Weird dead spot.

[KikRox]

Cleaned my carbs recently, tuned them, synced them, checked for vac leaks, buckled it all down. She sounds great she rides great. Until today, I hit a dead spot in my throttle more than once. Right at about 9000 rpm as im gonna go into fun time it just sits there. Doesnt bog, doesnt decellerate or chug just no more rpm being made. I've never encountered this issue yet. Any leads as to what would cause an intermittent dead spot? starvation? water? crank bearing? (lol!!)

[jkv45]

Carb slides not lifting fully would be my guess, meaning something is not assembled correctly or the diaphragms are damaged.

A restricted intake snorkel opening might do that as well.

[Dave Wolfe]

Mine was doing something similar and the tach needle started bouncing around the 9-12k rpm range. Turned out to be a bad ignition box.

[KikRox]

im super careful with the slides but perhaps its possible. I'll take peek tomorrow night, my tach isnt bouncing just no reply to throttle intermittently. sticky slide makes sense.

[Ghostt]

I'm thinking it's slides, those Cam be tricky to fit, if not done exactly perfect, you'll have issues and possibly damage them.

[KikRox]

i make sure they are seated before installing the caps but perhaps i got the side of a slide a little dirty. would a vacuum sync issue cause anything like this?

[ducatiman]

synch issue is not likely..but a intermittent vac *leak* could very well be.

Check *all* the vac hoses at the decel valve and the 2 points between (inside) the carb bodies.....all should be tight on their mounts. If swollen...could leak under throttle/high vacuum conditions...also make note..when hot, the hoses swell...thus intermittent under varying heat/demand conditions.

Within my services...I've seen a lot of these loose, with swollen ends and in need of replacement. If they can be easily removed with light finger pressure...replace. They should be on firmly, and the little spring clamps should be present and *actually clamping*.

It may be worth checking.

[Lazarus]

You said tuned the carbs. What's the tune look like? (Jet sizes, shimmed the needles?, float height, etc) reason I ask is I had the same problem and removed a washer from each needle so I only had one on each needle. Flat spot disappeared.

But we may have differing mods, just my .02 hope it helps.

[KikRox]

Tuned to stock spec, 98 mains, 38 pilots, around two turns right idle mixture, left is around 2.75 turns out. floats at 17 mm. just set everything up the way it should be.

I think i found something. my tank isnt venting right... was on my way to work again, hit the highway and boom she's not getting fuel again! i was like ok maybe its vapour lock... went to the gas station fueled up (didnt hear any woosh sound) went back on the highway and she reved up proper.

it did it again on the way home again so i rode it home with the lid open just a crack and it was fine. Easy fix atleast i hope it fixes it. That tank and petcock are suspect to begin with.

Might be water in my gas making my floats shut the fuel supply off too. two things worth checking before i take the 3 hours to remove, inspect and reinstall the carbs.

[Lazarus]

Glad you found the problem. There is a writeup around here somewhere on the tank vents.

[Ghostt]

I have a, write-up on the PreGen has cap vent, I've never even seen the NewGen but I can imagine it's similar

Sounds like it could be a venting issue, no worries it's a free and easy fix,

You need you to disassemble the gas cap and remove the two small red diaphragms, assuming this is your only problem.

The diaphragm gets hard and losses it's flexibility and gets stuck, and doesn't allow proper venting.

IMHO this modification should be done regardless to prevent future problems whatsoever.

They are ment to vent the tank, but in the case of an accident not allow gas to leak out, but more often cause problems then they fix.

Here are some pictures to help you.

The plastic piece houses the two small red diaphragm pieces, this one being mine, they are already gone, and you can leave the plastic piece out all together, as I'm going to do now.

Some things to watch out for are, there are 5 small springs under the round collar, and a small round collar as well on the locking mechanism, don't lose any of them.

Good luck.

[KikRox]

I assume on my 2011 this is one of them? It pops out by finger.

[Ghostt]

I would be more interested in the internal parts of the cap, I don't have a NewGen or even access to our.

[KikRox]

Originally Posted by Ghostt

I would be more interested in the internal parts of the cap, I don't have a NewGen or even access to our.

I think if i pop that out it will draw air from the overflow. The overflow isnt in the photo but the tube is located under the lid as well. Might try it and see what happens. thanks for the help btw. its nice having a few diff thoughts on the subject. if this doesnt solve it i'll pull the carbs tonight and white lithium grease the slides.

[Ram Jet]

Originally Posted by KikRox

I think if i pop that out it will draw air from the overflow. The overflow isnt in the photo but the tube is located under the lid as well. Might try it and see what happens. thanks for the help btw. its nice having a few diff thoughts on the subject. if this doesnt solve it i'll pull the carbs tonight and white lithium grease the slides.

Whoa! Hey Gordon feel free to chime in here. I don't think lithium grease on the slides is a good idea, it may be too viscous. Possibly silicone spray? Possibly dry. Dunno for sure. Ducatiman would know.

Bill

[KikRox]

Originally Posted by Ram Jet

Whoa! Hey Gordon feel free to chime in here. I don't think lithium grease on the slides is a good idea, it may be too viscous. Possibly silicone spray? Possibly dry. Dunno for sure. Ducatiman would know.

Bill

okies i've heard of others using it, perhaps just a mild whiping with a rag and a spray with some air and a check over for debris for now dry is probably best they really dont require lube. i'll keep an eye on the thread.

*EDIT* i popped the diaphragm out of my lid. 26 km ride to work, ZERO issues. Sucking back gas like a CHAMP. wicked. +1 for ghostt!! i'll rebuild the cap later.

[Ram Jet]

Originally Posted by KikRox

okies i've heard of others using it, perhaps just a mild whiping with a rag and a spray with some air and a check over for debris for now dry is probably best they really dont require lube. i'll keep an eye on the thread.

*EDIT* i popped the diaphragm out of my lid. 26 km ride to work, ZERO issues. Sucking back gas like a CHAMP. wicked. +1 for ghostt!! i'll rebuild the cap later.

Good deal on the gas cap. I dumped mine in favor of a non-locking after market cap. In 50 years of riding no one has ever siphoned gas from my tank.

Just a note on slide lubrication. My thought being, that throttle slide just "floats" in the carb body waiting for a change in air pressure to move it up and gravity to move it back down down - a CV carb. On a non CV carb you have a twist grip to pull it up/open and a spring to close it. In other words you force the throttle slide to do what you want. It just seems to me that sticky lithium grease will hang-up that throttle slide and off come the carburetors again.

Bill

[KikRox]

Originally Posted by Ram Jet

Good deal on the gas cap. I dumped mine in favor of a non-locking after market cap. In 50 years of riding no one has ever siphoned gas from my tank.

Just a note on slide lubrication. My thought being, that throttle slide just "floats" in the carb body waiting for a change in air pressure to move it up and gravity to move it back down down - a CV carb. On a non CV carb you have a twist grip to pull it up/open and a spring to close it. In other words you force the throttle slide to do what you want. It just seems to me that sticky lithium grease will hang-up that throttle slide and off come the carburetors again.

Bill

Yeah as far as i know the slides should be dry, they likely get saturated in gas anyways. i might have to invest in a rebuild kit for the gas cap later on. its actually working awesome at the moment, and that annoying squeeling to the tank vent is gone. funny how such a small thing can cause such a huge annoynce.