter=&eCatSupFldr=
 
D

Dhadley

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Re: To rejet my 120 or not????

Air jets affect the motor all the time. Regardless of what it says in any book. Especially the mid range jet. Thats why you need to be careful with it. If it's rich at idle then just play with the idle jet. That effects the motor the most from idle to about 1200 or so. It will still effect it after that though.
 
J

jy118lfd

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Joined
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Messages
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Re: To rejet my 120 or not????

Yep thats what I thought. It seems to be a little rough at idle but it clears up at 1200 so I assumed the idle jet was the culprit. <br /><br />The recirc valves were most of the problem though.<br />It probably needs only 2 or three thousands more jet to be right. I just blubbers a little and when I bring it up to 1200 it blubbers for a few seconds then clears out once it consumes the excess fuel<br /><br /><br />Thanks, I am almost there thanks to all who helped
 
J

jy118lfd

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Jun 18, 2004
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497
Re: To rejet my 120 or not????

Dhadley can I use the carbs from a 94 225 on my 120. I can get a complete set for a good price and they have the mixture screws. Will this help or not?
 
D

Dhadley

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Re: To rejet my 120 or not????

When you say a complete set do you mean the carb bodies and the throttle bodies? If so, yes indeed. Youll just have the bottom single assembly left off each side.<br /><br />You can then use the "thumbscrew" type airbox. <br /><br />Good find!
 
J

jy118lfd

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Jun 18, 2004
Messages
497
Re: To rejet my 120 or not????

Yes a matched set all 6 plus the throttle bodys
 
J

jy118lfd

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497
Re: To rejet my 120 or not????

Dhadley do you know where I can get that silencer as it is 150.00 from Ishop plus all the thumb screws and seals.
 
D

Dhadley

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Re: To rejet my 120 or not????

Call Jack at Superior Marine at 800-338-9281. I'd bet he has one. Just make sure you tell him its for a V4.
 
J

jy118lfd

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Jun 18, 2004
Messages
497
Re: To rejet my 120 or not????

Thanks I will try him once I win the auction. The guy also has 2000 225 carbs as well but I bid on the 94 carbs.
 
J

jy118lfd

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Jun 18, 2004
Messages
497
Re: To rejet my 120 or not????

Got the carbs on her today.<br />Dhadley is the link and sync the same err I mean does the base timing need to be at the 94 setting. I set it all up and had a little trouble getting the carbs adjusted. Can you or someone give me the procedure to adjust the idle screws. It is about 98% better than the old carbs. Top speed was 39.8 @ 5600 and only using 14.4 gph. It will now cruise at 4200 going 32mph and only use 8.7gph on the flowscan. I am very happy with this.<br /><br />Prop post that I have will be updated as well
 
ondarvr

ondarvr

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Apr 6, 2005
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Re: To rejet my 120 or not????

So you only lost about 4MPH dropping down from the V6 150 CF.
 
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