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Mechanics 101 Can't get it to run right? Find a trick to add HP?
From the first oil change to completely rebuilding the engine,
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Old 10-24-2010, 12:27 AM   #1
a_nomad_named_zero
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Default idle problem

after searching still no solid answer to my question. i have a 95 katana 600. it has a yoshimura exhaust i was told it was headder back but im not that familiar with the katana in the stock format. its a 4 into 1 headder that has no space for the oil filter to be removed and as far as i can tell there is no jet kit (pulled apt the carbs and cleaned ). running stock air box stock filter.

the problem is the bike wont start or idle without the choke on period. after cleaning the carbs, i took note that the air mix screws were set a follows. cyl 1-4 air mix screws turns out 3 3 1/4 3 1/4 and 6, that number seemed totally off to me. reset the screws to bottom and started at 2 out and increased 1/4 turn at a time. i am now at 4 turns out in all cyl. the bike wouldn't start with choke on at 2 turns but incrementally got better past 2 1/4 and would start with the choke on but wouldn't idle with the choke off . at 4 turns will idle with choke but it will fluctuates between 1k and 3k if i rev the bike up to 2k and remove the choke it will hold. until 4 turns out idle screw it would seem to bog till u got past 6 on snap throttle now it revs beautifully snap throttle very smooth but still wont idle or start with choke off period

so my question is am i needing a jet kit or do i just keep on turning those air mix screws. the exhaust system looks like its been on for a while. the guy i bought it from i think bought it and never rode it once it was outside and in pieces. i would imagine it had to of run with that pipe on there at some time .
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Old 10-24-2010, 06:25 AM   #2
Wild-Bill
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Start by cleaning your carbs and putting the AF screws back to 2 1/2 turns out.

I've got about the same exhaust setup on my 750 with stock jetting and it works great. Didn't at first when I got the bike but the answer was to clean the carbs really well and then chase down all the air leaks. Once I did that it all came together.
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Old 10-24-2010, 09:12 AM   #3
a_nomad_named_zero
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have pulled carbs apart twice and cleaned im new to motorcycles but am an automotive mechanic by trade they are deff clean after all day of cleaning yesterday have moved them into 2 turns twice and started from there with the same results both times
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Old 10-24-2010, 09:44 AM   #4
Wild-Bill
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Time to start looking for air leaks then. These Mikuni carbs are really sensitive to that. Start with the air box.

-Is the drain capped off?
-Are the boots glued to the airbox?
-Did you get the boots sealed to the carb intakes all the way around? (Install the box to the carbs before mounting the carbs in the bike.)
-Are the carb vacuum caps in good shape with the clips installed?
-How about the vacuum hose going from #4 to the petcock, is it in good shape and connected?
-Finally, look at the intake boots. Are they in good shape and sealed all the way around?

If all of that checks good then you're looking at the o-rings between the intake boots and the head. When I finally got there I pulled the intake boots (because I was sending the head in to have the valve seats ground) and the o-rings were so flat that I had to look twice before I was convinced they weren't just raised rings on the boots!

I never had any luck with spraying ether around looking for a change in idle speed or anything like that. It was just a matter of starting from one end and working to the other until the problem went away. Very frustrating!

Just to ask the stupid question, you did set the floats to 14.7mm, right?
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Old 10-24-2010, 10:39 AM   #5
a_nomad_named_zero
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yes they are set right i hope i didn't get in over my head with this thing i only paid 400 for it but there is a lot to fix and this running thing confuses me im a mech but never messed with a lot of carbs so its all Japanese to me even though im a jap mechanic

oh yeah and here is a question aside from the petcock there are three add lines coming off the bottom of the tank one that's straight one that comes out and 90s and one on the fuel level sending unit should there be anything going to these also there are 2 linmes that look like the fuel lines on the bottom of the carbs on the top of the carbs does anything go here ?

Last edited by a_nomad_named_zero; 10-24-2010 at 10:39 AM.. Reason: Automerged Doublepost
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Old 10-24-2010, 10:51 AM   #6
jesse23
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not sure if this will be any help, but on my old bike i had the same problem with it not idling properly and it turned out to be that the valve clearances needed to be adjusted
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Old 10-24-2010, 04:00 PM   #7
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There's a pair of drain lines coming from the bottom of the tank. One is coming from the depression around the fill tube and the other one comes off the fuel level sender. It's there in case things start to leak in there. You don't need to have hoses on there until something goes wrong. Then they keep fuel (and rain water) from ending up on top of the engine.

The two ports between carbs 1/2 and 3/4 that aren't attached to fuel lines are vents. They have tubing attached on some bikes but I don't see the point. If the carbs flood they'll do it through the engine first!
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Old 10-24-2010, 08:32 PM   #8
a_nomad_named_zero
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well at least that's comforting one more question off my mind . Just for peace of mind i ordered just about every part to rebuild my carbs today ill take apart re clean and rebuild new jets needles (just cause) new o rings and new diaphragms didn't mention it earlier cause it slipped my mind at the moment but at the edges of the diaphragms there sticky and glue like i don't figure that's good so replace here we come i didn't get jet kit per your running bike on stock set up and in regular mechanics make it work right b4 you make it go fast
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Old 10-28-2010, 10:12 PM   #9
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ok so have taken carbs apart for the 3rd time this time letting sit in the carb dunk over night and will be installing all the new goodies keep fingers crossed.
oh and to be on the safe side i ordered those seals for the manifold boots im gonna nail this sucker come hell or high water
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Old 10-31-2010, 05:02 PM   #10
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ok new parts in carbs re assembled she idles finally and wouldn't you know it petcock starts leaking go figure but minor bump in the road she idles now although 2 1/2 turns on the air mix screws dosnt seem to be to happy think she needs a lil more fuel wild bill yours may run a lil better there because 750 ? but thanks man info was really helpful
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