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1995 ZX1100D High Speed/Carb Problems.

4.1K views 8 replies 2 participants last post by  Fruitpunchenthusiast  
#1 · (Edited)
Title pretty much.

I can start this bike up without the choke, Just a little gas for 5-8 seconds and then it idles up to temperature perfectly fine.
Accelerates fine and I can get up to about 110 in 3rd gear, 4th Gear will let me up to 120 but the RPM’s drop to 10k.
5th Gear tops out at 8.5k and 6th Gear won’t go above 6.5k RPM’s

Keep in mind this is under load at speed, sitting still the bike idles and revs fine.
I believe the issue is something to do with the ram air.
Originally I didn’t have the ram air hooked up because I was still tuning the carbs. Even without the ram air I can get the bike to 120mph but not faster. I had to buy some new hose for the bowl pressure line.
If I had to take a guess it feels like it’s running rich when it hits the 120 mark. The engine bogs and will sometimes cut out.

The Pilot Screws are set at 3 turns out.
I have a K/N air filter, I believe the jets/needle may also be a stage1 dyno Kit.
Stock mufflers and pipes as well.

Here’s some pictures of the carbs and different areas on the bike encase anyone spots anything important that is needed.

Later today or tomorrow I’ll be taking the carbs off again to try and identify the jet sizes and compare those to the factory size I’ve had a lurking suspicion that the main jets may be too small or large.
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#6 ·
Ok so I pulled my plugs and here they are, cylinders 1-4 left to right.
I Pulled the carbs off going to tune them again tomorrow.

I was too lazy to check my idle jet since honestly it’s running great at that range anyways.

My main jet is a 155! ?
I thought the stock was like a 200? Wtf?

Picture below of spark plugs.
Those spark plugs look pretty good. It appears that you haven't been riding rich for very long, which would suggest that things are properly adjusted, at least for lower speeds.

I'm not sure what the correct size is for your model, but if the carb has a smaller jet, it was probably rejetted either because the owner lived at a higher altitude or perhaps was hoping to conserve some gas. I live at sea level, but my understanding is that you go smaller as you get more elevation. Smaller jets would allow less gas out, which would achieve a better ratio for thinner air. Regardless, you'd want to replace it with stock and get that working, before considering rejetting.

Since parts of the carb are disintegrating, I'd get a rebuild kit before everything gets put back together. A decent rebuild kit should include stock jets. Get one that has nitrile rather than rubber for any gaskets and then just replace everything that the kit provides with the new gear.
 
#3 ·
If you can start it without the choke, then it's likely running rich. (Assuming that it's not warm enough out to not need it).

It's a bit odd that the problem is happening in higher gears, it's more normal for the smaller jets that are used at slow speeds to clog as they're smaller. 3 turns out could be correct, 2.5 turns out is a generally suggested jumping off point for tune ups. An extra half turn doesn't seem unreasonable.

The proper tune for that is typically when the engine RPM no longer keeps increasing with further outward adjustment. You'd do a little at a time and follow it up with using the idle stop screw to drop the RPMs back down to spec and if necessary a carb sync.

But, if you don't have the ram air equipment set up, that alone would cause the bike to run rich at speed, even if it runs OK at lower speeds. The faster the bike goes, the more of a difference you should see.