[chrisknight]

I have a buddy that left gas in his 1997 yzf-1000 for a couple years.
Obviously, it's gummed up & needs torn down and cleaned. He wanted to put a jet kit on it since we were in there tearing it down anyway. He has a vance & hinds exhaust on it now. We decided on a DynoJet stage 1. Before we hit the buy button we decided to view the manual on the kit. Replacing the needle & main jet looks to be a breeze. The manual then says to adjust the air mix screw but there is no mix screw that I can find. Has anyone done a jet kit on this bike before? Here are some pictures of the carburetor for reference.

Thanks,
Chris

 

[Agent4573]

The air screw are covered by caps. The first time you adjust them you have to drill out the caps.

 

[chrisknight]

OK, thanks.
That means that a couple years before this project, when he took the bike in to the shop to have the carburetors synchronized, he got ripped off. Don't you have to adjust this screw to sync the carbs? ...Where do you find the vacuum lines to hook up the manometer?

Thanks,
Chris

 

[MaxxxEdge]

No, air mixture screws are capped because they are emissions related. Carb sync screws are different. I'm not familiar with those carbs in particular, but IIRC, some of the Yamaha's of that generation had a tapped hole in which you screwed in an adapter to attach the vacuum lines. Consult your manual.

 

[chrisknight]

OK Thanks guys... The jet kit was delayed due to weather so it looks like this weekend is out. How much difference will a stage 1 actually make?

 

[MaxxxEdge]

Not a huge difference, but it will be noticeable considering he already has the V&H (full system or slip-on???) and chances are very high he's running lean with stock carb settings. FWIW, I've always preferred the Factory Pro jet kits over the ones from DynoJet.

 

[chrisknight]

I think just cleaning the carbs alone will make this thing run well. There was gummy black gas/gunk in the bowls. I sprayed carb cleaner into every hole I could find... It is running lean. Its a full system (I think) & it pops like crazy. I thought about factory-pro but forgot about them the day we ordered. We decided on dynojet or Ivans but I don't think Ivans makes one for the 97 yzf1000.

 

[MaxxxEdge]

Make sure you also blow compressed air down each of the holes and that the pathway is unrestricted. Carb cleaner alone usually works, but sometimes it's not enough.

 

[chrisknight]

The rejet went great and actually made quite a bit of difference.
One of the problems we thought might solve itself after the rejet is a problem that has existed since before the rejet. My friend had the carb sync done hoping that it would make his bike run better, it really just needed cleaned well.

After the bike came back from the sync at the Yamaha dealer (years ago) the bike would act like the throttle would stick a bit while slowing down. You can let the throttle snap closed on its own and it appears to close all the way. Also, you cant manually roll it closed anymore, its closed all the way by itself. However, it will jump a bit like you just gave it a little gas from time to time. I have seen it myself, we're rolling along slowing down for a light and with his hand OFF of the throttle, I can hear the RPM's going up and then settle back down again after 2 seconds.

Tonight he had the bike on pushing it up into the barn in neutral, without touching the throttle it jumped up to 4000 RPM for 4 or 5 seconds.

If you look down at the butterfly as you operate the throttle, it looks like it is opening & closing correctly.

This all started after the carb sync, and now that it has bigger jets and running clean, the problem is a bit worse because it responds so quick now.

Can anyone help?

Thanks,
Chris

 

[DarksideMspts]

.....check for vacuum leaks, that'll definately make it surge, like that. It'll also make it run lean. Especially check the boots, where the carbs mount to the head, on both sides (carb side, and head side), also look for cracked boots.

 

[chrisknight]

We tightened the boots down harder on both sides and still no go. The boots feel rubbery and almost like new, not dry or cracked. We're almost positive its not coming from that area. Is there anything else we might check?

Thanks,
Chris