Jetting issue?

Josh42

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So my bike runs really well except at 1/4 throttle. While riding if I hold at quarter throttle it shudders badly and barely keeps speed. And while sitting still I have to roll on the throttle gently to get it to rev, otherwise it cuts out like in the video. I tried adjusting the idle mixture screw and it seems to do nothing. is this a jetting issue? or something else? The carbs are mikuni I think, the guy I bought it from put them on there so I'm not sure exactly what they are. Thanks.
 
Great shot of your wrist but ahem some pics of the carbs, air filters, and exhaust will help a lot more. Next you are going to have to find the specs for YOUR carbs and try to find a baseline of settings and jets for those carbs fitted to how YOUR bike is set up, THEN some of the smart guys here might be able to help narrow down the issue.
 
Yes, you've given no where near enough info to get any help.
 
I thought I had pictures as well I guess they didn't go through. They should be attached to this and I took some more of the exhaust and labels as well. It's dark now but you can see pretty well still. I was trying to show in what throttle position the issue occurred; in hindsight not the most helpful :p If the slide cutaway is the issue would that be fixed by adjusting the needle clip or altering the slide itself?

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Read this in conjunction with your answers...VM carb quide link important read for tuning and understanding your VM carbs.
 
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Could be a lot of things but I still think I'd start by checking proper float valve operation and float levels.
 
Josh, if you don't want to chase your tail you will set valve lash and cam chain tension, check compression, and troubleshoot the ignition carefully before you even think about monkeying with the carburetors. As to the carbs: they look like VM34s. No jet list, no comment. Don't take this the wrong way, but you won't get anything helpful here if you aren't willing to do some looking and some work. And no, fooling with the mixture screw and clip won't compensate for incorrect cutaway.
 
If it runs good everywhere but 1/4 throttle perhaps raise the needles by lowering the clips a notch. See if it improves.
 
+1 on float/ float level inspection,Gary. We almost always see eye-to-eye, but if I was dealing with a carb set that could have any cockamamie combination of parts in it, I sure would want to know every piece of brass in the SOBs before doing anything else.

Now here's a question we should have asked right off. Josh, did your motor fall on its face at quarter-throttle from the start, or did the problem develop after you'd had the bike for awhile? Also, what year is your bike and what ignition system do you have: 80-and-forward factory electronic ignition, 70-79 factory breaker point ignition, aftermarket ignition with factory mechanical advance unit, or aftermarket electronic ignition with electronic advance?
 
Thanks for the heads-up, Skull! I used to put in more work asking than the poster was willing to put in looking and telling, but I've concluded that life's too short for that game. I'm done on this thread.
 
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