kraher

Hello,

I've been doing some searching/reading, a lot of people relate my problems to the carbs and jets. In my case, that would seem unlikely.

The problem:

• Hesitation/Stutter starts at 3-4k RPM. Idles fine, seems ok @ higher RPM. Stutters from 3 all the way up to 5-6k RPM.
• Choke definitely affects the stutter, but it does not remedy the problem, although if you get the choke set just right it seems better. Then the bike warms up a little more, and you have to find the "sweet spot" again.
• Problem is a bit intermittent, sometimes I can ride around my neighborhood for a minute or two and all is well, then suddenly it starts to stutter.
• If it is stuttering and I reel in the clutch, it stalls about 50% of the time.
• Bike seems to idle as I remember, no strange noises noticeable, same when it is running properly for brief moments.

The background:

• The bike is just coming out of winter hibernation and it has the hessitation.
• I just finished switching from OEM to APE CCTs.
  • I know for certain that the rear cylinder did not jump timing as I had the covers off, used wire ties AND marked both sprokets and the chain with a sharpie...verified before installing the cover.
  • I did the 450deg trick to get to TDC of the front, I did not remove the cover though (wish I would have now). I did overshoot the mark on the initial 450deg rotation, but I rotated another two full rotations from that point and tried again.
  • Did not hear any clicks, thumps or any strange noises during the entire swap.
  • Rotated the crank by hand 8-9 times before I attempted to start the engine, rotation was smooth with no tightness/binding felt and no bizarre noises.
  • I adjusted the APE to finger tight, less a tiny bit (I figured tighter would be safer at first).
• I replaced the steering head bearings this winter.
• Bike has Yoshimura cans
• Bike has Dynojet kit
• Bike was running flawlessly this autumn before storing it.
• I did not put fuel stabilizer in the tank before storage, I have therefore removed as much of the fuel as possible (a cup or two left I am guessing) and I have drained the floats. Then I filled the tank with fresh premium fuel.

I think that is all the information I can think to give you.

I did my best not to touch the carbs which leads me to believe that the carbs/jetting shouldnt be the issue. Do you think that the carbs just need a shot of carb cleaner in the intake? What are the odds that the timing on the front cylinder jumped enough to make it run strangely, but not enough to make any odd noises?

As was suggested in one thread, I double checked the vacuum hose to the petcock. Just to be sure I replaced the clamp, to no avail.

What are you thoughts? Feel free to chime in with any suggestions. I am a fairly novice wrench, but I am getting more experience by the day and I am not afraid to try things. I love to learn, and I love to wrench.

g_clarke_2008

Welcome to the forum, I too live in Calgary, we'll have to get together for a ride out to Bragg Creek one weekend.

What are you running for an air filter? I bought mine with a full akropvic exhaust and a K&N filter and it was stuttering from 4 to 5k. I took out the K&N and put in an oem honda filter and now she runs like new.

supermatt996

carb sync. ?

inderocker

-If it was due to winter storage, then you would have a plugged pilot jet, but you said it was idling fine. I trust that you mean that it idles fine without the choke? The main jets can get plugged up and the needle can get varnish on it as well, but those are extreme cases. usually at that point the butterfly's are stuck and you can't turn the throttle.

-If it's a jetting issue and the choke makes it go away for the most part, then you are running lean. You may want to try raising the needle one position.

-The timing could be off on the front cylinder, there's only one way to check and you know how to do it. If it is off by one tooth then you won't notice it simply by rotating the engine manually as there won't be any interference.

It sounds more like a jetting issue but you said it ran great when you parked it, therefore I'm putting my money on improper cam timing.

Circuit_Burner

Make sure the CV slides are free and go up and down with finger pressure.
Thats an old stumper.

gboezio

I guess that you get carb farts when it stutter, both pale plugs would confirm a lean midrange, a lot of us experienced this, pull the needles one notch (make them shorter by positioning the clip lower), that will fix your issue.

Hotbrakes

You should also be running 87 octane. But I don't think that's the problem now. Check all the vacuum lines for dry rot/mouse damage. A small leak could cause some rough revs until the vacuum pressure overcomes the leak in the higher rpm's.

kraher

Thanks for the quick replies! Good info.


I will have to double check that with the PO, it does appear red similar to a K&N but that is about as un-scientific as it gets. Regardless, I didnt change it, I just cleaned it with compressed air and re-installed it. Seems like an unlikely fix.

Indeed it idles fine with or without choke.

The bufferflys feel smooth and when the airbox was off I looked inside and they appeared to move smoothly. Would a shot of carb cleaner in the intake clean this up?

Excuse my ignorance: Are you refering to the slides at the inlet to the carbs, just below the airbox? If so, those are moving smoothly, I checked those while it was apart.

Pale plugs? Not sure what you mean by that, I can tell you that mine are a little black if anything, they are also rather new plugs. I am guessing only a few thousand kms old.


I have read alot about electical problems causing this type of behaviour, I havnt touched most of the electrical components, except:

• Disconnected the fuel light at the tank.
• Disassembled and cleaned the side stand (switch causing the intermittent fuel cut?)
• Disconnected all lights to get the front fairing off.
• I think that is all I needed to disconnect to do the APEs and Steering Head bearings.

Any thoughts on potential electrical problems?

I know how one would check the timing on the front clyinder, but as I am not looking at the bike right now my memory is telling me that the frame would obscure your view of the cam sprockets. Any tips on how to accurately confirm the marks are level with the head? I am not crazy about using a mirror, but will if I have to.

Thanks a bunch, and keep the suggestions rolling.

lazn

What exactly did you check? The hose goes to the rear of the petcock, not the bottom. (leave the nipple on the bottom of the petcock with no hose on it)

Just to be sure, because replacing the clamp wouldn't help if the hose is still going to the wrong nipple.

g_clarke_2008

If it is a K&N and you cleaned it that could be the problem. Mine was running fine last year then I removed the K&N (which was filthy from th p/o) and cleaned it and when re-installed it was running lean and stuttering. I didn't want to mess with the jetting so I put in an oem filter and that took care of the problem. If you want to get together we can pull the stock filter out of mine and put it in yours to see. It doesn't take long and would be a cheap fix if it works.

Little_Horse

+ 1 on valve timing on the front

kraher

Are you joking?

Mine is definitely on the bottom of the petcock, if that was not the correct port I have difficulty believing that it would run at all. I am fairly sure that I removed the hose from the bottom to begin with, although I have been wrong before.

Can you explain to me how the wrong port would cause the described symptoms?

lazn

That is exactly how it behaves when you have it hooked up wrong.

The Petcock valve isn't opening, but the engine has enough pull through the gas lines to get some fuel, enough to idle, not enough to run strong.

Search for: PVLIR (That stands for Petcock Vacuum Line Inadvertent Relocation) enough people do exactly that as it looks like it should be hooked up to the bottom of the petcock that it has it's own acronym on the forum.

kraher

Wow, I bet thats it, As I said it is definitely 100% on the bottom port.

I sincerely hope it is, gotta love a cheap and easy fix to a potential serious headache....I shall try that after work and report back...Thanks a bunch!!!

Circuit_Burner

One of the worst to trace problems is the Ignitor or CDI unit.
If all the other inspection leads nowhere, always suspect the CDI.
A lot of Sun automotive machines from back in the day can be used to detect misfire, but its hard if you cant look at the firing rate.
One poor-mans trick on multi plug engines like a hawk is to remove one of the plug wires (theres 2 per cylinder remember) and feed a clean spark plug from it and visually check for misfire at various RPM.
Not perfect, but it works when you have nothing else.

inderocker

Any luck with that?

kraher

Still at work, going to try tonight.

Tweety

With the above info I'd say it's either that or the K&N being opened up from cleaning...

Those are the most likely culprits... Electrical problem in this way is almost a non issue on the VTR... It has one of the smallest "brains" you'll ever see on a "modern bike", so in that respect it usually either works, or is outright fried...

kraher

You Sir....ARE MY HERO!!!

Moved the hose, works like a charm. Seems so obvious based on hose size vs. port size and the shape of the petcock. Boy do I feel dumb.

Thanks everyone!!

oneup1982

You guys kick ***, you just helped me solve my problem.... Had it connected to the wrong port on the petcock... My bike would run on the freeway, but would surge like there is no tomorrow, then it felt like I had a clogged fuel filter.... Man, She runs like a champ now. THANKS!

oneup1982

Don't feel bad man, I am a mechanic and even I screwed it up.

dshakes