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· Registered
1 Posts
Discussion Starter · #1 ·
Ok first let me try to answer questions I know I’ll be asked.

I have a 2007 Yamaha Midnight RoadStar with a 1700 motor. The bike is new to me (4-5 months). Up till now, it’s run like a champ. It’s been well taken care of, mint condition. I have no reason to believe that basic maintenance hasn’t been done on it over the years with how well the bike/chrome has been upkept. The only upgrade I know on it is Vance and Hines pipes (grips have been changed too, but I don’t believe that would cause the problem I’m having).

Here’s what it’s doing:

The bike starts easily (on full choke, can turn choke off almost immediately after starting). It isles great, smooth, no up and down. Sounds just like it has since I got it. But when I give it a little gas (it doesn’t have a Tach, but I’ll guess around 500rpm above idle), it dies. If I really rev it up (1000-1500rpm above idle, estimate), it’ll keep going. Which means I have to really be it up to get going. Once I’m going it does this in every gear too (around the same rom). At 45-50mph in fifth gear you can hear the bike stalling, and starting itself again from momentum. The problem is not intermittent, it does it constantly, every time. And it didn’t gradually get to this point, one day it ran fine, 15 hours later the next day it did this strait out of my garage.

I thought it may have been a fuel problem (I had recently filled up. So I drained the gas, filled up with fresh gas from a different station, and added STP carb cleaner to the gas. That didn’t help, didn’t make things worse either, just made no difference at all.

Not a lot of good riding days left this year, I don’t wanna pack it up for the winter yet, but I also don’t have a lot of money to put into repairs at this time. So I’m trying to get ideas of what the issue can be so I can fix this fairly cheaply.

It sounds to me like a carburetor jet. But I can’t imagine that would just go bad in a day, without having any issues before hand (I’d think that would start out intermittent and build up to being constant, but I’m also really new to ownin motorcycles so I really don’t know).

Any advice here would be great! Thanks in advance for any responses

· Premium Member
6,225 Posts
Most CV carbs have transition fuel ports, which are fed from the same pilot system as the idle, but are not controlled by the pilot adjustment screw. They are on the upstream side of the throttle plate, so feed fuel into the air stream as the throttle begins to open. You could have drawn in a bit of stuff which stuck in these ports; that stuff could have come through the pilot air ports from a failing air filter, but missed getting into the idle port because of higher flow to the transition ports.

Or, it could be the throttle position sensor developing a 'flat spot' in the low-throttle position, because one usually spends more time operation in that position. This was a common problem when the TPS was introduced to cars, but seems to have been eliminated in the late '80s for cars. Perhaps you got a weak one.
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