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Post by usmcdoc on Feb 3, 2012 8:53:21 GMT -5
Got a minarelli with new 70cc BBK. After trying many jets....it finally runs well. The stock 70 and a 78 made it soft seize....jumped up to 90...and too rich...would not wind up and was sluggish. 85 was the magic number and it really goes! Dead stop to 47 mph is right now! But if I try to cruise half throttle at 30 mph....or when I decelerate....then try to speed up again....it bogs n sputters...like it is too lean..or too rich. Raised the needle clip up one notch...no change...dropped it down one notch.....no change. Adjusted the mixture screw and got a slight improvement....but it still bogs. Maybe I need a bigger pilot jet since it is a BBK and the pilot jet is still supplying fuel till about 1/4 to 1/2 throttle?....or something like that. I am very adept at 4 stroke carbs with BBK's....but this 2 stroker and all 2 strokes I have worked on seem so sensitive and picky. Any suggestions?
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Post by 90GTVert on Feb 3, 2012 10:31:33 GMT -5
I'd try the needle again now that you've adjusted the mixture with some improvement. Usually the pilot/mix screw won't make much difference past 1/4 throttle. If you can get it to idle well and act OK below 1/4 throttle, play with the needle first.
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Post by jmkjr72 on Feb 3, 2012 10:33:55 GMT -5
go 1 more main jet leaner and see if the mid range picks up
the needle effects so much of the throttle range it isnt even funny
you may even need a diffrent needle taper
and your running an unaltered oem airbox rigth
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Post by usmcdoc on Feb 3, 2012 16:00:06 GMT -5
90GTVert it idles beautiful...just midrange at about 30 mph. If I nail the throttle from a dead stop....it accelerates smooth and quick all the way to WOT.....but if I back down from there to half throttle it wants to die out.. Also yes....running stock pipe and stock airbox. has me baffled...
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Post by 90GTVert on Feb 3, 2012 20:01:54 GMT -5
Idle is the pilot and mix. The nailing it is your main circuit. That leaves you with basically the needle to play with on a stock carb. There's other stuff, but a stock carb really only has needle settings to play with without altering something. If it won't get right with needle settings then maybe go back and really fine tune the main jet like jmk said. Instead of skipping around multiple sizes, evaluate what each step is doing.
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Post by 190mech on Feb 3, 2012 20:28:37 GMT -5
You might have to do some CVT tuning also,but I'm not the one that can make suggestions on CVT's.. :stumped:
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Post by usmcdoc on Feb 4, 2012 20:27:40 GMT -5
Problem solved! I loaned the scoot to a buddy for 2 days while his car was getting fixed. Today I took the carb and whole airbox off....on the bottom side of my airbox he had drilled two 1/2" holes!! Wish he had told me. He said "They get more air that way and go faster"... I glassed over the holes with fiberglass cloth and resin. Runs like a champ now...doesn't miss a beat. Lesson learned is.....never loan anything of yours to an idiot with tools and no mechanical aptitude.... that believes everything they see in a You Tube video.... :swear:
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Post by 90GTVert on Feb 4, 2012 21:39:33 GMT -5
lol Glad it's fixed.
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Post by jmkjr72 on Feb 4, 2012 21:41:38 GMT -5
glad its working
and this is a good example of why to leave the oem air boxes alone on these little 2 strokes
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tango
Scoot Enthusiast
Ad agendum semper parati
Posts: 389
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Post by tango on Feb 4, 2012 21:52:41 GMT -5
When I decided to replace my busted up air box with a cone filter I figured that I would be doing myself a favour by letting the carb breathe freer. When I got problems I swore that as long as I lived I would never buy another 2-stroke because they just weren't as "tunable" as 4-strokes. Those were the utterances of somebody who simply did not understand 2-strokes. Now I know better. Now I wish my car was 2-stroke and air cooled! Both the way to go, in my opinion...
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Post by jmkjr72 on Feb 4, 2012 22:15:32 GMT -5
no i had air cooled 2 stroke and the liquid cooled is far better you can run leaner and not have to worry about blowing up
you can run higher compresion and dont have to worry about detonation
and you have no power loss when things get warm like on an air cooled engine
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Post by usmcdoc on Feb 4, 2012 22:23:41 GMT -5
glad its working and this is a good example of why to leave the oem air boxes alone on these little 2 strokes Yes...and NEVER loan your scoot...to a "Know it all with tools" That has to take his car to the shop to get plugs and wires replaced...as well front brake pads.....that should be basic stuff...for a guy who claims to know mechanics.... :lol: |
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Post by jmkjr72 on Feb 4, 2012 22:44:57 GMT -5
well ill tell you what i took my ranger in for plugs
it was the 4 cyl with dual plugs and you couldnt get to the passsanger side plugs
i also took a v6 front wheel drive buick in for new plugs as the only way to get to the rear bank was to unbolt the engine and jack it forward
even though i wrench now when it comes to the cages i may take it in as i just dont want to deal with some of the stuff any more
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Post by usmcdoc on Feb 4, 2012 23:48:46 GMT -5
jmkjr72 I had a car where you had to take each front wheel off to get the plugs....so I know what you mean. But you don't "mod" somebodys scoot without permission....that is what upset me...and then not to tell me until I found out... :banghead:
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tango
Scoot Enthusiast
Ad agendum semper parati
Posts: 389
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Post by tango on Feb 5, 2012 0:43:19 GMT -5
no i had air cooled 2 stroke and the liquid cooled is far better you can run leaner and not have to worry about blowing up you can run higher compresion and dont have to worry about detonation and you have no power loss when things get warm like on an air cooled engine You misunderstand. I want the simplicity. I hate liquid cooling because pumps fail, hoses leak, radiators crack. I am totally paranoid about my car overheating. There is NOTHING that scares the shit out of me like seeing my temperature gauge climb above half. I'll sacrifice the extra oomph for peace of mind. |
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