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I have a 85 z that is all stock minus a k+n filter. It was at all the factory settings. At wot it blubbers and if I let out of the throttle just a little it clears out. So I put a 480 jet in it and it got better but still blubbers at wot. So I went to a 490 and it got worse. So what do you guys think? Could it be the float set wrong or is it something else?
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A 480 jet???I think the stock main jet is a 137.5 Put it back in and test it as it was. Then try raising the clip on the needle one slot at a time (you want to raise the needle to let more fuel in) If raising it all the way to the top makes it run better but not great, put in a 140 and start all over again with the needle. That said don't put blinders on, it may run better with a smaller jet, or a lower needle position as the higher velocity you are likley getting with that filter may now be pulling more fuel up through the stock jet. Test and tune are your words for the day.
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The stock jet is a 470 for a 85 tri-z. That's what was in it when I got it. And the manual I have stars the same. From what I've read I didn't think the needle highth mattered at wot?
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470??????????
Power User
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I just looked it up on a parts diagram. Stock main is a 137.5. No offence, but are you sure your messing with the main jet? Are you sure its a stock carb? As far as the effect of the needle on your performance it takes you right up to WOT and to a minor extent is still blocking the orfice slightly when you are wide open. It may not have much effect after you are WOT for a few seconds, but of your main is off it will give you indications as to which way you need to go. i.e. a perfectly jetted main will usualy run best with clip set in the middle position. If you are running better in the upper midrange with the clip at either extream your main jet is likley off a bit.Originally Posted by Kart43
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The manual I have says stock jet is 470. That's what was in it when I got
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Check what brand carb it is ?
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Power User
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Check this out. http://yambits.co.uk/470-mikuni-main-jet-p-2223.html Go figure. Anyway the test and tune advice stands. Put the 480 in and play with the needle.
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You're fine. No offense yes it is a main jet. It is a mikuni carb. I have a ytz250n service owners manual and that's what it tells me as far as a stock jet. Is that the wrong manual. It came with the bike
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470? you might be running a TAD bit rich.... try like 145, my 250r would do the EXACT same thing then i leaned it out. ran PERFECT. try using the search bar up top. its awesome!
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The 85 Z was suggested between a 470-490 main, but they ran rich at that setting anyway.
The 86 Z ran a smaller main down around 360 if I recall correctly. But dont quote me on that. 86 carb was designed different so they leaned the main.
Mikuni carbs run significantly higher numbers than Kheins or PWK's.
If you try to put some obnixously low number main in a stock Z carb, you will have a nice new ashtray for your shop once the piston melts.
What jet did you start with? Did it run good then just start acting up?
How old is the K&N
Last edited by Mosh; 10-03-2011 at 09:11 AM.
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I just bought the bike two weeks ago. It had a 470 in it to start. As far as how old the k+n is I don't know. It did it the first time I rode it. And has been doing it since. I could take the filter off for a pass down the road and see if it helps
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http://www.ozebook.com/compendium/t500_files/mikuni.pdf
http://www.triumphrat.net/hinckley-c...jet-sizes.html
A couple of good sites if about jets. Keep in mind mikuni uses two types of main jets, hex (amal style) and slot, or "round" I suspect the chart on the second link showes the round jets which are not typicaly used in our trikes.
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Ok so I went from the second needle clip to the third and it didn't make much difference. So then I took the airfilter off and it got way worse. So with the air filter off it getting a bunch more air whichbis making it leaner obviously. So I will try another clip. Any other sugestions?
Power User
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Third from the top, or third from the bottom? Also, please don't run your engine without a filter. Snowmobiles can get away with it (no dust) but you will ruin your engine doing that in the summer.
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